The incubation period of classical swine fever virus (CSF virus) in individual animals is about seven to ten days. Infection with low or moderately virulent strains that do not cause typical signs of disease result in longer high-risk periods (up to several weeks) facilitating unnoticed spread of CSF to other farms.
Classical swine fever (CSF) is characterized by extremely variable clinical signs and may be confused with many other diseases (e.g. African swine fever, porcine reproductive and respiratory syndrome, post-weaning multisystemic wasting syndrome, porcine dermatitis and nephropathy syndrome; erysipelas, salmonellosis, pasteurellosis, and other bacterial infections causing septicaemia; cumarin poisoning, purpura haemorragica.
The virulence of the virus as well as the age of the animal influence the course of the disease. Losses in young animals are generally more severe than in adults.
Generally, three major clinical forms of CSF can be distinguished: