THE HEMOFLAGELLATES 



61 



young pigs, lambs, kids and calves with 

 a strain isolated from a raccoon in Mary- 

 land. The infections persisted at least 

 57 days in the pigs, 53 to 85 days in the 

 lambs, 38 days in a kid and 21 days in a 

 calf. 



Infection is common in the triatomid 

 vectors of Chagas' disease. In the endemic 

 regions of South and Central America, 40 

 to 60% of them are infected, while 20 to 

 25% are infected in Mexico and southwest- 

 ern United States. The triatomids infest 

 armadillo burrows and woodrat nests, and 

 thus maintain the infection in these animals. 

 They also infest houses, where they live 

 like bedbugs; it is these triatomids which 

 are responsible for the vast majority of 

 human infections. 



Because triatomids are rare in south- 

 eastern U. S. where T. criizi is common 

 in the opossums, and because they iso- 

 lated the organism from the urine of in- 

 fected opossums, McKeever, Gorman and 

 Norman (1958) believed that infections may 

 be passed from mammal to mammal by 

 contact with infected urine. 



For further information on the epide- 

 miology of T. cruzi infections see Dias 

 (1951, 1951a, 1951b, 1952, 1952a, 1952b), 

 Dias and Chandler (1951), Dias and Laranja 

 (1948), Dias, Laranja and Nobrega (1946) 

 and other papers by these authors. For 

 information on the epidemiology of T. 

 cruzi in southwestern United States, see 

 Elkins (1951) and particularly Wood (1950, 

 1953a, 1958), and Mehringer and Wood 

 (1958). 



Pathogenesis : Chagas' disease may 

 be either acute or chronic in man. The 

 great majority of acute cases occur in 

 infants and young children. The first sign 

 of disease is often swelling of the eyes and 

 conjunctiva. This swelling may affect 

 either one or both sides of the face. The 

 tear glands become inflamed, and the 

 cervical lymph nodes swell. Later on, 

 swellings may appear in other parts of the 

 body. Each swelling, known as a chagoma, 

 is due to an inflammatory exudate in the 

 region where the parasites are invading 

 the tissue cells. In addition to this edema, 



there may be anemia, more or less con- 

 tinuous fever, prostration and severe 

 headache. 



If the patient survives the acute phase, 

 the disease becomes more or less chronic. 

 Some authorities believe that it persists 

 for life. The lymph nodes are edematous 

 and inflamed, and the liver and spleen are 

 enlarged. The heart is affected in many 

 cases. Electrocardiographic abnormal- 

 ities are common. Inflammatory infiltra- 

 tion by phagocytes, fibrosis, separation of 

 the muscle cells and partial destruction of 

 the fibers by the multiplying parasites are 

 present. The death rate due to cardiac 

 conditions is increased in endemic areas. 



T. cruzi may cause an acute or chronic 

 disease in laboratory animals, depending 

 on the strain of the parasite and the age of 

 the host. Puppies and kittens are most 

 susceptible, followed in order by mice and 

 guinea pigs. The reservoir hosts are ap- 

 parently not seriously affected, nor are 

 farm animals. No clinical signs were ob- 

 served in the infected young pigs, lambs, 

 kids and calves studied by Diamond and 

 Rubin (1958). 



Diagnosis : In the acute stage of the 

 disease, T. cruzi can be found in thick 

 blood smears. In chronic or light infec- 

 tions, other methods must be used. One 

 of the most important is xeuodiagiios is, 

 the inoculation of susceptible vector hosts. 

 Laboratory-reared, parasite-free triato- 

 mids are allowed to feed on suspected in- 

 dividuals, and their droppings or intestines 

 are examined 7 to 10 days later for devel- 

 oping trypanosomes. Rhodnius prolixus 

 is often used for this purpose (Pifano, 1954a). 



Laboratory animals can also be inoc- 

 ulated. In descending order of suscepti- 

 bility, these are puppies, kittens, mice 

 and guinea pigs. The trypanosomes can 

 be cultivated in NNN medium, Weinman's 

 (1946) medium, Diamond and Herman's 

 (1954) SNB-9 (serum -neopeptone-blood) 

 medium, or in a number of other media. 

 The trypanosomes can also be found in 

 biopsy examinations of affected lymph 

 glands or, on necropsy, in sections of 

 heart muscle. 



