Porcine epidemic diarrhoea is caused by a coronavirus somewhat similar to that which causes TGE. This virus is widespread in Europe. The virus damages the villi in the gut thus reducing the absorptive surface, with loss of fluid and dehydration. After introduction of the virus into a susceptible breeding herd, a strong immunity develops over two to three weeks. The colostral immunity then protects the piglets. The virus usually disappears spontaneously from breeding herds particularly small ones (< 300 sows).
Acute outbreaks of diarrhoea occur when the virus is first introduced into a susceptible population. In such cases up to 100% of sows may be affected, showing a mild to very watery diarrhoea. Two clinical pictures are recognised: PED Type I only affects growing pigs whereas PED Type II affects all ages including sucking pigs and mature sows. The incubation period is approximately 2 days and diarrhoea lasts for 7 to 14 days. In sucking pigs the disease can be mild or severe with mortalities up to 40%.
In large breeding herds, particularly if kept extensively, not all the females may become infected first time round and there may be recrudescence. This only occurs in piglets suckling from sows with no maternal antibodies and is therefore sporadic.
Symptoms
Sows
- This can vary from very mild “cow pat” faeces through to a watery diarrhoea.
- Loose faeces.
Piglets
- Diarrhoea.
- Dehydration.
- Mortality may be high.
Weaners & Growers
- Acute watery diarrhoea with no blood or mucus.
- Mortality is usually low but morbidity can be high.
- When the virus is first introduced on to the farm there is a rapid spread of diarrhoea across all breeding and growing pigs with almost 100% morbidity (pigs affected) within 5 to 10 days. The incubation period is 2 to 4 days.
- Vomiting.
Causes / Contributing factors
- The immunological status of the herd i.e. no immunity.
- Disease may be perpetuated as susceptible pigs enter the finishing herd.
- Disease normally only seen when virus first enters the herd.
Diagnosis
This is based on the history, clinical signs and examination of faeces samples for evidence of porcine epidemic diarrhoea virus by ELISA tests or electron microscopy. Post-mortem examination of dead pigs and laboratory tests on the small intestine may be necessary to confirm the diagnosis.
PED must be differentiated from TGE by laboratory tests.