Development of Trypanosoma cruzi in Triatoma infestans: influence of temperature and blood consumption.

This work had 2 objectives. The first was to quantify Trypanosoma cruzi development within Triatoma infestans maintained at 2 different temperatures, using an experimental design that simulated the natural transmission process and, second, to learn how the vector blood consumption rate modifies the parasite's development. Two hundred and three, fifth-stage nymphs of T. infestans were infected with the X-1 strain of T. cruzi (about 10(4) trypanosomes/ml blood), maintained at 20 and 28 C, and daily offered the opportunity to feed on uninfected laboratory mice. From 24 hr to the 55th day after the infective meal, the total number of epimastigotes and rectal and fecal metacyclic trypomastigotes were counted. Epimastigote multiplication began on the first day after the infective meal at both temperatures. This parasitic stage developed similar population densities within the vector under both temperature regimes. Trypomastigotes appeared in the rectum and feces at 20 C, 32 and 24 days later, respectively, than at 28 C; however, once they became infective, insects developed similar population densities of fecal metacyclic forms. Blood consumption was related to epimastigote and rectal trypomastigote development at 28 C, but not to the number of trypomastigotes in the feces. A minimum of 120 and 180 mg of fresh blood consumed assured that all bugs developed epimastigotes and trypomastigotes. In spite of the delay in producing metacyclic forms at 20 C, the insect's infective capacity was similar at both temperatures.