Thompson Peter N, Sinclair Marna, Ganzevoort Boto
Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, South Africa.
Prev Vet Med. 2008 Aug 15;86(1-2):139-52. doi: 10.1016/j.prevetmed.2008.03.011. Epub 2008 May 19.
In a 2005 serological survey, carried out in response to an outbreak of H5N2 avian influenza (AI) in ostriches in the Eastern Cape Province, 16.3% of ostrich farms in the Western Cape Province of South Africa were found to be seropositive to H5 AI virus. We subsequently carried out a questionnaire-based census survey on all available registered Western Cape ostrich farms that still existed at the end of 2005 (367 farms, of which 82 were seropositive), in order to identify risk factors associated with farm-level seropositivity. A farm was classified as seropositive for H5 AI virus if one or more birds had tested positive (haemagglutination inhibition titre >1:16) in the 2005 survey, which had been designed to detect a minimum within-group seroprevalence of 10%. For each farm, risk factor information was collected using a questionnaire administered during a face-to-face interview with each farm owner or manager. Information was obtained on the ostrich population, movements of birds, environmental factors, management practices, and frequency of contact between ostriches and various wild bird species. Multiple logistic regression models were developed for the whole Western Cape Province and also for the two largest ostrich farming regions, "Klein Karoo" and "Southern Cape". Seroprevalence differed between regions, being highest in the Klein Karoo (31.6%). In all three models, increased risk of farm-level H5 AI virus seropositivity was associated with increasing numbers of ostriches, excluding chicks, present on the farm. Increased risk of seropositivity was associated with reduced frequency of cleaning of feed troughs (<1x/week vs. >1x/week), both overall (odds ratio (OR)=4.5; 95% confidence interval (CI): 1.5, 13.3) and in the Southern Cape (OR=53.6; 95% CI: 3.3, 864), and with failure to clean and disinfect transport vehicles, both overall (OR=2.3; 95% CI: 1.1, 4.8) and in the Klein Karoo (OR=2.6; 95% CI: 1.1, 6.5). Increased risk of seropositivity was also associated with increasing frequency of contact of ostriches with certain wild bird species: overall with white storks (Ciconia ciconia), in the Southern Cape with gulls (Larus spp.), and in the Klein Karoo with Egyptian geese (Alopochen aegyptiaca).
2005年，为应对东开普省鸵鸟爆发的H5N2禽流感疫情，开展了一项血清学调查，结果发现南非西开普省16.3%的鸵鸟养殖场对H5禽流感病毒呈血清阳性。随后，我们对2005年底仍存在的所有可获取的已注册西开普鸵鸟养殖场（共367个养殖场，其中82个呈血清阳性）进行了基于问卷调查的普查，以确定与养殖场层面血清阳性相关的风险因素。如果在2005年的调查中有一只或多只鸟检测呈阳性（血凝抑制效价>1:16），则该养殖场被归类为H5禽流感病毒血清阳性，此次调查旨在检测组内最低血清阳性率为10%。对于每个养殖场，通过在与每位养殖场主或经理进行面对面访谈时使用问卷来收集风险因素信息。获取了有关鸵鸟种群、鸟类流动、环境因素、管理措施以及鸵鸟与各种野生鸟类接触频率的信息。针对整个西开普省以及两个最大的鸵鸟养殖区“小卡鲁”和“南开普”建立了多重逻辑回归模型。不同地区的血清阳性率有所差异，小卡鲁地区最高（31.6%）。在所有三个模型中，养殖场层面H5禽流感病毒血清阳性风险增加与养殖场内成年鸵鸟数量增加有关。血清阳性风险增加与饲料槽清洁频率降低（每周<1次与每周>1次）有关，总体而言（优势比（OR）=4.5；95%置信区间（CI）：1.5，13.3）以及在南开普地区（OR=53.6；95%CI：3.3，864），还与运输车辆未进行清洁和消毒有关，总体而言（OR=2.3；95%CI：1.1，4.8）以及在小卡鲁地区（OR=2.6；95%CI：1.1，6.5）。血清阳性风险增加还与鸵鸟与某些野生鸟类接触频率增加有关：总体而言与白鹳（白鹳）有关，在南开普地区与海鸥（鸥属）有关，在小卡鲁地区与埃及雁（埃及雁）有关。
