Hidden sylvatic foci of Triatoma infestans in the Argentine Chaco: a threat to the vector elimination campaign?

CEBALLOS L. A., KITRON U., PICCINALI R. V. ,MARCET P. L. , CARDINAL M. V. , SCHACHTER-BROIDE J., DUJARDIN J. P. , DOTSON E. M. AND GÜRTLER R. E.

Philadelphia, Pennsylvania, United States of America

Congreso; 56th Annual Meeting of the American Society of Tropical Medicine and Hygiene; 2007

American Society of Tropical Medicine and Hygiene

Disease eradication programs depend on a time-limited intensive campaign and are likely to fail if resistance to insecticides or drugs (malaria) or sylvatic cycles occur (yellow fever). Chagas disease is the most important vector-borne disease in Latin America, with an estimated 10-18 million people infected. Triatoma infestans is the main vector in the southern cone of South America, and considered to be limited to domestic and peridomestic habitats throughout most of its range. It is s the target of an intergovernmental elimination program started in 1991. Only limited success was achieved in the Gran Chaco region due to repeated reinfestations, even in areas subject to intensive vector control efforts. In 2005 and 2006, we found in northern Argentina sylvatic colonies of T. infestans up to1900 m from the nearest house, and at 870-2230 m from the nearest infestation detected during the previous 18 months after full coverage residual insecticide spraying. We have also detected adult T. infestans and recently established small bug colonies of unknown origin in domestic and peridomestic habitats. Based on mitochondrial and microsatellite markers and on wing geometric morphometry, we conclude that the T. infestans found in sylvatic habitats are probably derived from domestic or peridomestic populations. Whether the sylvatic habitats provide a refuge for domestic/peridomestic populations following spraying and whether they can serve as a source for reinfestation remains to be determined. The occurrence of sylvatic foci of T. infestans in the Gran Chaco may pose a threat to ongoing vector elimination efforts.