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CSF Facts

ACUTE COURSE OF CLASSICAL SWINE FEVER VIRUS INFECTION

 

Weaners and fattening pigs most often display the acute form of CSF. The initial signs are anorexia, lethargy, fever, conjunctivitis, swollen lymphnodes, respiratory signs and constipation followed by diarrhoea. The typical haemorrhages of the skin are usually observed on the ear, tail, abdomen and the inner side of the limbs during the second and third week after infection until death. Neurological signs are frequently seen, such as a staggering hindlimb gait, incoordination of movement, and convulsions. A constant finding is fever. This is usually higher than 40°C, but in CSF infected adult animals fever may not exceed 39.5°C. CSFV causes severe leukopenia and immunnosuppression, which often leads to enteric or respiratory secondary infections. The signs of these secondary infections can mask or overlap the most typical signs of CSF and may mislead the farmer or veterinarian. Death occurs usually within 1 month. Recovery with production of antibodies does occur, most often in adult breeding animals which do not display severe clinical signs. Antibodies against CSFV are detectable from 2-3 weeks post infection onwards.

Pathological changes visible on post mortem examination are most frequently observed in lymph nodes, tonsils, spleen and kidneys. The lymph nodes become swollen, oedematous and haemorrhagic. Haemorrhages of the kidney may vary in size from hardly visible petechiae to ecchymotic haemorrhages. Similar haemorrhages can also be observed in the urinary bladder, larynx, epiglottis and heart and sometimes widespread over the serosae of the abdomen and chest. A non-purulent encephalitis is often present. Lesions due to secondary infections may also be seen which may mislead the veterinarian.

In general the acute form of African Swine Fever leads to a very similar clinical and pathological picture. When present, haemorrhages on the skin and ears are quite easy to detect and lead to suspicion of acute African or Classical Swine Fever. Few other diseases cause similar lesions.

Acute CSF must also be considered in case of suspected erysipelas, porcine reproductive and respiratory syndrome, cumarin poisoning, purpura haemorragica, post-weaning multisystemic wasting syndrome, porcine dermatitis and nephropathy syndrome, Salmonella or Pasteurella infections or any enteric or respiratory syndromes with fever which do not respond to antibiotic treatment.

CSF virus is shed in saliva, urine and faeces from the onset of clinical signs until death. CSF virus can also be shed via semen.

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