Small-scale field evaluation of the efficacy and residual effect of Fludora® Fusion (mixture of clothianidin and deltamethrin) against susceptible and resistant Anopheles gambiae populations from Benin, West Africa

Abstract

BackgroundIn recognition of the threat of insecticide resistance in vectors of malaria, the WHO Global Malaria Programme recommends the development of an appropriate and comprehensive response to insecticide resistance. In principle, good resistance management practice requires the application of multiple insecticides of different modes of action, for example, in rotations and mixtures. Insecticides recommended by the World Health Organization for indoor residual spraying and long-lasting insecticide nets are limited. It is, therefore, judicious to prevent the rapid spread of insecticide resistance by evaluating new insecticides formulations with different modes of action and long residual effect.MethodsFludora® Fusion, a new neonicotinoid IRS formulation (a mixture of 500 g/kg clothianidin and 62.5 g/kg deltamethrin applied 200 mg ai/sqm + 25 mg ai/sqm, respectively) was tested. Small scale field evaluation of this product was conducted in the district of Dangbo in Benin, to compare its efficacy and residual effect on cement and mud walls against those of clothianidin 200 mg ai/sqm (WG 70) alone, and of deltamethrin 25 mg ai/sqm (WG 250) alone. WHO wall cone bioassays were conducted monthly with laboratory susceptible Anopheles “Kisumu” and wild Anopheles gambiae sensu stricto (s.s.) population from Dangbo. The induced mortality by each treatment per wall substrate for 24 h, 48 h, and 72 h post exposure were recorded every month and analysed.ResultsFludora® Fusion and clothianidin WG 70 showed mortality rates over 80% WHO bio-efficacy threshold on cement walls either with susceptible or resistant An. gambiae s.s. over a period of 10 and 9 months, respectively. Treatment with Fludora® Fusion and clothianidin WG 70 on the mud walls showed residual effect for 6 months and 5 months respectively against both susceptible and resistant mosquitoes. During the whole evaluation period, deltamethrin WG 250 showed mortality rates below 80% against resistant Anopheles population. Furthermore, the knock down rates observed with the Fludora® Fusion combination were significantly higher (p < 5%) than those induced by Clothiandin WG 70.ConclusionBoth the Fludora® Fusion combination and clothianidin alone showed very good and lasting efficacy for IRS against resistant Anopheles with some residual benefit provided by the combination. The residual efficacy of the Fludora® Fusion combination evaluated at 10 months shows this product is a good candidate for IRS interventions.Electronic supplementary materialThe online version of this article (10.1186/s12936-018-2633-6) contains supplementary material, which is available to authorized users.

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

“…compared to deltamethrin on both mud and concrete substrates. The results confirm previous findings across Africa [ 11 , 15 , 16 ], thus demonstrating the suitability of Fludora® Fusion for indoor residual spraying in Benin and other malaria-endemic areas which are characterised by high intensities of pyrethroid resistance in local mosquito vectors.…”

“…The low mortality response with deltamethrin IRS in the experimental huts is very typical of studies conducted in this area of Benin [ 11 , 14 ] thus demonstrating the redundancy of solo pyrethroid products for IRS and further highlighting the need for novel non-pyrethroid IRS insecticides. Studies performed with Fludora® Fusion in West Africa have so far reported its efficacy on treated surfaces only in cone bioassays [ 15 , 16 ] which generally do not take into consideration the behaviour of vector mosquitoes. Our study demonstrates for the first time the efficacy of Fludora® Fusion against wild free-flying pyrethroid-resistant malaria vectors in household settings in Benin.…”

Rolling back malaria in Africa – challenges and opportunities to winning the elimination battle.

“…However, there are new insecticide classes and insecticide mixtures that have shown potential for replacing DDT, which is the current gold standard. [18,19] The main drawback of the new insecticides is the cost of purchasing them as well as their application. Drug resistance is also on the increase, beginning in the early 1980s with resistance to chloroquine, followed by resistance to sulfadoxine-pyrimethamine in the mid-to late 1990s.…”

Indoor spraying with chlorfenapyr (a pyrrole insecticide) provides residual control of pyrethroid-resistant malaria vectors in southern Benin

“…The question of who should pay to obtain this evidence also remains open. While higher levels of mortality of pyrethroid-resistant vector populations have been reported with other recently developed novel IRS insecticides in similar trials [7,[13][14][15], effective rotation of IRS insecticides for insecticide resistance management as recommended by the GPIRM will require a much larger and more diversified portfolio of IRS insecticides [2].…”

“…As a strategy for managing insecticide resistance in local vector populations, vector control programmes are encouraged to implement a rotational schedule of IRS insecticides of different modes of action to reduce selection pressure on the vector [11]. While the newly prequalified IRS insecticides show potential to improve the control of insecticide-resistant vector populations [12][13][14][15], an effective rotational strategy which will prevent the development of further resistance cannot rely on these compounds alone as they contain the same active ingredient (clothianidin) and thus share the same mode of action; a more diversified portfolio of IRS insecticides is required.…”