Malaria transmission potential of Anopheles gambiae s.l. in indoor residual spraying areas with clothianidin 50 WG in northern Benin

Abstract The study objective was to assess the frequency of the kdr-L995F and ace-1 G280S genetic mutations in Anopheles gambiae s.l. mosquitoes and examine their ability to transmit Plasmodium falciparum in areas where indoor residual spraying (IRS) was implemented with Clothianidin 50 WG. The study was conducted in six communes in the Alibori and Donga departments of which four were IRS-treated and two were untreated and served as control. Post-IRS monthly samples of adult mosquitoes were collected in study communes using human landing catches (HLC). An. gambiae s.l. specimens were processed to detect kdr-L995F and ace-1 G280S mutations via PCR as well as Plasmodium falciparum infectivity through CSP ELISA. Our data revealed a high and similar allelic frequency for the kdr-L995F mutation in both treated and control communes (79% vs. 77%, p = 0.14) whilst allelic frequency of the ace-1 G280S mutation was lower across the study area (2–3%, p = 0.58). The sporozoite rate was 2.6% and 2.4% respectively in treated and untreated communes (p = 0.751). No association was found between Plasmodium falciparum infection in Anopheles gambiae s.l. vectors and carriage of kdr-L995F and ace-1 G280S mutations regardless of genotypes. The study findings underline the need for an integrated approach to malaria control, combining different control methods to effectively target transmission. Regular monitoring of insecticide resistance and genetic mutations is essential to guide control strategies

Open Access

Impact of long-lasting, insecticidal nets on anaemia and prevalence of Plasmodium falciparum among children under five years in areas with highly resistant malaria vector

Insecticide-treated nets provide protection against malaria to children in an area of insecticide resistance in Southern Benin

Abstract Background Malaria control is heavily reliant on insecticides, especially pyrethroids. Resistance of mosquitoes to insecticides may threaten the effectiveness of insecticide-based vector control and lead to a resurgence of malaria in Africa. Methods In 21 villages in Southern Benin with high levels of insecticide resistance, the resistance status of local vectors was measured at the same time as the prevalence of malaria infection in resident children. Results Children who used LLINs had lower levels of malaria infection [odds ratio = 0.76 (95% CI 0.59, 0.98, p = 0.033)]. There was no evidence that the effectiveness of nets was different in high and low resistance locations (p = 0.513). There was no association between village level resistance and village level malaria prevalence (p = 0.999). Conclusions LLINs continue to offer individual protection against malaria infection in an area of high resistance. Insecticide resistance is not a reason to stop efforts to increase coverage of LLINs in Africa

Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: evidence from health facility data from Benin

Abstract Background Insecticide-based interventions have averted more than 500 million malaria cases since 2000, but insecticide resistance in mosquitoes could bring about a rebound in disease and mortality. This study investigated whether insecticide resistance was associated with increased incidence of clinical malaria. Methods In an area of southern Benin with insecticide resistance and high use of insecticide-treated nets (ITNs), malaria morbidity and insecticide resistance were measured simultaneously in 30 clusters (villages or collections of villages) multiple times over the course of 2 years. Insecticide resistance frequencies were measured using the standard World Health Organization bioassay test. Malaria morbidity was measured by cases recorded at health facilities both in the whole population using routinely collected data and in a passively followed cohort of children under 5 years old. Results There was no evidence that incidence of malaria from routinely collected data was higher in clusters with resistance frequencies above the median, either in children aged under 5 (RR = 1.27 (95% CI 0.81–2.00) p = 0.276) or in individuals aged 5 or over (RR = 1.74 (95% CI 0.91–3.34) p = 0.093). There was also no evidence that incidence was higher in clusters with resistance frequencies above the median in the passively followed cohort (RR = 1.11 (0.52–2.35) p = 0.777). Conclusions This study found no association between frequency of resistance and incidence of clinical malaria in an area where ITNs are the principal form of vector control. This may be because, as other studies have shown, ITNs continue to offer some protection from malaria even in the presence of insecticide resistance. Irrespective of resistance, nets provide only partial protection so the development of improved or supplementary vector control tools is required to reduce Africa’s unacceptably high malaria burden