Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, Ohio, United States of America.
Department of Veterinary Population Medicine, University of Minnesota, St. Paul, Minnesota, United States of America.
PLoS One. 2018 Apr 3;13(4):e0195282. doi: 10.1371/journal.pone.0195282. eCollection 2018.
Industry-driven voluntary disease control programs for swine diseases emerged in North America in the early 2000's, and, since then, those programs have been used for monitoring diseases of economic importance to swine producers. One example of such initiatives is Dr. Morrison's Swine Health Monitoring Project, a nation-wide monitoring program for swine diseases including the porcine reproductive and respiratory syndrome (PRRS). PRRS has been extensively reported as a seasonal disease in the U.S., with predictable peaks that start in fall and are extended through the winter season. However, formal time series analysis stratified by geographic region has never been conducted for this important disease across the U.S. The main objective of this study was to use approximately seven years of PRRS incidence data in breeding swine herds to conduct time-series analysis in order to describe the temporal patterns of PRRS outbreaks at the farm level for five major swine-producing states across the U.S. including the states of Minnesota, Iowa, North Carolina, Nebraska and Illinois. Data was aggregated retrospectively at the week level for the number of herds containing animals actively shedding PRRS virus. Basic descriptive statistics were conducted followed by autoregressive integrated moving average (ARIMA) modelling, conducted separately for each of the above-mentioned states. Results showed that there was a difference in the nature of PRRS seasonality among states. Of note, when comparing states, the typical seasonal pattern previously described for PRRS could only be detected for farms located in the states of Minnesota, North Carolina and Nebraska. For the other two states, seasonal peaks every six months were detected within a year. In conclusion, we showed that epidemic patterns are not homogeneous across the U.S, with major peaks of disease occurring through the year. These findings highlight the importance of coordinating alternative control strategies in different regions considering the prevailing epidemiological patterns.
产业驱动的猪病自愿控制计划于 21 世纪初出现在北美，自那时以来，这些计划一直被用于监测对养猪生产者具有经济重要性的疾病。此类举措的一个例子是莫里森博士的猪健康监测项目，这是一个全国性的猪病监测计划，包括猪繁殖与呼吸综合征（PRRS）。PRRS 在美国被广泛报道为季节性疾病，具有可预测的高峰，始于秋季并持续到冬季。然而，针对这种重要疾病，美国从未按地理区域进行正式的时间序列分析。本研究的主要目的是使用大约七年的繁殖猪群 PRRS 发病率数据进行时间序列分析，以描述美国五个主要养猪州（明尼苏达州、爱荷华州、北卡罗来纳州、内布拉斯加州和伊利诺伊州）农场层面 PRRS 暴发的时间模式。数据按周水平汇总，用于包含动物主动传播 PRRS 病毒的畜群数量。进行了基本描述性统计分析，然后对上述各州分别进行自回归综合移动平均（ARIMA）建模。结果表明，各州之间 PRRS 季节性的性质存在差异。值得注意的是，在比较各州时，以前描述的 PRRS 典型季节性模式只能在明尼苏达州、北卡罗来纳州和内布拉斯加州的农场中检测到。对于其他两个州，在一年内每六个月检测到季节性高峰。总之，我们表明，美国各地的流行模式并不均匀，全年都会发生重大疾病高峰。这些发现强调了考虑流行的流行病学模式在不同地区协调替代控制策略的重要性。
