Encephalomyocarditis

Infection caused by Encephalomyocarditis virus, present in the whole world, it usually has no clinical importance, but there are some myocarditis cases with high mortality or reproductive problems.

Alternative names: EMC

Information

The main reservoir and host of the Encephalomyocarditis virus is the rat, although the mouse may also transmit it. It infects and causes diseases to a variety of vertebrate animals but in North America, of all animal production, swine seem to be the most susceptible ones. The virus is found worldwide but differs in virulence and pathogenicity depending on the country and region. In most European countries, mainly in the European Union ones, it tends to be relatively mild or nonpathogenic and the disease is rarely diagnosed.

In Australia strains appear to be much more virulent for swine than those of New Zealand. Florida, Caribbean and probably Central American strains, affects the heart and cause death, while those same strains usually produce reproductive problems in the Midwest of the United States. 

 

Symptoms

Sows
First symptoms:

Some abortions near the end of gestation.

  • Number of mummified piglets and stillborn increases, as well as pre-weaning mortality.
  • Birth rate worsens.
  • Sows affected may show symptoms such as fever and lack of appetite.
  • Clinical signs are not usually observed in the affected farms during the fattening stage.
  • Embryonic death.

Lactating piglets

  • Sudden death.
  • Respiratory symptoms.
  • Tremors.
  • Lack of coordination or paralysis.
  • Low viability.
  • Usually none.

Nursery and fattening

  •  It is not present.

 

Causes / Contributing Factors

  • Pigs can become infected from rats or feed or water contaminated by rats.
  • The clinical disease usually occurs when the number of rats increases to constitute a plague.
  • It does not seem to spread widely among pigs.
  • Replacement gilts may be infected with pathogenic strains.

 

Diagnosis

To make a definitive diagnosis, the virus should be isolated and identified, or it must be demonstrated that there is an increase of antibodies in blood samples taken on two separate weeks. Encephalomyocarditis can be confused with Aujeszky, parvovirus and PRRS virus, although there are symptoms that differentiate these four infections. Encephalomyocarditis virus would be the last on the list of priorities of diagnosis in Europe. It is rare that parvovirus causes abortion or disease in sows or piglets; mummified piglets can be examined for evidence of this infection. 

 

Control/Prevention

  • There is no treatment.
  • Rat control.
  • A possible vaccine (its efficacy is not very clear).

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