It does not occur in Australia, New Zealand or Oceania. Cause The disease is caused by a Pestivirus. Although there is only one antigenic type, there are a number of different strains which vary in their virulence. The virus is capable of surviving for long periods of time in frozen, salted or smoked pork. This is an important characteristic in its potential geographical spread, as virus can easily be transferred from one place to another in pork products and cause disease outbreaks in pigs fed uncooked garbage.
Host species Pigs are the only natural host.
Transmission Infection of susceptible pigs is normally by the oral or nasal routes. Even before clinical signs develop, infected pigs shed virus in all their excretions and secretions. The normal means of spread is by direct contact between infected and susceptible animals, but airborne infection can occur over short distances. In chronic disease, virus persistence is characteristic. Infection of pregnant sows with low virulent strains often results in congenital infection in their piglets.