LOW PROBABILITY OF TRANSMISSION OF TRYPANOSOMA-CRUZI TO HUMANS BY DOMICILIARY TRIATOMA-SORDIDA IN BOLIVIA

The role of Triatoma sordida in the domestic transmission of Trypanoso ma cruzi was assessed in 7 rural localities in Velasco Province, Depar tment of Santa Cruz, Bolivia. Tri. sordida, the only triatomine specie s 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 tota l of 220 faecal samples from domiciliary bugs was examined microscopic ally and by the polymerase chain reaction for the presence of trypanos omes: 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 fo r Tryp. cruzi. Only 2 of a second group of 62 persons living in dwelli ngs infested by Trf. sordida were seropositive. Tryp. cruzi infection was demonstrated in dogs and domestic rats. Three other species of sma ll mammals were found to be infected with trypanosomes. In our study a rea, domestic Tri. sordida are mainly incriminated in the transmission of Tryp. cruzi to synanthropic animals, whereas transmission to human s is very rare. The presence in houses of small populations of Tri. so rdida infected with Tryp. cruzi is therefore currently insufficient fo r this insect to constitute a major epidemiological risk factor.