Vectors of Trypanosoma cruzi, parasite responsible for Chagas disease, are divided in intradomestic, peridomestic and sylvatic. The intradomestic are Triatoma barberi and Triatoma dimidiata, two species that represent the highest health risk among the Mexican population. Triatoma dimidiata is a species found mainly inside human habitats, but in Yucatan, it corresponds to the peridomicile vectors. Also in the peridomicile most of Chagas disease vectors are found: Meccus bassolsae, M. longipennis, M. mazzottii, M pallidipennis, M. phyllosomus, M picturata, Triatoma gerstaeckeri, T mexicana, T rubida, Dipetalogaster máxima (the last two are in the process of becoming adapted to the domicile), Panstrongylus rufotuberculatus which occasionally enters the domicile in its adult stage, and Rhodnius prolixus, which is practically controlled in the country. Peridomestic vectors are of lower risk in the transmission dynamics, as compared to the intradomestic ones. For the control of the intradomestic vectors, health education programs, improvements of housing, and the use of pesticides are essential To control the peridomestic vectors, health education programs are required, as well as the use of mosquito nets on doors and windows and around beds, aside from cementing the stone wall fences.

We performed a transversal-type epidemiological study in the state of Morelos, Mexico, to determine the presence of triatomines, their ecotopes, and importance in transmission of Trypanosoma cruzi Chagas. Sampling sites included domestic, peridomestic, and wild areas with collection based on the person per hour technique. We determined the entomological indices related to infestation, density, overcrowding, colonization, infection, and dispersion, which were used to calculate transmission risk. During the study, observations were made on the predominant building material, presence of cracks and illumination as factors fostering colonization. The most important results were related to infection indices, which were higher for domestic type triatomines (29%), whereas it was 4% for peridomestic sites, and 20% for sylvatic areas. The actual risk of human contact with the vector was of 0.51%, and the predominating ecotopes were stone heaps.

One of the most daunting challenges for Chagas disease surveillance and control in Mexico is the lack of community level data on vector distributions. Although many states now have assembled representative domestic triatomine collections, only two triatomine specimens had been collected and reported previously from the state of Guanajuato. Field personnel from the stateÕs Secretarṍa de Salud conducted health promotion activities in 43 of the 46 counties in the state and received donations of a total of 2,522 triatomine specimens between 1998 and 2002. All specimens were identiÞed, and live insects examined for Trypanosoma cruzi. In an effort to develop Þne-scale distributional data for Guanajuato, collection localities were georeferenced and ecological niches were modeled for each species by using evolutionary-computing approaches. Five species were collected: Triatoma mexicana (Herrich-Schaeffer), Triatoma longipennis (Usinger), Triatoma pallidipennis (Stål), Triatoma barberi (Usinger), and Triatoma dimidiata (Latreille) from 201 communities located at elevations of 870 Ð2,200 m. Based on collection success, T. mexicana had the broadest dispersion, although niche mapping indicates that T. barberi represents the greatest risk for transmission of Chagas disease in the state. T. dimidiata was represented in collections by a single adult collected from one village outside the predicted area for all species. For humans, an estimated 3,755,380 individuals are at risk for vector transmission in the state, with an incidence of 3,500 new cases per year; overall seroprevalences of 2.6% indicate that 97,640 individuals are infected with T. cruzi at present, including 29,300 chronic cases. . Nine of these species are considered as primary vector species (Ramsey et al. 2003), and most belong to two species complexes (phyllosoma and protracta) in the genus Triatoma (Lent and Wygodzinsky 1979). Multiple triatomine species are frequently found within a single region or state in Mexico. As a result, Ͼ71% of the Mexican population is at direct risk of acquiring T. cruzi infections from triatomines, and Ͼ96% of all T. cruzi transmission occurs via these vectors (Ramsey et al. 2003). KEY WORDSOne of the most signiÞcant challenges for Chagas disease surveillance and control in Mexico is the lack of Þne-scale (at the level of local communities) vector distribution data, as well as the almost complete ignorance of the diseaseÐtransmission characteristics and risk areas, both by the public health community and by at-risk populations. With improved malaria control in the country, in the last decade, "additional" operative vector control activities have focused primarily in urban environments owing to increases in classical and hemorrhagic dengue transmission. (To date, vector-borne disease control activities are budgeted only for malaria in the country.) Moreover, the recent decentralization of primary health care services to the state level has emphasized the need and the opportunity to review local and state health care prio...

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Los transmisores de Trypanosoma cruzi, flagelado causante de la enfermedad, se dividen en intradomiciliados, peridomiciliados y silvestres. Entre los intradomiciliados se encuentran, Triatoma barberi y Triatoma dimidiata, que son los que representan un mayor riesgo para la Salud Pública, en México. Aunque Triatoma dimidiata se encuentra principalmente dentro de la vivienda, en Yucatán tiene un comportamiento peridomiciliar, dentro de este grupo se encuentran la mayoría de los transmisores de la enfermedad de Chagas Meccus longipennis, M. mazzottii, M. pallidipennis, M. phyllosomus, M. picturatus, Triatoma gerstaeckeri, T. mexicana, T. rubida, Dipetalogaster máxima, Panstrongylus rufotuberculatus y Rhodnius prolixus. Los transmisores peridomiciliados son de menor riesgo en la dinámica de transmisión comparados con los intradomiciliados. Para el control de los transmisores intradomiciliados, se deben emplear programas de educación para la salud, mejoramiento de vivienda e insecticidas; mientras que para los vectores visitantes o peridomiciliados, son necesarios programas de educación para la salud, uso de mosquiteros, pabellones y cementación de las bardas de piedra.