Low probability of transmission of Trypanosoma cruzi to humans by domiciliary Triatoma sordida in Bolivia

Abstract

The role of Triatoma sordida in the domestic transmission of Trypanosoma cruzi was assessed in 7 rural localities in Velasco Province, Department of Santa Cruz, Bolivia. Tri. sordida, the only triatomine species identified in these localities, was found inside 58.0% of houses but not in large numbers (3.1 bugs per infested house on average). A total of 220 faecal samples from domiciliary bugs was examined microscopically and by the polymerase chain reaction for the presence of trypanosomes: 21.4% were infected. Analysis of blood meals of domiciliary Tri. sordida showed that humans were the commonest host (70.4%), followed by chickens and dogs. Four of 418 persons tested were seropositive for Tryp. cruzi. Only 2 of a second group of 62 persons living in dwellings infested by Tri. sordida were seropositive. Tryp. cruzi infection was demonstrated in dogs and domestic rats. Three other species of small mammals were found to be infected with trypanosomes. In our study area, domestic Tri. sordida are mainly incriminated in the transmission of Tryp. cruzi to synanthropic animals, whereas transmission to humans is very rare. The presence in houses of small populations of Tri. sordida infected with Tryp. cruzi is therefore currently insufficient for this insect to constitute a major epidemiological risk factor.

Vectorial capacity of Triatoma guasayana (Wygodzinsky & Abalos) (Hemiptera: Reduviidae) compared with two other species of epidemic importance

“…Triatoma sordida is in a more advanced domiciliary process (Noireau et al 1997), and this species is superior to T. guasayana regarding the feeding-defecation interval. Both species have very similar characteristics of metacyclogenesis, but this is insufficient for T. sordida to be considered an efficient vector in infested housing and its population dynamics may explain its low vectorial capacity (Noireau et al 1997). This last parameter, which was not considered in this study, should be studied in T. guasayana to see if it can be considered as a possible vector.…”

“…Various reports of T. sordida and T. guasayana in human environments in Southern Cone countries (Forattini et al 1982, Carcavallo et al 1988, Noireau et al 1997 make them vector candidates and this should encourage more studies on these species. With regard to the vectorial control of Chagas disease, the peridomicile vectors have a special importance due to their role in these processes and the re-infestation of housing during entomological surveillance.…”

“…It is clear that domiciliary transmission of T. cruzi depends on factors, such as the population size of triatomines, which has to reach a critical size (Noireau et al 1997). For this reason, from just considering the population dynamics, it is improbable that any of these species might be as efficient a vector as T. infestans (Schofield 1994).…”

Trypanosoma cruzi infection in Triatoma infestans and other triatomines: long-term effects of a control program in rural northwestern Argentina

“…In Brazil, long-term surveillance data showed very low rates of T. sordida domiciliary colonization, and T. cruzi infection rates ranging from 1%-4% (9,23). In certain parts of Bolivia, however, the pattern may be quite different (24).…”

Considerations on the epidemiology and transmission of Chagas disease in the Brazilian amazon

“…At this time we have only isolated reports of sylvatic triatomines colonizing houses. These species that are candidates for vectors are: P. rufotuberculatus, found colonizing houses in Bolivia , E. mucronatus seen in Peru and Bolivia (Torrico et al 1946, Lent & Wygodzinski 1979, Valencia-Telleria 1990, Noireau et al 1995, 1997, R. stali found in Cochabamba in Bolivia (Tibayrenc & Le Pont 1984) with various degrees of importance in the transmission of Chagas disease, and P. geniculatus, the most widely distributed species in South and Central America, especially in the Brazilian Amazon region (Valente et al 1994).…”