Porcine epizootic diarrhea (PED) is a diarrheal disease of pigs caused by coronaviruses that can be associated with a high mortality rate, especially in young piglets. There is no risk of infection for humans or other domestic animals

Worldwide

Pigs

Infection occurs through virus-containing feces

3-5 days

Vomiting, diarrhea, loss of appetite

There is no therapy

Strict biosecurity or hygiene measures. Vaccines are already available in Asia and America, but their efficacy is the subject of controversial debate.

PED virus was detected for the first time in Austria at the end of 2014.

Porcine epizootic diarrhoea (PED) or epizootic viral diarrhoea (EVD) is a diarrhoeal disease of pigs caused by coronaviruses, which can be associated with a high mortality rate, particularly in young piglets. Epidemic outbreaks of PED have been reported in North America since 2013. Acute outbreaks were reported in Germany in 2014; in Austria, the virus was detected in one farm in fattening pigs of German origin:

Only pigs are susceptible to this virus; there is no risk of infection for humans or other domestic animals. Infection occurs through faeces containing the virus via the faecal-oral route of infection. After experimental infection, the first signs of illness can appear after just 36 hours. If the pathogen is introduced into a naive herd, the typical signs of disease are visible within 3-5 days.

Spread

PED virus was first detected in Austria at the end of 2014. The detection and molecular biological determination of the virus was carried out at the Institute for Veterinary Investigations of AGES in Mödling. The case report on this first occurrence of PED in Austria was published in January 2016 in the journal BMC Veterinary Research (Steinrigl et al., First detection, clinical presentation and phylogenetic characterisation of Porcine epidemic diarrhea virus in Austria, BMC Veterinary Research (2015) 11:310 DOI 10.1186/s12917-015-0624-1).

Diarrhoeal diseases similar to PED were first observed in England in 1971 in fattening pigs and subsequently spread to several European countries. There are reports from Belgium (1978), the Czech Republic (1993), Hungary (1996) as well as from Germany, France, the Netherlands and Switzerland. After that, there were hardly any outbreaks of the disease in Europe - and if so, only isolated ones.

PED outbreaks have been reported in Korea, China, Thailand and other Asian countries since 2000 and continue to the present day. Since 2010, outbreaks with high mortality rates in piglets have increased significantly in these countries. In 2013, the first cases of PED occurred in the US states of Iowa and Minnesota. Within a short period of time, further outbreaks were recorded throughout the USA, Canada, Mexico and the Central American states. Molecular genetic analyses of the virus revealed a new variant of the PED virus (PEDV) in America and Asia, which appears to be more virulent than the virus originally isolated in Europe in the 1980s. In addition, a new coronavirus (deltacoronavirus) was detected in the course of genetic analyses, which may also be involved in the disease.

Acute outbreaks in Germany initially affected fattening pigs, but later also suckling piglets. Mortality was low in fattening pigs, but up to 70 % in suckling piglets. All available sequencing from the acute cases that occurred in Germany show a high genetic similarity to the less pathogenic variant of the strains that occurred in the USA. At present, cases of the disease in fattening herds are mainly described during the cold season.

Symptoms

The clinical manifestation of the disease symptoms and their course are strongly dependent on the age of the affected animals and the immunity status of the herd and are described as follows:

• If the animals in a herd had no contact with the virus before the virus was introduced (so-called naive or fully susceptible herd), the following symptoms are seen in suckling piglets (1-28 days of life): Almost 100% of the animals fall ill with vomiting; the piglets have acute watery diarrhoea. As a result of the severe loss of fluids and the resulting acidosis (hyperacidity of the blood), 50-80% of the piglets can die
• If the animals are already older, far fewer animals die (1-3%). Symptoms of diarrhoea and loss of appetite can be observed in pigs of all ages, including breeding sows
• Once the herd has overcome the acute disease (so-called endemic disease), the animals' performance almost returns to normal and diarrhoea only occasionally occurs in older or weaned piglets (3rd-6th week of life).

Prevention

As the virus is mainly transmitted through infected pigs, faeces or objects contaminated with faeces (manure, shoes, transport vehicles), strict biosecurity and hygiene measures such as cleaning and disinfection of contaminated stables, objects and means of transport must be observed. Of course, precautionary measures take centre stage, especially when moving animals from affected stables or regions to unaffected countries and regions. Vaccines are already available in Asia and America, although their effectiveness is the subject of controversial debate.

Based on the clinical symptoms in a foci, only a tentative diagnosis can be made, which must be confirmed by appropriate laboratory testing. Using modern molecular biological methods (PCR), rapid and reliable diagnostics are possible to clarify suspected cases.

The following sample materials are suitable for diagnostics:

• Feces from acutely ill live animals
• intestinal contents and intestinal tissue (small intestine, large intestine) from dead animals

The feces should be chilled (4 °C) and taken within the first 24 h after the onset of diarrhea. Since intestinal tissue becomes autolytic relatively quickly, organ samples or dead animals should be brought or shipped to the laboratory as quickly as possible and refrigerated.

Differential diagnosis should exclude various other diarrheal pathogens:

• Bacterial infections caused by: Escherichia coli, Clostridium perfringens, Salmonella.
• Viral infections caused by: transmissible gastroenteritis virus (TGE), rotavirus, circovirus type 2 (PCV-2), classical swine fever virus (CSF) and African swine fever virus (ASF).
• Parasite infestation: coccidia