Toyomaki Haruya, Sekiguchi Satoshi, Sasaki Yosuke, Sueyoshi Masuo, Makita Kohei
Veterinary Epidemiology Unit, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, Japan.
Center for Animal Disease Control, University of Miyazaki, 1-1 Gakuenkibanadai Nishi, Miyazaki, Japan.
Prev Vet Med. 2018 Feb 1;150:77-85. doi: 10.1016/j.prevetmed.2017.12.008. Epub 2017 Dec 11.
The objective of this study was to investigate factors that caused rapid spread during the early phase of the porcine epidemic diarrhea (PED) epidemic in Japan in 2013 and 2014. Anonymized datasets from all pig farms were provided by Kagoshima (709 farms) and Miyazaki Prefectures (506 farms). Semi-parametric survival analysis was conducted using the first 180 days from the first case on December 3, 2013 in Kagoshima Prefecture. To compare the hazard between different farm management types, univariable survival analysis was conducted. As farm sizes varied among different farm types, bivariable survival analysis was conducted for farm size categories and farm density per km for each management type. A case-control study using a postal questionnaire survey was conducted in September 2014, and risk factor analysis was performed using generalized linear models with binomial errors. The hazard was significantly higher in farrow-to-finish farms than fattening farms [hazard ratio (HR) = 1.6, p < 0.01], but was not significantly different between reproduction and fattening farms (HR = 1.3, p = 0.16). In separate bivariable survival analyses for each farm type, large- and middle-scale farms had higher hazard than small-scale farms in fattening (HR = 5.8 and 2.6, respectively, both p < 0.01) and reproduction farms (HR = 4.0 and 3.6, respectively, both p < 0.01). In farrow-to-finish farms, large-scale farms had higher hazard than small-scale farms (HR = 2.8, p < 0.01), and higher farm density per km was also a risk factor (HR = 7.6, p < 0.01). In the case-control study, questionnaires were returned from 78 PED virus-infected and 91 non-infected farms. The overall response rate was 34%. Risk factors of the final model were occurrence of porcine reproductive and respiratory syndrome in the past 5 years [odds ratio (OR) = 1.97, 95% confidence interval (CI): 0.97-4.00, p = 0.054], use of a common compost station (OR = 2.51, 95%CI: 1.08-5.83, p = 0.03), and use of a pig excrement disposal service (OR = 2.64, 95%CI: 1.05-6.63, p = 0.04). High hazard in farrow-to-finish farms suggested transmission from slaughterhouses to susceptible suckling piglets. Hazard associated with large-scale farms and high density might be due to frequent vehicle entrance and transmission by roads. Improvement of farm hygiene management and avoidance of risky practices associated with contact with pig excrement were keys in preventing invasion of PED virus to a farm.
本研究的目的是调查2013年和2014年日本猪流行性腹泻（PED）疫情早期导致其迅速传播的因素。鹿儿岛（709个猪场）和宫崎县（506个猪场）提供了所有猪场的匿名数据集。使用从2013年12月3日鹿儿岛县首例病例起的前180天进行半参数生存分析。为比较不同猪场管理类型之间的风险，进行了单变量生存分析。由于不同猪场类型的规模不同，对每种管理类型的猪场规模类别和每公里猪场密度进行了双变量生存分析。2014年9月进行了一项使用邮政问卷调查的病例对照研究，并使用具有二项式误差的广义线性模型进行了风险因素分析。分娩至育肥猪场的风险显著高于育肥猪场[风险比（HR）=1.6，p<0.01]，但繁殖猪场和育肥猪场之间无显著差异（HR=1.3，p=0.16）。在对每种猪场类型单独进行的双变量生存分析中，大型和中型猪场在育肥（HR分别为5.8和2.6，均p<0.01）和繁殖猪场（HR分别为4.0和3.6，均p<0.01）中的风险高于小型猪场。在分娩至育肥猪场中，大型猪场的风险高于小型猪场（HR=2.8，p<0.01），每公里较高的猪场密度也是一个风险因素（HR=7.6，p<0.01）。在病例对照研究中，收到了78个感染PED病毒的猪场和91个未感染猪场的问卷回复。总体回复率为34%。最终模型的风险因素包括过去5年发生猪繁殖与呼吸综合征[比值比（OR）=1.97，95%置信区间（CI）：0.97 - 4.00，p=0.054]、使用共用堆肥站（OR=2.51，95%CI：1.08 - 5.83，p=0.03）以及使用猪粪处理服务（OR=2.64，95%CI：1.05 - 6.63，p=0.04）。分娩至育肥猪场的高风险表明从屠宰场传播至易感哺乳仔猪。与大型猪场和高密度相关的风险可能是由于车辆频繁进出以及通过道路传播。改善猪场卫生管理并避免与猪粪接触的危险做法是防止PED病毒侵入猪场的关键。
