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 larvae 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. 



