Protection of horses against Culicoides biting midges in different housing systems in Switzerland

Abstract

Species belonging to the Culicoides complexes (Diptera, Ceratopogonidae), obsoletus andpulicaris, in Switzerland, are potential vectors of both bluetongue virus (BTV) and Africanhorse sickness virus (AHSV). The epidemic of BTV in 2006 and 2007 in Europe hashighlighted the risk of introduction and spread of vector-borne diseases in previously non-endemic areas. As a measure of prevention, as part of an integrated control programmein the event of an outbreak of African horse sickness (AHS), it is of utmost importance toprevent, or substantially reduce, contact between horses and Culicoides. The aim of thepresent study was to compare the effect of three protection systems, net, fan, repellent, or combinations thereof, with regard to their potential to reduce contact between horses andCulicoides. Three different equine housing systems, including individual boxes (BX), grouphousing systems (GR), and individual boxes with permanently accessible paddock (BP)were used. The efficacy of the protection systems were evaluated by comparing the totalnumber counts of collected female Culicoides, of non-blood-fed and blood-fed Culicoides,respectively, with UV black light traps. The study was conducted over 3 summer monthsduring 2012 and 2013 each and focused on the efficacy and practicality of the protectionsystems. The repellent was tested in 2012 only and not further investigated in 2013, as itshowed no significant effect in reducing Culicoides collected in the light traps. Net protec-tion system provided the best overall protection for the total number of female Culicoides,non-blood-fed and blood-fed Culicoides in all tested housing systems. The net, with a poresize of 0.1825 mm2, reduced the total number of Culicoides collected in the housing sys-tems BP, GR and BX by 98%, 85% and 67%, respectively. However, in the GR housing system,no significant difference between the effectiveness of the fan and the net were determinedfor any of the three Culicoides categories. The results of the present study demonstratedthat horse owners can substantially reduce their horses’ exposure to Culicoides, by usingnet protection in the housing systems BX, BP and GR. In GR housing systems, protectionagainst Culicoides using a fan is also recommended.