Vector Blood Meals Are an Early Indicator of the Effectiveness of the Ecohealth Approach in Halting Chagas Transmission in Guatemala

Abstract

Abstract. A novel method using vector blood meal sources to assess the impact of control efforts on the risk of transmission of Chagas disease was tested in the village of El Tule, Jutiapa, Guatemala. Control used Ecohealth interventions, where villagers ameliorated the factors identified as most important for transmission. First, after an initial insecticide application, house walls were plastered. Later, bedroom floors were improved and domestic animals were moved outdoors. Only vector blood meal sources revealed the success of the first interventions: human blood meals declined from 38% to 3% after insecticide application and wall plastering. Following all interventions both vector blood meal sources and entomological indices revealed the reduction in transmission risk. These results indicate that vector blood meals may reveal effects of control efforts early on, effects that may not be apparent using traditional entomological indices, and provide further support for the Ecohealth approach to Chagas control in Guatemala.

Ecological, Social and Biological Risk Factors for Continued Trypanosoma cruzi Transmission by Triatoma dimidiata in Guatemala

“…Blood meal analyses showed that chickens, rodents and dogs are important blood sources in this region, as in another study in a nearby Municipality [51]. Chickens are an important part of household nutrition and economy, and are allowed to nest inside the house.…”

“…The molecular detection of a blood meal indicates blood meals taken within the last 2–3 weeks [53]. The detection of multiple blood meals in nymphs, including human blood meals in outdoor structures, suggests that immature stages actively move in search of blood meals, as found in another Municipality [51] and for T. infestans in Peru and Argentina [4], [6]. This may be a situation that facilitates house re-infestation, as nymphs may find peridomestic shelters in rodent nesting areas, found within and outside the household, that do not receive insecticide treatment.…”

Information to Act: Household Characteristics are Predictors of Domestic Infestation with the Chagas Vector Triatoma dimidiata in Central America

“…The percentage of houses with good quality complete plastering increased by 21% and 13% in the two Ecohealth-intervention villages; one control village showed a 4% decline and another showed an 9% increase in good quality complete plastering. 24 After 5 years of interventions, the percentage of Triatoma dimidiata feeding on humans dropped from 38% to 7% and Trypanosoma cruzi infection in Triatoma dimidiata dropped from 49% to 16% in one intervention village, 26 whereas in the other intervention village, the number of Triatoma dimidiata dropped drastically and it was not possible to obtain an estimate of percent of insects feeding on humans. Infestation levels in that village have remained under the 5% threshold set by the Guatemalan Ministry of Health for insecticide application 27 and also under the suggested threshold of infestation (8%) at which Trypanosoma cruzi transmission becomes unlikely.…”

Hemi-Nested PCR and RFLP Methodologies for Identifying Blood Meals of the Chagas Disease Vector, Triatoma infestans

“…Fragments of the cytochrome oxidase b locus were previously used for taxonomic and phylogenetic studies [14] while the 12S and 16S rRNA loci were used to identify vertebrate species in forensic studies [15]. Some of these mitochondrial loci have also been used to identify blood meals in vectors [16], [17], and as potential indicators of community based interventions against Chagas disease [18]. These assays relied on DNA sequence analysis for species determination.…”