Impact of mosquito proofing of night shelters in refugee camps in Kitgum, northern Uganda

Abstract

To test the impact of long-lasting insecticide-treated netting, fitted to cover the eaves and ceilings of refugee shelters, on the incidence of nighttime mosquito biting. Entomological surveys in night-dwelling shelters at three camps for internally displaced persons in Kitgum, Uganda during August and November 2004: The impact of proofing against the nighttime incidence of mosquito biting was assessed through human landing catches and indoor resting catches in proofed and unproofed (control) shelters. Human landing catches were performed inside and outside four proofed and four control shelters at three locations, and indoor resting catches were performed in 37 proofed and 18 control shelters. The difference in biting rates was tested using paired and unpaired t-tests and multivariate analysis. Most mosquitoes caught during the survey were culicine (97%). The difference in landing rate (mlrph) differentials (outdoor-indoor) illustrated a significant (t = 3.26, P = 0.004) difference between mlrph between proofed (0.154) and control shelters (-0.110). Mean shelter density (msd) recorded during indoor resting catches was 6.7 times higher in the control shelters than in proofed shelters (P < 0.001). The number of blood-fed mosquitoes/person/night (bfmpn) was significantly higher (P < 0.001), by a magnitude of 17, in control shelters (one in five individuals receiving a bite) compared with proofed shelters (1 in 83 individuals). A multivariate analysis showed that the difference in biting rates was because of the intervention. The significantly lower mlrph, msd and bfmpn in proofed shelters demonstrate that the mosquito proofing strategies employed do reduce the exposure to mosquito biting in proofed compared with control shelters by a magnitude of 6-17. Although numbers of Anopheline mosquitoes were low, the biting rates of Anophelines were also significantly lower in proofed shelters compared with control shelters. Insecticide-treated netting appears to significantly reduce the mosquito nuisance-biting incidence. However, a higher incidence of Anopheline biting may be required to test the effect of proofing on malaria vectors and a subsequent study is therefore recommended.