Porcine Epidemic Diarrhoea
Also Known As: Coronaviral Encephalomyelitis — Coronaviral Enteritis — Epidemic Viral Diarrhoea — Ontario Encephalitis — PED — EVD — TOO (The Other One)
Caused By: Porcine Epidemic Diarrhoea Virus — PEDV — CV777
Introduction
Porcine Epidemic Diarrhoea is a neurological and gastrointestinal disease of pigs caused by a coronavirus.
EDV is very similar to the coronavirus that causes Transmissible Gastroenteritis Virus (TGE), also in pigs.
Distribution
Worldwide. Transmission is purely faecal-oral.
Signalment
Disease is most severe in neonatal pigs as they are more susceptible to dehydration.
Outbreaks have also been seen in fattening pigs and adults, often associated with moving and/or mixing of groups. Outbreaks may be recurrent over a period of several weeks.
Clinical Signs
Mortality in neonatal pigs is increased and may reach up to 50% in pigs <1 week of age, but is generally not as high as with TGE.
Gastrointestinal disease presents with pyrexia, watery diarrhoea and marked dehydration, vomiting/regurgitation, anorexia, bruxism, inappetance and abdominal pain.
Neurological disease is often a result of dehydration and may include weakness, paresis/paralysis, trembling, recumbency, coma, irritability, seizures, hyperaesthesia, blindness and nystagmus.
Skin signs, e.g. erythematous rash may be seen when dehydration is severe.
Respiratory signs are also present in some cases.
Acute back muscle necrosis has been observed in some finishing pigs with PED, causing sudden deaths.
Diagnosis
PEDV can be demonstrated by Immunofluorescence (IF) or Immunohistochemistry (IHC) applied to sections of small intestines from pigs euthanased less than 1 day after the onset of diarrhoea. This is the most sensitive, reliable and rapid method of achieving definitive diagnosis.
PEDV antigen can be detected via ELISA from faeces. This is useful for group disease screening.
PEDV antibodies can be detected serologically via IF and ELISA. High titres may persist for up to one year after infection.
On post-mortem, the small intestine is filled with yellow fluid and distended. Microscopically, exfoliation of enterocytes and villous stunting can be seen in the small intestine from 24h after infection. These changes are similar but less severe than those seen with TGE. The incubation period of PEDV is also longer than TGE: 22-36h compared to 18-24h.
Treatment
Treatment is supportive by providing free access to water. Electrolyte solutions and energy supplements are recommended in piglets. Withholding feed is advisable in fattening swine.
Control
Biosecurity can prevent introduction of virus to farms by animal and human traffic.
Deliberate transmission of PEDV by spreading virus contaminated faeces in with pregnant sows has been used to stimulate lactogenic immunity and shorten the disease on the farm by protecting neonatal stock.
When several consecutive litters are affected, movement onto the farm should be stopped and all pigs born within a four week period should be relocated to a different site.
PEDV is not deemed of enough economical importance to require a vaccine.
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References
Animal Health & Production Compendium, Porcine Epidemic Diarrhoea Virus datasheet, accessed 19/06/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, Porcine Epidemic Diarrhoea datasheet, accessed 19/06/2011 @ http://www.cabi.org/ahpc/