African Swine Fever: Causes, Symptoms, Treatment and Prevention
African Swine Fever: Causes, Symptoms, Treatment and Prevention
Introduction
African Swine Fever is a highly contagious viral disease of pigs that causes severe illness and very high death rates in affected herds. It is now one of the most important pig diseases worldwide, affecting both domestic pigs and wild boar and causing huge economic losses for farmers and the pork industry. Because there is no cure and no widely available vaccine, understanding the causes, symptoms, diagnosis, treatment options, and prevention of African Swine Fever is essential for every pig farmer, student of animal health, and pig owner.
This article explains in simple but accurate veterinary language what African Swine Fever is, how it spreads, the common clinical signs and symptoms of African Swine Fever, how veterinarians diagnose it, why there is no specific treatment, and the most effective methods for prevention and control of African Swine Fever on farms. It is designed as a practical guide to help you recognize the disease early, protect your herd, and know when to call a veterinarian or animal health authority.
What is African Swine Fever?
African Swine Fever (ASF) is a severe viral hemorrhagic disease of pigs caused by the African swine fever virus (ASFV), a large DNA virus belonging to the family Asfarviridae, genus Asfivirus. The virus infects domestic pigs and wild suids (such as warthogs and wild boar) of all ages and breeds, often causing peracute or acute disease with very high mortality that can reach up to 100% in susceptible herds.
ASF is characterized by damage to blood vessels and widespread bleeding (hemorrhage) in many organs, which leads to fever, depression, skin discoloration, and sudden death in many animals. Unlike many other pig diseases, African Swine Fever does not infect humans and is not a public health threat; pork from affected areas is safe to eat if properly cooked, although control regulations may restrict movement and sale.
The disease is listed as a notifiable transboundary animal disease by the World Organisation for Animal Health (WOAH, formerly OIE) because of its rapid spread and serious economic impact. Many countries require immediate reporting of any suspicion of ASF to veterinary authorities. Because there is no effective commercial vaccine and no treatment that kills the virus, control strategies rely strongly on early detection, strict biosecurity, and removal of infected and exposed pigs.
Causes of African Swine Fever
The cause of African Swine Fever is infection with African swine fever virus (ASFV), a complex, enveloped DNA virus that can survive for long periods in pig blood, tissues, and pork products, especially when chilled, frozen, or cured. ASFV is very resistant in the environment and can remain infective for weeks or months in contaminated manure, barns, and equipment if not properly cleaned and disinfected.
The main causes of African Swine Fever outbreaks on farms include:
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Direct contact with infected pigs – Healthy pigs can become infected when housed with or near sick pigs shedding the virus in blood, saliva, nasal discharge, urine, or feces. Mixing pigs from different sources without quarantine greatly increases this risk.
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Feeding contaminated pork products (swill feeding) – The virus can survive in raw or undercooked pork, sausages, and cured meats. Feeding kitchen waste or food scraps containing contaminated pork to pigs is a major cause of ASF spread and is banned in many countries.
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Indirect transmission via fomites – Vehicles, boots, clothing, tools, needles, and equipment contaminated with infected blood or secretions can carry the virus between farms if not properly disinfected. ASFV is easily moved by people who visit multiple farms without proper hygiene and biosecurity.
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Wild pigs and soft ticks – In parts of Africa and some other regions, wild suids (such as warthogs and wild boar) and soft ticks (Ornithodoros spp.) act as reservoirs and vectors of ASFV. Ticks can acquire the virus from infected pigs or wild hosts and then transmit it when they feed again. Double fencing and tick control are therefore important in these areas.
The immediate cause of disease in an individual pig is viral replication in cells of the immune system and blood vessel walls, which leads to severe inflammation, clotting disorders, and hemorrhage throughout the body. This explains the typical lesions and the sudden, high mortality observed in acute outbreaks.
Clinical Signs and Symptoms of African Swine Fever
The symptoms of African Swine Fever depend on the strain of the virus, the immune status of the pigs, and whether the infection is peracute, acute, subacute, or chronic. However, in most current outbreaks around the world, highly virulent strains cause acute disease with dramatic clinical signs and very high mortality in domestic pigs and wild boar.
Common clinical signs and symptoms of African Swine Fever include:
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High fever (often above 40.5–42°C / 105–107°F) that may be the first noticeable sign in affected pigs. Pigs may be hot to the touch and reluctant to move.
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Depression and loss of appetite – Pigs appear very dull, weak, and unwilling to eat. They may separate from the group and lie down more than usual.
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Skin changes and hemorrhages – Red to purple discoloration (cyanosis) of the ears, tail, snout, lower legs, and skin of the abdomen is typical in many cases. Small or large hemorrhages may be visible on the skin.
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Respiratory and digestive signs – Shortness of breath, coughing, vomiting, and diarrhea (sometimes bloody) can be present.
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Abortion and reproductive failure – Pregnant sows may abort or give birth to weak or dead piglets.
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Nervous signs – In some cases, incoordination, trembling, or convulsions may be seen just before death.
In peracute and acute forms, pigs may die suddenly with few obvious external signs, often within 2–10 days after infection. Mortality can be extremely high, sometimes affecting almost all pigs in the herd. Subacute and chronic infections, which are more often associated with less virulent strains, may show milder but prolonged fever, weight loss, skin ulcers, joint swelling, and respiratory signs, with lower mortality but ongoing poor performance.
Because the symptoms of African Swine Fever can resemble other diseases such as Classical Swine Fever, erysipelas, salmonellosis, and porcine dermatitis and nephropathy syndrome, laboratory confirmation is essential.
How to Diagnose African Swine Fever
Diagnosis of African Swine Fever is based on a combination of clinical suspicion, post-mortem findings, and specific laboratory tests to detect the virus or antibodies. Rapid and accurate diagnosis is critical for effective control and to prevent further spread between farms and regions.
When a veterinarian suspects ASF based on symptoms of high fever, cyanosis, sudden deaths, and hemorrhagic lesions at necropsy, they will collect appropriate samples for laboratory testing. Recommended samples include whole blood, spleen, lymph nodes, tonsils, and other tissues from sick or recently dead pigs. In chronic or later stages, serum may be collected for antibody testing.
Laboratory methods used to confirm African Swine Fever include:
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PCR (polymerase chain reaction) – Highly sensitive and specific tests that detect ASFV DNA in blood or tissues. PCR is now the primary method for rapid routine diagnosis.
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Virus isolation and haemadsorption (HAD) test – The haemadsorption test, based on the ability of ASFV-infected cells to bind red blood cells, is considered a definitive diagnosis when positive.
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Antibody detection (ELISA, indirect immunofluorescence) – These tests look for antibodies to ASFV and are more useful in subacute or chronic infections and in recovered animals. However, antibody responses can be variable and may lag behind infection.
Because African Swine Fever is a notifiable disease, many countries require that any suspected case be reported immediately to national veterinary authorities, who will coordinate official sampling and laboratory testing. Early recognition and official confirmation are vital to implementing movement controls, quarantine, and other emergency measures.
Treatment of African Swine Fever
Understanding how to treat African Swine Fever is crucial, but it is equally important to recognize the current limitations. At present, there is no specific antiviral treatment that can cure pigs infected with ASFV, and no fully licensed, widely available commercial vaccine for field use in domestic pigs in most countries. This means that once a herd is infected, options for saving affected animals are extremely limited.
Supportive treatment such as fluids, anti-inflammatories, or antibiotics to control secondary bacterial infections may improve comfort in mildly affected pigs, but it does not stop viral replication or prevent deaths in acute outbreaks. Because ASF is highly contagious and deadly, many countries do not recommend or allow attempts to treat infected pigs on affected farms, as this can prolong virus circulation and increase the risk of spread.
In most official control programs, the main “treatment” of African Swine Fever at herd level is stamping out – humane culling of infected and high-risk pigs, followed by safe carcass disposal and thorough cleaning and disinfection of facilities. This drastic measure is necessary to eliminate the virus from the farm and protect neighboring herds and the wider pig industry.
Researchers are actively working on vaccines and antiviral strategies, and several experimental vaccine candidates have shown promise in studies. However, vaccine development for ASF has been challenging due to the complexity of the virus, and any eventual vaccine will still need to be combined with strong biosecurity and surveillance.
Prevention and Control of African Swine Fever
Because there is no cure and no widely available vaccine, the most important strategy is the prevention and control of African Swine Fever through strict biosecurity, good farm management, and rapid response to any suspected cases. Preventing ASF means stopping the virus from entering your farm and minimizing the chances of pig-to-pig transmission.
Key measures for prevention and control of African Swine Fever include:
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Strict biosecurity at the farm gate
- Control entry of people, vehicles, and equipment; use disinfection points for boots and wheels.
- Limit visitors and never allow people who have been in contact with other pigs or wild boar to enter pig areas without proper downtime and cleaning.
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Safe feeding practices
- Do not feed pigs with kitchen waste or swill containing meat or meat products, especially pork. This practice is banned or strictly regulated in many countries because it is a major route of ASF introduction.
- Use only safe, commercially prepared feeds and store them to prevent contamination by wild animals.
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Separation from wild pigs and ticks
- Prevent contact between domestic pigs and wild boar or warthogs by secure fencing and preventing access to shared water sources or feeding grounds.
- In areas where soft ticks are involved, control tick habitats near pig housing and avoid using pig shelters that harbor Ornithodoros ticks.
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Internal farm hygiene and movement control
- Implement “all-in, all-out” systems, with cleaning and disinfection between batches.
- Use dedicated clothing, boots, and tools for each pig unit; avoid sharing equipment between farms.
- Isolate newly purchased pigs in quarantine and only introduce them after a suitable observation period.
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Surveillance and rapid response
- Monitor pigs daily for early symptoms of African Swine Fever such as fever, depression, and skin discoloration.
- Immediately report any suspicious signs or sudden increases in death rate to a veterinarian or animal health authority. Early detection allows rapid control measures and may save neighboring farms from infection.
At national and regional levels, control programs may include zoning, movement restrictions, bans on feeding food waste to pigs, intensified hunting and surveillance in wild boar populations, and public awareness campaigns for farmers and veterinarians. Effective control of African Swine Fever requires cooperation between pig owners, veterinarians, industry groups, and government agencies.
Frequently Asked Questions About African Swine Fever
Q: What animals can get African Swine Fever?
A: African Swine Fever affects domestic pigs and wild suids such as wild boar and warthogs. All ages and breeds of pigs are susceptible. Other livestock and companion animals do not get ASF, and humans are not affected by this virus.
Q: Is African Swine Fever dangerous to humans or is pork from affected areas safe to eat?
A: ASF does not infect people and is not considered a public health risk. Pork itself remains safe to eat if properly cooked, because the virus is inactivated by high temperatures. However, regulatory authorities may restrict movement, slaughter, or sale of pigs and pork products from affected areas for disease control reasons.
Q: What are the most important symptoms of African Swine Fever I should watch for?
A: The main symptoms of African Swine Fever include sudden high fever, depression, lack of appetite, red to purple discoloration of ears, tail, snout, and legs, breathing difficulties, vomiting, diarrhea (sometimes bloody), abortions in pregnant sows, and sudden deaths, especially in multiple pigs over a short time.
Q: How is African Swine Fever different from Classical Swine Fever?
A: Both African Swine Fever and Classical Swine Fever are serious viral diseases of pigs with similar clinical signs and lesions, including fever and hemorrhages. However, they are caused by completely different viruses and require different diagnostic tests. ASF is caused by a DNA virus in the Asfarviridae family, while Classical Swine Fever is caused by an RNA pestivirus. Laboratory testing is essential to distinguish between them.
Q: Can African Swine Fever be cured or treated with antibiotics?
A: No. Antibiotics do not kill viruses and therefore cannot cure African Swine Fever. There is currently no antiviral drug that clears ASFV from infected pigs. Supportive therapy may help temporarily, but in acute outbreaks mortality is usually very high. Control focuses on prevention, early detection, and rapid stamping-out to stop spread.
Q: Is there a vaccine against African Swine Fever?
A: At present there is no widely available, fully licensed commercial vaccine for African Swine Fever for routine use in domestic pigs in most countries. Research is ongoing and some experimental vaccines are under development, but for now prevention relies on strict biosecurity and surveillance.
When to Call a Veterinarian
You should call a veterinarian or local animal health authority immediately if you notice sudden deaths in pigs, especially if accompanied by high fever, depression, and red to purple discoloration of the skin on ears, tail, snout, abdomen, or legs. Do not wait to see if the pigs recover, as delay can allow the virus to spread within your herd and to neighboring farms.
Any suspicion of African Swine Fever, even if you are not sure, should be reported because ASF is a notifiable disease in most countries. Official veterinary services will arrange for proper sampling, laboratory diagnosis, and implementation of control measures such as quarantine and movement restrictions. Early reporting protects not only your animals but also the wider pig industry and national food security.
While waiting for veterinary assistance, isolate sick pigs as much as possible, stop all pig movements on and off the farm, and enhance hygiene measures such as disinfection of boots and vehicles. Do not sell, slaughter, or move pigs or pig products from the farm until authorities advise it is safe to do so.
Conclusion
African Swine Fever is one of the most serious diseases affecting pigs worldwide, causing severe hemorrhagic illness, very high mortality, and major economic damage wherever it appears. It is caused by a robust DNA virus that spreads easily through direct contact with infected pigs, contaminated pork products, and fomites such as vehicles and equipment, and in some regions through wild suids and soft ticks.
Because there is currently no effective treatment and no widely available commercial vaccine, control of African Swine Fever relies on prevention: strict farm biosecurity, safe feeding practices, separation from wild pigs, and rapid reporting and diagnosis of any suspected cases. Understanding the causes of African Swine Fever, recognizing the symptoms of African Swine Fever, and knowing the principles of diagnosis, “treatment” at herd level (stamping out), and prevention of African Swine Fever are essential skills for farmers, veterinary students, and pig owners.
By working closely with veterinarians and following national guidelines, pig producers can reduce the risk of ASF introduction, detect it early if it occurs, and help protect both their own livelihoods and the wider pig industry from this devastating disease.
