60 



THE HEMOFLACELLATES 



1951a) listed Triatoma pro Ir acta, T. san- 

 giiisiiga (= T. gerstaeckeri), T. lecliilar- 

 ius, T. longipes, T. neolomae and T. 

 rubida as having been found infected in the 

 U. S. Mehringer and Wood (1958) found 

 T. C7-uzi in 24% of 383 Triatuma prolracta 

 collected in the Boy's and Girl's Camp 

 areas in Griffith Park, Los Angeles, 

 Calif. Most of the conenose bugs were 

 taken in human habitations. 



Both the nymphs and adults of these 



reduviids can be infected and can transmit 

 the disease. In addition, it is possible to 

 infect sheep keds (Rodhain and Brutsaert, 

 1935), ticks {Orinthodorus){Bv\im'()i, 1939) 

 and bedbugs (Wood, 1951a) experimentally. 



After they have been ingested by the 

 triatomids along with a blood meal, the 

 trypanosomes pass to the midgut. Here 

 they turn into leishmanial forms which 

 multiply by binary fission and turn into 

 either metacyclic trypanosomes or cri- 

 thidial forms. The crithidial forms multi- 

 ply further by binary fission, and extend 

 into the rectum. Here they turn into meta- 

 cyclic trypanosomes, which are unable to 

 divide until they enter a vertebrate host. 

 The life cycle in the invertebrate host takes 

 6 to 15 days or longer, depending on the in- 

 sect species or stage and on the temperature. 



The infective trypanosome forms pass 

 out in the feces. They can penetrate the 

 mucous membranes or skin actively. 

 Triatomids commonly defecate after feed- 

 ing, and most human infections occur when 

 feces are rubbed into the eyes or mucous 

 membranes following a bite. Animals can 

 become infected by licking their bites or 

 by eating infected bugs or rodents. 



Epidemiology : Human infections 

 with T. cnui are common in many parts 

 of tropical America, including Brazil, 

 Bolivia, northern Chile, northern Argen- 

 tina, French Guiana, Paraguay, Uruguay 

 and Venezuela. In some localities 10 to 

 20% or even 507o of the inhabitants are 

 positive to the complement fixation 

 (Machado) test, but in other localities 

 where exposure to the vectors is minimal, 

 there are very few positive reactions. As 

 mentioned below, acute Chagas' disease 



occurs primarily in infants and children, 

 and the number of acute cases is far lower 

 than the numbers of chronic and unrecog- 

 nized infections. 



Chagas' disease becomes increasingly 

 uncommon to the north of the endemic area 

 even tho infected reservoir hosts and vec- 

 tors may be common. Less than 140 cases 

 of Chagas' disease had been reported from 

 Guatemala, Salvador, Nicaragua, Costa 

 Rica and Panama according to Dias (1952a) 

 while only 9 cases were known from Mexico 

 (Mazzotti and Dias, 1950). Only a single 

 indigenous case has been reported from 

 the United States, by Woody and Woody 

 (1955) in Texas. 



Chagas' disease is a zoonosis, infec- 

 tions occurring widely in animals and man. 

 The armadillo is thought by Hoare (1949) 

 to be the original source of the human dis- 

 ease in South America, but the opossum 

 and many other wild animals are also in- 

 fected. The most important wild reser- 

 voirs in the United States are woodrats of 

 the genus Neotoitia. Natural infections 

 have been found in the southwestern states 

 and southern California in jV. fuscipes, 

 N. albigida, N. micropus, in the deer- 

 mouse, Peromyscus boylii, and also in 

 the opossum, house mouse and nine -banded 

 armadillo {Dasypus novemcbictus). The 

 recent discovery of T. criizi infections in 

 raccoons {Procyon lotor), opossums, gray 

 foxes and skunks in Maryland, Georgia and 

 Florida (Walton t^/ «/. , 1956, 1958; Mc- 

 Keever, Gorman and Norman, 1958) 

 raises the question how widespread the in- 

 fection is in these animals. 



Cats and dogs are often naturally in- 

 fected in South America, and, because of 

 their closer association with man, are 

 probably more important as sources of 

 human infection than wild animals. Natur- 

 ally infected pigs have been found in South 

 America, and sheep and goats can be in- 

 fected experimentally with these South 

 American strains. 



In a study of the possible role of farm 

 animals as reservoirs of North American 

 strains of T. criizi. Diamond and Rubin 

 (1958) established low-grade infections in 



