The sudden and widespread appearance of a deadly swine virus is causing concern for producers. Porcine Epidemic Diarrhea Virus (PEDV) now has spread into five hog-producing states, but where it came from and how it arrived in the United States remains a mystery. PEDV previously was diagnosed in parts of Asia and Europe in the early 1980s and is a swine-only virus. As such, it poses no danger to humans or other animals, and the meat from infected pigs is safe for people to eat.
PEDV is similar to transmissible gastroenteritis (TGE) and causes severe watery diarrhea, vomiting and dehydration. It is most often fatal to young pigs. It also causes illness in older hogs, though their survival rate tends to be higher. Known as a "coronavirus" because of the crown-like spikes on its surface, the virus afflicted China in recent years and killed more than 1 million piglets.
Veterinarians and epidemiologists say pigs are infected through oral means. The virus is not airborne and does not occur spontaneously in nature. It is spread by pigs ingesting contaminated feces. Investigators are focusing on physical transmission, perhaps a PEDV infected pig, equipment marred with feces, or perhaps even a person wearing dirty boots or with dirty nails. As this is a new virus to the United States, even a small amount of virus transported on coveralls or footwear and worn onto a farm can infect the herd.
PED is labeled a “transboundary” disease by the USDA. The Food and Agriculture Organization of the United Nations (FAO) states Transboundary Animal Diseases (TADs) are defined as “those epidemic diseases which are highly contagious or transmissible and have the potential for very rapid spread, irrespective of national borders, causing serious socio-economic and possibly public health consequences.” Potential consequences of TADs are of such a magnitude that their occurrence may have a significant detrimental effect on national economies.
Sources at Michigan State University report the strain of PED virus found in the United States is 99 percent homologous (similar) to the Asian strain, which remains highly contagious. Mortality in piglets is high (up to 80 percent) due to dehydration. Mortality in sows, nursery and finisher pigs is lower with clinical signs of fever, vomiting and diarrhea. Sudden death may occur, likely due to twisted gut following vomiting.
Swine herds with confirmed PED in the United States were likely exposed to the virus 5-8 days prior to exhibiting clinical signs. The clinical expression can move through the affected barn unit rapidly, typically within 12-36 hours. Normally, producers will not see a difference in clinical signs between TGE and PED outbreaks. However, the PED virus survives well in high temperatures and is seen predominantly during the summer season. Confirmation of PED infections requires sampling and testing.