Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa.
Vet Parasitol. 2012 Apr 30;185(2-4):265-73. doi: 10.1016/j.vetpar.2011.09.037. Epub 2011 Oct 1.
Culicoides biting midges (Diptera: Ceratopogonidae) are vectors of a variety of pathogens including African horse sickness virus (AHSV), a member of the family Reoviridae, genus Orbivirus. AHSV causes African horse sickness (AHS), an endemic disease of equids with an extremely high mortality rate in horses in sub-Saharan Africa. Culicoides (Avaritia) imicola Kieffer is considered to be the principal vector of AHSV and is the dominant Culicoides species in South Africa. Due to the global distribution of Culicoides vectors, there is a potential risk of AHS spreading from endemic areas to areas traditionally free of the disease, which could have a severe economical impact on the affected equine industry. As part of any risk assessment it is essential to monitor known vectors as well as potential vector species. In the present study, sampling of Culicoides insects was compared using overnight collections in the conventional Onderstepoort light trap and mechanical aspiration of midges at sunset from bait horses. Culicoides imicola was confirmed as the predominant species using both trapping methods. Other species, mainly Culicoides (Avaritia) bolitinos Meiswinkel and Culicoides (Avaritia) gulbenkiani Caeiro, were highly underrepresented in the light trap collections, but made a significant contribution to the mechanical aspiration catches. The time for optimal collection differed between the trapping methods, leading to the conclusion that mechanical aspiration is a useful addition to conventional light trap collection and possibly the better choice when investigating insect vectors. An infection rate of 1.14% was calculated for the midge population based on real-time quantitative reverse-transcription polymerase chain reaction (RT-qPCR) assays of collected Culicoides midges, which exceeds previous estimates. This is probably due to the increased sensitivity of the RT-qPCR assay used in this study as compared to the virus isolation assays used in previous studies. RT-qPCR-positive midges were present in midge pools obtained from both light trap and mechanical aspiration. Seven of the positive pools consisted of C. imicola only, four contained mixed species and one pool contained no C. imicola, suggesting the presence of AHSV in midges of other species.
致蝇蚋（双翅目：蠓科）是多种病原体的媒介，包括非洲马瘟病毒（AHSV），该病毒属于呼肠孤病毒科、呼肠孤病毒属。AHSV 引起非洲马瘟（AHS），这是一种马属动物的地方病，在撒哈拉以南非洲地区的马中死亡率极高。致蝇蚋（Avaritia）imicola Kieffer 被认为是 AHSV 的主要媒介，也是南非的主要致蝇蚋物种。由于致蝇蚋媒介的全球分布，AHS 有从流行地区传播到传统上无病地区的潜在风险，这可能会对受影响的马业造成严重的经济影响。作为任何风险评估的一部分，监测已知媒介以及潜在媒介物种是至关重要的。在本研究中，通过在常规奥登堡灯下诱捕器中过夜收集和在日落时从诱饵马中机械抽吸致蝇蚋，比较了致蝇蚋昆虫的采样。两种捕蝇方法均证实致蝇蚋（Avaritia）imicola 是主要物种。其他物种，主要是致蝇蚋（Avaritia）bolitinos Meiswinkel 和致蝇蚋（Avaritia）gulbenkiani Caeiro，在灯下诱捕器收集的标本中严重代表性不足，但对机械抽吸的采集有显著贡献。两种捕蝇方法的最佳收集时间不同，得出的结论是机械抽吸是常规灯光诱捕收集的有益补充，并且在调查昆虫媒介时可能是更好的选择。根据收集的致蝇蚋实时定量逆转录聚合酶链反应（RT-qPCR）检测，致蝇蚋种群的感染率为 1.14%，高于以往的估计。这可能是由于本研究中使用的 RT-qPCR 检测比以前研究中使用的病毒分离检测更灵敏。从灯光诱捕器和机械抽吸中获得的致蝇蚋虫池中都存在 RT-qPCR 阳性的致蝇蚋。七个阳性虫池仅含有致蝇蚋（Avaritia）imicola，四个含有混合种，一个虫池不含致蝇蚋（Avaritia）imicola，表明其他种的致蝇蚋中存在 AHSV。
