Deltamethrin impregnated bednets for the control of urban malaria in Kumba Town, South-West Province of Cameroon

Abstract

This study was conducted from January to December 1992 in Kumba, a town situated in the rain forest region of the South-West Province of Cameroon, and consisted of a longitudinal survey including parasitological and clinical studies. Forty households were chosen for the study and randomly divided into two groups, each with approximately 240 inhabitants aged < or = 15 years. One group received deltamethrin impregnated bednets and the other group had no nets (control). For the months of April, June and August (rainy season), deltamethrin impregnated bednets did not reduce malaria prevalence significantly, but the overall malaria prevalence for all months of the study was significantly reduced (chi 2 MH = 9.17, P = 0.002). Enlarged spleen rates (chi 2 MH = 6.73, P = 0.009) and spleen sizes (P = 0.0002) were also significantly reduced by the nets. However, the reduction in the geometric mean parasite density (GMPD) was not significant. Even though some of these reductions were statistically significant, they were relatively low in a global context compared with previous work done mainly in rural areas. In an urban environment, parents and children usually stay up late, and probably receive many mosquito bites before going to sleep.

PIP: In 1992, in Cameroon, 40 households in two neighborhoods of Kumba, located in the rain forest region of the South-West Province, were randomly allocated to either the group that received deltamethrin impregnated bednets or the group who received no bednets. Each group had about 240 persons aged 15 years or under. The neighborhoods were Kossala (high malaria prevalence) and Mbonge Road (low prevalence). Parasitological, entomological, and clinical studies were conducted longitudinally so researchers could determine whether deltamethrin impregnated bednets would cause a reduction in malaria morbidity and parasitic indices. The geometric mean parasite density (GMPD) decreased with age, especially for 11-15 year olds, suggesting acquired immunity. The deltamethrin group was more likely than the control group to have lower malaria prevalence (29% vs. 41%; p = 0.002), spleen rates (18.5% vs. 30.4%; p = 0.009), and spleen sizes (p = 0.0002). GMPD was also lower, but not significantly so (764 vs. 1081/mcl). During the rainy season (April, June, and August), malaria prevalence was not statistically significant between the test and control groups. In Kossala, children aged 6-10 years had a higher malaria prevalence rate than other age groups. The deltamethrin impregnated bednets afforded better protection in Mbong Road than in Kossala, suggesting that they are most effective in areas of low malaria endemicity. The significant reductions in human/vector contact were relatively low when compared with earlier studies mainly conducted in rural areas. Parents and children in urban areas such as Kumba tend to stay up late (e.g., watching TV) and probably receive many mosquito bites while awake. Impregnated window curtains may improve protection in malaria endemic urban areas.