Infestation of peridomestic Attalea phalerata palms by Rhodnius stali, a vector of Trypanosoma cruzi in the Alto Beni, Bolivia

OBJECTIVES To determine (i) whether peridomestic Attalea phalerata palms in fragmented human-occupied areas of the Alto Beni, Bolivia, are infested by triatomines; (ii) the specific status of triatomines captured in the area; and (iii) the rate of natural Trypanosoma cruzi infection among those triatomines. METHODS One hundred and twenty-five live-bait traps were used to sample 47 A. phalerata palms in three Alto Beni localities. Active search for vectors was also performed in 10 chicken coops and three rice storage units. Only Rhodnius specimens were found. As nymphs of closely related Rhodnius species are morphologically undistinguishable, and because of controversy in the literature regarding which Rhodnius species occur in Bolivia, collected insects were identified through molecular taxonomy. Phylogenetic analyses of DNA sequences obtained for a fragment of the mitochondrial cytochrome b gene and for the nuclear ITS-2 ribosomal region were used as molecular markers. Natural infection rates were determined using a pair of primers that PCR-amplify a 330-bp fragment of the parasite's kDNA. RESULTS Twelve nymphs were captured in five A. phalerata palms (from two of the three localities studied), and an adult was collected from a chicken coop in Iniqua (and morphologically identified as Rhodnius stali). All nymphs (as well as the adult) were molecularly identified as R. stali based on the two molecular markers used. A single nymph was found to be infected with T. cruzi. CONCLUSIONS Attalea phalerata palms represent an important sylvatic ecotope occupied by R. stali in the Alto Beni region of Bolivia, where there are signs of T. cruzi transmission to humans, despite the preliminary indication of low level of natural infection of the vectors.