Porcine epidemic diarrhea

Porcine epidemic diarrhea is caused by a coronavirus leading to vomiting and diarrhea with mortality up to 100% within susceptible piglets under 2 weeks of age.

Alternative names: PED

Porcine Epidemic Diarrhea (PED) is caused by a coronavirus similar to the one causing Transmissible Gastroenteritis (TGE) and is extended though Europe and the Americas. Currently there is only one serotype recognized although there can be variation in disease severity between strains. The virus damages the intestinal villi, reducing the absorbing surface, with a subsequent fluid loss and dehydration. After the virus introduction in breeding susceptible animals, they develop a short life immunity (4 to 6 months). Lactogenic immunity (IgA) develops in about 10 days and is protective for nursing piglets.

The acute outbreaks occur when the virus is introduced for the first time to a susceptible population. Affected sow present diarrhea that can vary from mild to watery. Vomiting can be present. The incubation period is quick, approximately 12 to 24 hours, and the diarrhea lasts 7 to 14 days. In susceptible lactating piglets the disease is severe and may have a 100% mortality.

In big populations not all the sows are infected at the same time, so new outbreaks can be present. This only affects lactating piglets of sows that do not have maternal antibodies, so it is not very frequent. The infection can be chronic, especially in big farms. The infectious dose is very low, infected animals produce a huge amount of viruses in each gram of feces, for three to four weeks.

Sows

• Varies from a mild diarrhea (feces similar to cow’s feces) to a watery diarrhea.
• Loose feces.
• Vomiting.

Lactating piglets

• Diarrhea.
• Vomiting
• Dehydration.
• Mortality can be high, especially in piglets younger than 14 days of age. 

Weaners and growers

• Acute diarrhea with no blood or mucus.
• Mortality is usually low, but morbidity can be high.
• When a virus is introduced for the first time to a farm, the diarrhea is quickly spread into breeding animals and growing pigs.
• Vomiting.

• The disease can be perpetuated as susceptible pigs enter the growing/finishing or reproduction barns.
• Young pigs, especially those less than 2 weeks of age, shed extremely large amounts of virus for several day.
• Very low infectious dose in naïve animals.
• Normally the disease is only observed when the virus enters the farm for the first time.

Clinical signs might help, but cannot be differentiated from TGE. The presence of the organism is confirmed by PCR. Histological lesions are characteristic of PED and TGE, thus, immunochemistry (IHC) or PCR are used to confirm the disease. 

• Due to the fact that this is a viral disease, there is no specific treatment.
• Biosecurity in the farm must be implemented and highly maintained; high shedding rate and low infectious dose.
• If the virus enters the farm for the first time, it is important to make sure all adult animals get infected at the beginning, so they can develop immunity. This can be done by orally exposing the sows to diarrhea or contaminated material mixed with water in a bucket, and using it as a source of infection.
• Growing pigs usually recover without a treatment, unless there are recurrent diseases such as swine dysentery. All-in/all-out systems using disinfectants usually break the cycle of the disease.
• The virus is easily eliminated by phenolic disinfectants chloride, peroxides, aldehydes or iodofores. 
• Vaccine effectiveness has been variable with some effectiveness in helping stabilize chronically infected herds.