• 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. 123
Title: Screwworms in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026357/00001
 Material Information
Title: Screwworms in Florida
Series Title: Bulletin
Physical Description: 28 p. : ill. ; 23 cm.
Language: English
Creator: Bruce, W. G ( Wesley Gordon ), b. 1892
Sheely, W. J
Publisher: Cooperative extension work in agriculture and home economics
Place of Publication: Gainesville Fla
Publication Date: <1944>
 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. 28).
Statement of Responsibility: by W.G. Bruce and W.J. Sheely.
General Note: "January, 1944."
General Note: "A revision of Bulletin 86."
General Note: <Revision of no. 86 Oct., 1936>
Funding: Bulletin (University of Florida. Agricultural Extension Division)
 Record Information
Bibliographic ID: UF00026357
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 002571173
oclc - 44716559
notis - AMT7488

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 3
    Life history
        Page 4
        Page 5
    How to recognize infestations
        Page 6
        Plate I
        Plate II
    Effect on animals
        Page 7
    Treatment
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Treatment of difficult cases
        Page 12
        Page 13
        Page 14
        Page 15
    Prevention
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Plate III
        Plate IV
        Page 23
        Page 24
        Page 25
        Page 26
    Summary
        Page 27
    List of literature
        Page 28
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







Bulletin 123


January, 1944


(A Revision of Bulletin 86)

COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
AGRICULTURAL EXTENSION SERVICE, UNIVERSITY OF FLORIDA
FLORIDA STATE COLLEGE FOR WOMEN
AND UNITED STATES DEPARTMENT OF AGRICULTURE jl
COOPERATING
A. P. SPENCER, Director



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
Animal Husbandman, Florida Agricultural Extension Service


F t !lS. 74


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.

Single copies free to Florida residents upon application to
AGRICULTURAL EXTENSION SERVICE
GAINESVILLE, FLORIDA









BOARD OF CONTROL
H. P. ADAIR, Chairman. Jacksonville N. B. JORDAN, Quincy
THOSE. W. BRYANT, Lakeland T. T. SCOTT, Live Oak
R. H. GORE, Fort Lauderdale J. T. DIAMOND, Secretary, Tallahassee

STAFF, AGRICULTURAL EXTENSION SERVICE
JOHN J. TIGERT, M.A., LL.D., President of the University
H. HAROLD HUME, D.Sc., Provost for Agriculture
A. P. SPENCER, M.S., Director of Extension
J. FRANCIS COOPER, M.S.A., Editor'
CLYDE BEALE, A.B.J., Assistant Editor'
JEFFERSON THOMAS, Assistant Editor'
FRANK M. DENNIS, B.S.A., Supervisor, Egg-Laying Test
RUBY NEWHALL, Administrative Manager'
Agricultural Demonstration Work, Gainesville
W. T. NETTLES. B.S., District Agent
J. LEE SMITH, District Agent and Agronomist
E. F. DEBUSK, B.S., State Supervisor, Emergency Farm Labor
H. S. MOLENDON, B.A., Asst. State Supervisor, Emergency Farm Labor
P. H. SENN, Ph.D., Assistant VFV Leader
MRS. BONNIE J. CARTER, B.S., Assist. WLA Leader
HANS O. ANDERSEN, B.S.A., Asst. State Supervisor, EFL
H. G. CLAYTON, M.S.A., Coordinator with AAA
R. S. DENNIS, B.S.A., Assistant Coordinator with AAA
R. W. BLACKLOCK, A.B., Boys' Club Agent
W. W. BASSETT, JR., B.S.A., Assistant Boys' Club Agent2
A. L. SHEALY, D.V.M., Animal Industrialist'
HAMLIN L. BROWN, B.S., Dairyman
WALTER J. SHEELY, B.S., Animal Husbandman
N. R. MEHRHOF, M.AGR., Poultryman'
D. F. SOWELL, M.S.A., Poultryman'
A. W. O'STEEN, B.S.A., Assistant Poultryman
L. T. NIELAND, Farm Forester
C. V. NOBLE, PH.D., Agricultural Economist'
CHARLES M. HAMPSON, M.S., Agricultural Economist, Farm Management
R. H. HOWARD, M.S.A., Asst. State Supervisor, EFL
D. E. TIMMONS, M.S.A., Economist in Marketing
ZACH SAVAGE, M.S., Economist
JOSEPH C. BEDSOLE, B.S.A., Assistant in Land-Use Planning2
R. V. ALLISON, PH.D., Soil Conservationist'
K. S. MCMULLEN, B.S.A., Soil Conservationist
Home Demonstration Work, Tallahassee
MARY E. KEOWN, M.S., State Agent
RUBY MCDAVID, District Agent
ETHYL HOLLOWAY, B.S., District Agent
MRS. EDITH Y. BARRUS, District Agent
ANNA MAE SIKES, M.S., Specialist in Nutrition
VIRGINIA P. MOORE, Home Improvement Agent
ISABELLE S. THURSBY, Specialist in Food Conservation

Negro Extension Work, Tallahassee
A. A. TURNER, Local District Agent
FLOY BRITT, B.S.H.E., Local District Agent

1Part-time.
SOn leave.










SCREWWORMS IN FLORIDA
By W. G. BRUCE and W. J. SHEELY

CONTENTS
Page Page
History .................. ...... .............. 3 Treatment of Difficult Cases ..... ............. 12
Method of Attack ........... .. ....... 3 Prevention ............... .... ... .... .. 16
Life History .................................. ..... 4 Good Management Pays Two Ways...... 16
How to Recognize Infestations .............. 6 Suggested Preventive Measures ........ 19
Effect on Animals .... .............................. 7 Summary ........... .... .. 27
Treatm ent ....................... .. ............ 7 List of Literature ................ ... ......... 28

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 in Florida may be possible but
would be difficult. It is reasonable to expect that screwworms
will continue to be an important problem in every livestock
enterprise; 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 summer, they have spread to adjoining
states. 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. With the coming of warm
weather in the spring of 1934 screwworms spread to some 35
additional counties. Heavy losses of livestock from screwworm
attack were reported by hundreds of stockmen. During 1935
screwworms were found in every Florida county except Monroe.
They are not very active during winter in northern counties,
but continue active throughout the year in southern counties.

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

*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 ..... ............. 12
Method of Attack ........... .. ....... 3 Prevention ............... .... ... .... .. 16
Life History .................................. ..... 4 Good Management Pays Two Ways...... 16
How to Recognize Infestations .............. 6 Suggested Preventive Measures ........ 19
Effect on Animals .... .............................. 7 Summary ........... .... .. 27
Treatm ent ....................... .. ............ 7 List of Literature ................ ... ......... 28

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 in Florida may be possible but
would be difficult. It is reasonable to expect that screwworms
will continue to be an important problem in every livestock
enterprise; 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 summer, they have spread to adjoining
states. 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. With the coming of warm
weather in the spring of 1934 screwworms spread to some 35
additional counties. Heavy losses of livestock from screwworm
attack were reported by hundreds of stockmen. During 1935
screwworms were found in every Florida county except Monroe.
They are not very active during winter in northern counties,
but continue active throughout the year in southern counties.

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

*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 ..... ............. 12
Method of Attack ........... .. ....... 3 Prevention ............... .... ... .... .. 16
Life History .................................. ..... 4 Good Management Pays Two Ways...... 16
How to Recognize Infestations .............. 6 Suggested Preventive Measures ........ 19
Effect on Animals .... .............................. 7 Summary ........... .... .. 27
Treatm ent ....................... .. ............ 7 List of Literature ................ ... ......... 28

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 in Florida may be possible but
would be difficult. It is reasonable to expect that screwworms
will continue to be an important problem in every livestock
enterprise; 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 summer, they have spread to adjoining
states. 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. With the coming of warm
weather in the spring of 1934 screwworms spread to some 35
additional counties. Heavy losses of livestock from screwworm
attack were reported by hundreds of stockmen. During 1935
screwworms were found in every Florida county except Monroe.
They are not very active during winter in northern counties,
but continue active throughout the year in southern counties.

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

*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 ..... ............. 12
Method of Attack ........... .. ....... 3 Prevention ............... .... ... .... .. 16
Life History .................................. ..... 4 Good Management Pays Two Ways...... 16
How to Recognize Infestations .............. 6 Suggested Preventive Measures ........ 19
Effect on Animals .... .............................. 7 Summary ........... .... .. 27
Treatm ent ....................... .. ............ 7 List of Literature ................ ... ......... 28

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 in Florida may be possible but
would be difficult. It is reasonable to expect that screwworms
will continue to be an important problem in every livestock
enterprise; 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 summer, they have spread to adjoining
states. 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. With the coming of warm
weather in the spring of 1934 screwworms spread to some 35
additional counties. Heavy losses of livestock from screwworm
attack were reported by hundreds of stockmen. During 1935
screwworms were found in every Florida county except Monroe.
They are not very active during winter in northern counties,
but continue active throughout the year in southern counties.

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

*Cochliomyia americana C. and P.






Florida Cooperative Extension


(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 decay-
ing 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.
An intensive educational and control program, sponsored by
the Florida Agricultural Extension Service and the Bureau of
Entomology and Plant Quarantine, was in progress from 1935
to 1937 and resulted in effective screwworm control in Florida.
In 1943 a careful survey showed that screwworms are again
serious pests in every county in Florida.
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 age 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.

LIFE HISTORY
The female screwworm fly lays her eggs in shingled batches
on the edges of wounds of warm-blooded animals. She may
deposit 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






Screwworms in Florida


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 emerges.
During cool weather the pupal 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,
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,
especially during cool weather.






Florida Cooperative Extension


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
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.














































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


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.

TREATMENT
SMEAR NO. 62-A NEW REMEDY FOR SCREWWORMS
The USDA Bureau of Entomology and Plant Quarantine has
developed a new remedy which is efficient in rapidly killing all
screwworms in a wound and gives protection against infestation






Screwworms in Florida


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.

TREATMENT
SMEAR NO. 62-A NEW REMEDY FOR SCREWWORMS
The USDA Bureau of Entomology and Plant Quarantine has
developed a new remedy which is efficient in rapidly killing all
screwworms in a wound and gives protection against infestation






Florida Cooperative Extension


as good as, or better than, remedies previously recommended
for this purpose. It replaces both benzol and pine-tar oil.
The new remedy is known as Smear No. 62 and is composed
of the following ingredients.
Diphenylamine (technical grade).............. 3% parts by weight
Benzol (commercial) ................................. 31/ parts by weight
Turkey red oil (pH-10 or neutral)........ 1 part by weight
Lamp black .........----........................ ..... 2 parts by weight

The diphenylamine is dissolved in the benzol, preferably by
placing the 2 substances together and allowing them to stand
12 or 24 hours. In no event should the dissolving of the diphenyl-
amine in benzol be attempted by heating over an open flame.
Benzol is highly inflammable and should be kept away from
flames and lighted cigarettes or cigars. If heat is used to
hasten solution, the container holding the benzol and diphenyl-
amine may be placed in a vessel of hot water, the benzol con-
tainer being left uncorked until the dipheylamine is dissolved.
After the diphenylamine is dissolved the turkey red oil is
added and the mixture thoroughly shaken. The lamp black is
then stirred in gradually and the mixing continued until the
compound attains a smooth, even texture of about the con-
sistency of molasses. It is then ready for use. Smear No. 62
should be kept tightly covered and in a cool place.
Smear No. 62 is best applied to wounds with a small paint
brush. The smear should be brushed into the wound, especially
into all pockets made by screwworms, and brushed around the
wound, particularly where blood and pus have soiled the hair.
It is advisable to make a second application of the smear a day
or 2 after the first treatment and twice a week thereafter until
the wound is healed. This remedy kills screwworms quickly
and large numbers of worms drop out of the wound carrying
some of the material with them. Hence, it is a good practice
to apply a second treatment. For the protection of the unin-
fested wounds such as those caused by castrations, shear cuts,
dehorning and docking, it is sufficient to cover thoroughly the
raw flesh and surrounding area with the smear. Animals with
large open wounds should be kept in a hospital pasture until
all wounds are healed.
Smear No. 62 is also efficient in killing fleece worms, or wool
maggots, in sheep, and gives considerable protection against re-
infestation.






Screwworms in Florida


Smear No. 62 can be secured on the market under various
trade names.
BENZOL AND PINE-TAR OIL
Benzol and pine tar are still considered excellent materials for
the treatment of screwworm infestations in livestock and should
be used in the absence of Smear No. 62.
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 stupefied; for several minutes, they are killed. When
properly used benzol kills screwworms effectively without injury
to the healing 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).
Sometimes it is desirable to trim the hair or wool around


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.






Florida Cooperative Extension


the wound. Clean the wound by using cotton to remove pus
and blood. Apply a small amount of benzol, preferably by the
use of a small rubber bulb syringe or oil can. Benzol tends to
stop the flow of blood and pus and loosen accumulated 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 with benzol and pine-tar
oil 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
large end (rear) uppermost. The breathing apparatus (spir-
acles) is located on the rear end. Clean the wound thoroughly
so these spiracles are exposed to the benzol fumes.
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







Screwwzorms in Florida


-F-




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


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


L0 i &a







Florida Cooperative Extension


have dropped from the wound. Make a light application of
pine-tar oil in and around the wound 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.
The wound should again be treated with benzol, the cotton






Screwworms in Florida


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.




















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

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







Florida Cooperative Extension


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.






Screw worms in Florida


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
5 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
th e screwworm
flies.
Cases in Ears:
Lon g neglected
screwworm infes-
tations in the
ears of livestock,
especially follow-
ing ear marking
(Fig. 11), often
a r e difficult to
treat and slow to
heal. The worms
eat the tissues -
between the two M x .
layers of skin of
Fig. 11.-This ear became badly infested with
the ear and leave screwworms following marking, and was difficult to
a ragged wound. treat. (Note tipped horn.)
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.
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-
tion (Fig. 12). Examination of the mouths of the mothers
of such calves frequently discloses screwworms in their gums.
Do not use benzol or pine-tar oil in the mouths of livestock.






Florida Cooperative Extension


Simply remove the screwworms with blunt forceps and destroy
them.


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

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






Screwworms in Florida


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.







Florida Cooperative Extension


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

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-
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


During the late spring and early summer of 1935 and 1936,
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 Smear 62 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 Smear 62 around it. In
this connection, a light application of Smear 62 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. The 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.






Screwworms in Florida


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.






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
Smear 62. Dehorned animals should be examined daily and the
wounds treated with Smear 62 until the cavities are closed.


Fig. 16.-First step in using the bloodless emasculator -force the cord
to one side.
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. 17.-Second step in using bloodless emasculator -apply emasculator
to one side at a time, being careful not to overlap the center.


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

















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


Fig. 19.-Screwworm infestation following castration by use of the knife
without application of Smear 62.


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.






Florida Cooperative Extension


All castration wounds following the use of the knife should
be mopped with Smear 62 (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
Smear 62 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
applying Smear 62 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 Smear 62
at two-week intervals will kill the ticks attached to the ear
and will act as a repellent to ticks for about two weeks (Fig. 22).
This Smear 62 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






Screwworms in Florida


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-
per and results
in the railroad
company's hav-
ing to pay out
large sums of
money in
claims. Rough
handling of
cattle (as good,
experie n c ed
cattlemen will
tell you) causes
loss in weight
from unneces-
sary excite-
ment and
causes cripples
and wounds
(Fig. 24) by
cattle running
over each other
and jamming


/1


Fig. 22.-Mopping the ears of cattle with pine-tar
oil helps to control the Gulf Coast tick.


into the fences and through the gates. Rough handling by
the use of catchdogs 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.







Florida Cooperative Extension


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


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






Screwworms in Florida


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 Smear 62
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







Florida Cooperative Extension


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 Smear 62 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. USDA Farmers' Bulletin 1584. 1935.
2. GUSHING, 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. GUSHING and H. E. PARRISH. Biology of the pri-
mary screw worm fly, Cochliomyia americana, and a comparison of its
stages with those of C. macellaria. USDA Tech. Bul. 500. January,
1936.
7. MELVIN, ROY, C. L. SMITH, H. E. PARRISH and W. L. BARRETT, JR. A
New Remedy for the Prevention and Treatment of Screwworm Infesta-
tions of Livestock. USDA Bureau of Entomology and Plant Quarantine,
E-540. May, 1941.
8. SHEALY, A. L. Beef production in Florida. Fla. Agr. Exp. Sta. Bul.
260. 1933.
9. SHEALY, A. L., and W. J. SHEELY. Swine production in Florida. Fla.
Agr. Exp. Sta. Bul. 236. 1931.




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