The enteric disease of swine recognized in the early 1970s in Europe was initially described as “epidemic viral diarrhea” and is now termed “porcine epidemic diarrhea (PED)”. The coronavirus referred to as PED virus (PEDV) was determined to be the etiologic agent of this disease in the late 1970s. Since then the disease has been reported in Europe and Asia, but the most severe outbreaks have occurred predominantly in Asian swine-producing countries. Most recently, PED first emerged in early 2013 in the United States that caused high morbidity and mortality associated with PED, remarkably affecting US pig production, and spread further to Canada and Mexico. Soon thereafter, large-scale PED epidemics recurred through the pork industry in South Korea, Japan, and Taiwan. These recent outbreaks and global re-emergence of PED require urgent attention and deeper understanding of PEDV biology and pathogenic mechanisms. This paper highlights the current knowledge of molecular epidemiology, diagnosis, and pathogenesis of PEDV, as well as prevention and control measures against PEDV infection. More information about the virus and the disease is still necessary for the development of effective vaccines and control strategies. It is hoped that this review will stimulate further basic and applied studies and encourage collaboration among producers, researchers, and swine veterinarians to provide answers that improve our understanding of PEDV and PED in an effort to eliminate this economically significant viral disease, which emerged or re-emerged worldwide.

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Porcine epidemic diarrhea virus: An emerging and re-emerging epizootic swine virus

Evolution, antigenicity and pathogenicity of global porcine epidemic diarrhea virus strains.

Porcine epidemic diarrhea virus (PEDV), an Alphacoronavirus in the family Coronaviridae, causes acute diarrhea, vomiting, dehydration, and high mortality rates in neonatal piglets. PEDV can also cause diarrhea, agalactia, and abnormal reproductive cycles in pregnant sows. Although PEDV was first identified in Europe, it has resulted in significant economic losses in many Asian swine-raising countries, including Korea, China, Japan, Vietnam, and the Philippines. However, from April 2013 to the present, major outbreaks of PEDV have been reported in the United States, Canada, and Mexico. Moreover, intercontinental transmission of PEDV has increased mortality rates in seronegative neonatal piglets, resulting in 10% loss of the US pig population. The emergence and re-emergence of PEDV indicates that the virus is able to evade current vaccine strategies. Continuous emergence of multiple mutant strains from several regions has aggravated porcine epidemic diarrhea endemic conditions and highlighted the need for new vaccines based on the current circulating PEDV. Epidemic PEDV strains tend to be more pathogenic and cause increased death in pigs, thereby causing substantial financial losses for swine producers. In this review, we described the epidemiology of PEDV in several countries and present molecular characterization of current strains. We also discuss PEDV vaccines and related issues.

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Porcine epidemic diarrhea: a review of current epidemiology and available vaccines

Porcine epidemic diarrhea in China

Vaccines for porcine epidemic diarrhea virus and other swine coronaviruses.

The number of porcine epidemic diarrhea (PED) cases has increased over the past 20 years in Korea, with a major outbreak in 2013. A total of 27 Korean strains from 1998 to 2013 were analyzed (excluding the noncoding regions) and divided into two groups for comparison of the spike (S), ORF3, envelope (E), membrane (M), and nucleocapsid (N) genes with those of reference strains, vaccine strains, and previously identified strains based on phylogenetic analysis. Analysis of the selection patterns of PEDV isolated in Korea indicated positive selection of nine nonsynonymous sites in the S and N proteins and negative selection at 97 sites for all of the proteins. Interestingly, eight nonsynonymous mutations in S showed no significant pattern change over the 15-year period, and one of eight mutation sites was found only in IC05TK, GN05DJ, and KNU0802 in the epidemic years 2005 and 2008. These eight mutations were also present during the epidemic years in China. Furthermore, of the signs of positive selection in the S protein, the conservative substitutions were more frequent than radical substitutions in PEDVs, suggesting that the evolution of Korean strains has been slow. Serological cross-reactivity was detected between three field PEDVs and two vaccine strains, with different serum neutralization titers. In conclusion, although Korean PEDVs have been evolving slowly, their diverse antigenicity and genetics imply that multilateral efforts to prevent future PED outbreaks are required.

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Jongsun Jung

Papers

Genetic characterization of porcine epidemic diarrhea virus in Korea from 1998 to 2013