Spatio-temporal clustering of American Cutaneous Leishmaniasis in a rural municipality of Venezuela.

BACKGROUND: American Cutaneous Leishmaniasis (ACL) is an endemic disease in most Latin-American countries and a public health problem. The number of new cases in the world is thought to be about 1.5 million each year. A new epidemiologic pattern has been observed in the last years, in this sense, Geographic Information Systems (GIS) combined with methods of spatial analysis provide powerful new tools for understanding it. STUDY OBJECTIVE: To investigate the spatial and temporal features of American Cutaneous Leishmaniasis, in an area known to be endemic. METHODS: We retrospectively conducted a space-time cluster analysis of incident cases of ACL using cross sectional data recorded from 1348 confirmed cases from 1992 to 2007 in a rural municipality in Venezuela, to test whether the cases were distributed randomly over space and time. We used the space-time permutation scan statistic and GIS. The identified clusters were analyzed for age, sex and job. These allowed us to investigate transmission patterns of ACL without an explicit entomological study. RESULTS: The analysis showed statistically significant space-time clusters of ACL (p-value<0.01). The most likely cluster contained 35.47% of the total cases (n=177) from 1995 to 1998. Four secondary clusters were identified for different periods. There was an indication of ACL cluster spread from the northeast to other points of the municipality. Three transmission patterns (domiciliary, peri-domiciliary and sylvatic environments) were identified along the study area. CONCLUSION: The transmission of ACL has a spatial and temporal pattern in the studied area which is related to a complex cycle where the environment and other factors have a significant influence.

An inexpensive antigen for serodiagnosis of Chagas' disease.

UNLABELLED: In this prospective study we evaluated the performance characteristics of a specific and sensitive antigen preparation (AgA) used in an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-Trypanosoma cruzi antibodies in serum samples, for Chagas' disease diagnosis. The antigen production was achieved by combination of nutritional stress and autoclaving the parasites. Specificity and sensitivity were evaluated in two separate tests, using 152 sera from healthy individuals and 175 sera from Chagas' patients (70 by xenodiagnosis). Cross-reactivity was tested using 289 sera from patients who had a parasitological diagnosis of a disease known to induce antigenic responses towards T. cruzi. All of these sera were tested with our AgA-ELISA and with 3 commercial diagnosis kits. To evaluate the agreement of results between our AgA-ELISA and a "gold standard" test for Chagas, we tested 566 sera from an endemic area. RESULTS: sensitivity and specificity were 100%; cross-reactivity was the lowest compared with commercial kits. Overall agreement with the gold standard test was excellent (kappa = 0.92). AgA-ELISA exhibits levels of sensitivity, specificity and cross-reactivity comparable or superior to those shown, obtained with the commercial kits used in our country, while being at least 10 times less expensive. This balance between diagnostic accuracy and cost makes AgA-ELISA useful for blood bank screening in poor regions of the world suffering from Chagas' disease. Further validations of this antigenic formulation in other countries are necessary.

An inexpensive antigen for serodiagnosis of Chagas’ Disease

In this prospective study we evaluated the performance characteristics of a specific and sensitive antigen preparation (AgA) used in an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-Trypanosoma cruzi antibodies in serum samples, for Chagas’ disease diagnosis. The antigen production was achieved by combination of nutritional stress and autoclaving the parasites. Specificity and sensitivity were evaluated in two separate tests, using 152 sera from healthy individuals and 175 sera from Chagas’ patients (70 by xenodiagnosis). Cross-reactivity was tested using 289 sera from patients who had a parasitological diagnosis of a disease known to induce antigenic responses towards T. cruzi. All of these sera were tested with our AgA-ELISA and with 3 commercial diagnosis kits. To evaluate the agreement of results between our AgA-ELISA and a “gold standard” test for Chagas, we tested 566 sera from an endemic area. Results: sensitivity and specificity were 100 percent; cross-reactivity was the lowest compared with commercial kits. Overall agreement with the gold standard test was excellent (kappa=0.92). AgA-ELISA exhibits levels of sensitivity, specificity and cross-reactivity comparable or superior to those shown, obtained with the commercial kits used in our country, while being at least 10 times less expensive. This balance between diagnostic accuracy and cost makes AgA-ELISA useful for blood bank screening in poor regions of the world suffering from Chagas’ disease. Further validations of this antigenic formulation in other countries are necessary.

Este estudio fue realizado para evaluar las características de sensibilidad y especificidad de una formulación antigénica (AgA), producida a bajo costo, para detectar anticuerpos dirigidos a Trypanosoma cruzi, en muestras de suero de pacientes con enfermedad de Chagas. El AgA fue producido por el efecto combinado de estrés nutricional y autoclave de los parásitos. La especificidad y sensibilidad fueron evaluadas en dos estudios separados, con 152 sueros de individuos sanos y 175 de pacientes Chagásicos. La reactividad cruzada con 289 sueros de pacientes con diagnóstico parasitológico de enfermedades con anticuerpos que reaccionan con antígenos de T. cruzi. Estos sueros fueron evaluados con AgA-ELISA y con tres estuches comerciales. 566 muestras de suero provenientes de un área endémica, fueron empleadas para estudiar la concordancia entre nuestro diagnostico y una prueba designada por nosotros como patrón oro estándar. Resultados: la sensibilidad y especificidad fue de 100 por ciento. El AgA presento el más bajo porcentaje de reactividad cruzada, respecto a los estuches comerciales evaluados. La concordancia con la prueba patrón oro, en Venezuela, fue excelente (kappa=0,92). En conclusión, Aga-ELISA, presentó niveles de sensibilidad, especificidad y de reactividad cruzada, comparables o superiores a los obtenidos por los tres estuches comerciales mas empleados en el país, pero con costos de producción al menos 10 veces menor. Este balance conveniente, favorece su potencial uso para el despiste en los bancos de sangre de los países pobres y endémicos para la enfermedad de Chagas. Futuras validaciones de esta formulación en otros países es necesaria.