Studies in search of a suitable experimental insect model for xenodiagnosis of hosts with Chagas' disease: 4 - The reflection of parasite stock in the responsiveness of different vector species to chronic infection with different Trypanosoma cruzi stocks

Abstract

Previous studies (1982,1987) have emphasized the superiority of sylvatic vector species over domestic species as xenodiagnostic agents in testing hosts with acute or chronic infections by T. cruzi "Y" stock. The present study, which is unique in that it contains data on both infectivity rates produced by the same stock in 11 different vector species and also the reaction of the same vector species to seven different parasite stocks, establishes the general validity of linking efficiency of xenodiagnosis to the biotope of its agent. For example, infectivity rates produced by "São Felipe" stock varied from 82.5% to 98.3% in sylvatic vectors but decreased to 42.5% to 71.3% in domestic species. "Colombiana" stock produced in the same sylvatic vectors infectivity rates ranging from 12.5% to 45%. These shrank to 5%-22.5% in domestic bugs. The functional role of the biotope in the vector-parasite interaction has not been eluddated. But since this phenomenon has been observed to be stable and easy to reproduce, it leads us to believe that the results obtained are valid. Data presented also provide increasing evidence that the infectivity rates exhibited by bugs from xenodiagnosis in chronic hosts, are parasite stock specific. For example, infectivity rates produced by "Berenice", "Y", "FL" and "CL" varied in R. neglectus from 26.3% to 75%; in P. megistus from 56.3% to 83.8%; in T. sordida from 28.8% to 58.8% in T. pseudomaculata from 41.3% to 66.3% and in T. rubrovaria from 48.8% to 85%. Data from xenodiagnosis in the same hosts, carrying acute infections by the same parasite stocks, gave the five sylvatic vectors a positive rating of approximately 100%, thus suggesting that the heavy loads of parasites circulating in the acute hosts obscured the characteristic interspecific differences for the parasite stock. Nonetheless these latter were revealed in the same hosts with chronic infections stimulated by very low numbers of the same parasite stocks. Certain observations here described lead us to speculate as to the possibility of further results from other parasite stocks, allowing the association of the infectivity rates produced in bugs by different parasite stocks with the isoenzymic patterns revealed by these stocks.

Attempts to Improve Xenodiagnosis: Comparative Test of Sensibility Using Rhodnius neglectus, Panstrongylus megistus, Triatoma vitticeps and Triatoma infestans in Endemic Areas of Brazil

“…vitticeps were significantly higher than for T. infestuns. These results are in accordance with those obtained by P. -Szumlewicz et al (1990) and Pereira et al (1993Pereira et al ( ,1996.…”

“…-Szumlewicz et al (1988-Szumlewicz et al ( , 1990) emphasized the superiority of silvatic vectors over those from residences as xenodiagnostic agents in experimental hosts with acute and chronic infections caused by seven strains of T. cruzi, establishing that susceptibility varied according to the species used, giving top priority to P. megistus as an xenodiagnostic agent.…”

Sympatry influence in the interaction of Trypanosoma cruzi with triatomine

“…Our results are consistent with those of other authors who propose that strains of T. cruzi are biologically adapted to triatomine populations of the same geographic areas 19,20,42 . In addition, the data suggest that the infectivity of triatomine and its vector capacity might be the result of interaction of host genetics with parasite genetics, because group RR+AM14, which although ingested fewer parasites when compared to RR+PR2256, presented higher infectivity rate.…”

“…TcI, TcII, TcV, and TcVI DTUs are the main agents of human Chagas disease in the Americas 18 . Moreover, there is a tendency for local T. cruzi strains to more effectively infect vectors from the same geographic areas 19,20 .…”

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 finding of three marsupials positive between the 122 mammals examined and the failure to detect infection in R. rattus and armadillos, importants reservoirs, may be justified by the inefficiency of xenodiagnosis and hemoculture (Fernandes et al 1990, Perlowagora-Szumlewicz et al 1990). …”