Culicoides species in the Netherlands: a comparison between tent traps and an Onderstepoort black light trap and the effect of an insect blanket on the biting rate

Abstract

Biting midges of the Culicoides genus (Diptera: Ceratopogonidae) are haematophagous arthropods, which can serve as vectors for orbiviruses such as bluetongue virus, equine encephalosis virus, African horse sickness virus and the recently discovered Schmallenberg virus. Biting midges also cause insect bite hypersensitivity in horses. Twenty one species of Culicoides have been identified in the Netherlands. Only the females suck blood and produce batches of eggs. African horse sickness (AHS) is a non-contagious, vector-borne viral disease of equines that is transmitted by Culicoides spp. The main field vectors of AHS virus are Culicoides imicola and Culicoides bolitinos. African horse sickness virus (AHSV) may cause four forms of disease: horse sickness fever or mild form, cardiac form or “dikkop”, pulmonary form or “dunkop” and a mixed form. The estimated range of economic losses due to an outbreak of AHS in the Netherlands is 272-516 million euros. A form of protection against biting midges may be the use of an insect blanket, which covers the head, neck, back and belly of the horse. The aims of the present study were to determine which species in which numbers of Culicoides (that potentially serve as vectors for AHSV) are attracted to horses in the Netherlands and to compare these results with the Culicoides species and numbers caught in the Onderstepoort black light trap during the same period. The second aim was to evaluate the use of an insect blanket on the biting rate of Culicoides species. During the study a total number of 14, 032 Culicoides midges were caught, divided into twelve species: C. obsoletus, C. punctatus, C. dewulfi, C. chiopterus, C. fasciipennis, C. festivipennis, C. stigma, C. pulicaris, C. nubeculosus, C. circumscriptus, C. newsteadi and C. salinarius. C. imicola and C. bolitinos were not found. An insect blanket proved to be effective in preventing horses from being bitten by Culicoides: a horse without an insect blanket had a 2,271 times higher chance of getting bitten than a horse wearing an insect blanket.