The role of the peridomiciliary area in the elimination of Triatoma infestans from rural Argentine communities

Abstract

The purpose of this study was to identify the origin of Triatoma infestans reinfestation and study its dynamics following spraying with deltamethrin inside and around 94 houses in three rural communities in northwestern Argentina. The effectiveness of the spraying was evaluated immediately after the houses were sprayed and two months later. In addition, five residual peridomiciliary foci were found and sprayed, as well as three preexisting ones that had not been sprayed. To monitor reinfestation, biosensors were placed in the houses and each family was also asked to capture triatomines and keep them in plastic bags; in addition, triatomines were searched for in and around houses, using an aerosol that dislodged them from their hiding places. Selective sprayings were carried out only where a colony of T. infestans was found. During the 30 months of follow-up, the percentage of houses in which any T. infestans were captured varied between 3% and 9%. In six houses, T. infestans were captured during more than one evaluation. The number of peridomiciliary areas found to be infested (19) was double the number of infested houses (9). Colonies of T. infestans were found only in the peridomiciliary areas, where the number of T. infestans captured was six times higher than in the houses. Chickens were the host most frequently associated with peridomiciliary foci. This area was the origin and principal source of reinfestation. To reduce the speed of reinfestation and the frequency with which sprayings are needed, the following environmental and chemical control methods must be combined in the peridomiciliary area: reduce the number of hiding places of triatomines; restrict the raising of birds to structures that cannot be colonized by triatomines; apply an insecticide that is less likely to be degraded by exposure to the elements, or perform a second spraying 6 to 12 months after the first; and employ a device for early detection of the presence of T. infestans around houses.

Re-infestation of houses by Triatoma dimidiata after intra-domicile insecticide application in the Yucatán peninsula, Mexico

“…Infestation monitoring before and after insecticide spraying -While most studies focus on various houses that are usually monitored only once or twice after 6 month or a year following insecticide application (Cecere et al 1997, Diotaiuti et al 1998, Acevedo et al 2000, we decided to focus on four houses (two in each village) to be able to carry out a more frequent and detailed monitoring of re-infestation. We included representative houses with different characteristics as we had shown previously that there was no significant difference in apparent house infestation according to building materials (Dumonteil et al 2002).…”

Identification and characterization of microsatellite markers in the Chagas disease vector Triatoma infestans (Heteroptera: Reduviidae)

“…Persistence of residual populations may be explained by a failure in exposing all bugs to the insecticide, or after several sprayings, development of insecticide resistance, while immigration may be due to incidental human transport or active dispersal of the insect. Incomplete elimination of T. infestans following a single application of pyrethroid insecticides was considered the most likely source of reinfestation (Cecere et al, 1997;Dujardin et al, 1996;Gürtler et al, 2004). The peridomicile, where most failures in control and detection may occur, is usually the first area to be recolonized and contains the greatest abundance of T. infestans 1 year post-spraying (Cecere et al, 2002).…”

Identification and characterization of microsatellite markers in the Chagas disease vector Triatoma dimidiata

“…Vector control programs in South America have proven highly successful at reducing both home infestation rates and the incidence of new infections in affected areas (Schmunis et al, 1996). Unfortunately, reinfestation rates among treated houses have ranged from 3 to 88%, up to 7 years post spraying (Gurtler et al, 1994;Cecere et al, 1997;Dujardin et al, 1997;Rojas de Arias et al, 1999). In Guatemala, infestation rates of almost 20% have been reported in villages 1 year following insecticide spraying (C.C.R., unpublished data).…”