Short communicationThe effect of light trap height on the numbers of Culicoides midges collected under field conditions in South Africa
Introduction
Unanticipated outbreaks and apparent overwintering of bluetongue in northern Europe highlighted the devastating effect of the introduction of this disease for livestock in areas with large populations of susceptible animals (Darpel et al., 2007). The causative agent, bluetongue virus (Reoviridae), is almost exclusively transmitted by certain species of biting midges in the genus Culicoides (Diptera: Ceratopogonidae) (Mellor et al., 2000). The occurrence and spread of bluetongue over a relatively wide geographical area in several countries in Europe accentuated the need for data comparison between laboratories and the standardization of methods for the collection of Culicoides midges. The primary monitoring tools used are various models of light traps. These traps are usually deployed as close to livestock as practically possible and the heights at which these traps are hung are in many instances determined by the availability of suitable structures near livestock (Goffredo and Meiswinkel, 2004).
In this study the influence of relatively small variation in light trap height, on the number of Culicoides midges collected, was determined. Species composition and age-grading results at the various heights were also compared.
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Materials and methods
Onderstepoort 220 V down-draught black light traps were used at four sites at 0.6, 1.4, 2.2, and 2.8 m above ground level at the ARC-Onderstepoort Veterinary Institute (ARC-OVI) (25°39′S:28°11′E; 1219 m above sea level) for the collection of Culicoides midges. Light trap collections were made as described by Venter et al. (2009). To ensure that treatment means were independent of any effects due to sites or occasion, trap heights at the four sites were alternated in three replicates of a 4 × 4
Results
A total of 147 158 Culicoides midges, belonging to 20 species, was collected in 48 collections. Nearly half (44.8%) of the total number of midges were collected 2.8 m above ground level (Table 1). The abundance of Culicoides imicola Kieffer ranged from 94.6% at 2.8 m to 95.8% at 0.6 m (Table 1). The abundance of the second most abundant species at all four heights, Culicoides magnus Colaço, ranged from 2.2% at 2.2 and 2.8 m to 2.7% at 1.4 m (Table 1). Statistically significant differences between
Discussion
The presence and abundance of Culicoides midges in an area, as determined with light traps, is used as an indication of the risk of a virus spreading in that area (Venter et al., 2006, Meiswinkel et al., 2008). The numbers of Culicoides midges collected are also used to define vector-free periods (Losson et al., 2007, Meiswinkel et al., 2008). The age structure of a Culicoides population can be an important indicator of its potential vector status. The present study indicates that relatively
Conflict of interest
The authors declare no conflict of interest.
Acknowledgements
This study was partly initiated by a grant from the European Union in a project entitled: “Surveillance network of Reoviruses, Bluetongue and African Horse Sickness, in the Mediterranean basin and Europe” (MedReoNet) (Contract N 044285). We thank the ARC-OVI for supporting this work. We acknowledge the comments of Marie Smith and the late Edith van den Berg on the statistical analyses and thank Errol Nevill for constructive comments on earlier drafts of this manuscript.
References (13)
- et al.
The Culicoides ‘snapshot’: a novel approach used to assess vector densities widely and rapidly during the 2006 outbreak of bluetongue (BT) in The Netherlands
Prev. Vet. Med.
(2008) - et al.
Comparison of the efficiency of five suction light traps under field conditions in South Africa for the collection of Culicoides species
Vet. Parasitol.
(2009) - et al.
Effect of light trap height on catch of Culicoides (Diptera: Ceratopogonidae) in Israel
J. Med. Entomol.
(1993) - et al.
Clinical signs and pathology shown by British sheep and cattle infected with bluetongue virus serotype 8 derived from the 2006 outbreak in northern Europe
Vet. Rec.
(2007) The recognition of nulliparous and parous Culicoides (Diptera: Ceratopogonidae) without dissection
J. Aust. Entomol. Soc.
(1969)- et al.
Entomological surveillance of bluetongue in Italy: methods of capture, catch analysis and identification of Culicoides biting midges
Vet. Ital.
(2004)
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