The normal biting rate of Culicoides,caught in the proximity of sheep and horses in the Netherlands

Abstract

This report is a part of the Culicoides project of 2011 of Utrecht University (dr. M. Sloet) and Wageningen University and Research centre (dr. G. Nodelijk). This study was conducted to answer several questions considering Culicoides species in the Netherlands. The part of the study discussed here focused on the following question: What is the normal biting rate of Culicoides, caught in the vicinity of sheep and horses? The complete project was set up to determine which tactics could be used to prevent or reduce the transmission of African Horse Sickness (AHS) by Culicoides species which is considered to be a potential threat for the Dutch horse population (Maclachlan & Guthrie, 2010).

In the study the experimental mosquito trapping tents designed by Van der Rijt (Rijt 2008) and Griffioen (Griffioen 2010) were used in order to collect Culicoides spp. and other flying insects in de proximity of horses and sheep. After an hour the tents were closed and the insects were collected. All trapped Culicoides spp. were microscopically counted and identified. The total number of Culicoides caught widely varied at the test farms. During all trapping sessions with animals an ‘Onderste Poort black light trap’ was turned on to collect Culicoides. The line of thought behind this will be discussed later in this paper. This study addresses the research question; “What is the normal biting rate of Culicoides spp., caught in the vicinity of sheep and horses?” Moreover, it can be concluded that  The biting rate of Culicoides caught in the proximity of sheep is 77% for Culicoides spp and 67% for C. obsoletus.  The biting rate of Culicoides caught in the proximity of horses is 56% for Culicoides spp. and 58% for C. obsoletus.  The biting ratio of Culicoides spp. is 21% in the tests with sheep in an inner tent and 77% in the tests without an inner tent. The corresponding odds ratio is 8.77. This means that the odds of blood-fed Culicoides spp. found was 8.77 times higher in the group of sheep without an inner tent than in the group with an inner tent.