Susceptibility to DDT and pyrethroids, and detection of knockdown resistance mutation in <i>Anopheles gambiae sensu lato</i> in Southern Togo

Abstract

Insecticides play an important role in malaria control programmes especially in Sub-Saharan Africa. However, the development of resistance by vectors to most commonly used public health insecticides has become a very crucial problem. DDT (Dichlorodiphenyltrichloroethane) was used worldwide to control malaria vectors and pyrethroids have been used in many vector control projects due to their known efficiency and lower toxicity to humans and non-target organisms. In West Africa, resistance to pyrethroid in the major malaria vector, Anopheles gambiae, had been reported in several countries. The last publication on this phenomenon in Togo was done in Togo in 2005. An update on the susceptibility of the malaria vector and characterization of its resistance mechanism becomes therefore crucial. Newly emerged female mosquitoes of two to five days old were selected and exposed to DDT 4%, Permethrin 1% and Deltamethrin 0.05%, the WHO diagnostic doses. These adult mosquitoes were from larvae of Anopheles gambiae sensu lato collected from rural and urban settings and reared in an insectary. A susceptible laboratory strain of An. gambiae sensu stricto was used as reference. Species identification was made using the morphological characteristics, PCR (polymerase chain reaction), and HhaI (Haemophilus haemoliticus) restriction digest. Knockdown resistance mutation screening was conducted on both living and dead mosquitoes. An. gambiae sensu stricto was the only sibling species of the complex present in Kovié and Lomé. The molecular M form was predominant in the two localities (almost 100%). High resistance level was observed in Lomé 1.19%, 56.45% and 41.17%; and in Kovié 0.91%, 55.55% and 67% mortality respectively to DDT 4%, Deltamethrin 0.05% and Permethrin 1% with a very high knockdown time (TKD 50 ). Up to 70% of resistant individuals have been obtained in the two localities. It is important to inspect these localities through routine tests in order to decide on possible alternative strategies to be used. This study showed that An. gambiae is highly resistant to both DDT and pyrethroids in Lomé and Kovié, with the presence of kdr allele.

First report of the presence of L1014S Knockdown-resistance mutation in Anopheles gambiae s.s and Anopheles coluzzii from Togo, West Africa

“…In Togo, despite the huge investments in LLINs, information is still lacking on the routine monitoring of insecticides resistance in malaria vectors. An entomological survey was carried out since 2009 in two localities of the Southern coastal region (Lomé and Kovié) and revealed the involvement of kdr L1014F in insecticides resistance 20 . Additional knowledge on the mechanisms involved in insecticides resistance is needed across the country, as this is seminal to design new strategies for insecticides resistance management.…”

Perception de la chimioprévention du paludisme saisonnier au Niger

“…Ce point ne fut pas inscrit dans le questionnaire et constitue la principale limite de cette étude. La CPS sera bientôt une stratégie supplémentaire à la lutte intégrée contre le paludisme en Afrique au Sud du Sahara, au même titre que le contrôle des vecteurs par les insecticides (Ahadji-Dabla et al, 2014), la prise en charge des malades par les combinaisons thérapeutiques à base d'artémisinine (Kpaibe et al, 2016), la prévention du paludisme chez la femme enceinte par le traitement préventif intermittent et même la médecine traditionnelle par divers plantes en milieu rural (Denou et al, 2016).…”

Larvicidal activities of Biostop Moustiques^®, a botanical insecticide on field collected malaria mosquito <i>Anopheles gambiae</i> sensu lato in Togo

“…According to Ahadji-Dabla et al (2014), this wild population of Anopheles gambiae has developed some genetic resistance against synthetic insecticides such as pyrethroids. BM exhibits an interesting larvicidal activity with the same effect especially on L3 L4 at 20 mL/L both in laboratory and field collected strains of the malaria vector An.…”

“…In West Africa, especially in Togo, Anopheles gambiae is the major vector of malaria transmission (Ahadji-Dabla et al, 2014). The control of this vector is done through different strategies including the use of insecticide treated nets (ITNs), indoor residual spraying (IRS) and in some specific settings, larval control.…”