<i>Anopheles leesoni</i>Evans 1931, a Member of the <i>Anopheles funestus</i>Group, Is a Potential Malaria Vector in Cameroon

Background: Understanding the biology of Anopheles malaria vector species is essential to planning effective and sustainable malaria control strategies in endemic countries. This study reported the implication of Anopheles leesoni in malaria transmission in Cameroon, Central Africa. Methods: Mosquitoes were collected in three localities from May 2015 to March 2018 using electric aspirators and Centers for Disease Control light traps (CDC-LT). Anopheles funestus sensu lato (s.l.) mosquitoes were identified as species using polymerase chain reaction assay (PCR). Furthermore, Plasmodium falciparum infection status was determined using the enzyme-linked immunosorbent assay (ELISA) method. Results: A total of 12,744 Anopheles mosquitoes were collected by electric aspirator (N = 4844) and CDC-LT (N = 7900). Anopheles funestus s.l. (86.95%) was the major species and the main malaria vector in rural savannah and rural forest sites followed by A. gambiae s.l. (13.05%) whereas in urban areas, A. gambiae s.l. was by far the most abundant representing 91.45% of Anopheles mosquitoes collected. Two members of the A. funestus group were identified among 1389 analysed by PCR: 1307 A. funestus sensu stricto (s.s.) (94.10%) and 82 A. leesoni (5.9%). Plasmodium falciparum infection rate was 21.04% in A. funestus s.s. For the first time, A. leesoni was found positive for P. falciparum (infection rate: 10.98%) in Cameroon. Conclusion: A very high P. falciparum infection rate was observed in this study in A. funestus s.s., highlighting its high implication in malaria transmission in Cameroon. Furthermore, the detection of P. falciparum infection in A. leesoni calls for more attention towards this neglected vector species.

High efficacy of chlorfenapyr-based net Interceptor■G2 against pyrethroid-resistant malaria vectors from Cameroon

Background The increasing reports of resistance to pyrethroid insecticides associated with reduced efficacy of pyrethroid-only interventions highlight the urgency of introducing new non-pyrethroid-only control tools.Here,we investigated the performance of piperonyl-butoxide(PBO)-pyrethroid[Permanet 3.0(P3.0)]and dual active ingredients(AI)nets[Interceptor G2(IG2):containing pyrethroids and chlorfenapyr and Royal Guard(RG):containing pyrethroids and pyriproxyfen]compared to pyrethroid-only net Royal Sentry(RS)against pyrethroid-resistant malaria vectors in Cameroon.Methods The efficacy of these tools was firstly evaluated onAnopheles gambiae s.l.andAnopheles funestus s.l.from Gounougou,Mibellon,Mangoum,Nkolondom,and Elende using cone/tunnel assays.In addition,experimental hut trials(EHT)were performed to evaluate the performance of unwashed and 20 times washed nets in semi-field conditions.Furthermore,pyrethroid-resistant markers were genotyped in dead vs alive,blood-fed vs unfed mosquitoes after exposure to the nets to evaluate the impact of these markers on net performance.The XLSTAT software was used to calculate the various entomological outcomes and the Chi-square test was used to compare the efficacy of various nets.The odds ratio and Fisher exact test were then used to establish the statistical significance of any association between insecticide resistance markers and bed net efficacy.Results Interceptor G2 was the most effective net against wild pyrethroid-resistantAn.funestus followed by Permanet 3.0.In EHT,this net induced up to 87.8%mortality[95%confidence interval(CI):83.5-92.1%)and 55.6%(95%CI:48.5-62.7%)after 20 washes whilst unwashed pyrethroid-only net(Royal Sentry)killed just 18.2%(95%CI:13.4-22.9%)of host-seekingAn.funestus.The unwashed Permanet 3.0 killed up to 53.8%(95%CI:44.3-63.4%)of field-resistant mosquitoes and 47.2%(95%CI:37.7-56.7%)when washed 20 times,and the Royal Guard 13.2%(95%CI:9.0-17.3%)for unwashed net and 8.5%(95%CI:5.7-11.4%)for the 20 washed net.Interceptor G2,Permanet 3.0,and Royal Guard provided better personal protection(blood-feeding inhibition 66.2%,77.8%,and 92.8%,respectively)compared to pyrethroid-only net Royal Sentry(8.4%).Interestingly,a negative association was found betweenkdrw and the chlorfenapyr-based net Interceptor G2(χ^(2)=138;P<0.0001)with homozygote-resistant mosquitoes predominantly found in the dead ones.Conclusions The high mortality recorded with Interceptor G2 against pyrethroid-resistant malaria vectors in this study provides first semi-field evidence of high efficacy against these major malaria vectors in Cameroon encouraging the implementation of this novel net for malaria control in the country.However,the performance of this net should be established in other locations and on other major malaria vectors before implementation at a large scale.