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Vomiting And Wasting Disease / Ontario Encephalitis

(389) This is caused by a coronavirus called haemagglutinating encephalomyelitis virus (HEV). The virus is widespread in the pig populations of North America and is probably world-wide but is unimportant because clinical disease is rare. This is because most sows have been infected and are immune. They pass their immunity to their piglets in colostrum which protects them through the vulnerable period. Although the virus can infect susceptible pigs at any age it only causes clinical disease in newborn piglets.

Clinical signs

Although there is only one antigenic type of the virus there is a variation in virulence between strains resulting in two different disease syndromes. Both start at around 4 days of age, are sudden in onset and affect whole litters. The piglets are huddled and hairy. They vomit bright green-yellow vomitus which is often mistaken for acute scour. Infact they are constipated.

In the typical vomiting and wasting disease syndrome they lose their ability to suck or swallow, become very thirsty and stand with their heads over water but are unable to drink. They rapidly waste away, become severely emaciated and die.

In the typical encephalitis syndrome they froth and champ at the mouth, develop blueing of their extremities, their abdomens become bloated and they tremble. They have a stilted gait which rapidly progresses to partial paralysis of the legs. They lie down, go into convulsions, roll their eyes and die within two to four days of onset.


The clinical picture in 4 day old piglets of vomiting and constipation is characteristic of the disease. If you open up their abdomens the appearance is typical, gas in the stomach and intestine but no food, only some brightly coloured liquid. Firm faeces and sometimes brightly coloured crystals in the kidneys. A blood test is available.


  • None is available.
Management control and prevention
  • All the affected pigs will die so they are best destroyed. This is a one-off phenomenon which tends to occur in small herds in the litters of sows which have no immunity. The virus will circulate and immunise the herd. The disease will not occur again in these sows' litters or any others.

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