Epidemiological information of porcine epidemic diarrhea during the second epidemic year (2014 to 2015) in Miyazaki prefecture, Japan

Porcine epidemic diarrhea virus (PEDv) was first reported in Japan in the 1990s, and a PED live vaccine was approved in 1996 (Sueyoshi et al., 1995). Since then, only sporadic and relatively unimportant outbreaks were recorded. However, in 2013 and following the first PEDv case reported in Japan in seven years, detected in Okinawa prefecture in October, the virus rapidly spread across the country with 817 PEDv cases confirmed across 38 prefectures as of August 31, 2014.

Miyazaki prefecture is located on the southern island of Japan and is the major swine-producing area in Japan. In this prefecture, during the first year of the epidemic, PED was detected from December 13, 2013, to July 24, 2014. No more cases were detected until December 2014, when a new case epidemic wave started in Miyazaki prefecture. The objective of the study here was to investigate the epidemiological information of PED during the second epidemic year (2014 to 2015) in Miyazaki.

The present study was conducted in Miyazaki prefecture, Japan. Information on the location and characteristics of all swine farms in the prefecture was obtained from the prefecture database (including farm size, farm operation type, and basic information for livestock producers) in July 2015. The database included 511 pork producers. Between-farm distance and Kernel density was calculated using ArcGIS V10.2 (ESRI, Redlands, California, USA). Data on PED incidence in the region was obtained from Miyazaki Livestock Hygiene Service Center, and was available between December 2013 and July 2015. PED was first suspected based on the presence of clinical signs, and all cases suspected were confirmed by laboratory testing. Statistical analyses were performed in SAS V9.3 (SAS Institute Inc., Cary, NC, USA).

During the first epidemic year (2013 to 2014), 81 out of 511 (15.8%) farms broke with PED. The first case was detected in middle December, and a sharp increase was observed in early February and mid-March.

During the second epidemic year (2014 to 2015), 11 farms out of 511 (2.2%) farms broke with PED. Of the 11, 9 were new PED cases, whereas 2 were farms already positive in 2014. Of the total 11 cases, 7, 1 and 3 were farrow-to-finish farrow-to-wean, and wean-to-finish farms, respectively. The first case was detected in mid-December, and the following six cases occurred until January 2015. The outbreak was mainly seen in the southwest part of the Miyazaki prefecture.

In conclusion, the number of PED occurrences during the second epidemic year was significantly lower than that during the first year. Further epidemiological data are needed to investigate risk factors associated with PED outbreaks.

Disclosure of Interest: None Declared.