• TABLE OF CONTENTS
HIDE
 Historic note
 Front Cover
 Personnel
 Table of Contents
 Introduction
 History
 Method of attack
 Life history
 How to recognize infestations
 Effect on animals
 Treatment
 Treatment of difficult cases
 Prevention
 Summary
 List of literature














Group Title: Bulletin - University of Florida. Agricultural Extension Service ; no. 86
Title: Screwworms in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026356/00001
 Material Information
Title: Screwworms in Florida
Series Title: Bulletin
Physical Description: 27 p. : ill. ; 23 cm.
Language: English
Creator: Bruce, W. G ( Wesley Gordon ), b. 1892
Sheely, W. J
Publisher: Cooperative extension work in agricculture and home economics
Place of Publication: Gainesville Fla
Publication Date: <1936>
 Subjects
Subject: Domestic animals -- Parasites -- Florida   ( lcsh )
Screwworm -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 27).
Statement of Responsibility: by W.G. Bruce and W.J. Sheely.
General Note: "October, 1936."
Funding: Bulletin (University of Florida. Agricultural Extension Division)
 Record Information
Bibliographic ID: UF00026356
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 002570820
oclc - 44795172
notis - AMT7134

Table of Contents
    Historic note
        Historic note
    Front Cover
        Page 1
    Personnel
        Page 2
    Table of Contents
        Page 3
    Introduction
        Page 3
    History
        Page 3
    Method of attack
        Page 4
    Life history
        Page 5
    How to recognize infestations
        Page 6
        Plate I
        Plate II
    Effect on animals
        Page 7
    Treatment
        Page 8
        Page 9
        Page 10
    Treatment of difficult cases
        Page 11
        Page 12
        Page 13
        Page 14
    Prevention
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Plate III
        Plate IV
        Page 23
        Page 24
        Page 25
    Summary
        Page 26
    List of literature
        Page 27
Full Text





HISTORIC NOTE


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
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida






October, 1936


y COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMIC .
(Acts of May 8 and June 30. 1914)
AGRICULTURAL EXTENSION SERVICE, UNIVERSITY OF FLO~I v V
FLORIDA STATE COLLEGE FOR WOMEN
AND UNITED STATES DEPARTMENT OF AGRICULTURE
COOPERATING
WILMON NEWELL, Director
___________ ':ti-Winit af Agriculft~a


SCREWWORMS IN FLORIDA
By W. G. BRUCE
Division of Screwworm Control, Bureau of Entomology and Plant
Quarantine, United States Department of Agriculture
and
W. J. SHEELY
Agent in Animal Husbandry, Florida Agricultural Extension Service



kv;eli~fti


Fig. 1.-Close supervision of farm animals and careful treatment of
all injuries and open wounds are necessary to prevent and control screw-
worm infestations. A treating chute and stanchion are a great aid in
handling the animals.
Bulletins will be sent free to Florida residents upon application to the
AGRICULTURAL EXTENSION SERVICE
GAINESVILLE, FLORIDA







BOARD OF CONTROL
GEO. H. BALDWIN, Chairman, Jacksonville
OLIVER J. SEMMES, Pensacola
HARRY C. DUNCAN, Tavares
THOMAS W. BRYANT, Lakeland
R. P. TERRY, Miami
J. T. DIAMOND, Secretary, Tallahassee

STAFF, AGRICULTURAL EXTENSION SERVICE
JOHN J. TIGERT, M.A., LL.D., President of the University
WILMON NEWELL, D.Sc., Director
A. P. SPENCER, M.S., Vice-Director and County Agent Leader
J. FRANCIS COOPER, M.S.A., Editor
JEFFERSON THOMAS, Assistant Editor
CLYDE BEALE, A.B., Assistant Editor
E. F. STANTON, Supervisor, Egg-Laying Contest
RUBY NEWHALL, Administrative Manager

COOPERATIVE AGRICULTURAL DEMONSTRATION WORK
W. T. NETTLES, B.S., District Agent
H. G. CLAYTON, M.S.A., District Agent, Organization and Outlook Specialist
J. LEE SMITH, District Agent and Agronomist
R. S. DENNIS, B.S.A., Assistant District Agent
A. E. DUNSCOMBE, M.S., Assistant District Agent
R. W. BLACKLOCK, A.B., Boys' Club Agent
E. F. DEBUSK, B.S., Citriculturist
A. L. SHEALY, D.V.M., Animal Industrialist2
HAMLIN L. BROWN, B.S., Dairyman
N. R. MEHRHOF, M. AGR., Poultryman2
D. F. SOWELL, M.S., Assistant Poultryman
WALTER J. SHEELY, B.S., Agent in Animal Husbandry
C. V. NOBLE, PH.D., Agricultural Economist2
FRANK W. BRUMLEY, PH.D., Agricultural Economist, Farm Management
R. H. HOWARD, M.S.A., Asst. Agr. Economist, Farm Management
D. E. TIMMONS, M.S.A., Agricultural Economist, Marketing
A. E. MERCKER, Field Agent, Cooperative Interstate Marketing1

COOPERATIVE HOME DEMONSTRATION WORK
MARY E. KEOWN, M.S., State Agent
LUCY BELLE SETTLE, M.A., District Agent
RUBY McDAVID, District Agent
ANNA MAE SIKES, B.S., Nutritionist
VIRGINIA P. MOORE, Home Improvement Agent
ISABELLE S. THURSBY, Economist in Food Conservation
CLARINE BELCHER, M.S., Clothing Specialist

NEGRO EXTENSION WORK
A. A. TURNER, Local District Agent
BEULAH SHUTE, Local District Agent

1 In cooperation with U. S. D. A.
2 Part-time.









SCREWWORMS IN FLORIDA

By

W. G. BRUCE and W. J. SHEELY

CONTENTS
Page Page
History ......... ...... 3 Treatment of difficult cases .... 11
Method of attack 4 Prevention ..... .... 15
Life History 5 Good management pays two ways .. 15
How to Recognize Infestations (6 Suggested preventive measures 18
Effect on Animals 7 Summary ..... ... 26
Treatment .... 8 List of Literature .... 27

INTRODUCTION

Screwworms* are a serious pest of livestock in Florida. No
other insect affecting wild or domestic animals is as devastat-
ing in its attack nor as deadly in effect. Uncontrolled, this pest
is capable of wiping out entire herds of cattle, hogs, sheep, and
goats. But when control measures are employed, all losses
can be averted and screwworm injuries reduced to the minimum.
Eradication of screwworms is only a fond hope; actually, it
is improbable. It is reasonable to expect that screwworms will
continue to be an important problem in every livestock enter-
prise; the control of this pest may determine the success or
failure of that enterprise.

HISTORY

Screwworms have been known in Texas since about 1842.
Occasionally, during the summer months, they have spread to
adjoining states but most of the screwworm activity was con-
fined to Texas. Prior to 1933, screwworms were unknown in
Florida. During the summer of that year the first cases were
reported in the Southeastern states, including northern Florida.
By the end of the year screwworm infestations were reported
from 18 to 20 of Florida's northern counties. Screwworm activ-
ity subsided during the winter months but with the coming
of warm weather in the spring of 1934, screwworms spread to
some 35 additional counties during the summer. Heavy losses
of livestock from screwworm attack were reported by hundreds
of stockmen.

*Cochliomyia americana C. and P.









SCREWWORMS IN FLORIDA

By

W. G. BRUCE and W. J. SHEELY

CONTENTS
Page Page
History ......... ...... 3 Treatment of difficult cases .... 11
Method of attack 4 Prevention ..... .... 15
Life History 5 Good management pays two ways .. 15
How to Recognize Infestations (6 Suggested preventive measures 18
Effect on Animals 7 Summary ..... ... 26
Treatment .... 8 List of Literature .... 27

INTRODUCTION

Screwworms* are a serious pest of livestock in Florida. No
other insect affecting wild or domestic animals is as devastat-
ing in its attack nor as deadly in effect. Uncontrolled, this pest
is capable of wiping out entire herds of cattle, hogs, sheep, and
goats. But when control measures are employed, all losses
can be averted and screwworm injuries reduced to the minimum.
Eradication of screwworms is only a fond hope; actually, it
is improbable. It is reasonable to expect that screwworms will
continue to be an important problem in every livestock enter-
prise; the control of this pest may determine the success or
failure of that enterprise.

HISTORY

Screwworms have been known in Texas since about 1842.
Occasionally, during the summer months, they have spread to
adjoining states but most of the screwworm activity was con-
fined to Texas. Prior to 1933, screwworms were unknown in
Florida. During the summer of that year the first cases were
reported in the Southeastern states, including northern Florida.
By the end of the year screwworm infestations were reported
from 18 to 20 of Florida's northern counties. Screwworm activ-
ity subsided during the winter months but with the coming
of warm weather in the spring of 1934, screwworms spread to
some 35 additional counties during the summer. Heavy losses
of livestock from screwworm attack were reported by hundreds
of stockmen.

*Cochliomyia americana C. and P.









SCREWWORMS IN FLORIDA

By

W. G. BRUCE and W. J. SHEELY

CONTENTS
Page Page
History ......... ...... 3 Treatment of difficult cases .... 11
Method of attack 4 Prevention ..... .... 15
Life History 5 Good management pays two ways .. 15
How to Recognize Infestations (6 Suggested preventive measures 18
Effect on Animals 7 Summary ..... ... 26
Treatment .... 8 List of Literature .... 27

INTRODUCTION

Screwworms* are a serious pest of livestock in Florida. No
other insect affecting wild or domestic animals is as devastat-
ing in its attack nor as deadly in effect. Uncontrolled, this pest
is capable of wiping out entire herds of cattle, hogs, sheep, and
goats. But when control measures are employed, all losses
can be averted and screwworm injuries reduced to the minimum.
Eradication of screwworms is only a fond hope; actually, it
is improbable. It is reasonable to expect that screwworms will
continue to be an important problem in every livestock enter-
prise; the control of this pest may determine the success or
failure of that enterprise.

HISTORY

Screwworms have been known in Texas since about 1842.
Occasionally, during the summer months, they have spread to
adjoining states but most of the screwworm activity was con-
fined to Texas. Prior to 1933, screwworms were unknown in
Florida. During the summer of that year the first cases were
reported in the Southeastern states, including northern Florida.
By the end of the year screwworm infestations were reported
from 18 to 20 of Florida's northern counties. Screwworm activ-
ity subsided during the winter months but with the coming
of warm weather in the spring of 1934, screwworms spread to
some 35 additional counties during the summer. Heavy losses
of livestock from screwworm attack were reported by hundreds
of stockmen.

*Cochliomyia americana C. and P.






Florida Cooperative Extension


Again, during the winter months, screwworm activity sub-
sided in the northern counties and except for an occasional in-
festation little consideration was given to screwworms in that
portion of the state. However, by this time the pest had spread
to some of the southern counties where the winter was mild
and screwworm activity continued throughout the winter, slowly
spreading to adjoining counties. During 1935 screwworms
were found in every county in Florida except Monroe, the
southern tip of the state, where there are few wild or domestic
animals.
METHOD OF ATTACK
The screwworm is a true parasite and lives only in the living
flesh of warm-blooded animals. It is not found in gophers
(turtles), snakes, lizards, or other cold-blooded animals nor in
carcasses, dead fish, decaying meats, or decaying vegetable mat-
ter. The worms found in these cold-blooded animals and de-
caying materials are common blowflies and are not true screw-
worms. (Plates II, III, and IV.) Any warm-blooded animal
is subject to screwworm attack. Infestations have been found
in practically all kinds of wild and domestic animals, poultry,
and man.
Before the screwworm fly can lay eggs on an animal there
must be some opening in the skin of that animal. The worms
cannot eat through the unbroken skin of a healthy animal. The
opening through which the screwworm enters the flesh may be
as small as a tick bite, it may be through the navel cord of a
new-born animal, a scratch, a surgical operation, or some dis-
eased condition of the skin and mucous membrane, especially
around the natural openings. Any open wound is attractive to
the female screwworm fly and she loses no time in placing her
eggs on the edge of that wound.
After a wound is infested it seems to become more attractive
to the flies and constantly receives new batches of eggs. Fre-
quently screwworms of different sizes and ages are found in
a wound. As the larvae develop the wound increases in size,
there is constant dropping of grown larvae from the wound to
the ground as the animal walks from place to place, the animal
gradually becomes weaker, and there is danger of death. When
the animal is unable to stand, or the blood circulation is poor,
or when mohair, wool, or hair is soiled from the discharges of
wounds, ordinary blowflies may lay eggs on the animals.






Screwworms in Florida


LIFE HISTORY
The female screwworm fly lays her eggs in shingled batches
on the edges of wounds of warm-blooded animals. She may de-
posit as few as 10 or as many as 400 eggs at one time. The
eggs of the true screwworm can be distinguished from those of
other blowflies by the fact that they are placed in shingle-like
masses and are cemented together. Eggs of ordinary blowflies
are placed in haphazard fashion and are not securely cemented
together.
The eggs hatch in from six to 21 hours. The tiny worms
feed in clusters, eat into the live flesh and soon form a "pocket"
in the flesh (Fig. 2). After completing development, which takes


Fig. 2.-Screwworm infestation in brisket of cow, due to horn hook. Shows
the "pocket" formed in the flesh by the pests.

from 31/2 to 10 days, the screwworms leave the wound and bur-
row into the soil. The outer skin of the worm hardens and
forms a pupa. Seven to 14 days later the adult fly emerges.
During cool weather this latter stage may last for two months.
Five to 10 days after the flies emerge they are ready to mate
and lay eggs. The average life cycle is about 24 days. (The
life cycle is that period of time necessary for the egg to hatch,






Florida Cooperative Extension


the larva (worm) to mature, pupate, change to a fly and the
fly to become capable of laying eggs; in other words, from egg
to egg.) The life cycle may be much shorter under favorable
conditions or considerably longer under adverse conditions, es-
pecially during cool weather.

HOW TO RECOGNIZE INFESTATIONS
Animals infested with screwworms often stray from the herd
and hide in the underbrush or palmettos (Fig. 3). They appear


















Fig. 3.-This sheep, with a severe infestation of screwworms in the eye,
strayed from the flock and hid in tall grass.

nervous and try to scratch or lick the wound. It is quite evi-
dent that the worms are causing the animal considerable pain
and the animal, if not too weak, is making every effort to dis-
lodge the offenders.
The wound is characterized by a watery discharge of bloody
exudate and by an obnoxious odor. Once a stockman sees or
smells a screwworm infested wound, he will easily recognize
subsequent cases. If the bloody discharge is carefully wiped
from the wound with some absorbent cotton, the screwworms
will be found crowded close together in the pockets of the wound
with only their rear ends exposed. The front ends of these
worms are embedded in the living flesh and are provided with
two horn-like mouth hooks which are capable of tearing living
tissues and causing bleeding. If the wound is large and there














































PLATE I
Cochliomyia americana C. and P.
The primary screwworm fly lays eggs on wounds
of warm-blooded animals and these eggs hatch into
screwworms. This fly closely resembles Cochliomyia
macellaria, which develops in decaying flesh.


















/
/
/


\ /












PLATE II
Lucilia sericata Meig.


\ t


A green bottlefly which commonly develops in de-
caying meats during the warm months.


j


19






Screwworms in Florida


is some decaying (necrotic) flesh present, there may also be
some maggots of ordinary blowflies. These blowfly maggots
are not embedded in the live flesh but will be observed crawling
about on the surface of the wound.

EFFECT ON ANIMALS
Most untreated screwworm infestations will result in death
to the animal (Fig. 4). Death may be caused directly by screw-


Fig. 4.-This case of screwworm infestation in the head
of a calf, because of neglect, resulted finally in the animal's
death.

worms or from complications following such infestation. It must
be remembered that a wound is being continually reinfested with
screwworms; in fact, old screwworm cases are often more at-
tractive to the screwworm fly than fresh wounds. Just how
long the animal will live depends upon the location of the in-
festation. If the infestation is in the navel, death may result
more quickly than if that infestation is in some meaty and less
vulnerable part of the animal.






Florida Cooperative Extension


TREATMENT
Benzol and pine-tar oil are the only materials recommended
for the treatment of screwworm infestations in livestock. Benzol
(commercial 90 percent), produced by the distillation of coal
tar, is used to kill the screwworms. If the maggots are forced
to breathe the fumes of benzol for a few seconds they are stupe-
fied; for several minutes, they are killed. When properly used
benzol kills screwworms effectively without injury to the heal-
ing tissues of wounds.
Pine-tar oil (specific gravity 1.065 to 1.085, dehydrated and
acid-free), produced by the destructive distillation of dry pine
knots, is used to repel screwworm flies and as a dressing to aid
in healing the wound. Light applications of this material should
be made in and around the wound every day or two until the
wound is healed. Pine tar should not be used (Fig. 5).


Fig. 5.-This animal was improperly treated, pine tar being used in-
stead of pine-tar oil. Note swelling of right rump and blistering which
resulted.

Sometimes it is desirable to trim the hair or wool around
the wound. Clean the wound by using cotton to remove the
pus and blood. Apply a small amount of benzol, preferably by
the use of a small rubber bulb syringe or oil can. The benzol






Screwworms in Florida


tends to stop the flow of blood and pus and loosen the accumu-
lated exudates so they may be more thoroughly removed. Again
swab the wound with cotton very carefully so as not to cause
bleeding.


Fig. 6.-First step in treating a screwworm case-clean the wound
with cotton.
Close examination of the clean wound will reveal the screw-
worms closely packed in the far recesses or pockets of the
wound, each with its small end (head) buried in the flesh and
the large end (rear) uppermost. The breathing apparatus
spiracless) is located on the rear end of the worm. It is im-
portant to clean the wound thoroughly so these spiracles are
exposed to the fumes of benzol. If the wound is not thoroughly
cleaned, the treatment will n6t be effective because the benzol
cannot penetrate through the pus to the maggots.
Apply some more benzol to the wound and plug the opening
with a piece of dry cotton (Fig. 7). Use only enough cotton
to make a firm plug and leave it loose enough to work out in a
few hours. The benzol volatilizes (changes to a gas) rapidly
and the screwworms are forced to breathe the deadly fumes. As
soon as the wound is plugged, apply a thin coat of pine-tar oil
to the wound and cotton plug (Fig. 8). Examine the wound the
next day. The cotton plug and many of the dead maggots will







10 Florida Cooperative Extension


Fig. 7.-Second step in treating a screwworm case-apply benzol and
insert a cotton plug. Do not remove the worms.


p. I




r-


Fig. 8.-Third step in treating a screwworm case-apply pine-tar oil to
cotton plug and surrounding area.






Screwworms in Florida


have dropped from the wound. Make a light application of
pine-tar oil in and around the wound. These light applications
of pine-tar oil should be made every day or two until the wound
is healed.

TREATMENT OF DIFFICULT CASES
The treatment of simple screwworm cases is described above.
Frequently cases are found which are more difficult to treat
and special care is required to effect a successful treatment. In
very severe cases and in cases affecting valuable animals, it
is advisable to consult a competent veterinarian.
Navel Cases: The navels of young animals are a common
source of screwworm infestations (Figs. 9 and 10). These navels


Fig. 9.-Navels of calves, particularly calves dropped late in the season,
are often infested with screwworms.

have small openings and frequently are packed with screw-
worms and the cavity is too small to hold sufficient benzol to
kill all the worms. In these cases, it is advisable to clean the
wound and use as much benzol as the cavity will hold, then
insert a dry cotton plug for about 15 minutes. The cotton
absorbs some benzol but holds the fumes in the wound. After
about 15 minutes the cotton plug should be removed and most
of the stupefied larvae gently brushed from the wound. These
worms should be destroyed.






Florida Cooperative Extension


Fig. 10.-Navel infestations in late calves need careful treatment.

The wound should again be treated with benzol, the cotton
plug inserted, pine-tar oil applied to the whole area, and treat-
ment continued as described for ordinary infestations.
Stockmen should not try to remove the worms with forceps,
wire, or stick. If worms that are attached to the flesh are
pulled out, small blood vessels will be ruptured and bleeding
will result.
Cases Following Dehorning: Screwworm infestations follow-
ing dehorning are very difficult to treat and if proper care is
not exercised serious consequences may result. Benzol should
not be poured into these cavities because of the danger of this
material running down the horn cavity and into the sinuses. It
is preferable to moisten a piece of cotton with benzol and place
it in the horn cavity. At the end of a day the cotton plug is
removed and the dead larvae are taken out with blunt forceps.
A small cotton plug is then inserted into the cavity and pine-
tar oil applied to the cotton and around the edges of the wound.
Dehorn cases are so difficult to treat and so apt to result in
complications that dehorning during the season of screwworm
activity is not recommended.
Cases in Horses and Mules: One of the most difficult cases
to treat is a screwworm infestation in the penis and sheath of






Screwworms in Florida


a horse or mule. Such cases are quite common in the fall of
the year and require special attention. By careful manipula-
tion the penis must be withdrawn to expose the infested area
for treatment. These wounds are usually quite small and con-
tain only a comparatively small number of larvae. The use of
benzol and a cotton plug is recommended. While the benzol
is killing the maggots, the whole penis should be washed with
warm water and soap. Five or 10 minutes after the benzol is
applied, the cotton plug should be removed and the dead worms
carefully picked out with blunt forceps. Do not use pine-tar
oil on the penis, but vaseline or a vegetable oil may be used.
A light application of pine-tar oil is used on the sheath to repel
the flies and should be repeated daily until the wound is healed.
In some instances successful treatment of penis-sheath cases
has been accomplished by flushing the sheath with benzol and
then packing the opening of the sheath with a cotton plug
saturated with benzol and leaving it for 15 to 20 minutes.
Large Open Wounds (Old Wounds): Large open wounds con-
taining infestations of maggots are usually due to neglect in
not promptly treating a screwworm infestation. Often these
wounds appear to be difficult to treat, but with time and patience
they can be successfully treated. In old wounds there is some
decaying (necrotic) tissues. Maggots found on the surfaces of
such wounds are not screwworms but are ordinary blowfly mag-
gots. These maggots are crawling about the wound and are
not standing on end like true screwworms.
In treating wounds of this type two applications are neces-
sary. Place a pad of cotton or a clean cloth over the wound
and saturate it with benzol. After about five or 10 minutes
remove the pad and carefully brush the dead maggots from
the surface of the wound. Destroy the maggots. Now wipe
out the wound with clean, dry cotton. Upon careful examina-
tion of the wound one or more small pockets of true screw-
worms will be found. Insert a cotton plug moistened with ben-
zol in each of these pockets. Each pocket is to be treated as
a separate infestation. The cotton plugs are left in place and
pine-tar oil is applied over them and the entire wound.
Cases of this kind are not difficult to treat after the stock-
man understands the difference between ordinary blowfly mag-
gots and true screwworms. Prompt treatment of all screwworm
infestations and the application of pine-tar oil on all wounds
will eliminate infestations of this kind.





Florida Cooperative Extension


Cases in Dams: Screwworms frequently infest the vaginas
of dams during and after the birth of young. In such cases benzol
and a cotton plug should be used as in other cases. After about
five or 10 minutes remove the cotton plug and wash the entire
area with warm water and soap, at the same time brushing out
the dead screwworms with care to avoid injury. Pine-tar oil
should not be applied to the vagina, but a light application on
the surrounding
Areas will repel
:t h e screwworm
flies.
Cases in Ears:
L on g neglected
screwworm infes-
tations in the
ears of livestock,
especially follow-
ing ear marking
t.t (Fig. 11), often
are difficult to
treat and slow to
heal. The worms
eat the tissues
Between the two
layers of skin of
Fig. 11.-This ear became badly infested with the ear and leave
screwworms following marking, and was difficult to
treat. (Note tipped horn.) a ragged wound.
The difficulty in
getting cotton plugs to stick in such wounds makes it advisable
to restrain the animal until the benzol fumes have had time to
kill the maggots and to remove the maggots with blunt forceps.
Occasionally it is advisable to trim the ragged edges of the
ear with a sharp knife and apply pine-tar oil daily until the
wound is healed.
Screwworms in the Mouth: When treating screwworm cases
in cattle, sheep, and goats, it is always advisable to examine
the mouths of these animals for screwworms. These animals
lick their wounds and oftentimes get some of the maggots into
the mouth, where they become attached to the gums between
the teeth. This is especially true in calves with navel infesta-
tions (Fig. 12). Examination of the mouths of the mothers
of such calves frequently discloses screwworms in their gums.






Screwworms in Florida


Fig. 12.-This two-months old calf had gotten screwworms in its gums
by licking a navel infestation.

Do not use benzol or pine-tar oil in the mouths of livestock.
Simply remove the screwworms with blunt forceps and destroy
them.
PREVENTION
A study of the screwworm problem in Florida reveals the
fact that a vast majority of infestations are due to man-made
injuries or to injuries that can be prevented by man. Also it is
evident that the stockman who is familiar with the habits of
the screwworm, who has a knowledge of livestock and grasses
under Florida climatic conditions, and who practices good herd
management can prevent screwworm infestations and eliminate
losses.
GOOD MANAGEMENT PAYS TWO WAYS
Good management of the beef herd will pay the cattleman
two profits-it will enable him to produce more and better ani-
mals, and it will help him to prevent losses from screwworm
infestations. Practices which are best under ordinary condi-
tions are particularly desirable under screwworm infestations.
To a certain extent the screwworm is forcing the adoption of
these practices, to the benefit of the producer.
The annual calf crop must bear the expense of the entire






Florida Cooperative Extension


beef cattle operation; hence, losses in calves mean loss of revenue
from the cow herd. The size and quality of the calf crop de-
termines, in large measure, returns from cattle operations. Im-
provement of cattle should not be confined to quality, but should
include the productivity of the herd as well; that is, improve-
ment must be made in both quality and quantity of the calf
crop.
Under range and semi-range conditions a maximum calf crop
of high quality, with the calves dropped early in spring, is es-

















Fig. 13.-Pens and chutes such as these are to be avoided. Note rough
poles and projecting ends, which are quite apt to cause injuries which will
result in screwworm infestation.

sential. Early spring calves get full benefit of the grass grow-
ing season, attain larger size, and grow into better cattle than
late calves. Recent investigations have shown that a herd of
grade calves dropped during the period January to April, in-
clusive, averaged 139 pounds heavier at weaning time than did
calves born between May 1 and July 15.
Because of their larger size and greater vigor, early spring
calves can be weaned before winter and can be carried through
the winter on coarse feeds and pastures, thus reducing costs
of wintering.
At the same time the cow that drops an early calf improves
in flesh and goes into winter in much better condition. With
nutritious grasses for grazing, she is able to gain flesh while
suckling the calf. She is more apt to survive the winter and
to drop a calf the next year.






Screwworms in Florida


On the other hand, the cow that drops a late calf exposes her-
self and the calf to screwworm attack, and neither she nor the
calf has time before winter to gain the good fleshing and vigor
needed. Mid-season and late grasses are tough and less nu-





4











Fig. 14.-This is a good type of pen and chute for handling cattle. Note
smooth poles and carefully trimmed ends.

tritious and animals do not thrive on them. Resultant winter
losses among both cows and calves are heavy and many cows
surviving the winter are so weakened that they do not drop
calves the next year.
While breeding for early calves is good management practice
at any time, it is especially important during screwworm in-
festations. The number of screwworm flies is reduced during
the winter and calves dropped early in the spring will get
started ahead of the period of severe infestation. Late calves
-those dropped through May and June-are subject to heavi-
est screwworm infestation, are pestered by other insects, and
growth is hindered and life endangered.
The percentage of calves raised is important in all phases
of cattle production, but particularly in beef cattle management
where unfavorable environment and lack of close supervision
frequently result in calf crops as low as 40 to 50 calves per
100 breeding cows. To increase the percentage of the calf
crop and the quality of calves and to reduce the infestation by
screwworms and other insects, the following suggestions are
offered:






Florida Cooperative Extension


1. Have an adequate supply of thrifty, acclimated bulls; three
or four bulls to each 100 cows on the range.
2. Separate bulls from cows during late summer and fall.
3. Feed bulls during the winter and have them in good con-
dition for spring service.
4. Turn bulls with the breeding herd only during April, May,
and June.
5. Do not breed heifers before they are 18 to 24 months old.
6. Wean calves before winter.
7. Put yearling heifers in separate pastures.
8. Feed weak cows through the winter.
9. Separate steers and barren cows from the breeding herd.
10. Cull and market unthrifty, inferior heifers, and shy-
breeding, barren cows when grass-fat.
11. See that pastures and range grasses develop good grazing.
Good herd management practices will give an early calf crop
of uniform size and age, and reduce screwworm infestation.
A uniform calf crop gives the cattleman an opportunity to sell,
each year, a crop of beef from his herd.
Cows and bulls that are wintered well and turned to good
grass produce the maximum early spring calf crop. This early
calf crop not only escapes the infestation of screwworms, in-
jury, and death but makes maximum growth the first year and
can be sold to feeders as feeder calves, or sold to stockmen as
stockers, or sold to butchers as fat calves.

SUGGESTED PREVENTIVE MEASURES
Leading predisposing causes of screwworm attack and sug-
gested preventive measures are worthy of special consideration
and serve as bases for control of the pest. Careful supervision
of animals and treatment of all infestations during winter and
early spring months, when the fly is naturally reduced in num-
bers, will aid materially in keeping down the spread of the
pest in summer. Every screwworm and fly killed during winter
and early spring will mean several score less flies for late
summer.
Navel Cases: A majority of navel cases are in calves dropped
during late spring and summer months. In June 1934 a survey
in six Florida counties showed that 70% of the newborn calves
were infested with screwworms. In 1935, 23% of all screw-
worm cases reported were in the navels of newborn animals.
During the late spring and early summer of 1935 and 1936,






Screwworms in Florida


these cases represented from 30% to 75% of all screwworm
infestations.
All animals born during the screwworm season should re-
ceive proper care. A light application of pine-tar oil on the
navel will protect it from screwworm attack. When a calf is
born it is advisable to tie off the navel cord, cut off the surplus,
paint the cord with iodine, and apply pine-tar oil around it.
In this connection, a light application of pine-tar oil around
the vulva of the mother before and after giving birth to her
young will prevent many serious screwworm infestations.
Snags and Scratches: These are second in importance as pre-
disposing causes of screwworm cases. These wounds are caused
mainly by cattle with sharp horns hooking one another and by
the rough handling of all classes of livestock (Fig. 15). Other















Fig. 15.-Crowding cattle in poorly constructed pens causes injuries like
these, which provide ideal places for screwworm infestation.

injuries of this type are caused by livestock moving through
brush, thorns, and palmettos and by the use of the whip. The
rushing of livestock through gates and gaps and unnecessary
hurrying of cattle through the woods cause many injuries.
Most of these cases can be prevented by handling the live-
stock quietly, by seeing that the rough edges are smoothed off
gates and gaps, by removing protruding nails and slivered boards
from fences, pens, and chutes (Figs. 13 and 14), by not rushing
livestock through the woods, by avoiding the use of catch dogs,
and by dehorning or tipping the sharp points of horns, thus
preventing injury from hooking.






Florida Cooperative Extension


Fig. 16.-First step in using the bloodless emasculator-force the cord
to one side.


Fig. 17.-Second step in using bloodless emasculator-apply emasculator
to one side at a time, being careful not to overlap the center.






Screwworms in Florida


Dehorning should be done when calves are small, so that
the horn cavities will not become infested with screwworms and
the operation will not interfere with normal growth of the
animals. However, cattle may be dehorned after the horns have
reached full growth. Such dehorning should be done during
the winter months and the wounds should be mopped with pine-
tar oil. Dehorned animals should be examined daily and the
wounds treated with pine-tar oil until the cavities are closed.




















Fig. 18.-Third step in using the bloodless emasculator-close handles and
hold for about 10 seconds.

Sharp horns on old animals may be tipped at any time.
Purebred polled bulls of good beef conformation can be used
to advantage in breeding. Most of their calves will be polled,
and such calves appeal to feeders. A polled herd is not so apt
to develop injuries for possible screwworm infestation.
Marking, Branding, and Castration of animals accounts for
a large number of screwworm infestations. The infestations
from castration can be greatly reduced if not entirely eliminated
by castrating young calves by the use of the emasculator-the
bloodless castration method (Figs. 16, 17 and 18). Emasculators,
when properly used, can be successfully used on cattle, sheep,
and goats, but they have not proven successful on horses or
hogs.






Florida Cooperative Extension


Fig. 19.-Screwworm infestation following castration by use of the knife
without application of pine-tar oil.


Fig. 20.-Proper attention to injuries, wounds, breaks in the skin
made by branding, and other openings which will permit screwworm flies
to lay their eggs will aid greatly in keeping animals free of screwworms.
Pine-tar oil is applied as a repellent.

















V


2"

aI


PLATE III
Phormia regina Meig.
Black blowfly which ordinarily develops in decay-
ing meats during the cool months.










/


PLATE IV
Sarcophaga bullata Park.
A gray flesh fly which does not lay eggs but gives
birth to living maggots. These maggots develop in
decaying organic substances.


F1





Screwworms in Florida


All castration wounds following the use of the knife should
be mopped with pine-tar oil (Fig. 19). Keep these wounded
animals in a holding pasture for close observation. Hogs should
be kept in small dry pens so that they will not wash off the
pine-tar oil by wallowing in mud and water. It is possible to
make daily applications without catching the animals if a long-
handled mop is used for this purpose while the hogs are feeding.
Infestations from marking (Figs. 11 and 20) and branding can
be eliminated by doing this work during the winter and by apply-
ing pine-tar oil to the wounds.
Gulf Coast Ticks: During summer and fall a large number
of screwworm cases follow the bites of the Gulf Coast tick
(ear tick). (Fig. 21.) Dipping livestock for the control of

















Fig. 21.-Gulf Coast ticks, as shown in the ear of this ram, often permit
screwworm infestation through the holes they make by biting the skin.

these ticks is not economical nor has it proven to be successful.
Mopping the ears of cattle, sheep, and goats with pine-tar oil
at two-weeks intervals will kill the ticks attached to the ear
and will act as a repellent to ticks for about two weeks (Fig. 22).
This pine-tar oil will also aid in healing the tick bites and pre-
venting infestations of screwworms.
Rough Handling: It is a good plan to eliminate all unneces-
sary causes of wounds on animals. Nub the sharp horns of
cattle (Fig. 23), extract the long tushes from hogs, extract
the milk teeth from suckling pigs, separate animals in pens or
fields according to ages and sizes, and place fighting animals






Florida Cooperative Extension


in separate pens. Restrict the use of dogs in driving animals.
Substitute holding pens or lanes instead of dogs when handling
or vaccinating animals. In other words, handle the cattle quietly,
put them where they are wanted, but save by preventing un-
necessary injuries and subsequent screwworm infestation.
Rough hand-
ling of cattle
in the yards by
railroad crews
is a source of
loss and dam-
age to the ship-
t per and results
in the railroad
company's hav-
ing to pay out
large sums of
money in
claims. Rough
handling o f
cattle (as good,
experienced

tell you) causes
o loss in weight
from unneces-
sary excite-
ment and
causes cripples
and wounds
(Fig. 24) by
cattle running
Fig. 22.-Mopping the ears of cattle with pine-tar over each other
oil helps to control the Gulf Coast tick.
and jamming
into the fences and through the gates. Rough handling by
the use of catch dogs tears the lips and the legs of animals (Fig.
25). All of these injuries, plus the infestation of these fresh
wounds by screwworms, bring an annual loss to the cattle owner,
seriously interfere with the industry, and eat up the annual
income. This rough handling is unnecessary. Care and com-
mon sense in the handling of cattle under all conditions will
prevent all of these injuries and will eliminate a large number
of screwworm infestations.






Screwworms in Florida


Fig. 23.-Tipping or nubbing the horns of cattle will prevent many in-
juries which afford screwworm flies access to the flesh.


Fig. 24.-This horn knocked off due to rough handling let screwworms
get into the head, a very difficult place to treat.






Florida Cooperative Extension


SUMMARY
Good herd management will not only give an early calf crop
that will meet the market demand, but will also prevent serious
loss from screwworm infestation. Good herd management in-
cludes controlled breeding and proper utilization of climate and
natural growth of native grasses; having the calves dropped
to come along with the grass; eliminating non-breeders and shy-


Fig. 25.-The high cost of using catch dogs. Eight distinct screwworm
infestations on this hog are due to dog bites.

breeders; separating the breeding herd from the steers; feed-
ing bulls during winter and having them in good condition in
spring; castrating bull calves when they are young by the blood-
less operation; nubbing the sharp points of horns; marking
and branding during the winter season and using pine-tar oil
on these parts; using common sense in handling and driving
cattle; eliminating the use of the whip and catch-dogs; avoiding
the jamming of cattle into pens and chutes; arranging chutes
and pens so there will be no obstructions for wounds; eliminat-
ing unnecessary wounds and bruises of all kinds.
In addition, it has been found profitable in the handling of
livestock in screwworm control work, first, to examine livestock
frequently for wounds and injuries; second, treat all cases of






Screwworms in Florida


screwworm infestation promptly; third, provide chutes for treat-
ing animals and pens for holding infested animals; fourth, in
treating the animals, avoid making the wounds bleed; fifth, cas-
trate, mark, brand, and dehorn during the winter months; sixth,
use bloodless emasculators for castrating young cattle, sheep,
and goats; seventh, treat all wounds with pine-tar oil as a re-
pellent; eighth, during the summer inspect the ears of cattle,
sheep, and goats for Gulf Coast tick; and ninth, control breed-
ing so calves will be dropped in the early spring. Get an early
calf crop, avoid screwworm infestation, for profit!

LIST OF LITERATURE

1. BLACK, W. H., and V. V. PARR. Feed-lot and ranch equipment for
beef cattle. U. S. D. A. Farmers' Bulletin 1584. 1935.

2. CUSHING, E. C., and W. S. PATTON. Studies on the Higher Diptera of
medical and veterinary importance. Cochliomyia americana, sp. nov.,
the screw worm fly of the New World. Ann. Trop. Med. and Parasitol,
27: 539-551. 1933.

3. DOVE, W. E. Screw worm control. U. S. D. A. Bur. Ento. E-356. Aug.
1, 1935.

4. DOVE, W. E., and D. C. PARMAN. Screw worms in the Southeastern
states. Journ. Econ. Ento. 28: 5. October 1935.

5. KING, W. F., and G. H. BRADLEY. The screw worm outbreak in Florida.
Journ. Econ. Ento. 28: 5. October 1935.

6. LAAKE, E. W., E. C. CUSHING, and H. E. PARISH. Biology of the pri-
mary screw worm fly, Cochliomyia americana, and a comparison of its
states with those of C. macellaria. U. S. D. A. Tech. Bul. 500. Jan-
uary 1936.

7. SHEALY, A. L. Beef production in Florida. Fla. Agr. Exp. Sta. Bul.
260. 1933.

8. SHEALY, A. L., and W. J. SHEELY. Swine production in Florida. Fla.
Agr. Exp. Sta. Bul. 236. 1931.




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