Sylvatic foci of the Chagas disease vector Triatoma infestans in Chile: description of a new focus and challenges for control programs

Abstract

Chagas disease, caused by the protozoan Trypanosoma cruzi and transmitted by triatomine insect vectors, affects about 10 million people worldwide (Schmunis 2000) and is the third most important global parasitic disease after malaria and schistosomiasis (World Bank 1993). Because of effective vector control campaigns, the number of acute cases has decreased markedly and has been reduced to nearly zero in previously highly endemic areas of Uruguay, Chile and Brazil (Schofield et al. 2006).The Chagas disease vector Triatoma infestans (Klug 1834) was historically considered an e�clusively do-) was historically considered an e�clusively domestic insect, but it has now been reported in sylvan environments (Noireau et al. 2005, Noireau 2009). The first sylvatic population of T. infestans was reported in Cochabamba, Bolivia, inhabiting rock piles associated with wild guinea pigs (Torrico 1946). Other reports have shown T. infestans in Argentina (Mazza & Schreiber 1938, Mazza 1943, Ceballos et al. 2009), Paraguay (Velasquez & González 1959 and Brazil (Barretto et al. 1963) under rocks or trunks of fallen trees, in hollow trees, under bark, in shelters or burrows of marsupials and rodents and in bird nests occupied by owls, parrots or small rodents (Noireau et al. 1997). Wild T. infestans has been found in an e�tended geographical region throughout Chaco and three Andean departments of Bolivia: Cochabamba, La Paz and Potosí (Noireau et al. 1999, Cortez et al. 2007. T. infestans was considered to be eradicable due to its strictly domestic behavior and its non-autochthonous status outside of its apparent centre of origin in the Andean valleys of Bolivia. This theory has been challenged by empirical evidence of wild individuals collected by vector control programs and researchers over several decades (Gürtler 2009). Sylvatic triatomines may occasionally invade human residences, acting as founders of new colonies (Fitzpatrick et al. 2008). Hence, it is necessary to study the ecology and behavior of their populations to understand the domiciliation process and generate new strategies for their control (Beard et al. 2002, Guhl et al. 2009, Moncayo & Silveira 2009).In Chile, parasite transmission from vectors to humans occurs mainly in rural and suburban areas encompassing the northern desert and semiarid and Mediterranean environments, between latitudes 18°30'S and 34°36'S. The triatomine insects T. infestans, Mepraia spinolai (Porter 1934) and Mepraia gajardoi are the vector species that have been reported in that area (Spinola 1852, Neghme 1982, Lent et al. 1994, Frias et al. 1998.In 1991, several countries of South America, including Chile, established the Southern Cone Initiative for control of Chagas disease (INCOSUR-Chagas), which provided united strategy, control actions and an information system used to evaluate local control programs (Silveira 2002). The specific aims of the initiative were the following: (i) the elimination of T. infestans from dwellings and their surroundings in endemic areas, (ii) the reduction an...

Differential Pattern of Infection of Sylvatic Nymphs and Domiciliary Adults of Triatoma infestans with Trypanosoma cruzi Genotypes in Chile

“…There are probably more wild foci of T. infestans in the endemic area of Chile, not necessarily within bromeliads, as shown recently. 22 Thus, it is important to continue the search for this vector, particularly in areas where there are unexplained sources of winged adults that invade houses. It is critical to study the surrounding area when these triatomines are found infected with T. cruzi, given the higher risk of transmission of Chagas disease to their inhabitants.…”

“…20 Recently, T. infestans was found colonizing wild areas in rural localities of central Chile inhabiting terrestrial bromeliads of the genus Puya spp., 21 and rock piles. 22 The bromeliad Puya spp. provides shelter to numerous small mammals, 23 similar as in other countries, where species from the genera Rhodnius and Triatoma have also been found in bromeliads, among other ecotopes.…”

Susceptibility to deltamethrin of wild and domestic populations of Triatoma infestans of the Gran Chaco and the Inter-Andean Valleys of Bolivia

“…In addition to this important problem, in the last few years, wild foci of T. infestans have been described, mainly in the Inter-Andean Valleys and in the Gran Chaco [8,9]. This fact was also observed in Argentina, Paraguay and Chile, showing that wild T. infestans have dispersed more widely than expected [10][11][12][13][14]. In Bolivia, the epidemiological significance of wild foci of T. infestans has been stressed [10].…”

Susceptibility and resistance to deltamethrin of wild and domestic populations of Triatoma infestans (Reduviidae: Triatominae) in Bolivia: new discoveries

“…In the last few years, numerous sylvatic foci have been reported, principally in two ecoregions: Bosques Secos Interandinos and Gran Chaco (Buitrago et al 2010, 2012. Moreover, discoveries of sylvatic foci in Argentina, Paraguay and Chile show that sylvatic populations of T. infestans are more widespread than initially described (Ceballos et al 2009, Bacigalupo et al 2010, Rolón et al 2011. It is worth noting that these sylvatic populations have the potential to jeopardise control efforts because of possible free insect movements between the sylvatic environment and dwellings (Noireau et al 2005, Ceballos et al 2011.…”