Entomological and parasitological impacts of indoor residual spraying with DDT, alphacypermethrin and deltamethrin in the western foothill area of Madagascar

Abstract

BackgroundIn Madagascar, indoor residual spraying (IRS) with insecticide was part of the national malaria control programme since the middle of the twentieth century. It was mainly employed in the highlands and the foothill areas, which are prone to malaria epidemics. Prior to a policy change foreseeing a shift from DDT to pyrethroids, a study was carried out to assess the entomological and parasitological impacts of IRS in areas with DDT or pyrethroids and in areas without IRS.MethodsThe study was carried out from October 2002 to February 2005 in three communes of the western foothill area of Madagascar. Two communes received IRS with DDT in February 2003, then IRS with pyrethroids (alphacypermethrin or deltamethrin) in February 2004. The third commune remained untreated. Mosquitoes were collected at night using human landing catches and early in the morning in resting places. Blood smears were obtained from schoolchildren and microscopically examined for Plasmodium presence.ResultsIn total, 18,168 human landing mosquitoes and 12,932 resting anophelines were collected. The Anopheles species caught comprised 10 species. The main and most abundant malaria vector was Anopheles funestus (72.3% of human-seeking malaria vectors caught indoors). After IRS had taken place, this species exhibited a lower human biting rate and a lower sporozoite index. Overall, 5,174 blood smears were examined with a mean plasmodic index of 19.9%. A total of four Plasmodium species were detected. Amongst tested school children the highest plasmodial index was 54.6% in the untreated commune, compared to 19.9% in the commune sprayed with DDT and 11.9% in the commune sprayed with pyrethroid. The highest prevalence of clinical malaria attacks in children present at school the day of the survey was 33% in the untreated commune compared to 8% in the areas which received IRS.ConclusionIn terms of public health, the present study shows (1) a high efficacy of IRS with insecticide, (2) a similar efficacy of DDT and pyrethroid and (3) a similar efficacy of alphacypermethrin and deltamethrin. The use of IRS with DDT and pyrethroid greatly decreased the vector-human contact, with an associated decrease of the plasmodial index. However malaria transmission did not reach zero, probably due to the exophilic host-seeking and resting behaviours of the malaria vectors, thus avoiding contact with insecticide-treated surfaces indoors. The study highlights the strengths and weaknesses of the IRS implementation and the need for complementary tools for an optimal vector control in Madagascar.

Risk Factors for Malaria Infection in Central Madagascar: Insights from a Cross-Sectional Population Survey

“…The study was conducted in Tsiroanomandidy district in the region of Bongolava, a rural area in the western foothills of Madagascar which fringes the low transmission central highlands and the high endemicity tropical west coast ( Figure 1A). Plasmodium falciparum and P. vivax malaria are endemic in the area, with marked seasonal trends in their transmission intensity 2,17 (Supplemental Figure 1). The study site falls into the country's West Highland Fringe ecozone, an area with rapid diagnostic test (RDT)confirmed reported annual case incidence of 20.7/1,000 population in 2015, with higher incidence in children younger than 6 years compared with the rest of the population.…”

“…2 The primary local vector species is Anopheles funestus, although Anopheles arabiensis is also implicated in transmission. 17 The study was conducted in collaboration with three private health clinics that provide health care to a migrant population relocated from the generally malaria-free capital city, Antananarivo, to the rural endemic zone approximately 200 km west of the city. The relocation program is run by the nongovernmental organization (NGO) "Ankohonana Sahirana Arenina (ASA)" (http://www.asa-madagascar.org/).…”

Malaria prevention measures in Burkina Faso: distribution and households expenditures

“…A series of randomized control trials have demonstrated that insecticide-treated nets are highly effective in preventing malaria in children under 5 years of age [ 8 , 9 ]. The efficacy of IRS in reducing malaria transmission and malaria attacks in children has also been demonstrated [ 10 ]; so have dual interventions of ITN-IRS in combination in comparison to single intervention [ 11 – 13 ].…”

Methanol Extract of Peltophorum pterocarpum Stem Bark Has Antimalarial Activity and Normalizes Biochemical Changes Induced by Plasmodium berghei Infection

“…This is because changes in the red blood cell antigen structure brought about by the parasitic invasion may stimulate the production of antibodies against the red cell. This consequently triggers immune-mediated lysis of the red cell (Kotepui et al, 2014). In addition, the growing parasite consumes and degrades haemoglobin which may account for further decrease in Hb.…”