Classical Swine Fever in Pigs: Signs, Transmission, and Control
- See your vet immediately if a pig has high fever, depression, huddling, red or purple skin patches, diarrhea, or sudden deaths in the group.
- Classical swine fever is a highly contagious viral disease of pigs and wild boar. It does not infect people, but it can spread fast through a herd.
- The virus spreads by direct pig-to-pig contact and by contaminated feed, pork products, clothing, shoes, equipment, vehicles, and facilities.
- There is no specific cure. Care focuses on isolation, testing, supportive treatment when appropriate, and following State and Federal animal health guidance.
- Because this is a reportable foreign animal disease concern in the United States, suspected cases need urgent veterinary and regulatory involvement.
What Is Classical Swine Fever in Pigs?
Classical swine fever, also called hog cholera, is a serious viral disease of domestic pigs and wild boar. It is caused by classical swine fever virus, a Pestivirus in the Flaviviridae family. The disease can range from sudden, severe illness with high death loss to milder or chronic infection that is harder to recognize.
This disease matters because it spreads efficiently and can look like other dangerous pig diseases, especially African swine fever. Signs alone are not enough to confirm it. Your vet and a diagnostic lab are needed to sort out the cause.
For pet parents, small farms, and backyard pig keepers, the key point is urgency. A pig with fever, weakness, skin discoloration, diarrhea, or unexplained deaths should be treated as a medical and herd-health emergency until your vet says otherwise.
Classical swine fever is not known to infect humans, but people can still move the virus on boots, clothing, equipment, vehicles, and pork products. That makes fast isolation and strict biosecurity essential.
Symptoms of Classical Swine Fever in Pigs
- High fever, often around 106 F
- Depression, dullness, drooping head, or hunched posture
- Loss of appetite and huddling
- Constipation followed by diarrhea
- Reddened eyes or conjunctivitis
- Unsteady gait, weakness, or ataxia
- Purple or red skin discoloration, especially on ears, abdomen, or inner thighs
- Sudden deaths or high death loss in younger pigs
- Poor reproduction, abortions, or weak piglets
- Congenital tremors or neurologic defects in piglets from infected sows
Some pigs become very sick within days, while others show milder signs that still spread infection. Young pigs and immunologically naive groups may have the most severe disease. Chronic or prenatal infections can be harder to spot and may show up as poor growth, reproductive problems, or persistently weak piglets.
See your vet immediately if one pig has a high fever and looks depressed, or if several pigs in the group develop similar signs at once. Sudden deaths, purple skin patches, neurologic signs, or a cluster of sick pigs should be treated as an emergency.
What Causes Classical Swine Fever in Pigs?
Classical swine fever is caused by classical swine fever virus (CSFV). The virus infects pigs and wild boar and is shed in saliva, nasal secretions, urine, feces, blood, and other body fluids. Infected pigs can pass the virus before a herd realizes there is a problem.
Spread happens in two main ways: direct contact with infected pigs and indirect contact through contaminated people, clothing, boots, trailers, pens, feeders, tools, and vehicles. Feeding contaminated pork or improperly handled food waste to pigs is also a well-known risk. The virus can survive for long periods in chilled or frozen pork products.
Pregnant sows can infect piglets before birth. Those piglets may be born weak, abnormal, or persistently infected and may shed virus for extended periods. Wild boar can also play a role in disease spread in some regions.
In the United States, classical swine fever has been eradicated for decades, but it remains a major foreign animal disease concern because international movement of animals, pork products, and contaminated materials can reintroduce it. That is why prevention focuses so heavily on biosecurity and rapid reporting.
How Is Classical Swine Fever in Pigs Diagnosed?
Your vet will start with the pig's history, recent animal movements, feed exposure, travel exposure, and the pattern of illness in the group. Because classical swine fever can closely resemble African swine fever, salmonellosis, erysipelas, and other serious swine diseases, diagnosis cannot be made from signs alone.
Confirmation requires laboratory testing. Common tests include RT-PCR or RT-qPCR to detect viral RNA, antigen detection methods such as immunofluorescence on tissues, virus isolation, and antibody testing with assays such as ELISA or virus neutralization. Tonsil tissue, blood, serum, and other samples may be used depending on the stage of disease.
Antibody tests can help with surveillance, but they are not always the best early test because antibodies may not appear until later in infection. Cross-reactions with other pestiviruses can also complicate interpretation. That is one reason your vet may prioritize PCR-based testing in a suspected acute case.
In the United States, suspected cases should trigger immediate contact with animal health authorities through your vet. Fast reporting helps protect other pigs and speeds access to the right testing pathway.
Treatment Options for Classical Swine Fever in Pigs
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Immediate isolation of sick pigs
- Urgent call to your vet for foreign animal disease assessment
- Stopping pig movement on and off the property
- Basic supportive care such as fluids, temperature support, and nursing care when directed by your vet
- Strict boot, clothing, and equipment separation
Recommended Standard Treatment
- Full veterinary herd assessment
- Diagnostic sample collection and submission through approved channels
- Supportive care plan for affected pigs when appropriate
- Biosecurity plan for people, feed, equipment, and manure handling
- Coordination with State and Federal animal health officials because CSF is reportable
Advanced / Critical Care
- Intensive supportive care for valuable individual pigs when allowed and appropriate
- Expanded diagnostics and repeat sampling
- Advanced isolation logistics and dedicated staffing
- Facility disinfection planning and movement control
- Outbreak-level coordination with animal health authorities; vaccination may be considered only under official approval in specific outbreak settings
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Classical Swine Fever in Pigs
Bring these questions to your vet appointment to get the most out of your visit.
- Do my pig's signs fit classical swine fever, African swine fever, or another disease that looks similar?
- What samples need to be collected, and how quickly should testing happen?
- Should I isolate one pig, or should I treat the whole property as exposed right now?
- What biosecurity steps should every person follow before entering or leaving the pig area?
- Could feed, pork products, visitors, travel, or new pigs have increased risk on this property?
- What supportive care is appropriate while we wait for results, and what should I avoid doing?
- Are there reporting requirements in my State, and who will contact animal health officials?
- When can movement, cleaning, and normal herd routines safely resume?
How to Prevent Classical Swine Fever in Pigs
Prevention starts with strong biosecurity. Keep new pigs separated from the resident group for at least 30 days, monitor them closely, and care for isolated pigs after you handle the healthy herd. Limit visitors, clean and disinfect boots and equipment, and avoid sharing trailers, feeders, or tools unless they have been properly cleaned.
Do not feed pigs pork scraps, uncooked food waste, or questionable meat products. Secure feed from contamination by wildlife and keep pigs away from wild boar when possible. If you travel internationally or visit pig facilities abroad, clean and disinfect clothing and footwear before returning to any U.S. pig property, and avoid pig contact for the recommended waiting period.
Work with your vet on a written herd health and biosecurity plan. That plan should cover quarantine, visitor rules, cleaning protocols, feed sourcing, and what to do if a pig develops fever or sudden illness. Fast action can make a major difference.
Vaccines exist in some parts of the world, but in the United States their use requires USDA approval, such as in an outbreak response. For most U.S. pet parents and producers, prevention depends on biosecurity, early recognition, and immediate reporting of suspicious illness.