Risk of Trypanosoma cruzi I (Kinetoplastida: Trypanosomatidae) transmission by Panstrongylus geniculatus (Hemiptera: Reduviidae) in Caracas (Metropolitan District) and neighboring States, Venezuela

The collection of Panstrongylus geniculatus bugs by inhabitants of dwellings in Caracas city (Metropolitan District) and in theneighboring Miranda and Vargas Sates, Venezuela, allowed for the gathering of data on the potential role of this sylvatic triatomine bug as avector of Chagas disease in this area. The natural infection by Trypanosoma cruzi was recorded by examining fresh and stained faeces of thebugs. Additionally, a random amplification of polymorphic DNA technique for parasite identification and group typing was employed. A dot-ELISA test was used to identify the gut content of the triatomine bugs with the aim of assessing and quantifying the vector–human contact.Sixty-seven specimens (76.1%) were positive to T. cruzi (identified as T. cruzi I) and 60.2% (53/88) gave a positive reaction to the humanantiserum. The human blood-positive samples included mixed blood meals with domestic animals (dog, pig and cow) (9.4%) and with mouse(3.8%). The overall Human Blood Index, measured as the percentage of bugs whose gut contents reacted with human antiserum on the totalnumbers of bugs that reacted with all the antisera tested, was 98.1%. Almost 41% of the bugs that had fed on humans were also positive forT. cruzi. These data show that the feeding of P. geniculatus on humans does not seem to be accidental and that its rate of infection by T. cruziis high in this area which is not regarded as endemic for Chagas disease by the National Control Programme. This situation is particularlystriking because it occurs in and around Caracas, the capital city, where 20% of the whole population of Venezuela live, human migrationsfrom endemic areas are continuous, people in the crowded shantytown as well as people living in high-quality country houses are equally atrisk and the epidemiological cycle Didelphis marsupialis/Rattus rattus–P. geniculatus–human does appear to occur successfully.q 2005 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved