The CSF virus is transmitted by direct (animal to animal) and indirect contact (e.g. shoes, clothes, instruments, transportation vehicles). The most important factors for outbreaks of CSF are virus carriers and slaughterhouse and meat products carrying the virus. The virus can already be spread one day after infection via saliva, nasal, eye and throat secretions. Virus discharge via urine and excrement starts later. Seriously infected animals shed the CSF virus up to their death or up to one month after they have been cured. Chronically ill pigs and wasting or runt animals shed the virus for more than half a year. The virus makes its way into the animal’s body via the digestive system, in rare cases via the conjunctiva or the nasal mucosa membrane. The CSF virus is spread through contact in epidemic cases.
How CSF progresses depends on a number of factors (age, use, virus virulence, infection dose). Congenital CSF virus infections manifest in: weakness, “shaker pigs”, wasting pigs with dermatitis, leucopenia and a lack of coordination.
There are three main forms:
- Acute form (classical form)
- Chronic form
- Atypical form
The incubation period of acute CSF is 3-8 (12) days following natural infection, and 3-4 weeks for chronic and atypical CSF.
The acute form manifests in high fever (40-41° C), general health problems, lethargy, anorexia, weak hind legs, shaking (“shaker pig”), oedema, purulent nasal /eye discharge, diphtheriod coating in the mouth/on the tongue, erythema, preliminary constipation followed by diarrhoea, cramps. The mortality rate lies between 30 % and 100 %.
The chronic form manifests in the loss of appetite, weight loss, alternating phases of diarrhoea and constipation. The mortality rate is much lower in comparison to the acute form.
The atypical form is mild and prolonged; typical symptoms are unappeasable diarrhoea, wasting and disorders of the central nervous system.
CSF is an animal epidemic that must be reported to the authorities. The combating of CSF is based on
a) the prevention of importing and spreading the virus, and on
b) the “stamping out” method (elimination of infected animals and animals suspected of being infected).
Prophylactic vaccinations are prohibited in all EU Member States except Romania.