Classical swine fever is a cyclical general condition that occurs only in pigs. The disease is caused by the European swine fever virus (ESF, classical swine fever virus, CSF virus) of the genus Pestivirus, family Flaviviridae. ESF has been known to be an infectious disease since 1933 (Ohio, USA) and occurs worldwide, except in Australia and New Zealand. Only animals of the Suidae family (real pigs or old world pigs) are affected by swine fever. The classical swine fever virus is transmitted by direct (animal to animal) and indirect contact (e.g. shoes, clothing, tools, transport vehicles). The most important factors for an outbreak of classical swine fever are virus excreta and virus-containing slaughter and meat products. Shedding of the virus can start as early as one day after infection in saliva, nasal, eye and throat secretions. Shedding via urine and faeces starts later. Seriously ill animals shed the classical swine fever virus until death or until about one month after recovery. Chronically ill pigs and runts excrete the virus for six months. The virus is absorbed via the digestive tract, more rarely via the conjunctiva or the nasal mucosa. The incubation period of acute classical swine fever is 3-8 (12) days after natural infection and 3-4 weeks for chronic and atypical classical swine fever.
The type of classical swine fever course depends on several factors (age, type of use, virulence, infectious dose). Congenital infections with classical swine fever virus manifest by weakness, tremor, runts with dermatitis, leukopenia and incoordination.
Three forms can be distinguished:
- Acute form (classic form)
- chronic form
- atypical form
The acute form is accompanied by high fever (40-41 °C), disorder of the general condition, tiredness, anorexia, weakness of the hind hands, tremor, oedema (eye), purulent nasal/eye discharge, diphteroid deposits in the mouth/tongue, erythema, first constipation, followed by diarrhoea and cramps. The mortality rate varies between 30% and 100%.
The chronic form is manifested by loss of appetite, emaciation, frequent changes of diarrhoea and constipation. The mortality rate is much lower than in the acute form.
The atypical form is mild and prolonged; persistent diarrhoea, runting, and CNS disorders are typical symptoms.
Classical swine fever is a notifiable animal disease. The control of classical swine fever is based on
a) the prevention of the introduction and spread of the pathogen and
b) the "stamping out" method (= eradication of infected and suspected animals). Prophylactic vaccination is prohibited in all EU countries, with the exception of Romania.