Unravelling the relationships between Anopheles darlingi (Diptera: Culicidae) densities, environmental factors and malaria incidence: understanding the variable patterns of malarial transmission in French Guiana (South America)

Abstract

Anopheles darlingi, one of the main malaria vectors in the Neotropics, is widely distributed in French Guiana, where malaria remains a major public‐health problem. Elucidation of the relationships between the population dynamics of An. darlingi and local environmental factors would appear to be an essential factor in the epidemiology of human malaria in French Guiana and the design of effective vector‐control strategies. In a recent investigation, longitudinal entomological surveys were carried out for 2–4 years in one village in each of three distinct endemic areas of French Guiana. Anopheles darlingi was always the anopheline mosquito that was most frequently caught on human bait, although its relative abundance (as a proportion of all the anophelines collected) and human biting rate (in bites/person‐year) differed with the study site. Seasonality in the abundance of human‐landing An. darlingi (with peaks at the end of the rainy season) was observed in only two of the three study sites. Just three An. darlingi were found positive for Plasmodium (either P. falciparum or P. vivax) circumsporozoite protein, giving entomological inoculation rates of 0·0–8·7 infectious bites/person‐year. Curiously, no infected An. darlingi were collected in the village with the highest incidence of human malaria. Relationships between malaria incidence, An. darlingi densities, rainfall and water levels in the nearest rivers were found to be variable and apparently dependent on land‐cover specificities that reflected the diversity and availability of habitats suitable for the development and reproduction of An. darlingi.

The authors thank the official and traditional authorities of the ‘Village Inéri’, Midenangalanti, Bois Martin and Camopi village, for their warm welcome, and, especially, the mosquito collectors, for their commitment to the present study. They are also grateful to C. Grenier and M. Joubert, who are in charge of managing health centres and health posts in French Guiana. Access to the data on malaria incidence was facilitated by V. Ardillon and C. Flamand (who are in charge of epidemiological surveillance in French Guiana). The former head of the medical entomology unit of the Pasteur Institute in Cayenne (P. Rabarison) is thanked for his support, and, finally, the help of S. Chaney with editing the authors’ English is gratefully acknowledged.