Intradomiciliary and peridomiciliary captures of sand flies (Diptera: Psychodidae) in the leishmaniasis endemic area of Chapare province, tropic of Cochabamba, Bolivia.

In South America, cutaneous leishmaniasis is the most frequent clinical form of leishmaniasis. Bolivia is one of the countries with higher incidence, with 33 cases per 100,000 individuals, and the disease is endemic in 70% of the territory. In the last decade, the number of cases has increased, the age range has expanded, affecting children under 5 years old, and a similar frequency between men and women is found. An entomological study with CDC light traps was conducted in three localities (Chipiriri, Santa Elena and Pedro Domingo Murillo) of the municipality of Villa Tunari, one of the main towns in the Chapare province (Department of Cochabamba, Bolivia). A total of 16 specimens belonging to 6 species of the genus Lutzomyia were captured: Lu. aragaoi, Lu. andersoni, Lu. antunesi, Lu. shawi, Lu. yuilli yuilli and Lu. auraensis. Our results showed the presence of two incriminated vectors of leishmaniasis in an urbanized area and in the intradomicile. More entomological studies are required in the Chapare province to confirm the role of vector sand flies, the intradomiciliary transmission of the disease and the presence of autochthonous cases of cutaneous leishmaniasis.

Trypanosoma cruzi: effects of azadirachtin and ecdysone on the dynamic development in Rhodnius prolixus larvae.

The effects of azadirachtin and ecdysone on the Trypanosoma cruzi population in the Rhodnius prolixus gut were investigated. T. cruzi were rarely found in the gut compartments of azadirachtin-treated larvae. High parasite numbers were observed in the stomach of the control and ecdysone groups until 10 days after treatment and in the small intestine and rectum until 25 days after treatment. High percentages of round forms developed in the stomachs of all groups, whereas azadirachtin blocked the development of protozoan intermediate forms. This effect was counteracted by ecdysone therapy. In the small intestine and rectum, epimastigotes predominated for all groups, but more of their intermediates developed in the control and ecdysone groups. Azadirachtin supported the development of round forms and their intermediates into trypomastigotes. In the rectum, trypomastigotes did not develop in the azadirachtin group and developed much later after ecdysone therapy. The parallel between the effects of azadirachtin and ecdysone on the host and parasite development is discussed on the basis of the present results because ecdysone appears to act directly or indirectly in determining the synchronic development of T. cruzi forms from round to epimastigotes, but not metacyclic trypomastigotes, in the invertebrate vector.

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.

New insights on the spread of Triatoma infestans from Bolivia--implications for Chagas disease emergence in the southern cone.

Triatoma infestans, now eliminated from most of South America by control campaigns, has been and still is the main Chagas disease vector due to its ability to colonize rural dwellings. The traditional hypothesis put forth to explain T. infestans adaptation to the synanthropic environment rests on the domestication of wild guinea pigs, one of its natural hosts, by Andean tribes about 5000 BC. Here we present two new hypotheses, based on organized human social activities. The first involves maize production, storage and distribution during the Inca period. Maize granaries could host wild rodent populations that would attract sylvatic T. infestans that were later dispersed during maize distribution. The second hypothesis is associated with the contemporary Urkupiña Virgin festival, near Cochabamba, where thousands of pilgrims gather for rituals in an area that is part of a sylvatic T. infestans focus, thus favoring the contact with the insects and leading to their passive dispersal.

Bovine leukaemia-virus infection in Costa Rica.

The geographical distribution of bovine leukaemia-virus (BLV)-infected herds in Costa Rica and the isolation of BLV from cases of enzootic bovine leukosis are presented. It was found that BLV is prevalent throughout the country, affecting mostly dairy cattle (Bos taurus) located in the highlands around the central valley of Costa Rica. By contrast, beef cattle (Bos indicus) raised in the lowlands were affected to a lesser extent. One out of four isolates of BLV obtained from local cattle with lymphosarcomatous tumours was analysed and had similar physical, serological and biological characteristics to a reference strain of BLV isolated in the USA. However, different patterns of recognition of BLV-protein p24 were observed among naturally infected cattle using the western-blotting technique.