Modelling the effect of density vegetation coverage and the occurrence of peridomestic infestation by Triatoma infestans in rural houses of northwest of Córdoba, Argentina

CARDOZO MIRIAM; ESTALLO ELIZABET LILIA; SORIA CAROLA; RODRÍGUEZ CLAUDIA SUSANA; LÓPEZ ANA GRACIELA; NATTERO JULIETA; CROCCO LILIANA BEATRIZ

ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS.

ACAD BRASILEIRA DE CIENCIAS

Lugar: Rio de Janeiro; Año: 2021 vol. 93 p. 1 - 10

0001-3765

Chagas is one of the most important endemic diseases in Latin America. It is caused by the protozoan Trypanosoma cruzi, which is transmitted to humans and other mammals mainly via blood-sucking insects from the Reduviidae family, Triatominae subfamily (OMS 2007).In South America, Triatoma infestans is the vector of greatest epidemiological importance, characterized by its high adaptive capacity to human dwellings (Rabinovich 1972, Lent and Wygodzinsky 1979). They are found almost exclusively in domestic environments and peridomestic habitats such as chicken coops, goat pens, pig corrals and storerooms, which show optimum conditions for the establishment of colonies (OMS 2002). The Southern Cone Initiative to Control Chagas Disease (INCOSUR), launched in 1991, succeeded in reducing the distribution area of T. infestans to less than 1 million km2 through insecticide-based vector control, health education and house improvement program (Schofield et al. 2006). Nevertheless, in arid Gran Chaco areas of Argentina, Paraguay, and Bolivia, reinfestations of human dwellings continue to occur in several provinces or departments (Gürtler et al. 2009). Many authors agree that the persistence of triatomine infestation in the Chaco region is due to the difficulty of eliminating the vector population in peridomestic habitats (Cecere et al. 1997). After the residual application of pyrethroid insecticides, chicken coops, goat pens, pig corrals and other potential habitat in the peridomicile are the first to be recolonized (Canale et al. 2000), because their complex structure not only prevent good penetration of insecticides (Gürtler et al. 2009) but also provide optimal conditions for sustaining near domiciles abundant triatomines population (Cecere et al. 2006). Hence, the active dispersal of T. infestans (flying and walking) plays an important role in the local propagation of triatomines within and between neighboring households (Vazquez-Prokopec et al. 2004, Abrahan et al. 2011). Several studies conducted in semiarid regions of Argentina determine that at local scales, the spatial patterns of reinfestation of peridomicile and domicile habitats are determined by flight dispersal capacity, local abundance of triatomines and hosts, spatial configuration of households and vegetation cover (Vazquez-Prokopec et al. 2004, McGwire et al. 2006, Abrahan et al. 2011). However, little is known about how vegetation cover surrounding houses affects the spatial distribution of infestations. Some authors mentioned that dense vegetation cover and high trees may act as a barrier for triatomine dispersal (Vazquez Prokopec et al. 2004). The northwest region of Córdoba Province, located in the south of the Gran Chaco region of Argentina, shows a heterogeneous scenario of T. cruzi transmission related with differences in vector control interventions, land use changes and socioeconomic factors in the last decades (Moreno et al. 2010; 2012). Previous reports on the area (Crocco et al. 2019), showed a high peridomiciliar infestation, strongly associated with the presence of chicken coops. This peridomestic habitat is the most frequent in the area and the most vulnerable to infestation because the materials of construction (sticks, wood, or cardboard) provides excellent refuge sites for triatomines. Soria et al. (2019) report within the same area a high percentage of combined blood meals (goat, chicken, dog and human) on feeding profiles of T. infestans collected in peridomicile. This record does not seem to be related to host-feeding source choice nor to the main host residing in the peridomicile, since most of the triatomines that recorded mixed blood ingestion were found in peridomiciles with only one type of host present. Hence, this study evidence a high dispersion of adult T. infestans between peridomiciles in natural conditions, which reinforces the importance of better understanding how environmental and spatial factors may modulate the dispersal strategy of triatomines.The aim of our study was to evaluate the spatial effect of peridomestic infestation and density vegetation cover in a historically endemic area for Chagas disease, in order to add understanding on the dynamics of dispersion of T. infestans. We hypothesize that the density of the vegetation cover influences the dispersion of triatomines between nearby peridomicile by facilitating or preventing the transmission of physical and chemical signals from the peridomiciliary area. Infrared radiation, thermal signals emitted by domestic hosts as well as the mixture of odor cues and lights can be perceived in a range of meters by T. infestans, and may influence the appetitive searching and long-range orientation (Guerensten and Lazzari 2009; Catalá 2011).