58 



THE HEMOFLAGELLATES 



cause a mild disease, but in West Africa 

 they are usually fatal in some types of 

 cattle. Virulent strains may also occur 

 in East Africa. Unsworth (1953) found 

 that T. L'ivax is highly pathogenic for zebu 

 cattle in laboratory infections, and that 

 when these cattle were exposed to infec- 

 tion under natural conditions in Nigeria, 

 all of them died. 



Camels are less seriously affected 

 than cattle. T. vivax is apparently more 

 pathogenic for sheep than other trypano- 

 somes, and may be found in the central 

 nervous system. It is apparently less 

 pathogenic for goats. It causes a chronic 

 disease, often with spontaneous recovery, 

 in horses. It is not pathogenic for dogs, 

 pigs and monkeys, and only slightly so for 

 the common laboratory rodents. 



The signs of disease are similar to 

 those caused by T. coiigolense. There is 

 a wide variation in virulence between dif- 

 ferent strains, but the virulence of any 

 particular strain tends to remain constant. 



Diagnosis : T. vivax is detected most 

 readily in lymph node smears. Large 

 numbers are found in the blood only in 

 early infections. Inoculation of laboratory 

 animals is not particularly satisfactory; 

 inoculation of sheep or goats is better, 

 the trypanosomes appearing in 7 to 10 days. 



being smaller. It is 12 to 20 ji long, with 

 an average of about 16/j.. It occurs in 

 cattle, sheep, goats and antelopes, causing 

 a disease similar to that caused by T. vivax 

 (Wilson, 1949). Laboratory rodents are 

 refractory to infection. T. uniforme 

 occurs only in Uganda and the Belgian Congo. 

 It is transmitted by tsetse flies in the same 

 way as T. vivax. 



TRYPANOSOMA CRUZI 

 CHAGAS, 1909 



Synonyms : Schizotrypanum cruzi. 



Disease : American human trypano- 

 somosis, Chagas' disease. 



Hosts : Many species of wild and do- 

 mestic animals have been found naturally 

 infected with Trypanosoma cruzi, and 

 probably most mammals are susceptible. 

 Man is also susceptible, infants and young 

 children being most often affected. The 

 most important wild reservoir hosts are 

 probably armadillos (Dasypus) in South 

 America, opossums (Didelphis) in South 

 and Central America and the United States, 

 and woodrats {Neotoma) and possibly rac- 

 coons (Procyo)i) in the United States. The 

 dog, cat and possibly the pig are consid- 

 ered of some importance as reservoirs of 

 infection for man in South America. 



Cultivation : Same as for other try- 

 panosomes. 



Treatment : T. vivax can be success- 

 fully treated with the same drugs and in 

 the same dosages as T. congolense. It is 

 perhaps slightly more resistant, but not 

 significantly so. 



Control : Control measures are the 

 same as those for T. coiigolense infections. 

 In areas where tabanids are the vectors, 

 measures directed against these flies 

 should be practiced. 



TR YPANOSOMA UNIFORME 

 BRUCE et al. , 1911 



This species is similar to T. vivax, 

 differing from it morphologically only in 



Location : The trypanosomes are 

 found in the blood early in an infection. 

 Later, they invade the cells of the reticulo- 

 endothelial system, heart and striated 

 muscles and other tissues. In central nerv- 

 ous system infections, they are found in 

 the neuroglial cells. Trypanosome forms 

 occur in the blood, and leishmanial forms 

 within the cells. 



Geographic Distribution : T. cruzi 

 occurs in South America from Argentina 

 north, in Central America and in southern 

 United States. Dias (1953) published maps 

 of the distribution of Chagas' disease in 

 South and Central America together with 

 climatologic and other information. 



In the United States, T. cruzi had been 

 thought until recently to be confined to the 

 southwestern states, including Texas, 



