Rosendal Thomas, Dewey Cate, Friendship Robert, Wootton Sarah, Young Beth, Poljak Zvonimir
Department of Population Medicine, University of Guelph, Guelph, ON, Canada.
BMC Vet Res. 2014 Apr 5;10:83. doi: 10.1186/1746-6148-10-83.
The spread of PRRSV among pig herds has been investigated experimentally, but few observational studies have investigated this subject. Because PRRSV is endemic and live modified vaccines are used in Ontario, the spatial and temporal distributions of 6 PRRSV genotypes were investigated in the province during the period from 2004-2007. The purpose was to find evidence of spread of PRRSV genotypes and determine if spread could be attributed to supplier or ownership connections between herds. Sequence information from PRRSV ORF5 and related source-herd demographic information were obtained from diagnostic submissions to the Animal Health Laboratory, University of Guelph.
A spatial cluster that could not be attributed to supplier or ownership connections among herds in the cluster was detected for RFLP type 1-3-4. Because of genetic dissimilarity among members of the cluster, it was considered to be a result of past spread of the RFLP type. A spatio-temporal cluster detected for RFLP type 1-18-4 was attributed to a shared gilt supplier among the herds in the cluster. Significant spatio-temporal patterns detected for RFLP type 2-5-2, which is considered to be a vaccine-type virus were most likely due to grouping of herds in an ownership that used the corresponding vaccine. Clustering within herd-ownership was a risk factor for presence of five of the six genotypes investigated in the present study.
Although the literature indicates that PRRSV can spread via aerosol between pig herds, the present study found no strong evidence of this occurring in Ontario. The evidence pointed toward transmission of PRRSV occurring in this population by common sources of animals or similarity of herd ownership, which is a proxy measure for other connections between herds. It is also apparent that the recognition and testing of these connections between herds is a necessary part of interpreting spatio-temporal patterns of PRRSV genotypes.
猪繁殖与呼吸综合征病毒（PRRSV）在猪群中的传播已通过实验进行了研究，但很少有观察性研究涉及这一主题。由于PRRSV在安大略省呈地方流行性，且使用了活的改良疫苗，因此在2004 - 2007年期间对该省6种PRRSV基因型的空间和时间分布进行了调查。目的是寻找PRRSV基因型传播的证据，并确定传播是否可归因于猪群之间的供应商或所有权联系。从圭尔夫大学动物健康实验室的诊断提交材料中获取了PRRSV开放阅读框5（ORF5）的序列信息以及相关的源猪群人口统计学信息。
检测到一个RFLP 1 - 3 - 4型的空间聚集区，该聚集区不能归因于猪群之间的供应商或所有权联系。由于该聚集区内成员之间存在遗传差异，因此认为这是RFLP型过去传播的结果。检测到的一个RFLP 1 - 18 - 4型的时空聚集区归因于该聚集区内猪群之间共享的后备母猪供应商。检测到的RFLP 2 - 5 - 2型（被认为是疫苗型病毒）的显著时空模式很可能是由于使用相应疫苗的所有权内猪群的分组。在本研究中，六个调查基因型中的五个，猪群所有权内的聚集是其存在的一个风险因素。
尽管文献表明PRRSV可通过气溶胶在猪群之间传播，但本研究未发现安大略省发生这种情况的有力证据。证据表明，该种群中PRRSV的传播是通过动物的共同来源或猪群所有权的相似性发生的，而猪群所有权相似性是猪群之间其他联系的一种替代指标。同样明显的是，认识和检测猪群之间的这些联系是解释PRRSV基因型时空模式的必要部分。
