PARASITES AND PARASITIC DISEASES OF HORSES 31 
winged flies, ready to mate and to begin the process of egg laying 
once more. 
Symptoms and lesions —Bots often occur in large numbers, and it 
is not unusual to find several hundred of these maggots attached to 
the stomach wall of a horse. These parasites have large mouth 
hooks by means of which they attach themselves to the lining of the 
stomach and upper intestine. They also bear spines on much ‘of their 
body surface. With this armature they are capable of irritating the 
lining of the digestive tract with which they are in contact and of 
producing considerable irritation and injury. The attachment of 
nose bots to the rectum and edge of the anus before they pass out is 
very annoying and horses have been known to dislocate bones in the 
tail in their attempts to obtain relief from this annoyance. 
The damage caused by the adult flies, especially the nose fly, is 
very great. ‘Runaways may lead to serious accidents and farming is 
often “interrupted by the inability to work the frightened horses. 
Treatment—Carbon disulphide is the most effective treatment for 
the removal of bots. Carbon tetrachloride may also be used but is 
much less effective. Both of these drugs should be used in accord- 
ance with the recommendations given under the treatment for large 
intestinal roundworms. In cases in which carbon disulphide is con- 
traindicated, tetrachlorethylene may be used. 
Tetrachlorethylene frequently will remove from 50 to 75 per cent 
of the bots when the drug is used in single doses of 1 to 2.3 fluid 
ounces (30 to 70 cubic centimeters) for a 1,000-pound animal after 
fasting the horse 18 hours. The drug should not be accompanied by 
a purgative. Cases of dizziness have been reported occasionally in 
horses dosed with tetrachlorethylene, but this dizziness soon passes off. 
Nose bots which have reached the rectum or anus are not amenable 
to these treatments. Treatment should be administered in the winter 
after the adult flies are killed by frost and all the bots are present in 
the stomach or upper part of the small intestine. One month before 
the internal medication an application of one of the coal-tar creosote 
dips in about 2 per cent dilution to the parts of the animal bearing 
the bot eggs is advised so as to destroy the eggs and thus avoid 
subsequent “infestation. 
Prevention.—Preventive measures against infestation with bots 
include the use of various protective mechanical devices to prevent 
the flies from depositing their eggs on horses, shaving the hair where 
the eggs have been deposited, and the destruction of the eggs by 
certain medicinal applications to the skin. 
DISPOSAL OF MANURE 
inasmuch as manure is the source from which horses acquire nearly 
all their common parasites, either directly or indirectly, the proper 
disposal of manure from stables and yards is an essential part of 
sound management. Indiscriminate spreading of fresh horse ma- 
nure on horse pastures to supply fertilizer is an unwise and unsafe 
procedure because it disseminates infective eggs and larve of para- 
sites which have developed in stables and yards. Owners of 
Thoroughbred horse farms who have learned of the danger to horses 
as a result of spreading fresh manure on pastures have discontinued 
this practice and are discarding manure as fertilizer altogether. 
