Hidden sylvatic foci of the main vector of Chagas disease Triatoma infestans: threats to the vector elimination campaign?

CEBALLOS LA; PICCINALI RV; MARCET PL; VAZQUEZ-PROKOPEC GM; CARDINAL MV; SCHACHTER-BROIDE J, ; DUJARDIN JP; SCHIJMAN AG; DOTSON EM; KITRON U; GURTLER RE

PLOS NEGLECTED TROPICAL DISEASES

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2011 vol. 5 p. 1349 - 1349

1935-2735

Background: Establishing the sources of reinfestation after residual insecticide spraying is crucial for vector eliminationprograms. Triatoma infestans, traditionally considered to be limited to domestic or peridomestic (abbreviated as D/PD)habitats throughout most of its range, is the target of an elimination program that has achieved limited success in the GranChaco region in South America.Methodology/Principal Findings: During a two-year period we conducted semi-annual searches for triatomine bugs inevery D/PD site and surrounding sylvatic habitats after full-coverage spraying of pyrethroid insecticides of all houses in awell-defined rural area in northwestern Argentina. We found six low-density sylvatic foci with 24 T. infestans in fallen orstanding trees located 110–2,300 m from the nearest house or infested D/PD site detected after insecticide spraying, whenhouse infestations were rare. Analysis of two mitochondrial gene fragments of 20 sylvatic specimens confirmed their speciesidentity as T. infestans and showed that their composite haplotypes were the same as or closely related to D/PD haplotypes.Population studies with 10 polymorphic microsatellite loci and wing geometric morphometry consistently indicated theoccurrence of unrestricted gene flow between local D/PD and sylvatic populations. Mitochondrial DNA and microsatellitesibship analyses in the most abundant sylvatic colony revealed descendents from five different females. Spatial analysisshowed a significant association between two sylvatic foci and the nearest D/PD bug population found before insecticidespraying.Conclusions: Our study shows that, despite of its high degree of domesticity, T. infestans has sylvatic colonies with normalchromatic characters (not melanic morphs) highly connected to D/PD conspecifics in the Argentinean Chaco. Sylvatichabitats may provide a transient or permanent refuge after control interventions, and function as sources for D/PDreinfestation. The occurrence of sylvatic foci of T. infestans in the Gran Chaco may pose additional threats to ongoing vectorelimination efforts.