INTRODUCTION:Chagas disease has been a public health problem in Latin America for many years. In Venezuela the disease is mainly distributed in the rural populations and endemic areas with an overall seroprevalence index of 8,3% for the year 2000.OBJECTIVE:The infection seroprevalence of Trypanosoma cruzi was determined in the human population younger than 16 years. An the entomological index was obtained and the grade of knowledge of the Chagas disease was surveyed in the local inhabitants.MATERIALS AND METHODS:A descriptive cross-sectional field study was performed in two rural communities of the municipality Costa de Oro, State Aragua, Venezuela. Here, T. cruzi-seropositive testing was conducted in subjects younger than 16 years. The samples were processed using indirect hemagglutination and by ELISA (enzyme-linked immunosorbent assay). A questionnaire was administered to assess household risk factors, and knowledge about vectors and disease held by the local population. Searches for triatomines were conducted inside of dwellings.RESULTS:Seroprevalence in children less than 16 years old was 1.02%. Sixteen specimens of triatominae adults were captured. The vector species recognized were Panstrongylus geniculatus, Rhodnius pictipes, and Eratyrus mucronatus. The index of triatomid infestation with respect to site and house was respectively, 100% and 10.9%. No association was found between the seropositives and the other variables. Of the interviewed individuals, 95% knew that insects transmit diseases, but less than 46% knew that triatominds transmit Chagas disease or were aware of the disease pathology.CONCLUSION:The discovery of secondary vectors in the area outlines the necessity to carry out epidemiological and entomological studies that associate environmental variables with the habitat of these insects. This will allow the identification of risk factors responsible for the transmission of Chagas disease in this region.

A prospective study was conducted in El Brazilar, Curarigua, Lara State, Venezuela, a small rural focus of visceral leishmaniasis (VL) to investigate the burden and the evolution of Leishmania infection in the human and canine population. The incidence of the disease from February 1998 to February 2002 was recorded and two cross-sectional surveys using the leishmanin skin test (LST) and immunofluorescent antibody test (IFAT) were carried out. The dipstick test with recombinant r-K39 antigen was also applied in 2002. The incidence of the disease per year among the population (n=118) during the period of study was 0.004. The rate of new infections per year was 0.07 [95% confidence interval (95% CI): 0.15-1.09]. The overall prevalence of infection measured by LST was not significantly higher in 2002 (43.2%) than in 1998 (28.3%), but it was with IFAT [16.3%vs. 4.6%; odds ratio (OR): 4.01; 95% CI: 1.03-22.78; P=0.022] which would indicate an increasing transmission. The dipstick test only detected infection in children up to 10 years (19.4%). Prevalence in dogs was not significantly different in 2002 (57%) vs. 1998 (33%). The parasite was isolated from dogs and identified by a polymerase chain reaction based on telomeric sequences as Leishmania chagasi/infantum.

Mixed infestation of nymphs and adults of Rhodnius prolixus Stal, 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.