Home Economics American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research
Chagas disease in the Southern Cone countries
Historically the main vector for the region was T. infestans. However, with the eminent success of the Southern Cone program, having effectively eliminated T. infestans from Brazil, Chile, and Uruguay, and many parts of Argentina, it has been demonstrated that the center of radiation for the species is in Bolivia,99 where it most likely continues to cause a problem due to ready reinvasion from sylvatic foci. Domestic infestations continue to persist in the Chaco region where sylvatic foci of T. infestans are present. Several other species are implicated as secondary vectors, particularly since the control of T. infestans, and the presentation of the niche to other species. In northeastern Brazil, T. brasiliensis and T. psuedomaculata show strong tendencies to colonize domestic habitats along with Panstrongylus megistus in southern Brazil. Other species that have shown some potential to domiciliation are R. neglectus, T. vitticeps, and T. rubrovaria in Brazil. Triatoma sordida is an important secondary vector in Paraguay, Bolivia, northern Argentina, and southern Brazil. T. sordida and a related species, T. guasayana, demonstrate mass dispersal during the dry season, which can result in the invasion of domestic environments.100
T. cruzi subtypes TcII and TcVI predominate in both sylvatic and domestic cycles in this region. Interestingly TcI is also present in many arboreal hosts, such as Didelphis species. The absence of Rhodnius species in the southern part of this region and the lack of data for other triatomines carrying TcI present the possibility that transmission of TcI, in Didelphis at least, commonly occurs without vectors by direct contamination from the anal scent glands.101 However, P. megistus has been implicated with TcI transmission in southern central Brazil,102 as has as a species of Rhodnius, R. neglectus,1103 which has a distribution extending from the Amazon to southern Brazil. Also, Triatoma (Mepraia) spinolai in Chile has been reported to be infected with TcI.104 Other vector species may yet to be implicated in TcI transmission because it is often difficult to sample from sylvatic habitats directly. Table 5.2 summarizes the actions and strategies to be taken for controlling triato- mine species in the different initiatives in the Americas.
Tabie 5.2 Action to be taken for controlling autoctonous or introduced triatomine species in different control initiatives in the Americasa
Table 5.2 (Continued)
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