Typical 'button' ulcers in the large intestine may be found in protracted cases. Low virulent strains frequently cause abnormalities in foetuses and prenatal and neonatal deaths. Diagnosis When virulent virus strains are involved, the clinical picture in an infected herd will be strongly suggestive of the disease. With less virulent strains care must be taken that the disease is not ascribed to other causes, such as salmonellosis, even though such bacteria may be present. The disease may be difficult to differentiate from African swine fever which presents with a similar clinical signs.
Virus isolation provides the definitive diagnosis.
Virus can be recovered from a number of tissues, though tonsil is the preferred tissue. However , care must be exercised to use CSF specific monoclonal antibodies for such tests, as infection of pigs with bovine viral diarrhoea virus or border disease virus will cross react with swine fever antisera. Risk of introduction CSF could conceivably enter the country by means of infected pork products finding their way, untreated, to pigs fed garbage. This is what happened in the two outbreaks that have occurred in New Zealand. Legallyimported pork may only come from countries that are free from the important exotic diseases of pigs.