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MIXED DOMESTIC INFESTATION BY RHODNIUS PROLIXUS STÄL, 1859 AND PANSTRONGYLUS GENICULATUS LATREILLE, 1811, VECTOR INCRIMINATION, AND SEROPREVALENCE FOR TRYPANOSOMA CRUZI AMONG INHABITANTS IN EL GUAMITO, LARA STATE, VENEZUELA

Mixed infestation of nymphs and adults of Rhodnius prolixus Stäl, 1859 and Panstrongylus geniculatus Latreille, 1811 was detected in 3 (15%) of 20 dwellings in El Guamito, an endemic focus of Chagas disease in Lara State, Venezuela. In one of the houses, both species were positive for Trypanosoma cruzi: 14.3% (R. prolixus) and 20% (P. geniculatus ). The overall infection rate in 143 of 352 R. prolixus was 16.1%. Parasites isolated from R. prolixus were identified as T. cruzi I by random amplified polymorphic DNA analysis. Dot–enzyme-linked immunosorbent assays of 36 R. prolixus showed that 58.3% of the R. prolixus had fed on humans. The gut contents of one fifth-instar nymph of P. geniculatus that was positive for T. cruzi also reacted with anti-human serum. A questionnaire was used to gather data on the demographic and socioeconomic characteristics of the population. An indirect immunofluorescent test, an indirect hemaglutination test, and an ELISA were used to detect the presence of antibodies against T. cruzi in 84 of 86 inhabitants and in 15.5% of people more than 20 years old. The relative risk (RR) of infection was greater in men than in women (RR = 1.61, 95% confidence interval = 0.54–4.80). Of the people more than 15 years old, 36.6% had no formal education. All respondents recognized triatomine bugs, but they did not relate them to Chagas disease transmission. A total of 85.7% of the houses were "ranchos" suitable for the colonization of triatomine bugs. The possible domiciliation of P. geniculatus and the implications of competition with R. prolixus for resources are discussed. Since there is no clear separation of food sources, abiotic factors such as microclimatic variation within houses may be critical to predict the outcome of the process of competition and potential domestication of this generally sylvatic species.

Received August 18, 2003. Accepted for publication February 6, 2004.

Acknowledgments: We thank Carlos Mendez, Roseliano Visval, and Annhy Torrellas for their technical assistance.

Financial support: This work was supported by the Wellcome Trust (Project no. 062984/Z/00/Z). The Chagas Disease Intervention Activities – European Community, the MCT-FONACIT, S1-98000388, and the CDCH-UCV-09-34-4097-01.

Authors’ addresses: M. Dora Feliciangeli and Benny Suarez, Facultad de Ciencias de la Salud, BIOMED, Universidad de Carabobo, Núcleo Aragua, Apartado 4873, Maracay, Venezuela. Hernán Carrasco and Clara Martínez, Facultad de Medicina, Instituto de Medicina Tropical, Universidad Central de Venezuela, Caracas, Venezuela. James S. Patterson, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom. Mehudy Medina, Laboratorio de Chagas, Dirección General de Salud Ambiental y Contraloría Sanitaria, Ministry of Health and Social Development, Maracay, Venezuela.

Reprint requests: M. Dora Feliciangeli, Facultad de Ciencias de la Salud, BIOMED, Universidad de Carabobo, Núcleo Aragua, Apartado 4873, Maracay, Venezuela, Telephone : 58-243-233-5822, Fax: 58-243-242-5333; E-mail: mdora{at}telcel.net.ve.