Predictions of malaria vector distribution in Belize based on multispectral satellite data

Use of multispectral satellite data to predict arthropod-borne disease trouble spots is dependent on clear understandings of environmental factors that determine the presence of disease vectors. A blind test of remote sensing - based predictions for the spatial distribution of a malaria vector, Anopheles pseudopunctipennis, was conducted as a follow-up to two years of studies on vector-environmental relationships in Belize. Four of eight sites that were predicted to be high probability locations for presence of An. pseudopunctipennis were positive and all low probability site (0 of 12) were negative. The absence of An. pseudopunctipennis at four high probability locations probably reflects the low densities that seem to characterize field populations of this species, i.e., the population densities were below the threshold of our sampling effort. Another important malaria vector. An. darlingi, was also present at all high probability sites and absent at all low probability sites. Anopheles darlingi, like An. pseudopunctipennis, is a riverine species. Prior to these collections at ecologically defined locations, this species was last detected in Belize in 1946 (AU)

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

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 6:30 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)

Predictions of adult anopheles albimanus densities in villages based on distances to remotely sensed larval habitats

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 habitats. This type of habitat was detectable on a classified multispectral Systeme Probatoire d'Observation de la Terre image of northern Belize as a mixture of two isoclasses. A similar spectral signature is characteristic for vegetation of river margins consisting of aquatic grasses and water hyacinth, which constitutes another 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 adult collections near larval habitats, we defined a landing rate of 0.5 mosquitoes/human/min from 6:30 p.m. to 8:00 p.m. as the threshold for high (o 0.5 mosquitoes/human/min) versus low (< 0.5 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 that 1,500 m from the habitat. Predictions were verified by collections of mosquitoes landing on humans. The predictions were 100 percent accurate for the sites in the > 1,500-m category and 89 percent accurate for sites in the > 500-m category(AU)