Disease Risk.

Along with physical destruction that feral swine are well known for, there are many feral swine diseases of interest to hunters, landowners, farmers and ranchers.  Feral swine are known to carry or transmit at least 30 diseases (viral and bacterial) as well as host a minimum of 37 parasites that can affect humans, pets, wildlife or other livestock.  Feral swine present a significant risk to the domestic pig population and pork industry.  Introduction of certain diseases into the wild or domestic pig population would have severe economic consequences due to rapid and high pig mortality, loss of domestic and export markets for pork and pork products and quarantine regulations.  Costs to quarantine herds, monitor disease progression, and treat infected animals would amount to many billions of dollars.

Reportable diseases are considered to be of significant public health importance and are required to be reported whey they are diagnosed.  Some common reportable diseases associated with wild pigs include: brucellosis, leptospirosis, trichinellosis, and possibly others. 

Where feral swine and livestock interact, the best means of disease prevention is feral swine population control and exclusion of feral swine from feeding and watering areas. The illegal translocation of feral swine can spread these diseases to both livestock and humans.

Zoonotic Diseases

A zoonotic disease is an animal borne disease that can be contracted by humans. Most of the zoonotic pathogens in feral swine are transmitted to humans when they are cleaning (field dressing) feral swine or through consumption of undercooked meat or pork products.  Common Zoonotic Diseases found in feral swine are described below.

  • Brucellosis commonly causes symptoms such as joint pain, reduced appetite, headaches, chills, weakness, and fatigue, with severe cases potentially leading to abortion in women and testicular pain in men. Humans can contract the disease through contact with infected wild pigs or their fluids, as well as by ingesting contaminated food or water. Infected livestock may suffer abortions, produce weaker offspring, and have decreased milk production, while still harboring the bacteria even in healthy-looking offspring. Other symptoms in livestock can include retained placenta and, rarely, enlarged arthritic joints.

  • The bacteria affect the kidneys and reproductive tract and are excreted in urine and genital fluids. It requires warm, humid conditions to survive and does not last long in the environment. As a zoonotic disease, it affects all mammals. In humans, symptoms can range from flu-like signs to liver and kidney failure, however, it is uncommon to be spread from pig to humans. In swine, the primary symptoms are related to reproductive problems.

  • Salmonellosis is a disease in pigs caused by salmonella bacteria. It leads to inflammation and tissue damage in the small and large intestines, resulting in diarrhea. In some cases, certain strains of the bacteria can cause serious infections throughout the body. Pigs of all ages can get this disease, but it is most common in weaned and growing-finishing pigs. It can be spread to humans through contaminated pork products.

  • Toxoplasmosis in feral swine is a concern due to their ability to transmit foodborne illnesses. Toxoplasma gondii is a zoonotic parasite that can infect warm-blooded animals, including feral pigs. In some areas, feral swine have been the cause of elevated waterborne bacteria levels in streams and irrigation canals, which poses a risk for human health.

  • Lesions usually start on the head, especially the ears (resulting in head shaking), then spread over the body, tail, and legs. Itching can be intense and associated with an allergic hypersensitivity reaction to the mites. Hypersensitivity mange results in raised papules, erythema, and intense itching and occurs more frequently in fattening pigs. This can be spread to humans and is typically called scabies.

  • Rapidly progressive, disseminated disease with caseation and liquefaction of lesions. Nodules in the lymph nodes in the neck. Progressive disease involving the liver, spleen, and other organs of the abdominal and thoracic cavities. Tuberculosis can be spread from feral swine to humans through inhalation of aerosolized respiratory tract bacteria, ingestion of unpasteurized milk, and inoculation by contaminated instruments

  • Serious diseases that transfer from swine to humans are rare in the United States, but tularemia can be fatal. Feral hogs may also carry diseases like swine brucellosis and pseudorabies. Tularemia can be contracted through raw or undercooked meat, handling dead animals, inhaling contaminated air, drinking contaminated water, or bites from fleas and ticks.

  • Symptoms include Watery or creamy diarrhea (scour), Wet skin around the rectum and tail, huddling of piglets together or shivering, and Rapid dehydration in pigs. Humans can contract E. coli through contaminated pork products. Symptoms in humans include diarrhea, vomiting, fever, dehydration, and stomach cramps.

  • Trichinosis, caused by a nematode parasite known as a roundworm, affects humans primarily through the ingestion of infected muscle tissues, often from undercooked pork. While wild pigs usually show no symptoms, infected humans may experience abdominal pain, nausea, fever, muscle pain, and, if untreated, potentially fatal consequences. To prevent infection, wear gloves when handling feral hog meat, cook it to an internal temperature of at least 165°F, and note that freezing may not eliminate all strains of the parasite. Additionally, to prevent the spread of trichinosis to wildlife, bury or burn the carcasses of dead animals.

Animal Transmitted Diseases

A major concern in the livestock industry is the risk of diseases spreading from feral swine to livestock. While there are several diseases that are swine specific, there are others that can be contracted by both livestock and wildlife species. Transmission of these diseases occurs via contamination of water sources, contamination of feed troughs, and direct contact with infected animals. Common Animal Transmitted Diseases found in feral swine are described below.

  • Pseudorabies is not transmissible to humans but is often fatal in animals like cattle, sheep, cats, and dogs. In domestic swine, the virus spreads through asymptomatic carriers, causing severe symptoms in young pigs and milder issues in adults, such as fever and respiratory problems. Key symptoms include appetite loss, depression, staggering, spasms, and severe itching. It spreads through contact with saliva or nasal discharges, shared feed and water, particularly in wild pig populations, and ingestion of infected meat. The virus can survive on environmental surfaces like boots and equipment.

  • Bovine TB was first documented in white-tailed deer in the US in 1933. Other wildlife and feral species in North America where bovine TB has been detected include elk, mule deer, and bison. In New Zealand, wild deer and feral pigs are assumed to be spillover hosts for Mycobacterium bovis. The US livestock industry is concerned about bovine TB spread by feral pigs.

  • Hog cholera, or swine fever, is a highly contagious and often fatal disease caused by a virus that once affected domestic pigs. Infected pigs typically show symptoms such as depression, loss of appetite, fever, vomiting, and yellowish diarrhea, leading to severe weakness and potentially death within 10 to 20 days. Before dying, they may convulse violently, and if they survive, they can become chronic carriers of the disease. The virus spreads easily through direct contact or contaminated feeders and pens.

  • Brucellosis commonly causes symptoms such as joint pain, reduced appetite, headaches, chills, weakness, and fatigue, with severe cases potentially leading to abortion in women and testicular pain in men. Humans can contract the disease through contact with infected wild pigs or their fluids, as well as by ingesting contaminated food or water. Infected livestock may suffer abortions, produce weaker offspring, and have decreased milk production, while still harboring the bacteria even in healthy-looking offspring. Other symptoms in livestock can include retained placenta and, rarely, enlarged arthritic joints. The main difference is the strain and not how it presents itself in animals or humans.

  • Vesicular stomatitis is a viral disease primarily affecting horses and cattle but can also infect swine, sheep, goats, llamas, alpacas, and humans. It is characterized by painful vesicular lesions on the muzzle, lips, tongue, ears, sheath, udder, and abdomen. The disease is mainly spread by biting flies and midges and is common in North, Central, and South America. Laboratory testing is needed for a definitive diagnosis, as it resembles Foot and Mouth Disease.

Disease Prevention.

Follow these simple measures to avoid infection when handling or field dressing feral swine:

    • Wear latex or nitrile gloves; pathogens can enter the body through cuts on hands or torn cuticles.

    • Avoid splashing body fluids into your eyes or mouth.

    • Wash your hands thoroughly after field dressing and processing meat, even if you wear gloves.

    • Thoroughly clean and disinfect work areas and tools used to dress and butcher feral swine.

    • Dispose of animal remains, used gloves, and other materials properly. Animal remains should not be left for scavengers, nor should they be fed to dogs. Depending upon your jurisdiction, several methods of appropriate disposal may be considered. Check with your local health department or state wildlife agency.

    • Follow correct refrigeration, freezing, and cooking methods. Freezing to 0°F will render bacteria inactive but will not destroy them; once thawed, bacteria can again become active. Also, do not rely on home freezing to destroy Trichina and other parasites. Thorough cooking will destroy all parasites and kill bacteria. Cook feral swine meat to an internal temperature of 165°F to 170°F.