Distribution of domestic Triatominae and stratification of Chagas Disease transmission in Oaxaca, Mexico

Abstract

Mexico has 18 species of Triatomine bugs (Hemiptera: Reduviidae) reported to be vectors of Trypanosoma cruzi. Chagas Disease is widespread in Mexico, with up to 3.5% seropositivity of human transfusion blood. The State of Oaxaca has the longest history of endemic Chagas Disease, based on acute and chronic case reports, and of entomological surveys in the country. However, the State health care services need more information on current risks of vector transmission. In order to identify and characterize areas of transmission in Oaxaca and to stratify the vector potential, the distribution of domestic Triatominae was surveyed during 1996-98 in collaboration with the primary health care services and local communities. Villages were studied in 11% of 570 municipalities in Oaxaca. Eight triatomine species were found in domestic and peri-domestic habitats: Triatoma barberi Usinger, T. bolivari Carcavallo et al., T. dimidiata (Latreille), T. mazzottii Usinger, T. nitida Usinger, T. pallidipennis (Stal), T. phyllosoma (Burmeister) and Rhodnius prolixus Stal. For each triatomine species in Oaxaca, the range of distribution and habitat characteristics are described. Habitat partitioning, principally based on altitude and mean annual precipitation, limited the overlap of distribution between species. Relatively consistent altitude of human settlements facilitates the dispersion of individual species within microregions. Entomological indices of house infestation were used to estimate that approximately 50% of the human population (1,874,320 inhabitants) would be at risk of vector transmission, with a minimum of 134,320 infected people and 40,280 chronic cases of Chagas Disease currently in Oaxaca.

Geographic distribution and morphometric differentiation of Triatoma nitida usinger 1939 (Hemiptera: Reduviidae: Triatominae) in Guatemala

“…Previous reports from Costa Rica (Vargas & Montero-Gei 1971) and Mexico (Ramsey et al 2000) also indicate small numbers of these bugs inside human dwellings. However, in two houses an unusually large number of bugs were found (24 and 39), which is not commonly seen even with the more ubiquitous species T. dimidiata (Monroy et al 1998a).…”

“…There is a similar report for T. nitida in Oaxaca, Mexico, where only three insects were collected by homeowners in two out of 92 surveyed villages, within an altitude range of 1100 to 1520 m.a.s.l. (Ramsey et al 2000).…”

“…In the state of Oaxaca, two adults and one nymph of T. nitida were collected in domestic habitats by homeowners in two out of 92 surveyed villages. The authors attribute the presence of this species outside the Yucatan Peninsula to the passive transfer of bugs carried by migrant farm workers (Ramsey et al 2000).…”

Vigilancia de la presencia de triatominos mediante gallineros en el sur de Jalisco, México

“…Por otra parte, T. barberi fue recolectado exclusivamente en el intradomicilio, como ha sido reportado previamente en otras áreas de México (27,28), lo que podría ser indicativo de riesgo para los habitantes del área. Aparentemente, las poblaciones peridomésticas de esta especie, recolectadas previamente en la misma área geográfica, (7) no se sintieron atraídas a invadir los gallineros y, probablemente, invadieron las viviendas atraídas por la luz.…”

Elimination of Rhodnius prolixus in Central America

“…[32,39,40]]. A detailed survey of Triatominae in the state of Oaxaca reported three specimens of R. prolixus collected in 1998 from two villages near a previously reported collection site at San José de las Flores [41]; this appears to be the last published record this species in Mexico, although a further specimen was collected in Oaxaca in 2002 (C. Ponce, personal communication, see also [42]).…”