Studies in search of a suitable experimental insect model for xenodiagnosis of hosts with Chagas' disease. 1 - Comparative xenodiagnosis with nine triatomine species of animals with acute infections by Trypanosoma cruzi

Abstract

In search of a suitable vector species for xenodiagnosis of humans and animals with chronic Chagas' disease we first investigated the reactions of different vector species to acute infection with Trypanosoma cruzi. Vector species utilized in this study were: Triatoma infestans, Rhodnius prolixus and Triatoma dimidiata, all well adapted to human habitats; Triatoma rubrovaria and Rhodnius neglectus both considered totally wild species; Panstrongylus megistus, Triatoma sordida, Triatoma pseudomaculata and Triatoma brasiliensis, all essentially sylvatic but some with domiciliary tendencies and others restricted to peridomestic biotopes with incipient colonization of human houses after successful eradication of T. infestans. Results summarized in Table IV suggest the following order of infectivity among the 9 studied vector species: P. megistus with 97.8% of infected bugs, T. rubrovaria with 95% of positive bugs a close second followed by T. Pseudomaculata with 94.3% and R. neglectus with 93.8% of infected bugs, almost identical thirds. R. prolixus, T. infestans and T. dimidiata exhibited low infection rates of 53.1%, 51.6% and 38.2% respectively, coupled with sharp decreases occuring with aging of infection (Fig. 1). The situation was intermediate in T. brasiliensis and T. sordida infection rates being 76.9% and 80% respectively. Results also point to the existence of a close correlation between prevalence and intensity of infection in that, species with high infection rates ranging from 93.8% to 97.8% exhibited relatively large proportions of insects (27.3% - 33.5%) harbouring very dense populations of T. cruzi. In species with low infection rates ranging from 38.2% to 53.1% the proportion of bugs demonstrating comparable parasite densities was at most 6%. No differences attributable to blood-meal size or to greater susceptibility of indigenous vector species to parasites of their own geographical area, as suggested in earlier...<br>Em busca de um inseto adequado para xenodiagnóstico em homens e animais comforma crônica da doença de Chagas investigamos, primeiramente, a resposta à infecção aguda com Trypanosoma cruzi, empregando nove espécies vetoras: Triatoma infestans, Triatoma dimidiata e Rhodnius prolixus, todas bem adaptadas a domicílios humanos. Triatoma rubrovaria e Rhodnius neglectus consideradas totalmente silvestres, Panstrongylus megistus, Triatoma sordida, Triatoma pseudomaculata, Triatoma brasiliensis, todas essencialmente silváticas, porém umas com nítida tendência de domiciliação e outras com colonização incipiente de habitações mantidas sob controle após erradicação bem sucedida de T. infestans. As proporções de insetos infectados e as cargas parasitárias nos mesmos, determinadas a fresco no conteúdo do tubo digestivo nos diferentes intervalos após um único repasto em animais infectados indicam que P. megistus, T. rubrovaria, T. pseudomaculata e R. negletus constituem o melhor meio natural para evolução e proliferação da cepa Y do T. cruzi. Outras espécies em ordem descendente foram: T. sordida, T. b...

An Investigation on the Ecology of Triatoma vitticeps (Stal, 1859) and its Possible Role in the Transmission of Trypanosoma cruzi, in the Locality of Triunfo, Santa Maria Madalena Municipal District, State of Rio de Janeiro, Brazil

“…The mutations suffered by the domiciliated species due to the gradual adaptation to the domicile, also make the adaptation of the parasite difficult (Perlowagora-Szumlewicz & Müller 1982, Moreira & Perlowagora-Szumlewicz 1997.…”

Studies in search of a suitable experimental insect model for xenodiagnosis of hosts with Chagas' disease: 3 - On the interaction of vector species and parasite strain in the reaction of bugs to infection by Trypanosoma cruzi

“…The origin and history of these bugs, reared under ambient conditions was described previously (1982) 15 . Their life history parameters of major importance were reported by Perlowagora-Szumlewicz 13,14 .…”

“…Batches of bugs fed on infected animals: The scheme followed was essentially this described in 1982 with one major addition (Perlowagora-Szumlewicz & Müller 15 ). While previously the reaction of nine different vector species to infection by Y strain was studied, the herein described experiments were extended to the responsiveness of the same nine vector species to experimental infections produced by seven different strains.…”

“…This raised the immediate question, whether an insect that is as efficient as T. infestans, which has been repeatedly found to be one of the poorest responders to infection by T. cruzi Y strain 15,16 merits to be singled out as an adequate xenodiagnostic agent.…”

“…Studies reported by the authors' 15,16 in 1982 and 1987 were beginning to uncover an extraordinary variety of vector species (Panstrongylus megistus, Rhodnius neglectus, Triatoma sordida, Triatoma pseudomaculata, Triatoma rubrovaria), which are being identified as successful xenodiagnostic agents.…”