UVM Theses and Dissertations
Format:
Print
Author:
Pizarro Cortez, Juan Carlos
Dept./Program:
Biology
Year:
2007
Degree:
Ph. D.
Abstract:
Surveillance strategies for Triatoma infestans, the main vector of Chagas disease in the Southern Cone of South America are a critical component of maintaining the current downward trend in disease transmission. Success in reducing the number of people infected with the causative parasite, Trypanosoma cruzi, is the result of 15 years of a multi-national initiative aiming to eliminate the vector from its domiciliated habitat by insecticidal spraying in conjunction with measures to reduce the likelihood of transmission through a blood transfusion.
In Bolivia, vector control is not a panacea for Chagas disease control. The ideal strategy against tropical disease synthesized in the TDR precept "investigate, eliminate, eradicate" is far from the truth in the case of Chagas disease due to its zoonotic nature and the existence of sylvatic foci of T. infestans in the Sucre-Cochabamba valley and in the Southern Chaco region. In addition, Chagas disease disproportionately affects poor people especially those living in rural areas and in poor quality housing that offers an ideal environment for vector re-colonization. High levels of vector-borne transmission are still apparent in many areas of Bolivia where infection in school age children and house infestation are significant.
Effective strategies after insecticide treatment require knowing the source of recolonists and directing interventions against these ecotopes. It has been difficult to identify whether the newly established populations are remnants of the insecticidal spraying or they are coming from nearby untreated structures or sylvatic localities. Here we tackled this problem with two approaches: 1) using ten microsatellite loci, we studied the population genetics of this vector in Chuquisaca at different hierarchical levels to determine the geographic scale over which vectors move and thus the scale at which vector control is necessary and, 2) after developing PCR-based assays, we detected dispersion through the feeding patterns of domestic and peri-domestic T. infestans; and investigated the epidemiological importance of domestic and peri-domestic animals in the transmission dynamics of T. cruzi to humans in this area.
Based on the high level of population structure revealed by the microsatellites we were able to identify the panmictic unit of T. infestans as a single household. Our results also detected a trend of vector dispersion from peri-domicile to human habitations highlighting the fundamental role that these compounds play as source of colonists as well as the epidemiological relevance that dogs, pigs, guinea pigs and chickens have in the transmission of T. cruzi to humans in this particular region. As part of this research we developed a molecular approach based on PCR assays to detect the blood meal content and level of T. cruzi infection in T. infestans.
In Bolivia, vector control is not a panacea for Chagas disease control. The ideal strategy against tropical disease synthesized in the TDR precept "investigate, eliminate, eradicate" is far from the truth in the case of Chagas disease due to its zoonotic nature and the existence of sylvatic foci of T. infestans in the Sucre-Cochabamba valley and in the Southern Chaco region. In addition, Chagas disease disproportionately affects poor people especially those living in rural areas and in poor quality housing that offers an ideal environment for vector re-colonization. High levels of vector-borne transmission are still apparent in many areas of Bolivia where infection in school age children and house infestation are significant.
Effective strategies after insecticide treatment require knowing the source of recolonists and directing interventions against these ecotopes. It has been difficult to identify whether the newly established populations are remnants of the insecticidal spraying or they are coming from nearby untreated structures or sylvatic localities. Here we tackled this problem with two approaches: 1) using ten microsatellite loci, we studied the population genetics of this vector in Chuquisaca at different hierarchical levels to determine the geographic scale over which vectors move and thus the scale at which vector control is necessary and, 2) after developing PCR-based assays, we detected dispersion through the feeding patterns of domestic and peri-domestic T. infestans; and investigated the epidemiological importance of domestic and peri-domestic animals in the transmission dynamics of T. cruzi to humans in this area.
Based on the high level of population structure revealed by the microsatellites we were able to identify the panmictic unit of T. infestans as a single household. Our results also detected a trend of vector dispersion from peri-domicile to human habitations highlighting the fundamental role that these compounds play as source of colonists as well as the epidemiological relevance that dogs, pigs, guinea pigs and chickens have in the transmission of T. cruzi to humans in this particular region. As part of this research we developed a molecular approach based on PCR assays to detect the blood meal content and level of T. cruzi infection in T. infestans.