Trypanosoma (Herpetosoma) rangeli Tejera, 1920: mouse model for high, sustained parasitemia

The Neotropical mammalian parasite Trypanosoma (Herpetosoma) rangeli Tejera, 1920 is difficult to study due to the scarcity of blood forms in the vertebrate host. High and persistent parasitemias (up to 7 times the original inoculum at the peak, and persisting for up to 2 wk) were obtained by i.p. inoculation of infant (6.0 g) male white mice (NMRI strain) with 15 X 10(3) trypomastigotes/g body weight from 12-day-old cultures of the "Dog-82" strain of T. rangeli. This strain was cultured 15 mo at ambient temperature in LIT medium, modified by substituting defibrinated adult rabbit blood for fetal calf serum. These results underlined the importance of host age and time of culture of the parasite as factors influencing levels of parasitemia. The abrupt decline in the parasitemias may be due to an early development of a strong immunological response. Negative xenodiagnoses with Rhodnius prolixus may be due either to sterile immunity in the host mice, or to the low susceptibility of the strain of Rhodnius used. Concurrent experiments established that the T. rangeli strain was not naturally contaminated with T. cruzi.