Circular No. 148 



November 1930 . Washington, D. C. 



Revised July 1948 



UNITED STATES DEPARTMENT OF AGRICULTURE 



Parasites and Parasitic Diseases of Horses 



By Benjamin Schwartz, Chief, Zoological Division, Marion Imes, formerly 

 Veterinarian, and A. O. Foster, Parasitologist, Zoological Division, Bureau of 

 Animal Industry 



CONTENTS 



Page 



Internal parasites of horses 1 



Abundance and location 1 



Symptoms and damage pro- 

 duced by parasites 2 



General control measures 2 



Medicinal treatment 3 



Protozoa 4 



Worm parasites 4 



Bots 32 



Page 

 Internal parasites of horses — Con. 



Disposal of manure 34 



Summary of control measures, 36 



External parasites of horses 37 



Horse lice 37 



Horse mange 42 



Ticks 48 



Treating horses for external 



parasites 52 



**^>***>* +A*+ > m**+ * 



INTERNAL PARASITES OF HORSES 2 

 Abundance and Location 



THE TERM PARASITE as used in this circular refers to forms 

 of animal life which, lor the purpose of obtaining food and shelter, 

 live on or in the bodies of other animals which are larger than the para- 

 sites and are known as hosts. All classes of domesticated animals 

 harbor numerous kinds of parasites, and horses, in particular, are 

 liable to infestation not only with many different kinds but also with 

 very large numbers of injurious species. A horse's stomach may con- 

 tain hundreds of bots, and the small intestine may be packed with 

 large roundworms. The large intestine of the horse is a location 

 especially preferred by parasites, and very often the colon and cecum 

 are found to be teeming with hundreds or thousands of wriggling, 

 parasitic worms, some free in the lumen and others attached to the 

 walls of the gut. Several kinds of worm parasites present in the gut 

 and elsewhere have previously wandered through various parts of the 



1 This circular supersedes Farmers' Bulletin No. 1493, Lice, Mange, and Ticks 

 of Horses. 



2 By Benjamin Schwartz and A. O. Foster. Dr. Foster has revised most of the 

 section originally prepared by Dr. Willard H. Wright. Many of the illustrations 

 in this section of the circular were drawn by Joseph E. Alicata, former^ junior 

 zoologist. 



