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DISEASE
After an incubation period of 2-19 days (commonly 4-8 days), infection with ASF virus gives rise to acute, severe illness including high fever, inappetence, and severely impaired general condition. Dyspnoea, discolouration of the skin, diarrhoea and sometimes vomiting and haemorrhages are seen. Abortion is a common feature in pregnant sows. Milder forms of the disease have also been described. The National Veterinary Institute has been responsible for sample selection, sample analysis and reporting to the Swedish Board of Agriculture.
The serological analyses of ASF and analyses for ASF virus genome were performed at the National Veterinary Institute. ASF serology was done using a commercial kit (Ingezim PPA COMPAC 11.PPA.K.3) and in case of positive ELISA results a confirming western blot assay for detection of anti-bodies against ASFV was performed.
Passive surveillance
As clinical suspicion of ASF is notifiable for both veterinarians and farmers, cases with suspect clinical signs will be investigated following notification to the Swedish Board of Agriculture. The investigation includes restrictions on the farm during the investigation, sampling of sick or dead animals and examination of the herd for prevalence of clinical signs and production results. Due to the similarity of clinical signs, samples are analysed for both CSF and ASF. This strategy is strongly recommended by the EU.
Active surveillance
In 2012, all samples collected from the abattoir sampling part of the surveillance carried out by the Swedish Animal Health Service for porcine respiratory and reproductive syndrome virus (PRRS) were used for the active surveillance. See chapter on PRRS for details on sampling and population. ASF is included in the Swedish Act of Epizootic diseases (SFS 1999:657 with amendments) and the control of the disease is regulated in detail through EU-directives.] The purpose of the surveillance activities is to document freedom from ASF in the Swedish pig popu-lation and to contribute to the maintenance of this
Passive surveillance
Five investigations following clinical suspicion of CSF/ASF were carried out during 2012. One of these was a wild boar with neurological signs. The clinical manifestation of suspicions in domestic pigs were varying and included reproductive failure, increased mortality in piglets, fatteners or sows and circulatory disorders including haemorrhages. Following investigation that included sampling, the herds were declared negative for CSF/ASF.
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