PARASITES AXD PARASITIC DISEASES OF HORSES . 31 



manure, the nose bot reattaches itself to the rectum on its way out, 

 then becomes detached and reattaches itself to the anus, where it 

 may remain for three or four da}-s, and finally drops to the ground. 

 Usually all fully developed bots pass out of the body by October and 

 those which overwinter in the horse are the young forms. These 

 bots pupate in the ground and finally emerge as 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 ma} 7 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. 



Tetrachlorethylene frequently will remove from 50 to 75 per cent 

 of the bots in a single dose. This drug may be given in a dose of 6 

 to 12 fluid drams (25 to 50 cubic centimeters), for a 1.000-pound ani- 

 mal, after fasting the horse 18 hours. The drug need not be accom- 

 panied with a purgative. Cases of dizziness have been reported occa- 

 sionally in horses dosed with tetrachlorethylene, but this symptom 

 soon passes off. 



Nose bots which have reached the rectum or anus are not amenable 

 to these treatments. Treatment should be administered late in the 

 fall after the adult flies are killed by frost and all the bots are 

 present in the stomach or upper part of the small intestine. Simul- 

 taneously with 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 cer- 

 tain medicinal applications to the skin. 



DISPOSAL OF MANURE 



Inasmuch as manure is the source from winch 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 manure 

 on horse pastures to .supply fertilizer is an unwise and unsafe 



