Assessment of the repellent effect of citronella and lemon eucalyptus oil against South African Culicoides species.

Gert J. Venter,Karien Labuschagne,Solomon N.B. Boikanyo,Liesl Morey

doi:10.4102/jsava.v85i1.992

Gert J. Venter, Karien Labuschagne + Show 2 more

Open Access

https://doi.org/10.4102/jsava.v85i1.992

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Abstract

The use of insect repellents to reduce the attack rate of Culicoides species (Diptera:Ceratopogonidae) should form part of an integrated control programme to combat African horse sickness and other diseases transmitted by these blood-feeding midges. In the present study the repellent effects of a commercially available mosquito repellent, a combination of citronella and lemon eucalyptus oils, on Culicoides midges was determined. The number of midges collected with two 220 V Onderstepoort traps fitted with 8 W 23 cm white light tubes and baited with peel-stick patches, each containing 40 mg of active ingredient, was compared with that of two unbaited traps. Two trials were conducted and in each trial the four traps were rotated in two replicates of a 4 x 4 randomised Latin square design. Although more midges were collected in the baited traps, the mean number in the baited and unbaited traps was not significantly different. This mosquito repellent did not influence either the species composition or the physiological groups of Culicoides imicola Kieffer. The higher mean numbers in the baited traps, although not statistically significant, may indicate that this mosquito repellent might even attract Culicoides midges under certain conditions.

Highlights

Small (< 3 mm) blood-feeding flies of the genus Culicoides (Diptera: Ceratopogonidae) are associated worldwide with the transmission of several pathogens to a variety of hosts (Borkent 2005; Meiswinkel, Venter & Nevill 2004)
Of the more than 66 viruses (Borkent 2005) isolated from Culicoides midges, African horse sickness virus (AHSV) is probably the most devastating to South Africa owing to its effect on the horse industry
As in previous studies conducted on repellents in South Africa (Venter et al 2011), the number of midges collected with two 220 V down-draught Onderstepoort light traps baited with the repellent was compared with that of two unbaited control traps

Summary

Introduction

Small (< 3 mm) blood-feeding flies of the genus Culicoides (Diptera: Ceratopogonidae) are associated worldwide with the transmission of several pathogens to a variety of hosts (Borkent 2005; Meiswinkel, Venter & Nevill 2004). Of the more than 66 viruses (Borkent 2005) isolated from Culicoides midges, African horse sickness virus (AHSV) is probably the most devastating to South Africa owing to its effect on the horse industry. More than a million C. imicola females can be collected overnight in a single light trap near livestock (Meiswinkel et al 2004) These traps intercept only a relatively small percentage of the active blood-seeking females (Meiswinkel et al 2004) and do not always reflect the true biting rate on livestock (Carpenter et al 2008; Gerry et al 2009; Scheffer et al 2012; Viennet et al 2011), these numbers give an indication of the potentially high attack rate that horses and other livestock can be exposed to in endemic areas. Repellents and insecticides can be applied directly to livestock and/or to their immediate surroundings, for example gauze coverings of stable windows (Meiswinkel, Baylis & Labuschagne 2000)

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