Elisa Ponce

Chagas' disease diagnosis: a multicentric evaluation of Chagas Stat-Pak, a rapid immunochromatographic assay with recombinant proteins of Trypanosoma cruzi.

A rapid serologic test for diagnosis of T. cruzi infection (Chagas Stat Pak) was developed using recombinant proteins in an immunochromatographic assay. This cassette format test was evaluated first in blind with a panel of 393 coded serum samples. The Chagas Stat-Pak identified 197 infected (98.5% sensitivity) and 183 non-infected individuals (94.8% specificity). A second evaluation was performed with 352 sera from four Latin America countries tested independently in each country, showing a sensitivity of 100% and specificity of 98.6%. A third set of tests comparing sera with plasma and eluates from filter paper as well as serum preserved in 50% glycerol did show identical results as those obtained with serum. This rapid test (15 min) uses one device per sample, does not require refrigeration nor a laboratory structure or specialized skills to be performed, accepts different types of samples and may be stored for long periods of time for result checking and documentation. These attributes together with the high sensitivity and specificity demonstrated herein, make this test a suitable tool for field studies, small laboratories and emergencies at blood banks in the countryside of endemic areas.

La enfermedad de Chagas en la zona central de Honduras: conocimientos, creencias y prácticas

En el periodo de noviembre a diciembre de 1991 y en marzo de 1993 se realizo una encuesta en 17 comunidades rurales de la parte central de Honduras. Las comunidades correspondian a dos zonas en las que la enfermedad de Chagas es endemica. En una de las zonas habian tenido lugar actividades de control de la enfermedad. Fueron entrevistados 849 adultos, uno en cada uno de otros tantos hogares familiares. El objetivo de la encuesta fue investigar y comparar en ambas zonas los conocimientos sobre la enfermedad de Chagas y sus mecanismos de transmision, las practicas para evitar la presencia de triatomidos en las viviendas, las creencias acerca de los triatomidos y su control, y las fuentes a partir de las cuales la poblacion obtiene informacion sobre la enfermedad. Se utilizo un cuestionario de 23 preguntas validado y precodificado. Casi 100% de los entrevistados pudieron reconocer el vector y conocian sus habitos, pero solo 30,1% sabian que el Triatoma es vector transmisor de la enfermedad y apenas 6% pudieron mencionar su relacion con una afeccion cardiaca cronica. El 47,9% de los entrevistados indico que la responsabilidad de eliminar los triatomidos de la vivienda es personal, aunque 78% consideraron como medida de control la aplicacion institucional de insecticidas. El contacto personal entre el funcionario institucional y los miembros de la comunidad fue la principal fuente de informacion entre los que mencionaron haber oido de la enfermedad de Chagas (41,0%). Los resultados sugieren que al planificar medidas de control se debe incluir el componente de educacion sanitaria. Ha de ponerse enfasis en el papel que desempenan los triatomidos en la transmision, asi como en la importancia de mejorar la vivienda como medida eficaz y sostenible mediante la participacion de la comunidad. Este componente debera ser desarrollado por canales de comunicacion interpersonales para obtener un mayor impacto.A survey was conducted in late 1991 and early 1993 in 17 rural communities of Central Honduras to compare knowledge of Chagas disease and its transmission consequences and prevention in endemic areas benefiting or not from control programs. A 23-item questionnaire was administered to 682 adults in 15 villages where epidemiological and entomological studies had been conducted since the 1970s and where vector control activities had been recently initiated. 167 adults in 2 villages that had no control program served as controls. The socioeconomic characteristics of the respondents were very similar in the areas exposed and not exposed to control programs. 50% of respondents in the exposed group versus 33% in the control group knew about Chagas disease. 33% in the exposed group and 16% in the control group correctly identified the vector. Only 22% of respondents nearly all of whom were in the exposed group could identify any sign or symptom of the disease. Knowledge of the vectors habits and habitat was similar in both groups. Over 95% of respondents identified vector specimens in a Petri dish. Straw roofs and deteriorating adobe walls were frequently mentioned as habitats but piles of material surrounding the house were not. Over 75% of respondents identified application of insecticides as an effective control measure. 48% stated that elimination of vectors from households was a personal responsibility and 48% thought it should be done by the Ministry of Health. 44% who had heard of Chagas disease did so through personal contact with a health worker and 33% through talks at health centers. The results suggest that health education preferably through interpersonal communication should be included in control programs.

Treatment and seroconversion in a cohort of children suffering from recent chronic Chagas infection in Yoro, Honduras

Between 1999-2002, Médécins Sans Frontières-Spain implemented a project seeking to determine the efficacy and safety of benznidazole in the treatment of recent chronic Chagas disease in a cohort of seropositive children in the Yoro Department, Honduras. A total of 24,471 children were screened for Trypanosoma cruzi IgG antibodies through conventional enzyme-linked immunosorbent assays (ELISA) on filter paper. Recombinant ELISA (0.93% seroprevalence) showed 256 initially reactive cases, including 232 confirmed positive cases. Of these, 231 individuals were treated with benznidazole (7.5 mg/kg/day) for 60 days and were followed with a strict weekly medical control and follow-up protocol. At the end of the project, 229 patients were examined by the Honduras Secretariat of Health for post-treatment serological assessments; 88.2% seroconverted after 18 months and 93.9% seroconverted after three years. No differences were found in the seroconversion rates according to age or sex. Most of the side effects of the treatment were minor. These results support the argument that in areas where T. cruzi I is predominant and in areas affected by T. cruzi II, when vector transmission has been interrupted, Chagas disease diagnosis and treatment are feasible, necessary and ethically indisputable.

Performance levels of four Latin American laboratories for the serodiagnosis of Chagas disease in Mexican sera samples.

In nearly all of the previous multicentre studies evaluating serological tests for Trypanosoma cruzi infection, sera samples from Central or South American countries have been used preferentially. In this work we compared the reliability of the serological tests using Mexican sera samples that were evaluated in four independent laboratories. This included a reference laboratory in Brazil and three participant laboratories, including one in Central America and two in Mexico. The kappa index between Brazilian and Honduran laboratories reached 1.0 and the index for the Mexican laboratories reached 0.94. Another finding of this study was that the source of antigen did not affect the performance of the serological tests.