Seroprevalence of human Trypanosoma cruzi infection in diferent geografic zones of Chiapas, Mexico Soroprevalência da infecção humana pelo Trypanosoma cruzi em diferentes regioes de Chiapas, México

A serologic survey was carried out in four different geographic zones of Chiapas, Mexico. A total of 1,333 samples were collected from residents of thirteen communities located on the Coast, Central Mountain, Lacandon Forest and a zone called Mesochiapas. One hundred and fifty one seropositive individuals (11.3%) were identified. Human Trypanosoma cruzi infection was influenced by geography. In the Lacandon Forest and Central Mountains there was a higher seroprevalence 32.1 and 13.8% respectively, than on the coast (1.2%). In Mesochiapas there were no seropositive individuals among the 137 persons tested. An active transmission is probably continuing because seropositive cases (13.8%) were detected in children under 10 years of age. The vector recognized on the Coast was Triatoma dimidiata while in the Lacandon Forest it was Rhodnius prolixus. Key-words: Chagas’ disease. Trypanosoma cruzi. Seroprevalence. Seroepidemiologic survey. Resumo Foi feito um estudo sorológico em quatro zonas geográficas do estado de Chiapas México. Foram colhidas 1333 amostras dos habitantes das 13 comunidades situadas na costa, na região central montanhosa, na floresta lacandona e na região chamada mesochiapas. Cento cinqüenta e uma pessoas (11,3%) foram identificadas como soropositivas. A infecção pelo Trypanosoma cruzi teve a influência da geografia local. Na floresta lacandona nas montanhas centrais, foi encontrada uma prevalência de 32,1 e 13,8% respectivamente, mais que na costa 1,2%. Na zona de mesochiapas não foi encontrada nenhuma pessoa com sorologia positiva entre 137 estudadas. Como encontramos sorologia positiva em crianças menores de 10 anos, pensamos que exista uma transmissão ativa contínua. Na costa foi reconhecido o vetor Triatoma dimidiata e na floresta Lacandona o Rhodnius prolixus. Palavras-chaves: Doenca de Chagas. Trypanosoma cruzi. Soroprevalência. Estudo Soropidemiológico Chagas’ disease has been identified in Mexico since 19405. Epidemiological surveys carried out in different geographical regions of the Country have revealed a heterogeneous distribution of infection. Endemic zones have been identified mainly in the coastal and southern regions with high seropositivity in rural villages, as well as cases of chronic human disease7 12 13 14. Chiapas, a southern state, showed both characteristics: tropical and subtropical climate and high rural conditions. In 1983, Goldsmith et al1 reported 3.6% of seropositivity in human beings in Chiapas. The more recent National Seroepidemiological survey15 identified Chiapas as the highest seropositive state in Mexico, up to 5% in open population, while in voluntary blood donors Trypanosoma cruzi infection was 1.8%2. A serologic survey carried out in Chilón, a rural municipality in Chiapas, showed 29% seropositivity in 1993 (VM, personal unpublished data). The objective of this work was to update seroepidemiological data. A survey on 1,333 volunteers collected samples from residents of thirteen communities in four geographic zones within Chiapas revealed a relatively high seropositivity and suggested active transmission.