8 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 



horses that conclusions can be drawn, and these may be erroneous if 

 one is not familiar with the various species, their usual points of at- 

 tachment, and phenomena peculiar to each. 



SPECIES IMPLICATED. 



Gastrophilis intestinalis, "the common bot," attaches ordinarily 

 in the stomach, has been taken in the duodenum, but has never been 

 found permanently attached in any other regions (Table I, p. 10). 

 Rarely it may become temporarily attached in the rectum, but is not 

 present with an alveolus or lesion. 



G. nasalis, "the throat bot," attaches by preference in the duo- 

 denum, is often found in the stomach, and is the only known species 

 which attaches in the pharynx. Due to the attachment in the throat, 

 it not only becomes a species of vital importance when the bots 

 congregate in sufficient numbers to hinder or cut off the breathing of 

 the horse or cause an infection, but in this location they can not be 

 removed by an internal treatment. In the duodenum the infestation 

 may be sufficient to hinder or stop the passing of excreta. Table I (p. 

 10) shows the comparative abundance in the stomach and duodenum 

 during the period that larva3 are well developed and naturally drop 

 from the host. 



Various cases are on record in which this species has been removed 

 from the pharynx, in all of which the authors considered it a serious 

 detriment to the horse. While larvae which were not sufficiently de- 

 veloped to be determined with authenticity have frequently been 

 removed from the pharynx, 8 larvae of G. nasalis were collected in 

 the throat of a dray horse by J. L. Webb at Reno, Nev., on August 

 29, 1916. In numerous cases, both at Aberdeen, S. Dak., and at Dal- 

 las, Tex., the author has found lesions present in the pharynx, indi- 

 cating that the larvae had become fully developed and had passed out 

 of the horse. In making post-mortem examination of horses to de- 

 termine the attachment of young larvae in the pharynx extreme 

 care should be exercised, as young meat-infesting larvae may be con- 

 fused with Gastrophilus. Upon hatching they migrate from the 

 light into the nostrils and may be found in the pharynx and other 

 locations in the throat. 



Dr. Buffington (1905), of Brooklyn, Iowa, gives a valuable history 

 of a case in which a mare died as the result of an infestation of 

 G. nasalis in the pharynx. This animal had experienced difficulty 

 in eating for more than a month, and was unable to take food for a 

 week prior to November 26, 1903. At this time she would drink 

 water, but after masticating food a very little, would drop it out. 

 The symptoms were those of paralysis of the muscles of deglutition 

 and there was a very offensive odor about the head. Four days later, 

 when the animal died, the nasal, pharyngeal, laryngeal, and upper 

 portion of the oesophageal mucous membranes were found to be gan- 



