However, also the desquamation of intestinal cells and hereby the amount of virus at rectal swabs might vary. their offspring. The latter is the prerequisite for a sow vaccination concept that could help to prevent PED induced losses in the piglet sector. == Introduction == Porcine epidemic diarrhea (PED) is a highly contagious enteric disease of swine, affecting pigs of all ages. Severe clinical signs and high mortality rates are especially observed in suckling piglets and severity of disease decreases with age. However, strain virulence and management conditions also impact on the clinical disease and outcome13. The disease is mainly characterized by watery diarrhea and vomiting which leads to dehydration and deteriorating constitution. The causative agent is PED virus (PEDV), an enveloped, single-stranded, positive-sense RNA virus of the genusAlphacoronaviruswithin theCoronaviridaevirus family of the orderNidovirales4. Porcine epidemic diarrhea first emerged in 1971 in England termed Epidemic Diarrhea (ED)5,6. These early outbreaks were characterized by severe clinical signs and mortality rates of up to 100% in young fattening pigs. In the beginning, no cases were reported from suckling pigs. Later on, pigs of all ages showed similar disease in different European countries, and over the following years, PED was reported from Belgium, the United Kingdom (UK), The Netherlands, Germany, Hungary, Bulgaria, France, Switzerland, and Spain79. For unknown reasons, the occurrence of PED in Europe decreased markedly after the 1980s evidenced by lacking reports of further outbreaks and a very low seroprevalence in the nineties and the following years10,11. There were only sporadic outbreaks reported associated with low mortality, e.g. in The Netherlands, Hungary and the UK1214. In contrast, PEDV caused outbreaks of higher economic impact in Asia15,16. Still, endemic infections are reported from Asia, and the impact on the productivity of industrialized pig farms remains high17,18. Since 2005, PED cases were again sporadically reported from Europe, i.e. Italy, but without much leverage on the pig industry19. In 2011 and 2012, new, highly virulent PEDV variants were reported from China that caused Polidocanol tremendous losses, especially in the piglet sector20,21. In the following, starting in April 2013, PED occurred for the first time in the United States (US) and rapidly spread through nearly the whole country. High mortality rates of up to 95% were reported among suckling pigs, which led to unimaginable economic losses of whole piglet batches. The exact origin and introduction route of these highly virulent PEDV strains could not be finally elucidated22,23. Phylogenetic analyses showed that the causative strains cluster together with the above mentioned Chinese isolates from 2011 and 20122426. With the disease threatening to spread, European farmers and veterinarians were alerted and asked for data on PED prevalence and possible impact. Consequently, surveillance in Europe was reinforced and PED cases were indeed reported from Central Europe i.e. Germany27, the Ukraine28, France29, Austria30, Portugal31and Belgium32. In Germany, cases were reported starting from May 2014 especially in the South-Western and North-Western part25,27,33. In general, the impact on the pig industry remained low. Retrospective analyses demonstrated that a considerable seroprevalence was present only in Italy34. Thus, a recent re-introduction is most likely. Based on partial and full-genome sequences, strains from recent US outbreaks are clearly distinct from the original European PEDV strains25, and two different virus types were found. On the one hand there are so called original US PEDV, which are commonly referred to as NON-INDEL Rabbit Polyclonal to RAD17 strains (meaning no insertions and deletions in the open reading frame (ORF) encoding for the spike protein), and on the other hand so called S-INDEL variants that show insertions Polidocanol and deletions in spike protein encoding region35. The latter were supposed to cause milder disease Polidocanol course with low mortality. With exception of PEDV strains from Ukraine28, the current European strains were.