flammation, which interferes with 
digestion. 
Bots attached to the lower part of 
the stomach interfere with the pas- 
sage of food. Infested animals often 
suffer from colic or other gastric 
disturbances. 
The degree of damage done by the 
feeding of the larvae is roughly in 
proportion to the number present. 
Several hundred larvae may be 
found in one animal; more than 
1,000 have been found in the 
stomach of a colt. 
CONTROL 
Internal Treatment 
Two insecticides are available for 
the control of horse bots. Trichlor- 
fon may be administered by horse 
owners or veterinarians. The other 
insecticide, carbon disulfide, has 
been in use for many years. Al- 
though very effective, carbon 
disulfide is considered hazard- 
ous and should be administered 
only by veterinarians. Instruc- 
tions on the use of these materials 
are given below. 
Trichlorfon.—This insecticide 
may be administered in feed, in a 
gelatin capsule, as a drench, or by 
stomach tube. The rate of adminis- 
tration should not exceed 1.8 grams 
per 100 pounds of body weight or 
approximately 40 milligrams per 
kilogram. Thoroughbreds and other 
sensitive horses should be given 1.2 
grams per 100 pounds or 25 milli- 
grams per kilogram. A close ap- 
proximation of each animal’s weight 
should be made. The required dose 
may be calculated and packaged 
separately before administration. 
6 
The easiest way to give trichlor- 
fon is in feed. The required dosage 
may be used dry or dissolved in 
one to two cups of water and mixed 
thoroughly with a normal feed 
ration. Animals should not be fed 
for 12 to 18 hours before treatment 
so that they will be hungry enough 
to completely consume the treated 
ration. No other feed should be pro- 
vided until the treated ration has 
been consumed. Some horses not ac- 
customed to eating oats or commer- 
cial feeds, may refuse trichlorfon- 
treated feed. They must be given the 
chemical in a capsule or as a drench. 
A drench can be prepared by dis- 
solving the proper dosage of trich- 
lorfon in 4 to 1 pint of warm water. 
This solution may be given orally 
or by stomach. tube. 
Trichlorfon may be given in a 
gelatin capsule. The required dosage 
should be placed in the capsule and 
administered with a balling gun. 
Some horses may show signs of 
colic for a short time after receiv- 
ing treatment. If the colic is severe, 
a veterinarian should administer 
atropine sulfate. 
Trichlorfon treatments should 
not be given for at least 1 and pref- 
erably 2 months after the first kill- 
ing frost. The best time for treat- | 
ment varies with location but is 
ordinarily from November through 
Jan-ary, a period when all species 
of bots are concentrated in the 
stomach and intestines. Trichlorfon 
will kill the bots and they will pass 
out in the manure. One treatment 
a year is sufficient to control horse 
bots. 
Do not treat sick or debilitated 
horses, colts under 4 months of age, 
