Vomiting and wasting disease (Ontario encephalitis)

calendar icon 8 November 2018
clock icon 7 minute read

Background and history

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

Sows, weaners and growers

  • N/A


  • Huddled.
  • Hairy.
  • Vomit bright green-yellow vomitus.
  • Constipated.
  • In the typical vomiting and wasting disease syndrome piglets lose their ability to suck or swallow, become very thirsty and stand with their heads over water but are unable to drink.
  • They waste away, become severely emaciated and die.

In the typical encephalitis or brain infected syndrome they:

  • Froth and champ at the mouth.
  • Develop blueing of their extremities.
  • Abdomens become bloated.
  • Tremble.
  • Stilted gait which rapidly progresses to partial paralysis of the legs.
  • They lie down.
  • Go into convulsions.
  • Roll their eyes.
  • Die within four days of onset.


The clinical and pathological picture is diagnostic of the disease. If you open up their abdomens you will find gas in the stomach and intestine but no food, only some brightly coloured liquid. You will also see brightly coloured crystals in the kidneys. A blood test is available. There is no treatment.


Lack of immunity from sows to piglets via colostrum.


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.


No treatment available.

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