Reemergence of porcine epidemic diarrhea virus on Jeju Island

Abstract

Abstract : Porcine epidemic diarrhea virus (PEDV) strains responsible for recent outbreaks in the United States havebeen occurring in Mainland Korea since late 2013. Over the past 10 years, PEDV outbreaks have not been reportedon Jeju Island. However, in late March of 2014, PEDV re-emerged on Jeju Island and was found to be geneticallyidentical to PEDV strains currently circulating in Mainland Korea. The present study was conducted to provide a betterunderstanding of the epidemiology of PEDV and more effective preventive measures against PED.Keywords : Jeju Island, Korea, porcine epidemic diarrhea virus, reemergence, US strain-like strains Porcine epidemic diarrhea (PED) is a devastating pig entericdisease causing lethal watery diarrhea followed by severedehydration with high mortality in neonatal piglets [10]. Thedisease was first recognized in England in 1971 [7], andsince then, outbreaks have been reported in Europe, Asia,and recently, North America including the United States [1,9, 13, 14]. The causative agent of this disease, the PED virus(PEDV), belongs to the Alphacoronavirus genus within thefamily Coronaviridae of the order Nidovirales [8, 10]. Thespike (S) protein of PEDV is the major virion envelopeglycoprotein; interacts with the host cellular receptor forvirus entry and mediates neutralizing antibodies. Therefore,the PEDV S protein is an appropriate viral gene forsequencing and molecular analyses to investigate the geneticrelatedness of PEDV isolates and the epidemiological statusof PEDV in the field [4].The first case of PED in Korea was confirmed in 1992 [3]and since its emergence, PED outbreaks have continuouslyoccurred every year, leading to a serious production loss tothe Korean pork industry up until early 2010. However, aftersevere outbreaks of foot-and-mouth disease (FMD) in 2010and 2011, the prevalence of PEDV infections in Korea wassignificantly reduced with only sporadic outbreaks. InNovember of 2013, PEDV suddenly recurred and subsequently,has swept rapidly across Mainland Korea. Genetic andphylogenetic analyses revealed that PEDV isolates responsiblefor the recurrence in Mainland Korea are most highly relatedto PEDV strains currently circulating in the United States [5].The last PEDV outbreak on Jeju Island was reported in 2004and since then, PEDV has not emerged again on Jeju Islandin almost 10 years. Beginning in late March of 2014, PEDVre-emerged in the Hanlim area of Jeju Island and subsequentlyspread to other districts, resulting in high mortality innewborn piglets. To determine the origin and diversity ofPEDV responsible for the ongoing outbreaks on Jeju Island,we sought to determine the full-length sequences of the Sproteins of field isolates identified from affected pig farms.From late March 2014 through early April 2014, 5 stoolspecimens were taken from sows and piglets with acute waterydiarrhea at different swine farms. Fecal samples were processedinto 10% suspensions as described previously [4] and initiallysubjected to RT-PCR using a TGE/PED Detection Kit(iNtRON Biotechnology, Korea) according to the manufac-turer’s protocol. The PEDV-positive supernatants were storedat