Abstract
BackgroundSince late 2013, porcine epidemic diarrhea virus (PEDV) has reemerged in Japan and caused severe economic losses to the swine industry. Although PEDV vaccines have been used widely, the disease has swept rapidly across the county, and is commonly observed in PED-vaccinated farms, and has recurred in domestic herds. To better understand PEDVs responsible for the reemerging outbreaks in Japan, full-length spike (S), membrane (M), and nucleocapsid (N) genes of 45 PEDVs collected in Japan during 2013–2016, were sequenced and analyzed.ResultsPhylogenetic analysis based on S gene sequences revealed that all the recent field PEDVs were genetically distinct from the classical Japanese strains, and were classified into three genotypes: North American (NA), S INDEL, and Asian non-S INDEL. Our data suggested a possibility that multiple parental PEDV strains were introduced into Japan from abroad at the same time or similar times. The newly identified Japanese strains showed the closest relationship to the US strains. Two sublineages of Japanese strains circulating in Japan were similar to two sublineages identified in the US, suggesting common ancestors for these strains. In comparison with two vaccine strains used in Japan, the field strains had various changes in epitope regions, glycosylation sites, and phosphorylation sites. These substitutions, particularly observed in epitope regions of the S (521, 553, 568, and 570), M (5), and N (123, 252, and 255) proteins, may have affected antigenicity and vaccine efficacy, resulting in an unsuccessful PEDV control. Sequence comparisons between PEDVs collected from primary and secondary outbreaks in three herds revealed that the disease has developed to an endemic stage in which PEDV could persist for nearly two years in the herds or local regions, causing subsequent epidemics.ConclusionsThese results elucidate the genetic characteristics, origin, and molecular epidemiology of PEDVs circulating in Japan, as well as the PEDV strains causing recurrent outbreaks. This study provides a better insight into the PEDVs responsible for recent outbreaks in Japan, and could potentially help to develop measures for controlling and preventing the disease.
Highlights
Since late 2013, porcine epidemic diarrhea virus (PEDV) has reemerged in Japan and caused severe economic losses to the swine industry
Phylogenetic analysis based on the S gene sequences from the Japanese strains and reference strains identified from various countries revealed two major clusters: genogroup G1 divided into subgroups G1a and G1b, and genogroup G2 divided into subgroups G2a and G2b (Fig. 1)
The most dominant strains belonged to G2b, which comprised 42 of 45 current Japanese strains, along with the highly virulent (North American type) PEDVs isolated in the US, Canada, Mexico, South Korea, and Taiwan
Summary
Since late 2013, porcine epidemic diarrhea virus (PEDV) has reemerged in Japan and caused severe economic losses to the swine industry. PEDV has been reported in several other European countries, causing only sporadic outbreaks. In late 2010, new Chinese strains of PEDV were detected These new strains were clinically more severe than the classical strains, resulting in 80%–100% illness among infected swine herds and a 50%–100% mortality rate among infected suckling piglets [5]. In April 2013, a PEDV outbreak was confirmed in the US for the first time It swept across more than 30 states in the country, causing deaths of more than 8 million newborn piglets during the one-year-epidemic period, and subsequently spread throughout North America, including Canada and Mexico [6]. US-like PED epidemics have been reported in South Korea, Taiwan, Japan, Germany, France, and Belgium [4, 7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
