Abstract
BackgroundSpatial and longitudinal monitoring of transmission intensity will allow better targeting of malaria interventions. In this study, data on meteorological, demographic, entomological and parasitological data over the course of a year was collected to describe malaria epidemiology in a single village of low transmission intensity.MethodsEntomological monitoring of malaria vectors was performed by weekly light trap catches in 10 houses. Each house in the village of Msitu wa Tembo, Lower Moshi, was mapped and censused. Malaria cases identified through passive case detection at the local health centre were mapped by residence using GIS software and the incidence of cases by season and distance to the main breeding site was calculated.ResultsThe principle vector was Anopheles arabiensis and peak mosquito numbers followed peaks in recent rainfall. The entomological inoculation rate estimated was 3.4 (95% CI 0.7–9.9) infectious bites per person per year. The majority of malaria cases (85/130) occurred during the rainy season (χ2 = 62,3, p < 0.001). Living further away from the river (OR 0.96, CI 0.92–0.998, p = 0.04 every 50 m) and use of anti-insect window screens (OR 0.65, CI 0.44–0.94, p = 0.023) were independent protective factors for the risk of malaria infection. Children aged 1–5 years and 5–15 years were at greater risk of clinical episodes (OR 2.36, CI 1.41–3.97, p = 0.001 and OR 3.68, CI 2.42–5.61, p < 0.001 respectively).ConclusionThese data show that local malaria transmission is restricted to the rainy season and strongly associated with proximity to the river. Transmission reducing interventions should, therefore, be timed before the rain-associated increase in mosquito numbers and target households located near the river.
Highlights
Spatial and longitudinal monitoring of transmission intensity will allow better targeting of malaria interventions
Based on questionnaires used in an ancillary study (Shekelaghe et al in press), the vast majority of the population reside in the village permanently with travel outside largely restricted to the adult male population
This study describes the pattern of malaria transmission in an area of very low transmission intensity, quantified by an estimated entomological inoculation rate (EIR) of 3,43 infectious bites per person per year
Summary
Spatial and longitudinal monitoring of transmission intensity will allow better targeting of malaria interventions. Data on meteorological, demographic, entomological and parasitological data over the course of a year was collected to describe malaria epidemiology in a single village of low transmission intensity. The incidence and clinical presentation of Plasmodium falciparum malaria shows considerable variation between age groups [1], countries [2,3] and relatively short distances in single areas [4]. Transmission intensity is commonly quantified by the entomological inoculation rate (EIR), the estimated level of exposure to malaria infected mosquitoes. Spatial and temporal variation in transmission intensity is often not included in EIR estimates. This variation is important in areas of low transmission intensity where few infected mosquitoes are caught and focal hotspots of malaria transmission may exist. Similar to clustering of mosquitoes, clinical malaria episodes can be clustered in individuals [12] or housing groups [12,16,20]
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