Classical Swine Fever (Animal)

Primary reference(s)

OiE, 2020. Classical Swine Fever (CSF). World Organisation for Animal Health (OIE). Accessed 18 October 2020.

Additional scientific description

Classical Swine Fever (CSF) was first detected in the USA in the 19th century. An outbreak in the Netherlands in 1997 led to the destruction of 11 million pigs and cost USD 2.3 billion (OiE, 2020).

Classical swine fever is a contagious viral disease of domestic and wild swine. It is caused by a virus of the genus Pestivirus of the family Flaviviridae, which is closely related to the viruses that cause bovine viral diarrhoea in cattle and border disease in sheep. There is only one serotype of classical swine fever virus (CSFV) (OiE, 2020).

The most common method of transmission is through direct contact between healthy swine and those infected with CSFV. The virus is shed in saliva, nasal secretions, urine, and faeces. Contact with contaminated vehicles, pens, feed, or clothing may spread the disease. Animals that are chronic carriers of the disease (persistently infected) may show no clinical signs of illness but may shed the virus in their faeces. Offspring of infected sows can become infected in the uterus and once born can shed the virus for months (OiE, 2020).

The disease has acute and chronic forms, and can range from severe, with high mortality, to mild or even unapparent. In the acute form of the disease, in all age groups, there is fever, huddling of sick animals, loss of appetite, dullness, weakness, conjunctivitis, constipation followed by diarrhoea, and an unsteady gait. Several days after the onset of clinical signs, the ears, abdomen and inner thighs may show a purple discoloration. Animals with acute disease die within one to two weeks. Severe cases of the disease appear very similar to African swine fever. With low virulence strains, the only expression may be poor reproductive performance and the birth of piglets with neurological defects such as congenital tremor (OiE, 2020).

Classical swine fever is found in Central and South America, Europe, and Asia and parts of Africa. North America, Australia and New Zealand are currently free of the disease. In the 1990s large CSF outbreaks occurred in the Netherlands (1997), Germany (1993–2000), Belgium (1990, 1993, 1994) and Italy (1995, 1996, 1997). The World Organisation for Animal Health (OiE) standards for surveillance as applied have helped eradicate CSF from North America and much of Western Europe (OIE, 2020).

Classical swine fever virus can survive in pork and processed pork products for months when meat is refrigerated and for years when it is frozen (OiE, 2020). Pigs can become infected by eating CSF-infected pork meat or products (OiE, 2020).

It has been proven that in parts of Europe, the wild boar population may play a role in the epidemiology of the disease. The disease has been spread through legal and illegal transport of animals, and by feeding swill containing infective tissues to pigs (OiE, 2020).

Humans are not affected by this virus. Swine are the only species known to be susceptible (OiE, 2020).

Metrics and numeric limits

Not identified.

Examples of drivers, outcomes and risk management

Drivers: Lack of biosecurity, swill feeding.

Outcomes: Death of infected animals, spread of infection, trade ban.

Risk management: Vaccination programme, movement control, depopulate infected herd, improve biosecurity at farms.

Classical swine fever is a disease listed in the OIE Terrestrial Animal Health Code and must be reported to the OIE (OiE, 2019).

Classical swine fever disease prevention and control states that treatment if not attempted, affected pigs must be slaughtered and the carcases buried or incinerated.

The first barrier to prevent a CSF outbreak is to apply strict and rigorous sanitary prophylaxis, as defined in the OIE Terrestrial Animal Health Code (OiE, 2019). Good communication between veterinary authorities, veterinary practitioners and pig farmers, a reliable disease reporting system, and hygiene measures protecting domestic pigs from contact with wild boar are the most effective measures to prevent the disease. 

When an outbreak occurs, many actions must be set in place urgently: slaughter of all pigs on affected farms; safe disposal of carcasses, bedding, etc.; thorough disinfection; designation of infected zone, with control of pig movements; detailed epidemiological investigation, with tracing of possible sources (up-stream) and surveillance of infected zone, and surrounding area (OIE, 2020).

In areas where the disease is endemic, vaccination can prevent the spread of the disease. Vaccines used should be produced in accordance with the OIE standards for vaccine production (OIE, 2020). As the disease is brought under control, vaccination ceases, with continued surveillance. The OIE Terrestrial Animal Health Code defines the requirements for a country or a zone to be considered free of the disease (OiE, 2019).

In disease-free areas, a stamping-out policy is applied consisting of early detection, movement control, proper disposal of carcasses, and cleaning and disinfection. This policy has led to the elimination of CSF from North America, and much of Western Europe (OIE, 2020).