Protective efficacy of lambdacyhalothrin‐impregnated bednets against Phlebotomus orientalis, the vector of visceral leishmaniasis in Sudan

Abstract

Field investigations on the sandfly Phlebotomus orientalis (Diptera: Psychodidae), the vector of Leishmania donovani causing visceral leishmaniasis (VL) in Sudan, were undertaken in two villages (Bellow and Elgamel) and Dinder National Park, to determine the protective value of bednets (polyester, 100 denier) impregnated with lambda-cyhalothrin 10 mg a.i./m2 pyrethroid insecticide. After exposure to treated netting for 30 s, P. orientalis females all died within 1 h. When field-tested in Acacia woodland, treated bednets provided complete protection from bites of the vector. Numbers of P. orientalis females landing on human collectors without bednets or using untreated bednets averaged 32.0 +/- 8.3 or 6.9 +/- 2.7 per man-night, respectively, whereas collectors using treated bednets experienced no sandfly bites during the same period (18.00-06.00 hours, 12 nights in June 1995). Socio-behavioural observations on the bed-time of people living in both study villages indicated that the use of impregnated bednets against P. orientalis would give more potential protection for women and children than for male adults. Overall the proportions of people and their durations of exposure to the risk of sandfly bites (i.e. after sunset until they went to bed) were 40% unprotected for< 1h, 50% for 1-2h and >10% for > or = 2h. Because visceral leishmaniasis in Sudan occurs mainly in children, the use of impregnated bednets (outdoors as well as indoors), and going to bed early could provide a high degree of personal protection against this zoonotic infection.

Leishmaniasis in northern and western Africa: a review

“…A recent study in Sudan indicates a potentially strong reduction in VL incidence following a community distribution of Insecticide Treated Nets (Ritmeijer et al 2007). Further studies indicated that the use of impregnated bed nets and going to bed early could provide a high degree of personal protection against this VL (Elnaiem et al 1999). However, the potential use of bed nets for sandfly control in northern and western Africa is complicated by the fact that during the hot season it is considered too hot to sleep under the fine-mesh nets, which cut down ventilation (Ritmeijer et al 2007).…”

Evidence-based vector control? Improving the quality of vector control trials

“…Sample size calculations should be performed for all study outcomes, whether epidemiological or entomological. We identified several studies that did not report conducting sample size calculations for epidemiological and/or entomological (e.g., [67][68][69][70][71]) outcomes, including several studies that failed to show an effect of the intervention [72,73], indicating that the lack of an effect may simply be due to the study being underpowered. Parameters required for sample size calculations such as the prevalence or incidence of the outcome in the control group or the coefficient of variation may not be readily available [30], although the former can be estimated from a survey conducted before the study's start if it is not known.…”

Leishmaniasis: Epidemiology, Control and Future Perspectives with Special Emphasis on Egypt

“…Moreover, there were studies stated that the use of impregnated bed net and going to bed early could result in a high degree of personal protection against VL [30]. Despite the positive attitude, the use of bed nets in Northern and Western Africa as a sandfly control is restricted.…”