Front Cover
 Front Matter
 Table of Contents
 The indoor-battery problem
 Observations on battery plants
 Experiments under battery...
 Indoor-battery manifestations
 Relation of the problem to...
 Relation of the problem to experimental...
 Literature cited

Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 425
Title: The etiology of fowl paralysis, leukemia and allied conditions in animals
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00015137/00001
 Material Information
Title: The etiology of fowl paralysis, leukemia and allied conditions in animals
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Alternate Title: Relation of adverse atmospheric conditions to the development of this group of diseases under indoor-battery conditions
Physical Description: 43 p. : ill., charts ; 23 cm.
Language: English
Creator: Emmel, M. W ( Mark Wirth ), b. 1895
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1946
Subject: Avian leukosis   ( lcsh )
Marek's disease   ( lcsh )
Chickens -- Diseases   ( lcsh )
Chickens -- Housing   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 42-43.
Statement of Responsibility: by M.W. Emmel.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00015137
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925496
oclc - 18253251
notis - AEN6147

Table of Contents
    Front Cover
        Page 1
    Front Matter
        Page 2
        Page 3
    Table of Contents
        Page 4
        Page 5
    The indoor-battery problem
        Page 6
        Page 7
    Observations on battery plants
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
    Experiments under battery conditions
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
    Indoor-battery manifestations
        Page 28
        Page 29
        Page 30
    Relation of the problem to brooding
        Page 31
        Page 32
    Relation of the problem to experimental procedures
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
    Literature cited
        Page 42
        Page 43
Full Text

Bulletin 425

Octob e 1946-




XII. Relation of Adverse Atmospheric Conditions to the
Development of This Group of Diseases Under
Indoor-Battery Conditions



Single copies free to Florida residents upon request to


J. Thos. Gurney, Chairman, Orlando
N. B. Jordan, Quincy
Thos. W. Bryant, Lakeland
M. L. Mershon, Miami
J. Henson Markham, Jacksonville
J. T. Diamond, Secretary, Tallahassee


John J. Tigert, M.A., LL.D., President of the
H. Harold Hume, D.Sc., Provost for Agricul-
Harold Mowry, M.S.A., Director
L. O. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M.S., Asst. Dir., Admin.
J. Francis Cooper, M.S.A., Editor3
Clyde Beale, A.B.J., Associate Editors
Jefferson Thomas, Assistant Editors
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers
K. H. Graham, LL.DI., Business Managers
Claranelle Alderman, Accountants



W. E. Stokes, M.S., Agronomist'
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Agronomist'
G. B. Killinger, Ph.D., Agronomist
W. A. Carver, Ph.D., Associate
H. C. Harris, Ph.D., Associate
Fred A. Clark, B.S., Assistant


A. L. Shealy. D.V.M., An. Industrialist'1
R. B. Becker, Ph.I., Dairy Husbandmans
E. L. Fouts, Ph.D., Dairy Technologist3
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian3
L. E. Swanson, D.V.M., Parasitologist
N. R. Mehrhof, M.Agr., Poultry Husb.S
G. K. Davis, Ph.D., Animal Nutritionist
R. S. Glasscock, Ph.D., An. Husbandman
P. T. Dix Arnold, M.S.A., Asst. Dairy Hush.'
C. L. Comar, Ph.D., Asso. Biochemist
L. E. Mull, M.S., Asst. in Dairy Tech.
Katherine Boney, B.S., Asst. Chem.
J. C. Driggers, B.S.A., Asst. Poultry Husb.
Glenn Van Ness, D.V.M., Asso. Poultry
John S. Folks, B.S.A., Asst. An. Husb.
W. R. Krienke, M.S.A., Asso. Dairy Mfrs.


C. V. Noble, Ph.D., Agri. Economist' 3
Zach Savage, M.S.A., Associate5
A. H. Spurlock, M.S.A., Associate
ID. E. Alleger, M.S., Associate
D. L. Brooke, M.S.A., Associate

Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist
J. C. Townsend, Jr., B.S.A., Agr. Statistician2
J. B. Owens, B.S.A., Agr. Statistician2

Ouida D. Abbott, Ph.D., Home Econ.1
R. B. French, Ph.D.. Biochemist

A. N. Tissot, Ph.D., Entomologist and Act-
ing Head of Dept.
H. E. Bratley, M.S.A., Assistant


G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl, Ph.D., Asso. Horticulturist
F. S. Jamison, Ph.D., Truck Hort.
Byron E. Janes, Ph.D., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. K. Showalter, M.S., Asso. Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.
Victor F. Nettles, M.S.A., Asst. Hort.
F. S. Lagasse, Ph.D., Asso. Hort.2


W. B. Tisdale, Ph.D., Plant Pathologist1
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist and Botanist
Lillian E. Arnold, M.S., Asst. Botanist

F. B. Smith, Ph.D., Chemist' 3
Gaylord M. Volk, Ph.D., Chemist
J. R. Henderson, M.S.A., Soil Technologist
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils Chemist
C. E. Bell, Ph.D., Associate Chemist
L. H. Rogers, Ph.D., Associate Biochemist
R. A. Carrigan, B.S., Asso. Biochemist
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asst. Microbiologists
R. E. Caldwell, M.S.A., Asst. Soil Surveyor
Wade McCall, B.S., Asst. Chemist
J. B. Cromartie, B.S.A., Asst. Soil Surveyor

1 Head of Department.
2 In cooperation with U. S. D. A.
3 Cooperative, other divisions, U. of F.
In Military Service.
5 On leave.



J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
W. H. Chapman, M.S., Asso. Agron.
R. C. Bond, M.S.A., Asso. Agronomist
L. G. Thompson, Ph.D., Soils Chemist
Frank D. Baker, Jr., B.S., Asst. An. Hush.

Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Wewahitchka
J. B. White, B.S.A., Associate Agronomist


A. F. Camp, Ph.D., Vice-Director in Charge
V. C. Jamison, Ph.D., Soils Chemist
W. L. Thompson, B.S., Entomologist
J. T. Griffiths, Ph.D., Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, M.S., Plant Pathologist5
J. E. Benedict, B.S., Horticulturist
B. R. Fudge, Ph.D., Associate Chemist
C. R. Stearns, Jr., B.S.A., Asso. Chemist
James K. Colehour, M.S., Research Chemist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Asso. Horticulturist
H. O. Sterling, B.S., Asst. Horticulturist
J. A. Granger, B.S.A., Asst. Horticulturist
H. J. Reitz, M.S., Asso. Plant Path.
Francine Fisher, M.S., Asso. PI. Path.


R. V. Allison, Ph.D., Vice-Director in Charge
J. W. Wilson, Sc.IY., Entomologist
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
B. S. Clayton, B.S.C.E., Drainage Eng.2
W. D. Wylie, Ph.D., Entomologist
W. T. Forsee, Jr., Ph.D., Asso. Chemist
R. W. Kidder, M.S., Asst. An. Husb.
T. C. Erwin, Assistant Chemist
R. A. Bair, Ph.D., Asst. Agronomist
C. C. Seale, Asst. Agronomist
L. O. Payne, B.S.A., Asst. 'Agronomist
Russel Desrosiers. M.S., Asst. Plant Path.
N. C. Hayslip, B.S.A., Asst. Hort.


Geo. D. Ruehle, Ph.D., Vice-Director in
H. I. Borders, M.S., Asso. Plant Path.5
D. O. Wolfenbarger, Ph.D., Asso. Ento-
R. W. Harkness, Ph.D., Asst. Chemist


Clement D. Gordon, Ph.D., Poultry Geneticist
in Charge2


W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Associate Agronomist
D. W. Jones, B.S.A., Asst. An. Hush.
E. R. Felton, B.S.A., Asst. An. Hush.

R. W. Ruprecht, Ph.D., Chemist in Charge
A. Alfred Foster, Pi.D., Asso. Hort.
J. C. Russell, M.S., Asst. Entomologist
Ben F. Whitner, Jr., B.S., Asst. Hort.


G. K. Parris, Ph.D., Plant Path. in Charge

Plant City
A. N. Brooks, Ph.D., Plant Pathologist

A. II. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin, Ph.D., Truck Horticulturist

S. O. Hill, B.S., Asst. Entomologist2 4
A. M. Phillips, B.S., Asst. Entomologist2

J. R. Beckenbach, Ph.D., Horticulturist in
E. G. Kelsheimer, Ph.D., Entomologist
David G. Kelbert, Asso. Horticulturist
E. L. Spencer, Ph.D., Soils Chemist
Robert 0. Magie, Ph.D., Hort., Glad. Inv.
Donald S. Burgis, M.S.A., Asst. Hort.

Warren O. Johnson, Meteorologist2

1 Head of Department.
2 In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
4In Military Service.
6 On leave.



THE INDOOR-BATTERY PROBLEM ................ ........................................ 6

OBSERVATIONS ON BATTERY PLANTS ................. .. ....... ...................... 8

The Indoor-Hen-Battery Plant ...........-... ...-------- -- ........---- 8

The Outdoor-Hen-Battery Plant ... .......... .............. .................. 16

The Broiler and Fryer Plant .................. ..... .................. .. 19

EXPERIMENTS UNDER BATTERY CONDITIONS ................... ........................ 21

Indoor versus Outdoor Housing of Chickens ..................................-- ... 21

Birds Reared Outdoors to Maturity, Then Moved to Indoor-Batteries 22

Biologic Saturation Point ..-....--... ........ --. ..............--- -.... 23

INDOOR-BATTERY MANIFESTATIONS ..................................... ---..--........ 28

RELATION OF THE PROBLEM TO BROODING ...................... ............ ........ 31


DISCUSSION ..-........-- ..-............... .------- ..-----.. ---..-- 34

CONCLUSIONS ....................... .... .....-.--..-- .....-- .....--....... 40

SUMMARY ........--.......------.~.. ..... ..... ........ ..... ........... 41

LITERATURE CITED .....................---------- -- -----...... .........---- ....--- 42


XII. Relation of Adverse Atmospheric Conditions to the
Development of This Group of Diseases Under
Indoor-Battery Conditions'


Previous publications (2-7)2 have indicated that the group of
diseases under study can be induced by micro-organisms of the
paratyphoid and typhoid groups and that intestinal parasites-
coccidia, capillaria, the common round worm and tape worms-
are important as predisposing factors, particularly in the estab-
lishment of the micro-organism in the intestinal tract of the
bird and in creating, or assisting to create, an avenue of in-
fection through the intestinal mucosa. Hemocytoblastosis has
been found to be a basic process leading to the development of
many of the pathologic manifestations under these conditions.
Reference has been made previously (5) to the difficulties en-
countered in raising experimental birds free of hemocytoblastosis
under battery conditions. It has been observed that leukemia,
one of the manifestations under consideration, occurs frequently
in indoor-hen-battery plants. Paralytic symptoms also occur
to a varying extent under these conditions. Associated with
the development of these is another manifestation in which the
affected bird becomes extremely emr-iated before death.
One of the apparent advantages of the hen-battery has been
its increased facilities for sanitation which should be an aid to
disease control. However, in many plants this method of hous-
ing birds has resulted in mortality which often has ranged from
40 to 60 percent. In many instances the high rate of mortality
from these manifestations has resulted in a problem so acute
that the operator has been unable to cope with the situation and
has been forced to discontinue operations. Leukemia, as it
occurs under battery plant conditions, appears to be identical
with that occurring under field conditions which experiments
in this series have shown to be induced by micro-organisms of
SThe author is grateful to J. H. Burrell, Purina Mills, St. Louis, Mo.,
and to the late Carl Schroeder, Larro Research Farm, Detroit, Mich., for
helpful suggestions during the conduct of these experiments.
Italic figures in parentheses refer to Literature Cited.

Florida Agricultural Experiment Station

the paratyphoid and typhoid groups associated with intestinal
parasitism. While the paralytic symptoms do not differ ma-
terially from those of true fowl paralysis, they usually are
non-spastic. This mortality problem in indoor-hen-battery plants
appears so closely related to the manifestations under consider-
ation that it was considered advisable to study the problem
A preliminary survey of 4 indoor-hen-battery plants indicated
that neither micro-organisms of the paratyphoid or typhoid
groups nor intestinal parasitism could be associated with the
occurrence of leukemia and paralytic symptoms. As previously
mentioned, this association has been reported to exist in out-
breaks of these diseases under field conditions. Therefore, it
seemed apparent that other agents or factors are responsible
for the development of these diseases under indoor-hen-battery
It is the purpose of this paper to describe the indoor-hen-bat-
tery mortality problem and its associated syndrome and to
report the results of an endeavor to determine the conditions
responsible for their development. The problem is important
not only to the hen-battery plant operator, but also of vital
concern to investigators working with this group of diseases as
well as being of practical importance to all indoor battery and
brooder operations.

Reference has been made in a previous publication (5) to
the difficulty encountered in raising hemocytoblastosis-free birds
for experimental purposes under indoor-battery conditions. Dur-
ing early investigations, experimental birds were raised from
baby chicks to experimental age in a room provided for this
purpose. This room was an integral part of the building in
which birds included in many infection-experiments were housed.
Numerous variations in management and sanitation failed to
permit birds to be raised hemocytoblastosis-free. A movable
house for rearing experimental birds far removed from infec-
tion-experiments has been described (6). While this house
aided materially in reducing the degree of hemocytoblastosis in
birds raised therein, the problem was not solved completely.,
The opportunity has been afforded to observe the occurrence
of "light" and anemia in young birds in fryer and broiler-battery
plants. In some instances the occurrence of these manifesta-

The Etiology of Fowl Paralysis

tions under these conditions has constituted an important mor-
tality problem. In some of these outbreaks, coccidiosis has
been associated definitely with the occurrence of disease. While
birds have responded to sanitary measures and the dried milk
treatment for coccidiosis in most instances in which parasitism
was associated with the outbreak of disease, other instances
have occurred in which the response to this treatment was not
satisfactory. The hypothesis was advanced, previously, that
such outbreaks probably were caused by particularly virulent
strains of the micro-organism, as it has been shown in young
birds that hemocytoblastosis and an occasional other manifesta-
tion can be induced by oral administrations of the micro-organ-
isms, S. aertrycke, S. enteritidis and S. schottmitlleri to parasite-
free birds (4, 6). As a wider opportunity developed for the
study of such outbreaks, it has become apparent that other
factors have been concerned.
In other fryer and broiler-battery plants owners have reported
the occurrence of respiratory diseases, principally colds and
roup, which have failed to yield to the usual treatments for these
diseases. The observation has been made that although seasonal
variation has not been associated definitely with the occurrence
of this condition, its occurrence often is intermittent, particularly
as far as severity is concerned.
Still other fryer and broiler plants make a practice of raising
birds in batteries until about 5 weeks of age and finishing them
for market in outside pens. Two such plants have been observed.
Although no problem in the batteries was apparent to the
owner, birds often developed colds and roup after being placed
outside. This problem was quite disconcerting to the owners,
since at about the time the birds were of the proper age for
market many of them were not properly fleshed or were affected
with colds and roup.
Many poultrymen commonly raise their laying and breeding
birds under battery conditions until 6 to 8 weeks of age and
then place them on the range for growth to maturity. In many
such instances birds have not done well when changed from
battery conditions to range and considerable loss has resulted.
In other instances in which mortality has not occurred there
appears to have been a detrimental influence on the development
of the bird. This is important from a practical standpoint, as
this period in the life of the bird is of utmost importance to the
development of a healthy, vigorous bird at maturity.

Florida Agricultural Experiment Station

A study of the mortalityproblem in 4 hen-battery plants has
indicated that leukemia and paralysis constituted the majority
of losses under these conditions. Since previous experiments
have indicated that hemocytoblastosis is a fundamental process
in the development of fowl paralysis and leukemia, the problem
involved in birds kept under these conditions should have a
direct bearing upon a full understanding of the group of diseases
under study.
The efforts of most hen-battery plant operators to reduce mor-
tality from these manifestations have not proved of sufficient
practical application to control mortality. The result has been
that although this system of maintaining laying birds is estab-
lished with great enthusiasm with all the earmarks of being an
ideal system from the sanitation and management standpoints,
the mortality problem has forced many hen-battery operators to
close their plants and many broiler and fryer-battery operators
have been forced at times to take severe losses.

A study of mortality among birds in 4 indoor-hen-battery
plants has indicated that losses occur principally from paralysis,
leukemia and emaciation. The intensity of the problem varied
in the different plants. All of the indoor-hen-battery plant
operators agreed that mortality is their most serious problem.
Since the conditions observed were so similar in all plants studied,
a general discussion will give a better understanding of the
problem involved (9).
Maturity of Birds.-In 3 hen-battery plants an opportunity
was presented to observe the development of young, battery-
raised birds intended as replacements. Marked variation did
not seem manifest until the birds began to reach maturity. At
this time exceptionally poor development could be noted in a
few of the birds.
The head was coarse and lacked femininity; the comb and wat-
tles were poorly developed and appeared pale and wrinkled;
the bone structure of the body showed poor development.
In a fourth plant the young birds were raised to maturity on
wire floors and sun porches. Poor development did not occur,
but after the birds were placed in the indoor-batteries mortality
soon became as high as that in the other 3 plants.

The Etiology of Fowl Paralysis

In the 4 indoor-hen-battery plants studied, even though some
birds failed to show satisfactory maturity, mortality did not
become an important problem until a number of weeks after
the majority of the birds came into production.
Production.-Poorly matured battery-birds rarely came into
egg production. After a variable number of weeks, they died
as a result of either paralysis, leukemia or emaciation; occasional
birds developed more than 1 manifestation. Other birds ap-
parently normal in every respect came into good production,
maintained it satisfactorily for a variable period of from 3 to 12
weeks, then ceased production suddenly. Some of these birds
after a varying period of perhaps 6 to 12 weeks developed 1
of the pathologic manifestations. Other birds would resume
egg production after a non-production period of 10 days to 6
An interesting observation was the extreme variation in the
egg clutch of different birds and often in the same bird. Satis-
factory production was maintained only spasmodically if at
all. Birds would lay almost every day for a period of 10 days
to 3 weeks, then would cease production suddenly for 10 days
to 5 or 6 weeks and then would resume production as before
(Fig. 1). Practically every producing bird in the hen-battery
plants observed passed through a variable period of production
followed by a variable period of non-production. Some birds
showed considerable regularity in these periods while others
did not. At any time, and without warning, individual birds
ceased to lay and shortly thereafter developed 1 of the patho-
logic manifestations eventually resulting in death.

Fig. 1.-Typical egg record of bird maintained under adverse conditions
in an indoor hen battery.

Florida Agricultural Experiment Station

Molting.-In the 4 indoor-hen-battery plants observed fre-
quent molting occurred. In 2 plants some of the birds in the
flock were continuously in molt. Various degrees of molting
of the entire flock were observed at irregular intervals from
no apparent cause in the other 2 plants.
Mortality.-Paralysis, leukemia and emaciation were the chief
causes of mortality. Losses ranged from 20 to 60 percent in
the plants studied.
The symptoms of paralysis were similar to those of true fowl
paralysis occurring under field conditions, although paralysis
occurring in the various battery plants was less spastic than
that occurring in the field and the onset of symptoms usually
was more gradual. Of the various leukemias, myeloid leukemia
was observed most frequently, whereas erythroblastic erythro-
leucosis was observed occasionally and lymphatic erythroleucosis
was encountered rarely. Birds affected with emaciation showed
a progressive condition which continued over a period of 3 to 6
weeks until death, at which time the birds were extremely
emaciated. Marked hemocytoblastosis, which was not greatly
different from the type of hemocytoblastosis leading to the de-
velopment of lymphatic erythroleucosis, occurred in these birds.

Fig. 2.-Birds maintained in an indoor battery. Combs of the 3 hens in
the top row are apparently normal. Those of the 3 hens in the bottom row
are shriveled, grayish, scaly and harsh-indicating the development of a
pathological condition.

The Etiology of Fowl Paralysis

The first indications of the development of 1 of these patho-
logic manifestations was a flaccid, pale, shriveled, greyish, scaly
comb (Fig. 2). This was in marked contrast to the combs of
apparently normal birds; such combs, although occasionally
somewhat pale, were full, turgid and did not have a tendency to
wilt. After a variable period of 2 to 12 weeks, emaciation,
leukemia or paralysis developed, although occasionally symp-
toms of paralysis developed suddenly.
Efforts to Decrease Mortality.-Most of the owners found by
experimentation that it made no difference on the ultimate out-
come whether the bird was placed in the top tier of cages, usually
3 high, or in the lower 2 tiers. Some operators observed that
at times greater difficulties were encountered in certain portions
of the room than in others.
One plant had practiced a system by which only birds from
parent stock bred and raised under battery conditions were
used. The current birds in this plant originated from birds
maintained under these conditions for 3 years. However, it is
doubtful if much had been accomplished by this system of breed-
ing, since this operator's mortality problem became so acute
he was forced to close his plant.
Of particular interest is the observation of 2 operators that
birds placed outdoors as soon as symptoms were observed even-
tually recovered. Each operator maintained a small house with
sun parlor for this purpose. A few birds showing symptoms
of paralysis would recover under these- conditions. However,
in case birds were transferred outdoors after symptoms had
been observed for some time the percentage of recovered cases
was reduced.
In 1 instance the installation of exhaust and intake ventilating
fans greatly reduced mortality.
Hemocytoblastosis.-Noting the occurrence of paralysis and
leukemia as part of the mortality problem, blood smears from a
representative number of birds from the 4 indoor-hen-battery
plants were examined. Previous publications (2, 4-6) have
shown that hemocytoblastosis is a basic manifestation leading
to the development of fowl paralysis and leukemia. The ob-
servation was made that hemocytoblastosis occurred in varying
degrees not only in birds in which paralysis and leukemia had
developed, but in every bird from which a blood smear was
made. Whether or not the bird then appeared in excellent
condition with no visible symptoms of illness or was in produc-


S. ) Eosinophile
*SM t -------
0 "

C) c4 C)~ p ~C)

Lymphocyte ,
Ca 0 ) I

I. ~ > ;4 iH
C) ,1 l C)
C E 0~ -
>C M r.
0 s-















10 66
- 61
12 72
12 56
14 66
18 41
- 59
16 66
17 62

-I -
5 7 3

- -| 5 -

7 5- )
S |-I -5 3
- -I -
- I I -

2,480 43,600
2,160 33,600
2,750 38,800
2,400 37,500
2,250 39,400
2,300 33,900
2,710 43,600
2,450 27,400
2,380 45,200



0 a

m) t


3 -

8 -

3 -

- 1
2 -


9 2
3 -
13 -

* Hereafter the vacuolar lymphocyte will not be classified under lymphocytes for reasons suggested on page 4 of Bul. 306.

The Etiology of Fowl Paralysis

tion at the time, hemocytoblastosis was present universally.
The manifestation in which progressive emaciation was the
predominant symptom was diagnosed as chronic hemocytoblas-
tosis which, heretofore, has not been described. Since this
manifestation is a new one associated with the development of
this group of diseases, a more detailed discussion of it will be
included later in this paper.
Table 1 gives the total and differential blood counts of some
indoor-hen-battery birds under the conditions observed.
Plant No. 1.-The building was 60 x 80 feet, concrete block
construction, concrete floor and with screened double sash win-
dows on 3 sides of the structure; the roof formed the ceiling.
Buffers opening at the top of the bottom sash were arranged
so there was no direct breeze from the outside on the birds.
Two ventilators were placed in the ridge of the roof and each
was equipped with a 14-inch exhaust fan. The operator was
able to maintain a fairly uniform temperature. At 1 time
1,500 birds were housed in the building in metal batteries. Sani-
tation was excellent.
Practically all of the difficulties previously described as oc-
curring in indoor-hen-battery plants were encountered. The
plant started operation with approximately 1,000 almost mature
pullets which had been purchased in another state and which
had been reared in a battery plant. These birds were from
parent stock reared and bred under battery conditions for 3
years. After the plant had been in operation for 4 months,
colds and occasional cases of roup were observed. From the
owner's standpoint this was difficult to understand since the
birds apparently were housed ideally. The usual treatments for
colds did not relieve this condition. Shortly thereafter leukemia,
paralysis and chronic hemocytoblastosis began to appear. Mor-
tality from these diseases the first year reached 25 percent,
with chronic hemocytoblastosis being responsible for 50 percent
of these losses; there was very little difference in the percentage
of losses from leukemia and paralysis.
Hemocytoblastosis in some degree was found to exist in all
birds examined, even though many of them appeared to be in
good physical condition. Pullets which were raised for replace-
ments in a room partitioned from 1 corner of the building also
were found to be affected with hemocytoblastosis. Considerable
improvement was observed in the pullet room after an intake
fan had been installed. However, when these birds were placed

Florida Agricultural Experiment Station

in the main battery room losses occurred as in the remainder
of the flock.
Plant No. 2.-The building was a wooden structure 20 x 40
feet, concrete floor and with windows 4 feet from the floor at
4-foot intervals o6 2 sides. The windows could be opened com-
pletely and were screened. There was a small opening about
2 feet square covered with screen in each gable; the screen
was obstructed almost completely by the accumulation of dust.
The batteries were home-made, 3 tiers high, and crowded. The
plant housed 800 birds. Ventilation and sanitation were poor.
The owner had experienced all the difficulties previously de-
scribed. Mortality reached 40 percent in 1 year, the chief mani-
festation being chronic hemocytoblastosis; the remaining losses
were from leukemia and paralysis. The plant was merely a side
issue with the operator and his determination to make the plant
profitable led to the construction of a small house with wire
floor and sun porch to which birds were removed immediately
upon showing symptoms of illness. Birds so handled usually
recuperated over a period of 3 to 6 weeks and were placed back
in the battery plant. In this manner the owner had been able
to reduce his mortality to 10 percent, although he had never
been satisfied with egg production which had ranged from 30
to 50 percent.
Blood smears from approximately 50 birds were taken on 2
occasions from birds picked at random and all were found to
have varying degrees of hemocytoblastosis.
Plant No. 3.-The building was constructed entirely of gal-
vanized corrugated metal, 75 x 100 feet, concrete floor, and with
double sash windows every 10 feet on 3 sides. The roof, which
contained 3 metal ventilators, formed the ceiling. There was
no forced ventilation. All openings were screened. The bat-
teries were 3 tiers high, home-made and constructed of metal.
The building housed 2,000 birds. Sanitation was good.
During the 4 years the plant had been in operation mortality
had ranged from 35 to 53 percent. Chronic hemocytoblastosis
constituted the majority of losses. Leukemia and paralysis were
responsible for the remainder and cases of leukemia outnum-
bered paralysis about 2 to 1. Egg production had never ex-
ceeded 50 percent. Young birds raised outside on wire floors and
sun porches presented an excellent appearance when placed at
maturity in the main plant. However, shortly after coming into

The Etiology of Fowl Paralysis

production the usual mortality problem appeared. Finally, the
owner was forced to close his plant.
An opportunity was presented to observe closely all the birds
in the flock. The problem appeared similar in every respect to
that which has been described previously. Blood smears from
a large number of birds taken at random showed that all birds
so examined were affected with various degrees of hemocyto-
Plant No. 4.-The building was constructed of wood, 18 x 50
feet, concrete floor, with 1-sash removable screened windows
about every 10 feet on the 2 long sides of the structure. A
ventilator was constructed in the ridge of the roof near the
middle of the building. The ventilator was covered with screen
which was obstructed almost completely with accumulations of
dust. There was no forced ventilation. The building was low,
rather dark, but fairly sanitary. The batteries were 3 tiers
high, home-made, and of wood construction. The building
housed 450 birds.
Young birds were raised in another building of similar con-
struction. Mortality from paralysis, leukemia and emaciation
varied during the 3 years the plant was in operation from 40
to 60 percent and the losses were about equally divided between
the 3 manifestations. Egg production never exceeded 45 per-
cent. The owner had experimented with a large number of
well-known commercial feeds and found that losses could not
be materially affected in this manner. Unable to reduce mor-
tality, the owner finally closed this portion of his plant.
During each of 2 visits to this plant, blood smears were taken
from 40 birds picked at random and all were found to be affected
with various degrees of hemocytoblastosis.
Postmortem Findings.-Seventy-seven birds were received
from the above 4 plants, collectively, over a period of 10 months.
Twenty were found to be affected with leukemia, 17 myeloid
leukemia and 3 erythroblastic erythroleucosis. Gross lesions
and blood pictures in these cases were similar to those encoun-
tered under natural conditions in the field.
Most of the 26 cases of paralysis showed symptoms apparently
identical with those observed in naturally occurring field cases
of true fowl paralysis but failed to show nerve lesions as fre-
quently as may be demonstrated in the latter instance.
The 31 birds which showed emaciation were diagnosed as
being affected with chronic hemocytoblastosis. The stimulus

Florida Agricultural Experiment Station

apparently existing over a long period had caused a chronic
process which eventually resulted in an exhaustion of the hema-
topoietic tissues.

In the southern half of Florida, climatic conditions are favor-
able for outdoor-hen-battery plants. Three such plants were
studied for purposes of comparison. In general, mortality was
not a problem in these battery plants. The only manifestation
which occasionally developed in 2 plants was chronic hemocyto-
blastosis. When symptoms were first shown, the affected birds
were placed on the ground. After recovery, which usually oc-
curred in from 2 to 4 weeks, the birds were returned to the
batteries, where-they came into production again and became
profitable. Table 2 gives the total and differential blood counts
of representative birds confined to outdoor batteries.
Hen-Battery Plant No. 1.-The operator of this plant had been
experimenting with the outdoor battery for 11 years and prob-
ably was the first operator of an outdoor-hen-battery plant in
The owner had 800 birds, ranging in age from 1 to 5 years,
in batteries; at one time he had 1,500 birds. The batteries oc-
cupied an area 30 x 150 feet and were arranged in 2 rows between
2 rows of orange trees. Replacements were raised in outdoor
batteries 4 times a year, thus allowing a constant supply of eggs
throughout the year. A yearly egg production average of 50
percent had been maintained for a number of years.
Losses from disease seldom occurred. One or 2 birds each
month developed a shriveled, scaly comb, showed scant, greenish-
white droppings and some emaciation-the early symptoms of
chronic hemocytoblastosis. The owner immediately placed these
birds on the ground and in 2 to 4 weeks they recovered suffi-
ciently to be placed in the battery, where they resumed produc-
The owner stated that birds molted more than they should
but that egg production was consistent. Spasmodic production
as observed in indoor-hen-battery plants did not occur.
Blood smears of representative birds were examined for hemo-
cytoblastosis. The examination included 20 birds 2 and 3 years
old which had a record of 300 eggs or over during their pullet
year, and 20 birds 4 and 5 years old which had never touched
foot to the ground. All of these birds were found to have a mild


Eosinophile Lymphocyte a 8

S- PLANT No. 1
48 2,750 51,000 50 80 10 88 2 I -

95 .0 2,560 36,000 51 160 15 69 8 8 -
53 o 2,680 38,800 52 105 23 67 7 --- -
60 48 2,38750 1,00 51 50 12 68 1- 5 +
51 2,94780 32,000 52 70 42 3 -61 -1 -

4895 2,83560 436,000 51 160 2215 4 8 60 6 -
4253 2,680 38,800 52 12205 23 4 -56 8 10 -
6142 2,910 3041,500 52 50 2211 4 11 68 16 -
4865 2,840 33,800 54 207 27 7 66 5 1 -
55 a 2,800 3540,200 54 148 26 60 8 -
65 2,700 34,200 52 1 1 -6 -
50 2,640 34,00 50 1 73 8 --
60 2,380 36,400 61 52 1 69 14 5 +
58 2,940 32,000 56 58 27 3 61 -8 5 -
548 0 2,830 41,000 55 120 22 4 8 60 6 --
42 U3 2,670 34,800 55 122 22 4 56 8 3
61 .4 2,950 30,800 57 70 22 -- 62 -- -
65 20 1 3,00 56 82 20 7 60 12 -
56 2,760 35,500 51 64 26 66 8 -
65 P 2,850 34,000 54 68 34 -61 5 -
54 2,810 34,400 155 66 33 73 54 --1 -

2,670 38,200
2,750 32,400
2,730 36,000
2,910 30,500
2,980 33,800
2,800 36,500
2,790 32,400
2,900 40,000
2,950 36,400

92 19
120 34
66 35
72 20
104 29
48 26
53 17
90 16
67 25

- 77
- 49
3 50
- 62
- 57
8 52
- 63
- 78
- 62



-- 2 -
- 12 -
-1 2 -
-I 14 2 -
2 12 -
- 81- -
- 13| 2 -| -






Florida Agricultural Experiment Station

degree of hemocytoblastosis. The operation of the plant was
upon such a satisfactory basis that hemocytoblastosis could not
be considered to be of important significance.
The owner had a second type of battery in which 4 series of
batteries, each holding 60 birds, were placed under 1 roof. This
battery was constructed a number of years ago and had been
remodeled. Originally the roof on the back of the shed con-
tinued to a point 4 feet from the ground; the edge of the roof
on the front was 7 feet from the ground. The gable ends of
the roof were solid, the bottom edge reaching about 6 inches
above the bottom of the top tier of cages.
Under the original construction, birds housed in the 2 lower
tiers of cages reacted similarly to those housed in other outdoor
batteries. In the top tier of cages, however, egg-production was
intermittent and similar to that occurring in indoor-hen-battery
plants. A few more birds developed chronic hemocytoblastosis
in the top tier than in the lower 2 tiers. The owner recently
had made alterations in which the gable ends of the roof were
opened and the back roof reduced to the size of the front roof.
Since this alteration was made, the difficulties formerly ex-
perienced in the upper tier of cages have not occurred.

Fig. 3.-An outdoor hen battery in which the pathological conditions ob-
served in hens kept under indoor-battery conditions do not occur.

The Etiology of 'Fowl Paralysis

Plant No. 2.-This plant housed 200 birds in home-made
wooden batteries. Birds had been kept under these conditions
for 5 years. The batteries, illustrated in Fig. 3, were under
the shade of chinaberry trees. Replacements were raised on
the ground.
Mortality seldom occurred. Egg production was constant and
averaged above 50 percent. Blood smears from representative
birds showed a mild degree of hemocytoblastosis.
Plant No. 3.-The plant contained 600 birds in batteries simi-
lar to that illustrated in Fig. 3. The batteries were placed among
orange trees. The young birds were raised in outdoor batteries.
Mortality seldom occurred. Egg production was satisfactory,
An occasional case of chronic hemocytoblastosis occurred but
birds so affected recovered readily when placed on the ground.
Blood smears from representative birds in the flock showed the
presence of a mild degree of hemocytoblastosis.

Plant No. 1.-The birds in this plant were housed in a stucco-
on-burlap building divided into 2 rooms, 1 a starting room and
the other without heat. The ceiling in each room was 8' feet
high with a small door for ventilation in the center. The loft
was ventilated through louvered windows at each gable. There
was no forced ventilation.
When the plant was visited an oppressive heat was evident
when the starting room door was opened. The room contained
500 birds under 2 weeks of age. Heat was furnished from a
central heating system. Very little mortality occurred in this
At 3 weeks of age the birds were moved to the second room,
where they remained until 5 or 6 weeks of age. This room had
a small screened window in each of 2 sides. The room contained
2,500 birds which had an average of % cubic foot of air space
per bird. A lack of uniformity of development and poor feather-
ing were the most outstanding characteristics of birds of the
same age in this room. No mortality was reported.
At the end of the sixth week the birds were moved to outside,
wire-floored cages. Colds and roup began to develop almost im-
mediately. As a result, when the birds should have been ready
for market as broilers and fryers a large percentage were culled,
due to respiratory diseases. This condition tended to become

Florida Agricultural Experiment Station

chronic in many birds and, in all instances, was difficult to treat
Blood smears taken from birds in the house as well as out-
doors indicated that all had marked hemocytoblastosis.
Plant No. 2.-The starting room was of frame construction
and approximately 8 feet square with a central heating system.
There was only 1 window in the room. Each gable had a small
triangular screened area near the ridge of the roof for ventila-
tion. When the plant was visited these screens were heavily
laden with dust. The floor was earth. The brooders were home-
made and constructed of wood. Sanitation was poor. The at-
mosphere was oppressive when one entered the room from the
As a general rule 400 baby chicks were started in this room.
When 3 weeks of age, they were moved to wooden batteries in
a shed connected to the starting room. The shed was closed on
2 sides as a protection from inclement weather. Sanitation in
this portion of the plant was improved greatly over that in the
starting room.
When the birds were moved from the starting room, colds
and roup began to develop even under ideal climatic conditions.
Variations in growth and feathering soon occurred. Representa-
tive birds were examined and all were found to have marked
degrees of hemocytoblastosis.
Plant No. 3.-This plant was marketing 300 broilers and fryers
each week. The equipment was modern and sanitation was
excellent. The owner complained of extreme variations in the
growth of birds. Approximately 25 percent of the birds showed
slow growth; many were poorly feathered.
As an experiment the operator culled these birds from 1 hatch.
Representative birds from this group had marked hemocyto-
blastosis. The birds were moved to a remote section of the farm,
placed in a colony brooder house with a wire sun porch. Within
3 weeks these birds showed remarkable improvement and were
marketed later as first-class fryers. The owner repeated the
experiment and obtained similar results. When cull birds re-
mained in the batteries of the main plant, poor growth and
feathering continued to occur. The installation of an intake
and an exhaust fan in this plant reduced the problem consider-

The Etiology of Fowl Paralysis


Experimental Procedure.-Birds included in these experiments
were raised from day-old chicks to 3 weeks of age in a commer-
cial battery brooder. At 3 weeks of age the birds were divided
as evenly as possible into 3 groups. Group I was placed in bat-
teries in a room 8 x 10 feet with 12-foot ceiling; the windows
were kept closed; an inside door to a semi-closed room was kept
open at all times. Group II was raised in batteries in a room
12 x 24 feet with a 12-foot ceiling; a window at each end of the
room was kept closed at all times; there was an outside door
in each end of the room, 1 kept open at all times and the other
closed only at night. Group III was placed outdoors in batteries
without access to direct sunlight. These latter birds had the
benefit of reflected sunlight from the north. The birds were
all managed as nearly alike as possible and fed a good grade of
commercial feed which contained an adequate amount of cod
liver oil.
The experiments extended over a period of 10 months. As
the experiments were conducted from a mortality standpoint
no other records were kept. Two trials were conducted. Barred
Plymouth Rock chicks were used in all of the experiments.
Results.-In Group I mortality among 60 birds during the
first trial was 20 at the end of the 10-month period; 4 birds died
of paralysis, 8 of leukemia, 7 of chronic hemocytoblastosis and
1 bird of other causes. During the second trial, which extended
over a similar period, the group consisted of 65 birds; the mor-
tality was 23; 3 birds died from paralysis, 7 from leukemia, 11
from chronic hemocytoblastosis and 2 from other causes.
In Group II 61 birds were used in Trial I and 64 in Trial II.
In each instance 11 birds died during the 10 months' period.
The losses from paralysis, leukemia and chronic hemocytoblas-
tosis were 3, 2 and 6, respectively, in Trial I and 3, 3 and 4,
respectively, in Trial II.
In Group III, which was raised outdoors after 3 weeks of age,
no losses occurred from paralysis, leukemia or chronic hemo-
cytoblastosis. In Trial I, 1 bird of the 60 and, in Trial II, 3 birds
of the 65, died of other causes.
A summary of mortality in these experiments is presented in
Table 3. Mortality from paralysis, leukemia and chronic hemo-
cytoblastosis began to occur in Group I at 16 weeks of age in

Florida Agricultural Experiment Station

Trial I and 18 weeks of age in Trial II. In Group II mortality
began to occur in Trial I at 18 weeks of age and in Trial II at
19 weeks of age.

Num- Mortality
Groups Trial of Paral- Leu- Hemocyto- Other
Birds ysis kemia blastosis Causes Total

I 60 4 8 7 1 20
I __________________________
Indoor (closed)
II 65 3 7 11 2 23

I 61 3 2 6 11
Indoor (open)
II 64 3 3 4 1 11

I 60 1 1
Outdoor I
II 65 3 3

The variations in the losses from paralysis, leukemia and
chronic hemocytoblast6sis in the 3 groups were attributed to
atmospheric conditions as concerned with ventilation.

Since the previous experiment showed that there was in-
creased mortality from paralysis, leukemia and chronic hemo-
cytoblastosis among birds maintained in indoor-batteries as com-
pared with outdoor batteries it was considered advisable to
conduct experiments in which birds were raised outdoors to
maturity and then moved to indoor-batteries.
The birds included in these experiments were Rhode Island
Red pullets which were reared under conditions similar to Group
III in the preceding experiments until 4 months of age. After
being placed in the indoor-batteries in a room in which the
ventilation was considered inadequate, the experiments extended
over a, period of 8 months. Control birds remained outdoors.
Results.-In the first trial 12 birds were moved to an indoor
hen battery. Three birds developed chronic hemocytobastosis

The Etiology of Fowl Paralysis

after periods of 6, 11 and 16 weeks. Death occurred after an
illness of 3 to 5 weeks.
In the second trial 31 birds were placed in indoor batteries.
Over a period of 8 months 2 birds developed paralysis, 5 leu-
kemia and 8 chronic hemocytoblastosis. The first bird to show
symptoms developed chronic hemocytoblastosis in 8 weeks.
Fifteen of the 27 birds in the third trial developed symptoms
of the various manifestations after being placed'in indoor bat-
teries. Three developed paralysis, 6 leukemia and 6 chronic
hemocytoblastosis. The first bird to show symptoms developed
chronic hemocytoblastosis in 10 weeks after being placed indoors.
In the fourth trial 1, 3 and 4 birds developed paralysis, leu-
kemia and chronic hemocytoblastosis, respectively. There were
23 birds in the group. The control birds, which remained out-
doors, failed to develop any of the manifestations shown by
birds moved to indoor batteries. Table 4 gives a summary of
these experiments.

Num- Mortality
Trials her Chronic More Than
of Paral- Leu- Hemocyto- One Mani- Total
Birds ysis kemia blastosis festation*
I 12 3 3

II 32 2 5 8 3 15
-----------j -
III 27 3 6 6 2 15

IV i 23 1! 3 4 I 8

(controls) 21 1- -

Diagnosed as first manifestation shown.

Farr (10, 11), in studying human populations in England,
concluded that "death rate varies directly with the density of
population". Le Blanc (12), who studied human populations
in the United States, claimed that Farr's law did not hold but
did not refute the existence of this law as applied to lower

Florida Agricultural Experiment Station

organisms in view of the work of Pearl (14) with populations
of the fruit fly, Drosophila melanogaster. Pearl found that the
rate of reproduction of Drosophila varied inversely with the
density of population, which conforms to Farr's law but with
a different point of origin.
Pearl found that "the density of a population varies directly
with the volume of the universe". In other words, "the abso-
lute size of a population varies as the square of the volume of
the universe in which it grows". In a series of experiments he
determined the number of Drosophila that could be raised in a
half-pint bottle. Knowing the saturation point for a half pint,
the above law enabled him to compute this point for 1 and 2
pints. The computed theoretical saturation point for these
larger volumes conformed surprisingly with the actual satur-
ation point as determined by counting the population.
Pearl (15) was probably the first investigator to apply these
laws to flocks of chickens. Three pens consisting of 50, 100
and 150 laying birds were so arranged that the flocks of 50 and
100 birds had an allotment of 4.8 square feet of floor space per
bird while the flock of 150 birds had an allotment of 3.2 square
feet of floor space per bird. Thus, these experiments furnished
data on the influence of increased numbers of birds when the
floor space was the same and on the influence of decreased floor
space per bird. The general trend of the results was consistent
throughout the 3 years the experiment was conducted. In com-
paring the flocks containing 100 and 50 birds and which had the
same floor space per bird, the results indicated that the larger
the flock the lower the egg production per bird. Since egg pro-
duction may be considered a phase of reproduction, the experi-
ments conformed to the laws of Pearl, evolved from his Droso-
phila experiments. The conclusion was reached that the density
of population had a profound effect upon many of the general
and fundamental biological processes.
More recently Bechtel, Shroeder and Wilson (1) have found
that certain space factors have an influence on the response of
growing chicks. Newlon and Buster (13) showed that there
was a definite relationship between space and death rate of
chicks. When 100 chicks were confined to less than 35 square
feet of floor space the percent mortality was 26.3; when confined
to 35 to 49.9 square feet the mortality was 16.2 percent; while
allowed 50 square feet of floor space and over the percent
mortality was 13.9.

The Etiology of Fowl Paralysis

For many years overcrowding has been regarded as an im-
portant factor in the management of a flock of chickens. Other
investigators have shown that overcrowding caused increased
death rates, decreased growth curve in growing birds and de-
creased fertility. However, overcrowding is still an evil exist-
ing on many poultry farms.
Other investigators in statistical studies on fish and other
forms of life have shown that under given environmental condi-
tions a biological saturation point is reached and if the popu-
lation is increased beyond that point mortality increases and
the population is reduced to the numbers that such environ-
mental conditions can support.
With the advent of the confinement method of raising birds
there seemed to be no definite limit in the number of birds one
could keep in a house. The raising of birds in confinement
offered some advantages over the old system of raising birds.
The chief advantage seemed to be from the sanitation stand-
point and the improved control of disease which should-result
therefrom. While confinement had all the outward appearances
of an ideal method to house and raise birds, it soon was realized
that there are unknown limiting factors which complicated this
method. It was not so successful as had been anticipated,
particularly in instances in which the birds were kept under
these conditions for long periods. Under most hen-battery
conditions birds are under confinement during their entire life.
With the development of the battery brooder large numbers
of chicks have been and are being housed in 1 room with natural
ventilation. It is not illogical to present the analogy between
Pearl's experiments in which Drosophila were raised in a half
pint milk bottle and attempts to raise a large number of chicks
in a comparatively small room with natural ventilation. Such
environmental conditions differ from the milk bottle only in size.
Six-week-old chicks have been observed in battery confinement
under such conditions that there was less than 1 cubic foot of
air space per bird. In another plant birds remained in battery
brooders until 3 weeks of age in a room in which there was
but 0.5 cubic feet of air space per bird. Representative chicks
chosen at random from both of these plants were affected with
marked hemocytoblastosis. It is necessary to realize that birds
may be affected with hemocytoblastosis with no outward symp-
toms of illness. Although these birds appeared to be healthy,
their resistance actually was lowered as shown by the develop-

Florida Agricultural Experiment Station

ment of colds and roup when they were removed from these rooms
and placed in other quarters which apparently were more
nearly ideal.
Experiments have been conducted for 3 years in which vary-
ing number of birds were housed in batteries during each suc-
cessive 12-month period. The room was 12 x 12 feet with 12-
foot ceiling, a single open window and an inside door. The
window was closed and the door was open at all times.
During the first year 75 Barred Plymouth Rock chickens were
raised in batteries in this room. Two birds died during the
first week. No mortality then occurred until the fifth month.
During the next 4 months mortality from paralysis, leukemia
and chronic hemocytoblastosis reduced the population to 42 by
the end of 12 months.
During the second year 100 Barred Plymouth Rocks were
raised in the same room. Major mortality from paralysis, leu-
kemia and chronic hemocytoblastosis began to occur at the end
of the fourth month and continued through the next 5 months,
reducing the population to 41 at the end of 12 months.
During the third year 37 Barred Plymouth Rocks were raised
in the same room. No major mortality occurred and at the end
of 12 months 36 birds still remained.'
Figure 4 contains a graph of the populations during the
progress of these experiments.
It seems apparent, therefore, that there is a definite limita-
tion to the number of birds that can be housed under given
environmental battery conditions. In case a population above
this point is maintained, mortality from paralysis, leukemia
and chronic hemocytoblastosis occurs. In case the population
is below this point such mortality does not occur. Therefore,
the conclusion is reached that each indoor-hen-battery plant has
a rather definite biologic saturation point. It is evident that
this population varies under the specific conditions surrounding
each hen-battery plant. It should be realized that conditions
leading to mortality under these circumstances are of a chronic
nature and that the longer birds are kept under such environ-
mental conditions the more opportunity they have for develop-
ing paralysis, leukemia and chronic hemocytoblastosis.
It is the practice of many indoor-hen-battery plant operators
to replace birds lost through mortality. If the population of
their plant is above the biologic saturation point, which usually
is the case, the adverse environmental conditions are maintained,
with the result that mortality becomes a continuous problem.


- &

I Z 3 5 6 T 83 12
ASe i0 monin
Fig. 4.-Mortality in 3 groups of birds of same strain and breed for 3 years under indoor battery conditions. After the
first month mortality was due to fowl paralysis, leukemia and chronic hemocytoblastosis.

Florida Agricultural Experiment Station


Paralysis.-The symptoms of paralysis in indoor-battery birds
are similar to those of true fowl paralysis induced by micro-
organisms of the paratyphoid group in experiments already re-
ported and to those observed as occurring under field conditions.
However, there are several points of difference which are worthy
of consideration. Under indoor-battery conditions paralytic
symptoms are rarely spastic. The onset of symptoms usually
is gradual; emaciation more frequently accompanies the develop-
ment of symptoms or occurs shortly thereafter; and macroscopic
nerve lesions so characteristic in true fowl paralysis seldom are
Leukemia.-There are but few differences between leukemia
as it occurs in the indoor-battery and undei the stimulus of
micro-organisms of the paratyphoid group or under field condi-
tions. It is worthy of note, however, that myeloid leukemia is
the most prevalent type occurring in the indoor-battery. Ery-
throblastic erythroleucosis occasionally occurs, while lymphatic
erythroleucosis is seldom observed.
It has been suggested previously that myeloid leukemia is
more chronic in its development than erythroblastic erythro-
leucosis and lymphatic erythroleucosis. The incidence of the
leukemias in the indoor-hen-battery plants would tend to sub-
stantiate this observation.
Chronic Hemocytoblastosis.-Throughout this series of pub-
lications the term hemocytoblastosis has been regarded as ap-
plying to a reversible process. According to the experimental
data which have been presented, hemocytoblastosis is a funda-
mental and basic condition which can lead to many other mani-
festations under consideration in this study. Under experimental
conditions the period of infection necessary to induce this group
of diseases by micro-organisms must be over a certain period of
time, depending upon a number of factors. During this period
various degrees of impetus are given to hemocytoblastosis in
individual birds. The original impetus may be of sufficient
intensity, combined with other factors, to induce other manfesta-
tions. In case other manifestations are not induced, hemocyto-
blastosis reaches the peak of its intensity and then subsides.
Under favorable conditions 2 or 3 months may be required for
the return of the blood picture to "normal". Thus hemocyto-
blastosis, itself, may be a reversible process.

/ \


// V i s



|2 3 5 ( 7 a
Fig. 5.-Growth curves of 3 birds which developed chronic hemocytoblastosis.

Florida Agricultural Experiment Station

Under adverse atmospheric conditions in the indoor-battery
plant, hemocytoblastosis is under constant stimulus. Here too,
the stimulus varies according to the adversity of atmospheric
conditions. When birds are subjected to these conditions for
sufficient time hemocytoblastosis may reach the point at which
recovery cannot occur even though the stimulus responsible for
its presence is removed. In this case death results and the
manifestation has been termed chronic hemocytoblastosis.
Chronic hemocytoblastosis can be diagnosed by clinical symp-
toms, lesions and history of the cases and must be considered
a distinct manifestation. Thus, chronic hemocytoblastosis must
be added to the list of manifestations comprising the leucosis
Chronic hemocytoblastosis is characterized by progressive
emaciation over a period of 4 to 8 weeks. Figure 5 illustrates
the growth curve of 3 birds affected with chronic hemocyto-
blastosis. The comb becomes scaly, greyish, shriveled and some-
what pale in color. The droppings are scant and, particularly
in the terminal stages of the manifestation, often are whitish
green in color. At death the bone marrow is degenerative and
usually exhausted.
Postmortem examination reveals the liver, kidneys, intestines,
gizzard and spleen to be atrophied. The smallest liver found in

Fig. 6.-Comparison of livers and spleens of battery-maintained birds.
The liver on the left came from a 1,268-gram bird affected with myeloid
leukemia and weighed 230 grams; the spleen weighed 5 grams. The 34-
gram liver and 1.9-gram spleen in the center came from an apparently
normal 1,537-gram bird. The liver and spleen on the right weighed 16
and 0.4 grams, respectively, and came from a bird affected with emaciation.
The kidneys also are included with the 2 specimens to the right.

The Etiology of Fowl Paralysis

an adult bird affected with chronic hemocytoblastosis weighed
11 grams as compared with livers weighing from 40 to 53 grams
in normal control birds of the same age. The spleens of many
birds have been found to be no larger than a large English pea
and weighing from 0.15 to 0.2 grams (Fig. 6).
Syndrome Associated with Mortality.-The syndrome asso-
ciated with mortality in the indoor hen battery consists of:
(a) poor body development of some birds, (b) irregular egg pro-
duction, and (c) molting. This syndrome has been observed in
commercial plants as well as under experimental conditions.
All have been described previously in this paper in a discussion
of observations on indoor-hen-battery plants. This syndrome
is more pronounced in plants experiencing a high rate of mor-
tality than in one in which the rate of mortality is low and,
therefore, may be said to vary directly with the rate of mortality.

The preceding experiments have shown that the mortality
problem encountered in indoor-battery plants apparently is asso-
ciated with adverse atmospheric conditions through inadequate
ventilation. During the conduct of other experiments in this
entire study it has seemed apparent that various makes of brood-
ing equipment have given better results than others insofar as
the raising of hemocytoblastosis-free chicks was concerned. As
a result, an effort has been made to compare the degree of hemo-
cytoblatosis occurring in chicks in various types of brooders
chosen as to their adaptability to ventilation by natural means.
As far as this study of hemocytoblastosis is concerned, it can
be only upon a comparative basis, since unpublished data have
shown that the day-old chick hatched under artificial incubation
is affected with hemocytoblastosis.
Figure 7 illustrates the relative amounts of open to closed
surface area as compared with volume in 4 types of brooders in
which chicks were raised during these experiments. Types I
and II had a row of small holes around the sides through which
the chicks had access to feed 'and water. As the remaining
surface area of the 2 brooders was closed, these small openings
also served as the only means of ventilation. The chief differ-
ence in Types I and II brooders was that in Type II a larger
percent of these openings could be closed. Type III was a more
open brooder; the closable surface area was in the heating
compartment. Thus, the ventilation in this brooder was much
better than in Types I and II. Type IV brooder was a still more

Florida Agricultural Experiment Station



I I Closed at all times
':.i' ':::.':.:-. Open or closed
SOpen at all times
Fig. 7.-Percentage of closed and open surface area in 4 types of brooders,
as compared with their total volume.

open brooder; 50 percent of the surface area of the brooder was
open at all times.
In 1 experiment 15 day-old chicks were placed in the Type I
brooder, 16 in the Type II, 17 in the Type III, and 16 in the
Type IV. The numbers of chicks in each brooder were varied
to compensate for the variation in total volume. The chicks
were brooded in these brooders for 6 weeks. Two trials were
conducted. The degree of hemocytoblastosis after 6 weeks was
in general more intense in brooders of Types I and II than in
those of Types III and IV. The chicks brooded in Type IV
brooder had the mildest degree of hemocytoblastosis.
In 2 other trials 50 chicks were brooded in each brooder. As
they became crowded chicks were removed at random. An
attempt was made, however, to maintain crowded conditions.
After 6 weeks the degree of hemocytoblastosis in 15 chicks
picked at random from each group was more intense in brooders
of Types I and II and progressively less in brooders of Types
III and IV. The degree of hemocytoblastosis in the chicks exam-
ined in Type IV brooder was higher in these experiments than
in chicks brooded in the'same brooder under uncrowded condi-
The differences in the degree of hemocytoblastosis shown by
the chicks in these various experiments were attributed largely
to adverse atmospheric conditions resulting from inadequate
ventilation of the brooders.

The Etiology of Fowl Paralysis

A previous publication (5) has made reference to the import-
ance of "active" and "recessive" hemocytoblastosis as it concerns
investigations dealing with this group of diseases. In case birds
are affected with active hemocytoblastosis they are more sus-
ceptible to further stimuli which incite this process. In other
words, it is easier to incite a more intense degree of hemocyto-
blastosis in birds in which this process already exists in an
active state than in birds which are hemocytoblastosis-free. On
the other hand, recovery from hemocytoblastosis results in a
certain degree of immunity to further stimuli. Theoretically,
the degree of immunity is relatively proportional to the intensity
of hemocytoblastosis from which recovery occurred.
Thus, birds to be used for experiments dealing with fowl
paralysis, leukemia and allied conditions must be raised with
considerable care. Ever since the initiation of this study diffi-
culty has been encountered from time to time in raising birds
hemocytoblastosis-free. A previous publication (6) has described
a house far removed from infection experiments and in which
birds for experimental purposes have been raised after the
difficulties mentioned above are encountered in earlier experi-
ments. This house partially solved the problem but did not
eliminate it completely. The experiments reported in this pub-
lication have been an outgrowth of a further endeavor to deter-
mine the factors responsible for the development of hemocyto-
blastosis in birds raised under battery conditions.
The following experiments were conducted on birds raised out-
doors versus indoors to determine any variations in susceptibility
when the birds were exposed later to Salmonella aertrycke. The
birds raised indoors were confined in batteries in a room in which
adverse atmospheric conditions were considered to be present.
The outdoor-birds were raised in confinement on wire. A
slightly cloudy suspension of a 24-hour nutrient agar culture
of S. aertrycke (0.5 ml.) was injected intravenously 2 or 3 times
a week until 6 to 9 injections had been given. All of the birds
in each experiment were of the same age and received similar
doses and injections of suspensions of the microorganism.
Table 5 gives a summary of the results of this group of ex-
periments. Fifteen of 65 birds raised outdoors and 35 of 65
birds raised indoors developed 1 of the manifestations as a result
of the intravenous injection of S. aertrycke. In this group of

Florida Agricultural Experiment Station

experiments rearing birds indoors increased susceptibility from
20 to 40 percent.

Salmonella aertrycke.
Raised Outdoors Raised Indoors
Experi- Breed Num- No. De- IINum- No. De-
ment and ber veloping Percent I er veloping Percent
SAge of Mani- Sus- of Man- Sus-
| Birds festation ceptible Birds festation cetible
SB.P.R. 1
I I 16 weeks 10 1 2 20 10 .6 60
II | 20 weeks 1 15 4 26.6 15 8 53.3
1I R.I.R. 5 |
III | 15 weeks 1 10 1 10 10 5 50
IV 114 weeks 10 3 30 10 5 50
11 B.P.R. [
V 1118 weeks 10 2 20 10 5 50
1 B.P.R. I
VI | 16 weeks 1 10 3 30 10 6 60
R.I.R.-Rhode Island Red.
B.P.R.-Barred Plymouth Rock.

In experiments reported previously it has been concluded that
the micro-organisms, S. aertrycke, S. enteritidis and S. schott-
miilleri can induce fowl paralysis, leukemia and allied manifesta-
tions under certain conditions of infection (2-8). It has been
shown that these micro-organisms induce the basic process of
hemocytoblastosis which then leads to the development of the
various manifestations and that the micro-organisms are, in a
general way, only indirectly concerned in the development of
most of these manifestations (7). The preceding experiments
and observations on birds maintained in indoor-hen-battery
plants indicate that the development of leukemia, paralysis,
chronic hemocytoblastosis and the associated syndrome under
these conditions occurs as the result of adverse atmospheric
conditions rather than being of bacterial origin associated with
intestinal parasitism.
Initiation of Hemocytoblastosis Under These Conditions.-The
fundamental basis for the development of hemocytoblastosis un-
der these conditions is considered similar to that which occurs
when bacteria are the stimulating agent. As explained in a pre-
vious publication (7), initiation of hemocytoblastosis by bacteria

The Etiology of Fowl Paralysis

of the paratyphoid group is based upon the destruction of blood
cells with a subsequent effort on the part of the body defense
mechanism to replace them. This process of destruction and
replacement gives rise to the presence of degenerative, imma-
ture, as well as mature blood cells in the circulation-a blood
picture of hemocytoblastosis.
Under the stimulus of adverse atmospheric conditions, which
really is a condition of partial suffocation, the tissues are unable
to obtain sufficient exygen to function normally, with the result
that degeneration of blood cells occurs. When blood cells de-
generate the body defense mechanism replaces them with young
cells. Once this process has been initiated, other factors become
involved just as in the instance when hemocytoblastosis is stimu-
lated by bacteria; a discussion of these factors will be contained
in a later publication. Thus, it may be said that the stimula-
tion of hemocytoblastosis under adverse atmospheric conditions
fundamentally is similar to that occurring under bacterial stimu-
lus. Under both conditions wide variations occur in the degree
of hemocytoblastosis which results. The more adverse the at-
mospheric conditions, the higher the degree of hemocytoblastosis
which develops.
When birds are maintained under adverse atmospheric condi-
tions hemocytoblastosis is under constant stimulus. Time, there-
fore, is an important factor. Thus, when birds are maintained
under these conditions, approximately 5 or 6 months or longer
are required for the development of other manifestations. Ex-
periments reported herein show that when birds are raised out-
doors and moved to indoor-batteries at maturity, many of them
develop 1 of the manifestations in a comparatively short time.
It seems probable that the sudden change from favorable to
unfavorable atmospheric conditions is responsible for this oc-
currence. When birds are raised indoors subject to adverse
atmospheric conditions the slowness of the process of hemo-
cytoblastosis probably allows them to develop a certain amount
of resistance to unfavorable atmospheric conditions.
Development of Manifestations in the Indoor-hen-battery.-
Observations on outdoor-hen-battery plants as compared with
indoor-hen-battery plants have shown that the outdoor plants
did not experience mortality due to paralysis, leukemia and
chronic hemocytoblastosis or the accompanying syndrome as
observed in the indoor plants. Blood studies showed that indoor-
battery-birds had a somewhat lower erythrocyte count and hemo-

Florida Agricultural Experiment Station

globin reading and a higher leucocyte count than outdoor-battery
birds. Differential counts showed that the indoor birds had
lower and usually irregular eosinophile count, a higher degener-
ative lymphocyte and premyelocyte count than the outdoor birds.
The percentages of granule-bearing eosinophiles and monocytes
were higher in the outdoor birds. According to the concept of
hemocytoblastosis advanced in this study these blood cell counts
would indicate a greater degree of hemocytoblastosis in indoor-
hen-battery birds than in outdoor-hen-battery birds. It is not
definitely understood at this time why outdoor-battery birds
have a mild degree of hemocytoblastosis; it is considered pos-
sibly a nutrition problem. However, as has been previously
mentioned, this degree of hemocytoblastosis apparently does not
have a marked effect upon the-bird.
The production of 1 of the leukemias under indoor-hen-bat-
tery conditions is based upon the same principle as under other
conditions. Hemocytoblastosis once established must become a
progressive and eventually a self-perpetuating process. When
it becomes self-perpetuating-capable of active progress without
further extraneous stimulus-1 of the leukemias must result.
Some differences in paralysis occurring under adverse atmos-
pheric conditions and under field conditions when birds are
raised on soil already have been mentioned. The onset of
symptoms usually is more gradual; they are rarely spastic;
emaciation frequently accompanies symptoms or occurs shortly
thereafter; and, macroscopic enlargements of nerves so char-
acteristic of true fowl paralysis are not observed often. A
previous publication (7) has stated that true fowl paralysis
resulting from stimulus of micro-organisms of the paratyphoid
group is induced by nerve injury from neurotoxic endotoxin and
the deposition of pathologic cells present in the blood by reason
of hemocytoblastosis in the injured tissue resulting in an en-
largement of the affected nerve. Under indoor-hen-battery con-
ditions hemocytoblastosis proceeds slowly but under constant
stimulus. Hemocytoblastosis represents a state of tissue auto-
lysis; the degeneration of blood cells gives rise to an intoxication
factor. The theory is advanced that this factor is responsible
for nerve injury but that the degree of hemocytoblastosis is
insufficient to result in a deposition of pathologic cells in the
injured area. The gradual onset of symptoms logically could
result from the gradual effect of this intoxicating factor at the
point of nerve injury.

The Etiology of Fowl Paralysis

The production of the manifestation herein termed chronic
hemocytoblastosis is considered to be due to the exhaustion of
the hematopoietic tissues by constant stimulation of hemocyto-
blastosis under adverse atmospheric conditions. It should be
mentioned that hemocytoblastosis is represented by a destruc-
tion of blood cells on the 1 hand and their replacement by the
blood-cell-forming organs on the other hand. When the blood-
cell-forming organs reach the limit of their ability to produce
blood cells, emaciation and death must occur.
The syndrome of poor body development of some birds raised
under these conditions, irregular egg production and molting is
considered to be due to the ill effects of hemocytoblastosis on
the physical condition of the birds.




boo /

600 / /

500 /
/ /

300 -


I z J 4 6 7 8 10
A&e io weeks

Fig. 8.-Solid line: Average growth curve of 26 Barred Plymouth Rock
chicks (13 female and 13 male) under adequately ventilated battery condi-
tions. Broken line: Average growth curve of birds of same sex and breed-
ing under similar conditions but subjected to severely inadequate ventilation.

Florida Agricultural Experiment Station

Adverse Atmospheric Conditions in the Broiler and Fryer
Plant.-The time factor is important in the absence of mortality
in the broiler and fryer plant under adverse atmospheric condi-
tions. Under extremely unfavorable environmental conditions
deaths occur from "light" and anemia. It has been shown pre-
viously (5) that hemocytoblastosis retards growth and may be
responsible for poor feathering and there also is evidence to
indicate that the state of the blood during this process is re-
sponsible for lowered physical resistance. Figure 8 graphically
portrays the difference in growth curves when birds are raised
under favorable and unfavorable atmospheric conditions. In
the broiler and fryer plant adverse atmospheric conditions re-
sult principally in: (a) retarded growth rate, (b) lack of uniform
growth, (c) poor feathering, (d) and lowered physical resist-
ance. When birds are raised under adverse atmospheric condi-
tions and moved to other quarters disastrous results frequently
occur, particularly when the latter conditions are considerably
different from the former. The undesirable results accruing
under adverse atmospheric conditions in the broiler and fryer
plant are considered to be due to the effects of hemocytoblastosis.
Biologic Saturation Point.-It has been shown that there was
a rather definite biologic saturation point for 1 room used in
indoor-battery experiments. There appears to be little doubt
that there is a rather definite biologic saturation point for every
specific battery plant. In case the population exceeds this point,
manifestations induced by adverse atmospheric conditions will
occur. It is the common practice of many indoor-hen-battery
plant operators to make replacements as mortality occurs.
Mortality from these manifestations indicates that the plant
is already overcrowded. When replacements are made the popu-
lation of the plant is maintained and mortality continues to
occur. Thus the practice of making replacements in an already
overcrowded plant merely causes a continuation of the entire
Correction of Adverse Atmospheric Conditions.-There are
many factors associated with these conditions in a battery plant.
Preliminary experiments have shown that the installation of an
adequate .forced ventilating system will correct many of the
evils under discussion in this paper. It is extremely doubtful
if the most economical use can be made of an indoor-battery
. plant without a system of forced ventilation. The correct venti-
lation of a battery plant is a specific problem in each plant, as

The Etiology of Fowl Paralysis

many factors associated with the problem vary in different loca-
One cannot stress with too much emphasis the importance of
adequate ventilation in battery plants. Since this study has
been initiated, many observations in the field have made the
author cognizant of the extreme prevalence of adverse atmos-
pheric conditions in such plants. Unfavorable environmental
conditions associated with inadequate ventilation have resulted
in tremendous economic losses to poultrymen.
Relation of the Problem to Brooding and Incubation.-The
variations in the degree of hemocytoblastosis in the brooding
experiments were attributed largely to adverse atmospheric con-
ditions resulting from inadequate ventilation. Overcrowded con-
ditions in the brooders used were responsible for higher degrees
of hemocytoblastosis in the same brooders than uncrowded condi-
tions. During the past several years there has been a tendency
on the part of many manufacturers of brooding equipment
towards the production of open types of brooders. These ex-
periments indicate that the open types of brooders are more
desirable than the closed types.
In this discussion of brooding there is another point which
should receive consideration. The room in which battery-brood-
ing equipment is placed is just as important as the equipment
itself. Thus, open types of brooders can be placed in a room
and if the ventilation of the room is inadequate for the chick
population, adverse atmospheric conditions will prevail. In other
words, there must be adequate ventilation in the room housing
the equipment as well as adequate ventilation in the brooder
Unpublished data have shown that most incubator-hatched
day-old chicks are affected with hemocytoblastosis and that the
degree of hemocytoblastosis is higher in these chicks than in
hen-hatched chicks. The conclusion has been reached that
artificial incubation can be improved and that adverse atmos-
pheric conditions, particularly as they pertain to the proper
respiration of the developing embryo, furnish a logical approach
to the problem. As in the case of brooder equipment, there are
indications also that in certain types of incubators the problem
is less acute than in other types of incubators. The discussion
concerning ventilation of rooms in which battery brooders are
maintained should be pertinent also in the consideration of in-
cubator rooms. The respiration requirements of the embryo,

39 .

Florida Agricultural Experiment Station

although not as large, are just as important as those of the
hatched chick.
Relation of the Problem to Experimental Work.-The problem
as discussed in this bulletin should be of interest also to the in-
vestigator working with this group of diseases. One of the early
problems encountered in this study was the raising of birds
relatively free of hemocytoblastosis. The experiments reported
herein are an outgrowth of many of the difficulties encountered.
Many investigators, including the author, have observed the
development of some of the manifestations in control groups
of birds. It is possible that many of these difficulties have been
directly or indirectly associated with adverse atmospheric condi-
tions. There is no question but that these conditions have
resulted to some extent in a misinterpretation of some results
and have given the investigator concerned a distorted vision of
some phases of the problem under investigation. Since the con-
clusion of these experiments the former difficulty experienced
in raising hemocytoblastosis-free birds has been reduced ma-
There are still other problems relating to the raising of hemo-
cytoblastosis-free birds which must be studied. The reports of
many investigators who have conducted transmission experi-
ments dealing with this group of diseases give widely varying
results. It is not unlikely that adverse atmospheric conditions
may have been a factor concerned in the conduct of many of
these experiments.
For purposes of clarity as well as emphasis, it should be
stated that the data reported herein do not conflict with those
reported in previous publications in this series.
Experiments reported to date indicate that when birds are
reared on soil leucosis results from infection by micro-organisms
of the paratyphoid and typhoid groups following their establish-
ment in the intestinal tract as a sequel to intestinal parasitism.
The prevention of leucosis under these conditions depends mainly
upon the ability of the poultryman to rear birds relatively free
of intestinal parasites-coccidia, capillaria, common round worms
and tapeworms. This can be done through the proper rotation
of yards, sanitation, systems of management, and the judicious
use of reliable worm remedies.
3 These conclusions pertain not only to the data contained herein, but
to those contained in this entire series of publications.


The Etiology of Fowl Paralysis

Under indoor-hen-battery conditions, leucosis and the accom-
panying syndrome develop as a result of adverse atmospheric
conditions. These conditions in the broiler and fryer battery
plant result in the detrimental effects described in this publica-
tion, due chiefly to lowered physical condition resulting from
hemocytoblastosis; other manifestations of leucosis usually do
not occur as the time factor is insufficient for their development.
In addition to the above conclusions, observations have been
made which indicate that regardless of the conditions under
which birds are reared, whether on soil or in batteries, breeding
is considered an important factor in determining susceptibility.

Paralysis, leukemia and chronic hemocytoblastosis, accom-
panied by a definite syndrome, are a major disease problem in
most indoor-hen-battery plants. Chronic hemocytoblastosis is
characterized by progressive emaciation, atrophy of the visceral
organs and an exhaustion of the hematopoietic tissues. The
syndrome associated with indoor-hen-battery mortality consists
of (a) poor development of some birds, (b) irregular egg pro-
duction and (c) molting. The occurrence of these diseases and
the associated syndrome, the intensity of which is usually pro-
portional to mortality, is incited by adverse atmospheric condi-
tions amounting to partial suffocation and results in the develop-
Sment of hemocytoblastosis.
These manifestations and their accompanying syndrome oc-
curred to a negligible degree in the 3 outdoor-hen-battery plants
Birds reared outdoors to maturity and then placed in indoor-
hen-batteries, as well as birds reared and kept indoors, developed
these manifestations. Control birds maintained outdoors did
not develop any of these manifestations.
Birds raised and kept under indoor-battery conditions usually
do not begin to show indications of manifestations other than
hemocytoblastosis until about the age of maturity or at any time
Adverse atmospheric conditions in the broiler and fryer plant
result principally in (a) lowered resistance, (b) reduced growth
rate, (c) poor feathering, and (d) lack of uniformity. These
are considered to be concerned with hemocytoblastosis. Birds
are not maintained in indoor-battery broiler and fryer plants

Florida Agricultural Experiment Station

long enough for other manifestations to develop except under
extreme conditions.
There appears to be a rather definite biologic saturation point
for the environmental conditions of each indoor-battery plant.
Since varying factors surround each battery plant, the correc-
tion of adverse atmospheric conditions is regarded as a specific
problem for each plant.
Adverse atmospheric conditions are considered to be of prac-
tical importance in incubation, brooding and in all battery-reared
Preliminary experiments have indicated that the proper instal-
lation of a forced-air ventilating system corrects many of the
evils attendant to this method of maintaining birds.

sponse of growing chicks to certain space factors. Abst. Poult. Sci.
16: 346. 1937.

2. EMMEL, M. W. The etiology of fowl paralysis, leukemia and allied
conditions in animals. I. Introduction. History and a bacterial
theory of the etiology of these diseases. II. The intravenous in-
jection of suspensions of Salmonella aertrycke in the chicken. Fla.
Agr. Exp. Sta. Bul. 284. 1935.

3. The etiology of fowl paralysis, leukemia and allied con-
ditions in animals. III. The intestinal flora of chickens affected
with enteritis associated with intestinal parasitism. IV. The patho-
logic manifestations of the causal micro-organisms in the fowl.
Fla. Agr. Exp. Sta. Bul. 293. 1936.
4. The etiology of fowl paralysis, leukemia and allied con-
ditions in animals. V. The oral exposure of chickens affected with
various species of coccidia to Salmonella aertrycke. VI. The oral
exposure of chickens infested with Ascaridia, Taenia, and Capillaria
to Salmonella aertrycke. Fla. Agr. Exp. Sta. Bul. 305. 1936.

5. The etiology of fowl paralysis, leukemia and allied con-
ditions in animals. VII. Hemocytoblastosis in chickens as induced
by Salmonella aertrycke. VIII. Hemocytoblastosis in naturally oc-
curring cases of fowl paralysis, lymphomatosis and in other birds
from the same flocks. Fla. Agr. Exp. Sta. Bul. 306. 1936.
6. The etiology of fowl paralysis, leukemia and allied con-
ditions in animals. IX. Salmonella enteritidis as a causal micro-
organism for this group of diseases in the chicken. X. Salmonella
schottmulleri as a causal micro-organism for this group of diseases
in the chicken. Fla. Agr. Exp. Sta. Bul. 313. 1937.

The Etiology of Fowl Paralysis 43

7. The etiology of fowl paralysis, leukemia and allied con-
ditions. in animals. XI. The mechanism by which Salmonella
aertrycke induces hemocytoblastosis in the chicken. Fla. Agr. Exp.
Sta. Bul. 422. 1946.
8. The nature of leukemia: a new fundamental principle
leading to the development of specific disease. Jour. Amer. Vet.
Med. Asso. 93: 316. 1938.
9. Indoor-hen-battery mortality. Jour. Amer. Vet. Med.
Asso. 96: 372. 1940.

10. FARR, W. Causes of high mortality in town districts. Fifth Ann.
Rpt. Reg. Gen. Births, Deaths and Marriages in England. P. 406.
11. Effects of density of population on health. Sup. 35th
Ann. Rept. Reg. Gen. Births, Deaths and Marriages in England
(2nd Ed.). P. 23. 1875.

12. LEBLANC, T. J. Density of population and mortality in the United
States. Amer. Jour. Hyg. 4: 501. 1924.

13. NEWLON, W. E., and M. W. BUSTER. Brooding and pullet management.
Calif. Agr. Ext. Serv. Cir. 28. 1929.

14. PEARL, RAYMOND. The biology of population growth. Alfred Knopf.
New York. 1925.
15. Biology of population growth. Bur. of Animal Ind.
Bul. 110, U. S. Dept. of Agriculture. 1909.

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