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Understanding the Role of An. coustani Complex Members as Malaria Vector Species in the Democratic Republic of Congo

thesis
posted on 2021-04-19, 00:00 authored by Allison L. Hendershot

Malaria continues to be major health burden for sub-Saharan Africa, particularly for the Democratic Republic of Congo, where it causes nearly 12% of deaths worldwide. In recent years, the Anopheles coustani group have demonstrated their importance to malaria transmission throughout Africa, as studies have begun to document their vectorial competence, propensity for human biting, and most importantly early evening exophagy. These epidemiologically relevant bionomics have been shown to vary at the local level, leaving questions as to how members of this species group (including An. coustani, An. paludis, and An. caliginosus) contribute to malaria transmission in the Democratic Republic of Congo. This dissertation attempts to fill gaps in understanding Coustani Group bionomics and vector capacity by taking a thorough molecular approach to identifying species and characterizing behaviors, as well as providing a clearer understanding of how methods of Plasmodium detection impact our understanding of potential vectors.

For objective one, characterize temporal Coustani Group populations, bionomic characteristics, and contribution to transmission, this research found that in two sites of the DRC—Lodja and Kapolowe—biting patterns of Anopheles paludis and An. caliginosus varied considerably, as reflected in the morphological and molecular data, where early evening biting in Lodja indicates the bionomic potential of this species to circumvent LLINs. Two genetically distinct populations of coustani-like species were identified between the sites, offering a possible explanation to the varying bionomics observed. With respect to vector status, 12 An. paludis specimens were identified by PCR with Plasmodium parasites, however only a single specimen was confirmed with sporozoites by CSP ELISA.

As prompted by conflicting data regarding vector status of An. paludis, the second objective of this research sought to evaluate molecular methods for vector incrimination—the COX-1 PCR and CSP-ELISA. This dissertation research has demonstrated that the COX-1 PCR is highly sensitive to non-sporozoite parasites present in the head and thoraces following an infected bloodmeal. Compared to CSP-ELISA, PCR results are highly discordant at early life stages, though improve in later timepoints following sporozoite development. Its lack of life-stage specificity makes it a poor candidate as a primary method for vector incrimination, and thus results following this method alone should be interpreted with caution or supplemented with CSP-ELISA.

Taken together—the bionomic characterization and vector incrimination—the role of Coustani Group species in the DRC becomes clearer. There is no evidence gained from this research that suggests that An. caliginosus is a vector of malaria in the DRC. While there is no evidence to suggest that An. paludis currently plays a major role in transmission, it has demonstrated its vectorial capacity and behaviors which circumvent LLINs, and should thus be monitored.

History

Date Modified

2021-06-04

Defense Date

2021-02-12

CIP Code

  • 26.0101

Research Director(s)

Neil F. Lobo

Committee Members

Seth Irish David Severson

Degree

  • Doctor of Philosophy

Degree Level

  • Doctoral Dissertation

Alternate Identifier

1252917253

Library Record

6025918

OCLC Number

1252917253

Program Name

  • Biological Sciences

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