Anophelines of Papua New Guinea
Members of the Anopheles punctulatus species complex serve as vectors for Plasmodium falciparum, P. vivax, P. malariae, P. ovale and Wuchereria bancrofti. Recent advances in molecular diagnostics allow us to accurately identify morphologically similar members of the An. punctulatus group. It is now known to comprise 12 species, including major malaria vectors: An. farauti, An. punctulatus, An. hinesorum, An. koliensis and An. farauti 4. These mosquitoes exhibit heterogeneities in distribution, host-seeking behaviors and capacity to transmit disease.
Our group is interested in characterizing larval habitat, distribution, degree of endophagy, host preference and peak biting times for the major vectors. We have found that certain species seek a human host outdoors in the early evening, whereas others are more likely to bite indoors late at night. We have also observed significantly different vector species compositions within a village, throughout the year, and following control interventions. These characteristics, paired with species-specific susceptibilities to disease, strongly influence malaria and filariasis transmission dynamics.
The combination of mosquito/parasite diversity and abundance in Papua New Guinea contributes to a variable transmission landscape. This complex matrix of vector and parasite presents the perfect opportunity to study natural relationships between species.
We are currently conducting field surveys around Papua New Guinea to better understand parasite distribution as well as strain-specific associations. We are also able to observe the impacts of disease interventions, such as drug treatments and long-lasting insecticidal nets, on transmission in the wild.
Through experimental infections of W. bancrofti and Plasmodium spp. in our insectary, we are able to determine each mosquito species’ capacity to develop an infection and transmit disease. We are studying the impacts of mixed-species infections and parasite density on transmission potential as well as the mosquito immune response and barriers to infection. How does disease burden affect mosquito survivorship and the ability to mount an immune response? How might a primary infection affect development of a secondary infection? How will the elimination of filariasis impact malaria transmission?
Vector-borne disease control
With such ecological and behavioral diversity among vector species, it is likely that one approach to vector control will not be sufficient. Long-lasting insecticidal nets have been distributed throughout Papua New Guinea and we are evaluating their efficacy through field and laboratory studies. In the field we monitor mosquito feeding behaviors to determine when and where transmission occurs, and whether any changes are observed following LLIN distribution. We are measuring changes in abundance and transmission over time to determine the long term impacts and limitations of the intervention.
In our laboratory we screen for genetic mechanisms of pyrethroid resistance that may compromise insecticide based control measures. We are also testing the efficacy of used LLIN’s to determine optimum conditions for use, storage, and recommended time to replacement.