Efficacy of Fludora® Fusion (a mixture of deltamethrin and clothianidin) for indoor residual spraying against pyrethroid-resistant malaria vectors: laboratory and experimental hut evaluation

Abstract

Background A new generation of IRS insecticides which can provide improved and prolonged control of pyrethroid-resistant malaria vector populations are being developed. Fludora® Fusion is a new IRS insecticide containing a mixture of deltamethrin and clothianidin, a neonicotinoid. Methods The efficacy of Fludora® Fusion IRS was evaluated over 11–12 months on concrete and mud substrates in laboratory bioassays and experimental huts against wild free-flying pyrethroid-resistant Anopheles gambiae (sensu lato) in Cové, Benin. A comparison was made with the two active ingredients of the mixture; clothianidin and deltamethrin, applied alone. CDC bottle bioassays were also performed to investigate resistance to clothianidin in the wild vector population. Results Fludora® Fusion induced > 80% laboratory cone bioassay mortality with both susceptible and pyrethroid-resistant An. gambiae (s.l.) for 7–9 months on concrete block substrates and 12 months on mud block substrates. The vector population at the experimental hut site was fully susceptible to clothianidin in CDC bottle bioassays. Overall mortality rates of wild free-flying pyrethroid-resistant An. gambiae (s.l.) entering the experimental huts during the 11-month trial were < 15% with deltamethrin and significantly higher with Fludora® Fusion (69–71%) and clothianidin alone (72–78%). Initial high experimental hut mortality rates with Fludora® Fusion (> 80%) only declined by 50% after 8 months. Monthly in situ wall cone bioassay mortality of susceptible mosquitoes was > 80% for 9–12 months with Fludora® Fusion and clothianidin alone. Fludora® Fusion induced significantly higher levels of early exiting of mosquitoes compared to clothianidin alone (55–60% vs 37–38%, P < 0.05). Conclusions Indoor residual spraying with Fludora® Fusion induced high and prolonged mortality of wild pyrethroid-resistant malaria vectors for 7–10 months mostly due to the clothianidin component and substantial early exiting of mosquitoes from treated huts due to the pyrethroid component. Fludora® Fusion is an important addition to the current portfolio of IRS insecticides with the potential to significantly reduce transmission of malaria by pyrethroid-resistant mosquito vectors.

Efficacy of broflanilide (VECTRON T500), a new meta-diamide insecticide, for indoor residual spraying against pyrethroid-resistant malaria vectors

“…By contrast, our study demonstrated longer residual efficacy of VECTRON T500 in laboratory cone bioassays with the susceptible Kisumu strain on mud block substrates (> 80% mortality for 18 months) compared to cement block substrates (> 80% mortality for 6 months). This corroborates our previous findings in similar studies with another IRS insecticide 27 . The improved residual efficacy with the mud block substrates could be attributed to the addition of a small amount of cement to the mud paste during the preparation of the block substrates, in line with local practices in some areas in Benin, making the substrates more stable and less porous.…”

“…This delayed activity could be attributed to its mechanism of action; broflanilide has to be metabolized to its active form, desmethyl-broflanilide, before binding to its site of action 18 . Delayed mosquito mortality effects has also been observed with clothianidin 14 , 27 and chlorfenapyr 15 , 28 which are the main active ingredients in newly approved IRS insecticide formulations and insecticide treated nets for malaria vector control 13 . While the relative impact of such slow acting insecticides is yet to be fully assessed, modelling studies have suggested that development of resistance to these insecticides may be slower compared to fast-acting neurotoxic insecticides 29 .…”

Reduced exposure to malaria vectors following indoor residual spraying of pirimiphos-methyl in a high-burden district of rural Mozambique with high ownership of long-lasting insecticidal nets: entomological surveillance results from a cluster-randomized trial

“… CDC LT US Centers for Disease Control light trap, HLC human landing collection, IRS indoor residual spraying, PM pirimiphos-methyl a From 2016 pre-intervention census[ 18 ] …”

“…The first of these products to receive WHO recommendation as a malaria vector control tool was a microencapsulated formulation of the organophosphate insecticide pirimiphos-methyl (PM): Actellic® 300CS (Syngenta AG, Basel, Switzerland). While initial results showing the impact of Actellic and other 3GIRS products have been encouraging [ 12 – 18 ], questions remain about where and how to best deploy them to maximize their impact.…”

Efficacy of broflanilide (VECTRONTM T500) a new meta-diamide insecticide, for indoor residual spraying against pyrethroid-resistant malaria vectors.

“…Cement and mud block substrates used in cone bioassays were prepared and treated using similar methods described in previous studies by our group 37 . Blocks were moulded in Petri dishes (9cm diameter and 5mm thick) and dried at 27 °C ±2 °C and 80 ±10% RH for 30 days before insecticide application.…”