Date of Award

1-1-2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Biomedical Sciences

Content Description

1 online resource (xiv, 196 pages) : illustrations (some color), color maps.

Dissertation/Thesis Chair

Jan E. Conn

Committee Members

Robert Glaser, Alexander Ciota, Linda Styer, Kevin Emerson, Dionicia Gamboa

Keywords

Amazon, Larval ecology, Malaria, Nyssorhynchus darlingi (formerly Anopheles darlingi), Population genetics, Vector biology, Mosquitoes as carriers of disease, Anopheles, Mosquitoes, Deforestation

Subject Categories

Biology | Entomology | Public Health

Abstract

Malaria is the most deadly vector borne disease, causing substantial morbidity and hundreds of thousands of deaths worldwide each year. In the Americas, the incidence of malaria has increased steadily since 2014. The factors driving continued malaria transmission are complex and highly variable across endemic areas. These factors include inadequate access and financial commitment to prevention, diagnosis, and treatment, and a failure to target interventions to heterogeneous malaria transmission patterns and vector populations. Nyssorhynchus darlingi (formerly Anopheles darlingi), the predominant malaria vector in Latin America, is known for behavioral, phenotypic, and genetic variability across its range, which allow it to adapt readily to changes in its environment. Environmental changes caused by human activity, including deforestation, the creation of artificial water bodies that can be used as vector larval habitats, and the use of insecticides, are known to have effects on vector populations that impact malaria transmission and control activities. My dissertation research focuses on the effects of such alterations on the biting behavior, larval ecology, and population genomics of malaria vector populations in Amazonian Peru and Brazil. First, I investigated the biting behavior of Ny. darlingi over three years between distributions of long-lasting insecticidal nets in two villages in Amazonian Peru. There was evidence of a behavioral shift, suggesting that Ny. darlingi had increased outdoor biting soon after the nets were distributed, then, as the nets aged, returned to increased indoor biting. As there was no evidence of genetic differentiation of indoor and outdoor-biting populations of Ny. darlingi in these villages, it is possible that the biting behavior shift was the result of behavioral plasticity. Second, I found that Ny. darlingi larval habitats in eight villages in Amazonian Peru were associated with landscapes that had experienced recent deforestation, which supports the hypothesis that malaria risk in the Amazon is highest at the forest fringe. Furthermore, Ny. darlingi larvae were collected from every active fish pond sampled in these villages, supporting adaptation of this species to artificial water bodies. Third, I found no evidence of population genetic structure of Ny. darlingi across a range of forest cover levels in four municipality groups in Amazonian Brazil, indicating that adaptation to deforestation has not led to genome-wide differentiation in Ny. darlingi populations in these municipalities. Overall, my dissertation research provides two examples of adaptation in Ny. darlingi in response to anthropogenic environmental changes: 1) a behavioral shift associated with changes in vector control interventions, and 2) oviposition in water bodies in human-modified landscapes. As malaria endemic countries move towards elimination, more research into such adaptive responses in vector populations in the Amazon and elsewhere is needed, so that interventions can be better targeted to local heterogeneity in the risk of malaria transmission.

Download

Share

COinS