Efficacy of a novel mode of action of an indoor residual spraying product, SumiShield® 50WG against susceptible and resistant populations of Anopheles gambiae (s.l.) in Benin, West Africa

Abstract

BackgroundScale-up of the distribution of long-lasting insecticide-treated bed nets and indoor residual spraying with insecticides over the last decade have contributed to the considerable decrease of malaria morbidity and mortality in sub-Saharan Africa. Due to the increasing pyrethroid resistance intensity and the spread of carbamate resistance in Anopheles gambiae (s.s.) mosquitoes and the limited number of insecticides recommended by the WHO for vector control, alternative insecticide formulations for IRS with long-lasting residual activity are required to sustain the gains obtained in most malaria-endemic countries.MethodsSumiShield 50WG (clothianidin 300 mg ai/m2) developed by Sumitomo Chemical was evaluated alongside deltamethrin 25 mg ai/m2 (K-Othrine 250 WG) against a pyrethroid resistant Anopheles gambiae (s.l.) population in experimental huts in Covè, Benin. Residual activity was also tested in cone bioassays with the susceptible An. gambiae “Kisumu” strain and the local wild resistant population.ResultsThe results showed very low toxicity from deltamethrin (mortality rates ranged between 1–40%) against host-seeking resistant Anopheles populations. SumiShield in contrast gave an overall mean mortality of 91.7% at the 120 h observation across the eight- month observation period following spraying. The residual activity measured using cone tests was over the 80% WHO threshold for 24 weeks for resistant wild Anopheles population and 32 weeks for the susceptible strain “Kisumu” after the spraying.ConclusionsSumiShield is a good candidate for IRS in areas of permanent malaria transmission and where Anopheles populations are resistant to other conventional insecticides such as pyrethroids. It would be interesting to complete experimental huts studies by assessing the efficacy and residual effect of SumiShield 50WG at community level (small-scale field testing) in an area where vectors are highly resistant to insecticides.

Systematic review of indoor residual spray efficacy and effectiveness against Plasmodium falciparum in Africa

“… Pyrethroids (3 x deltamethrin [7 a , 17 a , 18 a ]), Clothianidin (200 mg m -2 ) [7 a ] 8 39 Burkina Faso West African Unknown Walls (not ceiling) Holed nets A. gambiae s.l . Bendiocarb 9 26 Tanzania East African Mud Walls and ceiling No nets A. arabiensis Actellic® 300CS 10 68 Benin West African Cement No nets A. gambiae s.l . Pyrethroids (deltamethrin), Sumishield® 50WG Additional data from unpublished studies 11 unpublished data 1 Vincent Corbel Benin West African Concrete Walls and ceiling No nets A. gambiae s.l .…”

“…Row 4 summarises the best fit probability outcomes per feeding attempt for a mosquito to successfully blood-feed (red), exit without feeding (orange), be deterred before entering (green) or be killed (blue) for the different IRS products; pirimiphos-methyl: Actellic®300CS (column 1), pyrethroids: lambda-cyhalothrin, deltamethrin and alpha-cyhalothrin (column 2), bendiocarb: bendiocarb (1 spray round per year) (column 3) and neonicotinoids: clothianidin, SumiShield®50WG (column 4). Symbol shapes indicate the different studies (legend key references study numbers in Table 2 corresponding to 1 63 , 2, 14 and 15 64 , 3 17 , 4 and 13 25 , 5 65 , 6 and 16 66 , 7, 17 and 18 67 , 8 39 , 9 26 , 10 68 , 11 and 12 are previously unpublished data). Solid lines indicate the best fit statistical model to the mean data, weighted by sample size in different studies, and the dark-shaded area shows the 90% credible intervals around these best fit lines.…”

The role of windows of selection and windows of dominance in the evolution of insecticide resistance in human disease vectors

“…Firstly, mosquitoes do not naturally encounter insecticides in cone and bottle bioassays, so there is some doubt whether findings based on bioassays reflect mortality that occurs in the field (Malima et al, 2008). The use of bioassay data is supported by the fact that the windows of selection shown in Figure 4a are based upon free-flying mosquitoes in experimental huts (Agossa et al, 2018) and…”

Patterns of pesticides usage in agriculture in rural Tanzania call for integrating agricultural and public health practices in managing insecticide-resistance in malaria vectors

“…Chlorpyrifos, an organophosphate, was earlier recommended by WHO Pesticide Evaluation Scheme (WHOPES) for the control of juvenile mosquitoes [66] and has been evaluated for net impregnation against mosquitoes [49]. Additionally, imidacloprid (,neonicotinoids) a nicotinic acetylcholine receptor stimulator, is also being considered as an alternative or in combinations with the commonly used pyrethroids [53].…”