Title: Enzootic bronchopneumonia of dairy calves
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00026861/00001
 Material Information
Title: Enzootic bronchopneumonia of dairy calves
Physical Description: Book
Creator: Sanders, D. A.
Publisher: University of Florida Agricultural Experiment Station
Publication Date: 1940
Copyright Date: 1940
 Record Information
Bibliographic ID: UF00026861
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aen5204 - LTUF
18229706 - OCLC
000924577 - AlephBibNum

Table of Contents
        Historic note
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida

Bulletin 346 June, 1940






Single copies free to Florida residents upon request to

John J. Tigert, M.A., LL.D., President of H. P. Adair, Chairman, Jacksonville
the University3 W. M. Palmer, Ocala
Wilmon Newell, D.Sc., Directors Chas. P. Helfenstein, Live Oak
Harold Mowry, M.S.A., Asst. Dir., Research R. H. Gore, Fort Lauderdale
V. V. Bowman, M.S.A., Asst. to the Director N. B. Jordan, Quincy
J. Francis Cooper, M.S.A., Editors J. T. Diamond, Secretary, Tallahassee
Jefferson Thomas, Assistant Editors
Clyde Beale, A.B.J., Assistant Editors BRANCH STATIONS
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers NORTH FLORIDA STATION, QUINCY
K. H. Graham, Business Managers J. D. Warner. M.S., Agronomist Acting in
Rachel McQuarrie, Accountants Charge
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
MA STATI AI Elliott Whitehurst, B.S.A., Asst. An. Husb.
MAIN STATION, GAINESVILLE Jesse Reeves, Farm Superintendent
W. E. Stokes, M.S., Agronomist' A. F. Camp, Ph.D., Horticulturist in Charge
W. A.'Leukel, Ph.D., Agronomists John H. Jefferies, Superintendent
G. E. Ritchey, M.S., Associate2 Michael Peech, Ph.D., Soils Chemist
Fred H. Hull, Ph.D., Associate L. H. Greathouse, Ph.D., Chemist
W. A. Carver, Ph.D., Associate B. R. Fudge, Ph.D., Associate Chemist
John P. Camp, M.S., Assistant W. L. Thompson, B.S., Asso. Entomologist
Roy E. Blaser, M.S., Assistant W. W. Lawless, B.S., Asst. Horticulturist
R. K. Voorhees, M.S., Asst. Plant Path.
A. L. Shealy, D.V.M., Animal Husbandman1 3 EERG LDES STATION, BELLE GLADE
R. B. Becker, Ph.D., Dairy Husbandman3 J. R. Neller, Ph.D., Biochemist in Charge
W. M. Neal, Ph.D., Asso. in An. Nutrition J.W. Wilson, Sc.D., Entomologist
D.A. Sande, DV.M VeterinarianF. D. Stevens, B.S., Sugarcane Agronomist
M. W. Emmel, D.V.M., Veterinarians Thomas Bregger, Ph.D., Sugarcane
N. R. Mehrhof, M.Agr., Poultry Husbandman8 Physiologist
W. G. Kirk, Ph.D., Asso. An. Husbandmans Frederick Boyd, Ph.D., Asst. Agronomist
R. M. Crown, M.S.A., Asst. in An. Husb. G. R. Townsend, Ph.D., Plant Pathologist
P. T. Di Arnold, M.S.A., Assistant Dairy R. W. Kidder, B.S., Asst. An. Husbandman
"Husbandman M W. T. Forsee, Ph.D., Asso. Chemist
L. L. Rusoff, M.S., Asst. in An. Nutrition B. S. Clayton, B.S.C.E., Drainage Engineers
W. M. Fifield, M.S., Horticulturist Acting in
R. V. Allison, Ph.D., Chemist' Charge
Gaylord M. Volk, M.S., Chemist S. J. Lynch, B.S.A., Asst. Horticulturist
F. B. Smith, Ph.D., Microbiologists Geo. D. RuehIe, Ph.D., Asso. Plant Pathologist
C. E. Bell, Ph.D., Associate Chemist
H. W. Winsor, B.S.A., Assistant Chemist W. CENTRAL FLA. STA., BROOKSVILLE
J. Russell Henderson, M.S.A., Associates W. F. Ward, M.S., Asst. An. Husbandman
L. H. Rogers, M.S., Asso. Biochemist in Charge2
Richard A. Carrigan, B.S.. Asst. Chemist in Charge

C. V. Noble, Ph.D., Agricultural Economist' 3 Leesburg
Bruce McKinley, A.B., B.S.A., Associate M. N. Walker, Ph.D., Plant Pathologist in
Zach Savage, M.S.A., Associate Charge
A. H. Spurlock, M.S.A., Assistant K. W. Loucks, M.S., Asst. Plant Pathologist
A. N. Brooks, Ph.D., Plant Pathologist
Ouida Davis Abbott, Ph.D., Specialist'
Ruth Overstreet, R.N., Assistant Cocoa
R. B. French, Ph.D., Associate Chemist A. S. Rhoads, Ph.D., Plant Pathologist
J. R. Watson, A.M., Entomologist1 A. H. Eddins, Ph.D., Plant Pathologist
A. N. Tissot, Ph.D., Associate Monticello
H. E. Bratley, M.S.A., Assistant Samuel O. Hill, B.S., Asst. Entomologist2
G. H. Blackmon, M.S.A., Horticulturist1 Jos. R. Beckenbach, Ph.D., Truck Horticul-
A. L. Stahl, Ph.D., Associate tourist in Charge
F. S. Jamison, Ph.D., Truck Horticulturists David G. Kelbert, Asst. Plant Pathologist
R. J. Wilmot, M.S.A., Specialist, Fumigation Sanford
R. D. Dickey, M.S.A., Assistant Horticulturist R. W. Ruprecht, Ph.D., Chemist in Charge,
J. Carlton Cain, B.S.A., Asst. Horticulturist Celery Investigations
Victor F. Nettles, M.S.A., Asst. Hort. W. B. Shippy, Ph.D., Asso. Plant Pathologist
E. S. Ellison, Meteorologists
W. B. Tisdale, Ph.D., Plant Pathologist1 B. H. Moore, A.B., Asst. Meteorologists
George F. Weber, Ph.D., Plant Pathologists
L. O. Gratz, Ph.D., Plant Pathologist 'Head of Department.
Erdman West, M.S., Mycologist "In cooperation with U.S.D.A.
Lillian E. Arnold, M.S., Assistant Botanist 3Cooperative, other divisions, U. of F.


LITERATURE ...........-... -.......-...-.. ---- --....- -... ................... .......-....... --............ 3
POSTMORTEM LESIONS .... ...............-- ......... .................. ........................... ............... 5
BACTERIOLOGICAL FINDINGS --........ --....-.................. .......--.......-- .....--...... ... 5
PARASITOLOGICAL FINDINGS .................................--...... .....-. .... ....... .......-----...... 6
M ATERIALS AND M ETH ODS .............. ..........-- ......... ....... ........................ ...... 6
EXPOSURE OF CALVES TO P. boviseptica ......................... ............... .............. 7
EXPOSURE OF CALVES TO DISEASED TISSUES ................. ..................................... 8
EXPOSURE OF CALVES BY BLOOD INOCULATIONS .................... .. ..................... 8
EXPOSURE OF CALVES BY CONTACT IN ISOLATION PENS ...................................... 9
DISCUSSION --......... ...- ..-.... ...--......- -.......... --...... ...... .-...--.....-........ ............... 10
SUM MARY .-..-............ ... .... ......-- ..... .......- ..-- ............... ............... ... ......-......... 11
L ITERATURE CITED ........ ....- ....... .. ........... ........ ............. ... ... .............. ...... 11

Enzootic bronchopneumonia, septic pneumonia, or pneumo-
enteritis of young animals has been encountered by workers since
the middle of the last century. The disease is reported to be
common among dairy calves less than six months of age, and
losses also have been recorded in lambs, pigs, kids and foals.


Enzootic bronchopneumonia of dairy calves has been described
by Edmonds (1)' in the British Isles and South Africa, and by
Hutyra and Marek (2) in European countries. Roberts (3)
gave a recent account of tropical pneumoenteritis of dairy calves
in the Dominican Republic and in the states of Sao Paulo and
Minas Geraeas, Brazil. This writer reported the disease to be
common in calves from a few days to six months of age and
stated that, regardless of the treatment used, 80 percent of the
-linical cases and all theerious cases succum o e al tmerit.
A report of the disease in Florida was given by an ers in
1939. Various writers, including Poels, Jensen, Van den
Maegdenberth and Lienaux (quoted by Hutyra and Marek (2))
concluded that a bacillus resembling the swine plague organism
often was responsible for a disease which they described as an
enzootic or septic pneumonia of calves. Other microorganisms
considered to be the cause of enzootic bronchopneumonia of
calves include species of Streptococcus and Staphylococcus,
Bacillus pyogenes, Bacillus pyocyaneus, and bacteria of the colon-
typhoid group.

lItalic figures in parentheses refer to "Literature Cited" in the back of
this bulletin.
Acknowledgement.-The author is indebted to Dr. G. Dikmans of the
Bureau of Animal Industry for identifying several species of internal para-
sites encountered.

4 Florida Agricultural Experiment Station

Opportunity has been afforded for making observations on the
nature of enzootic bronchopneumonia occurring in calves and
yearlings on dairy farms in Florida. This condition corresponds
in clinical symptoms, postmortem lesions, bacteriological findings
and occurrence to enzootic septic bronchopneumonia or pneumo-
enteritis as described by Poels and others (2). The disease as
observed in this state has many features in common with that
occurring in South America and in the Dominican Republic.
Enzootic bronchopneumonia of calves, as observed in Florida,
may assume either an acute or a chronic form. Both types of
the disease may be present simultaneously within the same herd.
The disease may occur at any time throughout the year but is
more frequent during the warm, moist weather of the summer
months. It abates to a large extent during the dry periods of
the year. Chronic cases of enzootic bronchopneumonia which
have their incipient stages during the wet periods of the year
often linger for weeks without regard to season or moisture con-
ditions. In the herds under observation there was a tendency for
the condition to recur year after year, causing heavy losses
among young calves.
When first introduced into a herd the disease usually started
among the young calves as an acute infection of the gastroin-
testinal tract. Affected calves showed a roughened coat, loss of
appetite, elevation of body temperature, weakness and presence
of a persistent foetid diarrhea containing blood coagula. During
this period many calves developed symptoms of septicemia and
died three to seven days later. Symptoms of pneumonia usually
developed in calves which survived this stage of infection. The
affected calves coughed, exhibited a mucopurulent nasal dis-
charge, swelling of the sublingual region, labored respiration and
emaciation. Periods of temporary improvement often were
followed by a prolonged illness of several weeks' duration
characteristic of the chronic form. During the chronic stages
acute symptoms of gastroenteritis disappeared and the appetite
and general appearance of affected animals improved. As the
chronic condition progressed the animals continued to cough
and were exhausted easily. They showed evidence of nutritional
disturbance and anemia, regardless of the improved appetite.
Affected animals remained lying a great portion of the time.
They assumed a characteristic position of sternal recumbency

Enzootic Bronchopneumonia of Dairy Calves 5

with head and neck extended and often rested their cervical and
mandibular regions on the ground. The affected animals often
lingered for weeks exhibiting symptoms of bronchopneumonia.
In the more advanced cases oral breathing was common, the
tongue protruded, the mouth contained a frothy exudate, and
the animals showed evidence of a grave inspiratory and expira-
tory dyspnea. Fatal cases exhibited a tenacious bilateral nasal
discharge and succumbed with pronounced symptoms of pulmon-
ary edema and pneumonia.
The mortality rate frequently amounted to 60 to 70 percent
of the annual calf crop. Animals which survived the infection
were often undesirable individuals, undersized, unthrifty and
unprofitable for beef or dairy purposes.

Postmortem examinations of those animals which succumbed
during the acute stage of the condition showed lesions of a violent
gastroenteritis, pulmonary congestion, and inflammation of the
internal organs. The liver was enlarged, friable and yellow.
Postmortem examinations of calves made during various stages
of the chronic form showed a progressive bilateral hepatization
of the lung tissue. The solidifying process of the lungs began in
the lower apical lobes and gradually extended to involve the
cardiac and diaphragmatic lobes. Fatal cases showed solidifica-
tion of the entire lung tissue with the exception of a very small
portion of the dorsal border of the diaphragmatic lobes. The
intralobular connective tissue of the lungs was thickened and
yellowish in appearance, and areas of necrosis appeared through-
out the affected lung substance. Extensive adhesive pleurisy
with a fibrinous exudate in the pleural cavity occurred often.
The non-solidified portions of the lungs were inflamed and ede-
matous, and the trachea and bronchi were filled with a frothy
The large losses of calves in infected herds drew attention to
this problem. Consequently, studies were undertaken regarding
the nature and transmission of the disease at it occurred under
local conditions. Various species of bacteria were found associ-
ated with the diseased tissues. Escherichia coli was isolated
from the intestinal tract and from the blood-flecked droppings of
acute cases. Pasteurella boviseptica was the predominating
bacterial species encountered upon microscopic and cultural ex-

6 Florida Agricultural Experiment Station

amination of diseased lung tissue. The virulency of this organ-
ism for small laboratory animals was typical of the Pasteurella
group. Species of Staphylococcus and Penicillium were isolated
from the lung tissue of several calves that were autopsied in
advanced stages of the chronic form of pneumonia.

Careful microscopic search was made of stained blood smears
obtained from chronic cases of enzootic bronchopneumonia for
presence of the hematozoon, Anaplasma marginale, without
obtaining evidence of this infection. Clinical examinations of
cases of enzootic bronchopneumonia showed that many of the
animals were infested with the blood-sucking louse, I ':.... '*! ...
vituli. Microscopic examination of fecal samples secured from
young calves during the early stages of the disease showed pres-
ence of coccidia, Eimeria sp., and nematode ova. Microscopic
examination of the feces of older calves suffering from the
chronic form of enzootic bronchopneumonia revealed the pres-
ence of heavy nematode and cestode infestations in addition to
the coccidia. Postmortem examinations of yearlings which sur-
vived an acute attack often showed the presence of several
species of internal parasites including hookworm, Bunostomum
phlebotomum; tapeworm, Monezia benedeni; nodular worm,
Oesophagostomum radiatum; stomach worm, Haemonchus con-
tortus; whipworm, Til', ;i, ;. ovis; lungworm, Dictyocaulus
viviparus; and thread-like worm, Setaria labiato papillosa.

Strains of organisms used in studying the relation between
Pasteurella boviseptica and enzootic bronchopneumonia were
secured by culturing diseases lung tissue of calves that died
or were killed during acute or chronic stages of the infection.
Other strains were secured by aspirating secretions from the
nasopharyngeal region of calves during various stages of pneu-
monia. P. boviseptica was isolated from these secretions by
inoculating laboratory animals and by plate cultures. Other
strains were obtained by culturing the heart blood of laboratory
animals which received injections of edematous tracheal exudate
and minced portions of affected lung tissue of calves that died of
enzootic bronchopneumonia. After isolation of the various
strains of P. boviseptica the organisms were grown and main-
tained under conditions which have been described in a previous

Enzootic Bronchopneumonia/of Dairy Calves 7

publication (4). P. boviseptica grown and maintained under
these conditions was highly virulent for small laboratory ani-
mals, as proven by intraperitoneal or intravenous inoculations
using minute quantities of the stock cultures.

It has been considered that a primary etiological relationship
existed between species of Pasteurella and enzootic broncho-
pneumonia of young animals. Since P. boviseptica was readily
isolated from diseased lung tissue of calves affected with the
chronic form of enzootic bronchopneumonia, it was deemed im-
portant to study the relation of this organism to the infection.
Attempts were made to reproduce cases of enzootic bronchopneu-
monia by exposing calves to P. boviseptica which were isolated
from diseased lung tissue.
Experiment 1.-Eight young healthy calves were secured from
premises where pneumonia did not occur. These calves were
exposed to cultures of the organism by way of the digestive and
respiratory tracts, by instillation of the organisms into the con-
junctival sac and by intradermal injections. Amounts varying
up to 200 cubic centimeters of 24-hour blood bouillon culture were
given as a drench. The hearts, spleens and livers of laboratory
animals which died 18 hours after intraperitoneal injections of
P. boviseptica were minced in saline solution and administered
as a drench. Cultures of the organism were sprayed into the
nasal passages and instilled into the conjunctival sac. Twenty-
four hour agar cultures of P. boviseptica were washed off with
saline solution and injected intradermally. The pliable skin of
the caudal fold and that of the scrotum were used as sites for in-
jections. In making the intradermal injections the areas selected
were swabbed with pledgets of cotton saturated with 70 percent
alcohol. A small quantity of the culture was deposited intra-
dermally by means of a small gauge needle so as to obtain a
tiny bleb at each of several points injected in the area. No evi-
dence of pneumonia developed in any of the calves thus exposed
to P. boviseptica. Marked edematous infiltration developed at
the sites of the intradermal injections. All evidence of swelling
disappeared within 48 to 72 hours without producing any un-
toward effect. No difference was found as to the media used in
growing or maintaining P. boviseptica as influencing its virul-
ency for calves.

8 Florida Agricultural Experiment Station

Results of these tests led to the belief that P. boviseptica was
not the primary etiological agent responsible for enzootic bron-
chopneumonia of calves.

Experiment 2.-It seemed important to determine if enzootic
bronchopneumonia as encountered in these studies could be trans-
mitted by exposing calves to diseased lung tissue, bronchial and
tracheal exudate and nasal secretions of calves suffering from
the disease. Material for this purpose was secured from infected
calves which were presented for observation during the course
of the investigation. Diseased tissues representing acute and
chronic stages of infection were obtained from calves in differ-
ent herds. Diseased portions of the lung tissues and contents
were removed from the carcass and minced in saline solution.
The edematous tracheal or bronchial exudate and nasal secretions
often present were incorporated with the minced lung in saline
solution. Immediately after preparation the material was ad-
ministered as a drench to young, healthy calves. During the
course of these investigations 20 calves were exposed in this
manner in an effort to reproduce the disease. In addition five
calves were exposed by means of nasal sprays to bacteria-free
filtrates of diseased tissues prepared from animals during vari-
ous stages of pneumonia.
Neither enzootic bronchopneumonia nor any other unfavorable
sequelae developed in the test calves as a result of these exposure

Experiment 3.-The following test was conducted to determine
if enzootic bronchopneumonia could be transmitted by inoculat-
ing healthy calves with blood of infected animals. Twenty cubic
centimeter samples of jugular blood were secured from each of
10 cases of enzootic bronchopneumonia encountered in the field.
The blood was collected in sterile tubes containing sodium
citrate solution and injected into the jugular vein of young test
calves that were secured from premises where the disease did
not occur. These blood collections were made from calves repre-
senting various stages of enzootic bronchopneumonia.
No evidence of transmission was obtained in any of the healthy
calves thus inoculated with blood from affected animals.

Enzootic Bronchopneumonia of Dairy Calves 9

Experiment 4.-Contact exposures of calves to active cases of
enzootic bronchopneumonia were undertaken. A total of eight
calves representing acute and chronic stages of the infection
were selected from naturally occurring field cases and confined
with a similar number of young healthy calves. The exposure
was made in specially constructed insect-proof isolation pens
(4) having concrete floors with slatted platforms. The floors
and platforms were scrubbed each day. Acute gastroenteritis
typical of early stages of the naturally occurring disease de-
veloped in these test calves within 10 days following exposure.
E. coli was isolated from the diarrheal discharge of the test
calves. The organism produced acute gastroenteritis in young
healthy calves when 24-hour bouillon cultures were given as a
drench. Although diarrhea typical of early stages of the disease
developed in the calves thus exposed by contact, typical enzootic
bronchopneumonia similar to that observed under field conditions
did not develop.
It was concluded that E. coli was instrumental in producing
symptoms characteristic of the early stages of enzootic broncho-
pneumonia but that additional factors were necessary for the
successful transmission of the chronic form of the disease.

Experiment 5.-Failure to transmit enzootic bronchopneu-
monia by exposure methods described above suggested the possi-
bility that the necessary predisposing factors influencing suscep-
tibility of calves to this trouble would be' found associated with
environment incident to crowded insanitary permanent calf lots.
Heavy gastrointestinal parasitic infestations occurring in af-
fected herds under natural conditions further strengthened this
suspicion. To test this point a plot of ground containing a
heavy sod of grass was fenced for purposes of confining diseased
animals with healthy individuals. Calves affected with early
stages of bronchopneumonia and yearlings in a state of chronic
infection were confined on the plot at irregular intervals. The
animals were removed as necessary to prevent killing the grass.
Droppings of the diseased animals were allowed to remain on
the soil. When it became necessary to remove the animals to
prevent killing the grass by overstocking, the feces of the dis-

10 Florida Agricultural Experiment Station

eased animals were collected and scattered over the plot. By
this method the experimental plot became thoroughly contami-
nated with droppings of animals affected with acute and chronic
enzootic bronchopneumonia. After the plot had become con-
taminated in this manner over a period of 10 months, young
healthy calves were introduced into the enclosure, where they
were confined and reared with clinical cases of bronchopneu-
Typical bronchopneumonia, similar to those cases observed
under natural conditions, subsequently developed in a number
of the test calves. Postmortem examinations of such reproduced
cases showed lesions similar to those occurring in herds where
heavy losses had been sustained. Animals so affected developed
symptoms of acute gastroenteritis associated with coccidia and
virulent colon organisms. The experimental calves which sur-
vived the acute attack of gastroenteritis developed symptoms of
bronchopneumonia. Postmortem examinations of such cases
showed the progressive development of a chronic bilateral hepati-
zation of the lungs similar to that observed in natural outbreaks
of the disease. Microscopic and cultural examinations of the
bacterial flora of the diseased lung tissues showed the predomi-
nating organism to be P. boviseptica. A heavy infestation of
gastrointestinal parasites developed in these induced chronic
cases of bronchopneumonia.
Results of the test showed that predisposing factors incident
to the environment of crowded, insanitary, permanent calf lots
were sufficient to reproduce the disease as observed under field
conditions. DISCUSSION
Field and experimental observations indicate that enzootic
bronchopneumonia of dairy calves as encountered in this section
depends upon a number of predisposing factors. This condition
appears where calves are confined in crowded insanitary perma-
nent lots, and is more prevalent during the warm moist seasons
of the year. These conditions are favorable to development of
various bacterial infections of the gastrointestinal tract and of
the umbilicus, and to infestations with external and internal
parasites. Calves kept under such conditions are frequently
undernourished. These weakening influences lower the body
resistance sufficiently to permit development of pneumonia.
Since it has been shown (4) that P. boviseptica is an inhabitant
of the upper respiratory passage of cattle, it is readily under-
stood why this organism constitutes the predominating species

Enzootic Bronchopneumonia of Dairy Calves 11

encountered in diseased lung tissue. Enzootic bronchopneumonia
has not been observed on premises where strict sanitary methods
of rearing calves are practiced. The incidence of this type of
bronchopneumonia in infected herds has been reduced in direct
proportion to employment of hygienic methods in rearing calves.

Enzootic bronchopneumonia causes heavy loss among dairy
calves confined in crowded insanitary permanent lots. These
conditions are favorable to development of various bacterial
infections of the gastrointestinal tract and the umbilicus, and to
infestations with external and internal parasites.
Escherichia coli, Pasteurella boviseptica, and species of Staphy-
lococcus and Penicillium were found to be associated with the
diseased lung tissue. Calves affected with bronchopneumonia
were infested with various species of internal parasites, including
coccidia, Eimeria sp.; hookworm, Bunostomum phlebotomum;
whipworm, Trichuris ovis; tapeworm, Moniezia benedeni; nodu-
lar worm, Oesophagostomum radiatum; lungworm, Dictyocaulus
viviparus; stomach worm, Haemonchus contortus; filaria, Setaria
labiato-papillosa; and the external blood sucking louse, Linogna-
thus vituli.
These weakening influences lower the body resistance of calves
sufficiently to permit the microorganisms colonizing in the respi-
ratory passage to exert a pathogenic action resulting in develop-
ment of bronchopneumonia. Enzootic bronchopneumonia has
not been found to exist on premises where strict sanitary methods
of rearing calves are practiced. Incidence of the disease on
affected premises has been reduced in proportion to employment
of hygienic methods in rearing calves.
1. EDMONDS, C. R. Diseases of animals in South Africa. Bailliere, Tindall
and Cox. Pages 175-176. 1922.
2. HUTYRA, F., and J. MAREK. Special pathology and therapeutics of the
diseases of domestic animals. Third Authorized American Edition,
Alexander Eger. II: 684-694. 1926.
3. ROBERTS, G. A. Tropical pneumoenteritis of calves. Vet. Med. 33:
121-123. 1938.
4. SANDE.S, D. A. Hemorrhagic septicemia: The significance of
Pasteurella boviseptica encountered in the blood of some Florida
cattle. Fla. Agr. Exp. Sta. Bul. 322. 1938.
5. SANDERS, D. A. Some observations on the nature and transmission of
enzootic bronchopneumonia (pneumoenteritis) of dairy calves. Jour.
Amer. Vet. Med. Assn. 94: 28-32. 1939.

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