Neumann E J, Morris R S, Sujau M
EpiCentre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
N Z Vet J. 2007 Dec;55(6):326-36. doi: 10.1080/00480169.2007.36789.
To determine the frequency with which porcine reproductive and respiratory syndrome (PRRS) virus (PRRSv) would become established in a non-commercial pig herd in New Zealand due to illegal feeding of uncooked food waste containing virus-contaminated pigmeat. To determine the likelihood of a single incursion resulting in a multi-farm outbreak of the disease, and describe the spatio-temporal characteristics of such an outbreak.
A Monte Carlo simulation model was constructed to determine the expected annual frequency of PRRSv infection being initiated in a non-commercial pig herd as a result of inadvertent feeding of pigmeat imported from countries endemically infected with the disease. Once the likelihood of PRRSv becoming established in a single pig herd was determined, stochastic spatially explicit infectious disease modelling software was utilised to model the temporal and spatial characteristics of the resulting epidemic.
Assuming the proportion of imported pigmeat remained at current levels, consumption patterns of pigmeat in households in New Zealand remained steady, and limited compliance with recently reintroduced regulations to prevent feeding of uncooked food waste, at least 4.3 pig herds per year were predicted to become infected with PRRSv. Simulation modelling of PRRSv epidemics related to initial infection of a non-commercial farm produced an estimate that 36% of these incursions would spread from the initial herd, and that these outbreaks would involve 93 herds on average in the first year. By increasing the estimated persistence of PRRSv infection in small herds, an average of 205 herds became infected in the first year.
Given a mean of 4.3 infected premises per year and a 36% probability of infection spreading beyond the initial infected herd, there was a 95% likelihood of a multi-farm PRRS outbreak occurring within 3 years.
Introduction of PRRSv through importation of virus-contaminated pigmeat presents a high risk for establishment of the disease in the pig industry in New Zealand.
确定由于非法投喂含有病毒污染猪肉的未煮熟食物垃圾，猪繁殖与呼吸综合征（PRRS）病毒（PRRSv）在新西兰一个非商业性猪群中定殖的频率。确定单次引入导致该病在多个猪场爆发的可能性，并描述此类爆发的时空特征。
构建蒙特卡罗模拟模型，以确定因无意中投喂从该病地方流行国家进口的猪肉而导致非商业性猪群中PRRSv感染的预期年频率。一旦确定PRRSv在单个猪群中定殖的可能性，就利用随机空间明确传染病建模软件对由此产生的疫情的时间和空间特征进行建模。
假设进口猪肉的比例保持在当前水平，新西兰家庭猪肉消费模式保持稳定，且对最近重新出台的防止投喂未煮熟食物垃圾规定的遵守情况有限，预计每年至少有4.3个猪群会感染PRRSv。与非商业农场初始感染相关的PRRSv疫情模拟模型估计，这些引入事件中有36%会从初始猪群传播开来，且这些疫情在第一年平均会涉及93个猪群。通过增加PRRSv在小猪群中感染的估计持续时间，第一年平均有205个猪群被感染。
鉴于每年平均有4.3个感染场所，且感染传播到初始感染猪群之外的概率为36%，在3年内发生多猪场PRRS疫情的可能性为95%。
通过进口受病毒污染的猪肉引入PRRSv对新西兰养猪业中该病的定殖构成高风险。
