Predictions of adult Anopheles Albimanus Densities in villages based on distances to remotely sensed larval habitats

ABSTRACT

Remote sensing is particularly helpful for assessing the location and extent of vegetation formations, such as herbaceous wetlands, that are difficult to examine on the ground. Marshes that are sparsely populated with emergent macrophytes and dense cyanobacterial mats have previously been identified as very productive Anopheles albimanus larval habitat. This type of habit was detectable on a classified multispectral Systeme Probatoire d'Observation de la Terre image on northern Belize as a mixture of two isoclasses. A similar spectral signature is characteristic for vegetation of river margin consisting of aquatic grasses and water hyacinth, which constitutes another productive larval habitat. Based on the distance between human settlements (sites) of various sizes and the nearest marsh/river exhibiting this particular class combination, we selected two groups of sites; those located closer than 500 m and those located more than 1,500 m from such habitats. Based on previous adults collections near larval habitats, we defined a landing rate of 0.5 mosquitoes/human/min from 630 pm to 8 pm as the threshold for high (o 0.5 mosquitoes/human/min) versus low (05 mosquitoes/human/min) densities of An. albimanus. Sites located less than 500 m from the habitat were predicted as having values higher than this threshold, while lower values were predicted for sites located greater than 1,500 m from the habitat. Preditions were verified by collections of mosquitoes landing on humans. The predictions were 100 percent accurate for sites in the > 1,500-m category and 89 percent accurate for sites in the < 500-m category (AU)