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MALARIA: Obstacles and Opportunities
Regulation of Anopheline Populations
Factors affecting larval survival and mechanisms controlling adult production in aquatic habitats are largely unknown, even for the most important vector species. There is limited information on the foraging habits of larvae (what they eat), and the extent to which natural populations are limited by intra- and/or interspecific competition and predation is unknown. The failure to understand population survival strategies and natural mechanisms of competitive exclusion among Anopheles taxa presents obstacles for the development of population replacement strategies, whereby attempts could be made to replace a vector species with introduced non-vector mosquitoes. Another obstacle involves difficulties in identifying larvae belonging to species complexes. Lack of knowledge in all of these areas hinders malaria control efforts.
RESEARCH FOCUS: The foraging habits of larvae and the role of intra- and/or interspecific competition and predation in regulating vector populations.
Country-Wide Vector Surveillance
Geographic variation in the intensity of malaria transmission is of prime importance for the development and stratification of control measures. In most endemic countries, there is little or no information on patterns and intensities of transmission on a national scale. Efficient new surveillance techniques are needed to establish country-wide networks for monitoring the disease in human populations, patterns of drug resistance in parasites, and transmission intensity by vector populations. In areas of tropical Africa, where vectors are highly anthropophilic and endophilic, vector sampling inside houses and corresponding evaluation of sporozoite rates by immunoassay would provide sensitive indicators of transmission intensity (estimates of EIR). There are unexplored possibilities for assaying human blood meals of mosquitoes for the presence of stage-specific malaria antibodies (objective: analogous to serosurveys), malaria parasite antigens (objective: analogous to prevalence surveys), antimalarial drugs (objective: monitor drug use by humans), and even drug-resistant parasites (objective: monitor drug resistance). Progress in the area of vector surveillance for monitoring malaria on a national scale will minimize the need of traditional mass blood surveys and would promote more effective measures for predicting epidemics and allocating resources for malaria control.
RESEARCH FOCUS: Innovative vector surveillance strategies for assessing malaria transmission by vector popu-