Susceptibility of Culicoides species biting midges to deltamethrin‐treated nets as determined under laboratory and field conditions in the Balearic Islands, Spain

Abstract

Culicoides Latreille (Diptera: Ceratopogonidae) are vectors of several arboviruses, including bluetongue virus (BTV) and African horse sickness virus (AHSV), which cause diseases in, respectively, sheep and cattle, and horses, and have economic repercussions mainly as a result of trade restrictions. Insecticides can be used to reduce vector populations and hence the spread of disease. Despite the economic importance of these diseases, relatively few studies have evaluated the efficacy of commercially available insecticides and the effectiveness of treated nets against Culicoides species. The aim of the present study was to evaluate the insecticidal effect of commercially available polyethylene nets (ZeroVector(®) ) treated with deltamethrin (4.4 g/kg ± 15%) on Culicoides species. Laboratory and field trials were conducted in Culicoides populations collected in Majorca in the Balearic Islands, Spain. The present study shows that deltamethrin-treated nets provoke high and rapid mortality (90-100%) in Culicoides midges under laboratory conditions and increase mortality by 13% when deployed in the field.

Efficacy of alphacypermethrin-treated high density polyethylene mesh applied to jet stalls housing horses against Culicoides biting midges in South Africa

“…Increased mortality rates in midges collected in light traps have been determined after contact with insecticide treated nets (Calvete et al, 2010;Del Río et al, 2014b). Unfortunately the mortality rate of midges collected in light traps in the present study was not investigated, therefore the degree of incapacitation of midges that were able to enter the light trap after passing through the treated mesh is unknown.…”

“…Unfortunately the mortality rate of midges collected in light traps in the present study was not investigated, therefore the degree of incapacitation of midges that were able to enter the light trap after passing through the treated mesh is unknown. Nonetheless, during contact bioassays with the alphacypermethrin-treated mesh midge mortality was assessed and observed from 5 min post-exposure (Page et al, 2014), and signs of intoxication and mortality were observed 6 min post-exposure to a deltamethrin-treated mesh (Del Río et al, 2014b). It is considered likely, based on the significant reduction in attack rate determined by aspiration, that the host-seeking ability of the midges (and hence potential for viral transmission) was adversely affected soon after contact with the mesh.…”

Mechanistic model for predicting the seasonal abundance of Culicoides biting midges and the impacts of insecticide control

“…No single Culicoides vector control method is in routine field operation [52]. Our approach is motivated by recent experimental evidence of field efficacy of some chemical control methods, focussing on insecticide control that targets host-seeking adult midges [18, 19, 53, 54] as being the best control option currently available [54]. In particular, insecticide screening of animals has high potential value in the early stages of an epidemic and during transport of susceptible animals to prevent further spread [52].…”

“…Field studies with deltamethrin-treated nets controlling Culicoides species in Spain showed that mortality (probability of death) was approximately 13% [19]. In a field study on sheep applied with insecticide the short-term mortality rate was 49% [18].…”

“…They found a maximum mortality rate of 49% at 4 days post-application, and duration of lethal effect was predicted to be as short as 10 days, with susceptibility differences for the different Culicoides species. Using deltamethrin treated nets, another study showed that the insecticide was 90–100% effective in the laboratory test, but this dropped to 13% in field conditions [19]. Despite these findings on mortality rates, reductions in midge population sizes, biting rate or arbovirus transmission as a result of insecticide application have been harder to demonstrate under field conditions [20, 21] and there has been no study of how control impacts might vary seasonally.…”