Wild pigs are susceptible to several serious swine diseases: swine brucellosis, pseudorabies, classical swine fever and African swine fever. African swine fever—a major foreign animal disease—has never been found in the United States. The U.S. Department of Agriculture (USDA) eradicated classical swine fever (formerly known as hog cholera) from this country in 1976. Although swine brucellosis and pseudorabies have been eliminated from U.S. commercial-production swine herds, hunters and farmers need to be aware that wild pigs may be infected with these diseases and can readily transmit them to domestic pigs. Moving untested wild pigs to new areas or allowing them onto farms that have domestic pigs is illegal and can have disastrous consequences.
Swine brucellosis is caused by bacteria very similar to the organism that causes brucellosis in cattle, and both diseases are a public health concern. Swine brucellosis causes abortions in sows and infertility in boars. Although this disease does not kill pigs outright, it causes losses in reproduction that decrease profits for swine producers.
The swine brucellosis organism is transmitted in reproductive discharges, particularly the afterbirth, from infected sows or in semen from infected boars. Infected swine are disease carriers for life and there is no effective treatment. Detecting infected swine through blood tests and culling these animals is the only way to remove the disease from the herd.
Swine brucellosis has been reported in wild pig populations in at least 14 States based primarily on serological prevalence. The disease can be spread to domestic swine if wild pigs are introduced into local herds. Introduction could be intentional, or wild pigs could break into pastures or pens to breed with domestic sows.
Pigs infected with swine brucellosis can serve as a source of infection to domestic animals. Cattle can also become infected if they come in close contact with infected wild pigs.
Humans can get swine brucellosis through handling infected tissues of wild pigs. Hunters are at risk when they field-dress and butcher wild pigs and should take the following precautions:
- Always wear disposable plastic or rubber gloves when field-dressing, cleaning, and butchering a wild pig carcass. Avoid direct contact with blood and reproductive organs.
- As soon as possible, wash hands with soap and hot water after dressing wild pigs.
- Burn or bury gloves and remains from butchered wild pigs.
- Cook wild pig meat thoroughly.
- The symptoms of swine brucellosis in humans are not distinctive enough for a clear-cut diagnosis. Most people report recurring fever, chills, sweating, weakness, headaches, pains in muscles or joints, loss of appetite and weight loss. People with these symptoms who have been exposed to wild pigs should consult their doctor about swine brucellosis.
Another important disease harbored by wild pigs is pseudorabies. Despite its name, this disease, caused by a herpesvirus, is not related to rabies and does not affect people. However, pseudorabies is of great economic importance to the domestic swine industry. It weakens pigs, leaving them susceptible to other problems and causes abortions and stillbirths.
Adult swine can be silent carriers of pseudorabies and will periodically shed the virus through the nose and mouth. Once infected, the pig is a lifetime carrier and there is no effective treatment. Pseudorabies can be detected by blood testing and evidence of pseudorabies infection in wild pigs has been found in at least 11 States.
Pseudorabies is a fatal disease in other farm animals, such as cattle, sheep and goats and in dogs and cats. Wild mammals, such as raccoons, skunks, foxes, opossums and small rodents, also can be fatally infected. The virus attacks the nervous system in these animals and can produce intense itching followed by paralysis and death. Although people are not directly at risk, hunters need to know that their dogs could become fatally infected through exposure to wild pigs with pseudorabies.