Risk factors associated with house infestation by the Chagas disease vector Triatoma pallidipennis in Cuernavaca metropolitan area, Mexico

Abstract

Chagas disease caused by infection with Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae) is widespread in Mexico, transmitted by various triatomine bugs (Hemiptera: Reduviidae). The only domestic vector in Cuernavaca (population 650 000) is Triatoma pallidipennis (Ståhl) with T. cruzi seroprevalence ranging from 1% to 9% in the resident human population. We surveyed possible risk factors for T. pallidipennis infestation at Cuernavaca (altitude 1200-2200 m) on south-western slopes of the Sierra Madre Occidental. This metropolitan area (with five administrative counties) has rapid urbanization, forested environs and proliferation of 'weekend housing' for visitors from Mexico City, 60 km to the north. To assess factors associated with T. pallidipennis infestation, we first stratified Cuernavaca by altitude and by socio-economic status of population catchment units (PCUs). Within each PCU, one to three blocks were chosen for cluster sampling (three houses/block) and information about Chagas disease was distributed. After obtaining signed consent from householders, representative houses were routinely and opportunistically inspected for T. pallidipennis and surveyed for demographic, economic, physical and other potential risk factors. Of the 1129 houses assessed, T. pallidipennis was found in 4.1% (range 3.0-6.8% per county) and the T. cruzi infection rate was approximately 50% in bugs. Rates of house infestation in poor PCUs were double those in higher socio-economic strata (odds ratio 2.12, confidence interval 1.03-4.3), with >4-fold greater crowding index of T. pallidipennis. The bug density index was inversely correlated with PCU altitude and socio-economic category (altitude of homes being associated with prosperity), while the bug colonization index (presence of nymphs indicating breeding) did not vary significantly across the PCU categories, but did vary according to altitude. Multivariate regression analysis showed that the most significant risk factors associated with T. pallidipennis infestation were lower altitude (linked with lower socio-economic status), garden area >80 m(2), dogs at liberty to enter the house, occurrence of squirrels and opossums around the house, presence of pigs in the surrounding area and having at least one of the adjacent lots empty (unconstructed). Householders who had received information about Chagas disease comprised 33% from infested houses (14/42) but only 15% from non-infested houses (148/984). Hence, the awareness of Chagas disease was significantly associated with having a bug-free house (P < 0.01). When shown specimens of T. pallidipennis, the proportions of householders who recognized them were 78% from infested houses but only 29% of those with uninfested houses. Given the low infestation rates and the high capacity of the population to act appropriately once they have received information regarding this disease and its vector, relevant health education is expected to have a significant impact on triatomine control in this metropolitan area.

Risk factors for intradomiciliary infestation by the Chagas disease vector Triatoma dimidiatain Jutiapa, Guatemala

“…Different areas should evaluate their particular risk factors, but as studies throughout the years have evidenced the poor hygiene and the defective construction of typical rural houses, which are linked to low socioeconomic status, are the common denominators that increase odds of infestation with various triatomine species 3,7,8,16,17 .…”

“…For example, in rural areas of Morelos, Mexico, T. pallidipennis was more likely to be present in houses with adobe walls and with agricultural products stored inside the house; other risk factors included the lack of bed nets and number of rabbits 7 . But in urban areas of Morelos, the risk factors included the location of the house at lower altitudes (which was an indication that houses were of a lower socioeconomic status), the presence of a garden area of more than 80m 2 , an adjacent empty lot, and the presence of a diversity of animals around the house (dogs, pigs, squirrels, opossums) 8 .…”

Prevalencia de anticuerpos anti-T. cruzi en mujeres edad fértil en Socotá, Boyacá, 2014

“…Sin embargo, en el municipio se ha observado la presencia de vectores en las zonas urbana y rural, a pesar de la altitud en la cabecera municipal, lo que coincide con otros estudios en los que se han reportado personas y animales domésticos seropositivos en regiones ubicadas a más de 2.000 msnm (43,44). Esto se explicaría por la capacidad de adaptación y de resistencia del vector, que le permite resistir a grandes cambios ambientales e invadir nuevos nichos tróficos.…”

Riesgo de transmisión de Trypanosoma cruzi en el municipio de Metztitlán, estado de Hidalgo, México, mediante la caracterización de unidades domiciliares y sus índices entomológicos

“…Posiblemente esta capacidad la posea T. barberi pues se ha visto que coexiste con especies como T. dimidiata y T. pallidipennis (Zárate et al 1980, Guzmán 2001, se ha propuesto que es quizá debido a producción de feromonas que se liberan atrayendo o de alguna manera facilitando la convivencia interespecífica (Ramsey et al 2005).…”