PROTOZOA CAUSING DISEASE 411 



with a small amount of blood containing the trypanosomes 

 to be cultivated. They multiply in this water of condensa- 

 tion in some cases quite abundantly. 



Disease Produced. — The only disease occurring in the 

 United States caused by a trypanosome is the dourine of the 

 horse, sometimes termed Jiorse sypMlis. The disease is also 

 known from various parts of western and southern Europe 

 and northern Africa. It has been introduced at various 

 times with imported animals and cases have been known 

 from several of the states in the Mississippi Valley and in 

 Canada. Animals which are infected gradually become 

 emaciated and swellings appear upon the genitals and 

 whitish chalklike areas (plaques) develop in the skin and 

 mucosa of the external genitalia. The disease is usually 

 chronic in form and recovery does not frequently occur. 

 The disease is probably transmitted by the stallion. It is 

 claimed by some authors that the disease can also be trans- 

 mitted by means of the stable fly but this probably does not 

 occur frequently. 



Disease produced by trypanosomes (so-called trypanoso- 

 miases) are of great importance in tropical countries and 

 in the southern hemisphere. There are large areas in 

 Africa, for example, where it is quite impossible to keep 

 horses because of the presence of the so-called nagana or 

 tsetse fly disease. The organism is found among certain of 

 the wild animals and is inoculated into the horse by the 

 bite of the tsetse, a fly somewhat resembling a horsefly. 

 In South America a disease known as mal de caderas or 

 rump evil of the horse is known. In this disease there is 

 progressive emaciation of the horse, the hind quarters 

 become weak, the horse when walking will scarcely raise 

 the hoofs off the ground. The method of transmission is not 

 certainly known. Another trypanosome causes the 6am- 

 bian horse sickness in Africa, another the so-called baleri 

 of horses, cattle, sheep and goats in the French Congo. 



