Indoor residual spray bio-efficacy and residual activity of a clothianidin-based formulation (SumiShield® 50WG) provides long persistence on various wall surfaces for malaria control in the Democratic Republic of the Congo

Abstract

BackgroundBio-efficacy and residual activity of SumiShield® 50WG (50%, w/w) with active ingredient clothianidin, a neonicotinoid compound, was assessed using an insecticide-susceptible laboratory strain of Anopheles arabiensis. Implications of the findings are examined in the context of potential alternative insecticides for indoor residual spraying in Lualaba Province, Democratic Republic of the Congo.MethodsContact surface bioassays were conducted for 48 weeks on four types of walls (unbaked clay, baked clay, cement, painted cement) in simulated semi-field experimental conditions using two different doses of clothianidin active ingredient (200 mg ai/sq m and 300 mg ai/sq m). Additionally, two types of walls (painted cement and baked clay) were examined in occupied houses using the 300-mg dosage. Laboratory-reared An. arabiensis were exposed to treated surfaces or untreated (controls) for 30 min. Mortality was recorded at 24-h intervals for 120 h.ResultsUnder semi-field experimental conditions, there was no significant difference in mortality over time between the two doses of clothianidin. The mortality rates remained above 60% up to 48 weeks on all four wall surface types. The formulation performed better on cement and unbaked clay with a mean final mortality rate above 90%. Under natural conditions, there was no significant difference in response between baked clay and painted cement walls with a mean final mortality rate above 90%. The insecticide also performed significantly better in natural settings compared to semi-field experimental conditions.ConclusionDepending on the type of experimental surface, the residual activity of the two doses of clothianidin was between 28 and 48 weeks based on a 60% mortality endpoint. Clothianidin at 300 mg ai/sq m applied on two house walls (baked clay or painted cement) performed equally well (> 80% mortality) on both surfaces up to week 41 (approximately 9.5 months). Extended bioassay holding periods (up to 120 h) may present with excess natural mortality in the untreated controls, thus complicating analysis.

Effect of wall type, delayed mortality and mosquito age on the residual efficacy of a clothianidin-based indoor residual spray formulation (SumiShield™ 50WG) in southern Mozambique

“…The 24h mortality of young (2-5 days) and old (13-26 days) laboratory-reared mosquitoes that were exposed to walls sprayed with SumiShield TM 50WG, was consistently below the WHO threshold of 80% [15] for both cement and mud-plastered surfaces. These findings corroborate previous studies that have documented the delayed killing effect of SumiShield TM 50WG [16,[30][31][32] and confirm that its active ingredient, clothianidin, is slow acting. Clothianidin is a neonicotinoid and acts on the insect nicotinic acetylcholine receptor [33], which in turn causes systemic toxicity upon contact and poison the mosquito gut [34,35].…”

“…following WHO's current guidelines and assess 24h mortality post-exposure only [14]) will lead to an underestimation of the efficacy of SumiShield TM 50WG. Furthermore, this additional (delayed) mortality will lead to a further reduction in mosquito vector populations and potentially disease transmission risk, compared to considering 24h mosquito mortality alone [30][31][32].…”

Diagnostic dose determination and efficacy of chlorfenapyr and clothianidin insecticides against Anopheles malaria vector populations of western Kenya

“…SumiShield (Sumitomo Chemical, Japan) and Fludora ® Fusion (Bayer Environmental Science, Germany) are IRS products with clothianidin as the active ingredient. SumiShield was demonstrated to last up to 6 months in various surfaces in experimental huts [38]. With the availability of an LLIN treated with a pyrethroid plus chlorfenapyr and two IRS products with clothianidin along with LLINs treated with a synergist (piperonyl butoxide), management of insecticide resistance among wild Anopheles populations is more feasible.…”

Compensatory mechanisms in resistant Anopheles gambiae AcerKis and KdrKis neurons modulate insecticide-based mosquito control

“…We then studied in both in vitro and in vivo if these physiological modifications can be associated with an alteration in insecticide effectiveness. Comparative experiments were performed with the neonicotinoid insecticide, clothianidin, a new class of chemistry for public health, known to act as an agonist on insect nAChRs 41 – 44 . Using calcium imaging, clothianidin (0.1 nM, Fig.…”

“…Therefore, these data confirm the need for understanding these specific physiological compensatory mechanisms associated with the point mutations to adapt control strategies. This is particularly true for clothianidin, which is now recommended as a vector control product against Anopheles species and used as clothianidin‑based formulation 41 , 42 . In this case, it is interesting to mention that the effectiveness of the formulation containing a mixture of deltamethrin/clothianidin against wild pyrethroid-resistant malaria vectors may be explained by previous studies indicating that deltamethrin, used as synergistic agent, can optimize insecticide efficacy via intracellular calcium rise in insect 70 .…”