Wild Pigs

Hidden Danger for Farmers and Hunters

Free-ranging populations of wild pigs (also called feral swine) are present in at least 18 States in this country. Some experts estimate their numbers at over 1 million. Additionally, private landowners in several States have set up enclosed hunting preserves stocked with wild pigs. These wild animals have become popular for sport hunting, but unfortunately, wild pigs can cause a great deal of damage. Hunters, farmers, and landowners should be aware that wild pigs can harbor infectious diseases and can destroy crops, livestock pastures, native plants, and wildlife habitat. Moving wild pigs to new areas or allowing them onto farms that have domestic pigs can have disastrous consequences

Wild Pig, Russian Boar, Razorback, Piney-Woods Rooter. . .

In the United States, wild pigs are called many names, and this reflects their mixed ancestry. Wild pigs are not native to North America and should not be confused with the collared peccary (javelina) of the Southwest. Swine first came to this continent in 1539, when the Spanish explorer Hernando de Soto brought them to Florida. After that, it was common practice for settlers to allow their domesticswine to roam freely. Many years later, sport hunters introduced true European wild boar into certain areas of the United States, and their bloodlines have become mixed with those of the wild pig.

Today, some of these animals have the classic “wild boar” appearance while others resemble common domestic pigs in body shape and color. It is often difficult to distinguish wild pigs from free-ranging domestic swine based solely on appearance.

Important Diseases

Wild pigs are susceptible to two serious swine diseases: swine brucellosis and pseudorabies. Hunters and farmers need to be aware that wild pigs can also carry these diseases to domestic pigs.

Swine brucellosis is caused by an organism that is very similar to the brucellosis organism in cattle. Swine brucellosis causes abortions in sows and infertility in boars. Although this disease does not kill pigs outright, it causes losses in reproduction that can decrease profits on pig farms.

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.

Wild pigs in 10 States have been found to be infected with swine brucellosis. It can be spread to domestic swine if wild hogs are introduced into local herds. Introduction could be intentional, or wild boars could break into pastures or pens to breed with domestic sows.

Other farm animals are rarely threatened by swine brucellosis, although cattle can become infected if they are exposed to the afterbirth of infected wild pigs. Humans can get swine brucellosis through handling infected tissues of wild pigs. Hunters are at risk when they dress wild pigs and should take the following precautions:

1. Always wear disposable plastic or rubber gloves when dressing and cleaning wild pigs. Avoid direct contact with blood and reproductive organs.
2. As soon as possible, wash hands with soap and hot water after dressing wild pigs.
3. Burn or bury gloves and remains from dressed wild pigs.
4. Cook meat from wild pigs thoroughly.

The symptoms of swine brucellosis in humans are not distinctive enough for a clearcut 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 infect people. But pseudorabies is of great economic importance to the domestic swine industry because this infection weakens pigs, leaving them susceptible to other problems, and causes abortions and stillbirths. Like swine brucellosis, pseudorabies causes productions losses and decreased profits.

Adult swine can be silent carriers of pseudorabies and will periodically shed the virus that causes it 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 11 States.

Pseudorabies is a fatal infection 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 themselves at risk, hunters need to know that their dogs could become infected by exposure to wild pigs.

To minimize the threat that wild pigs pose to domestic swine operations, farmers should take the following precautions:

1. Do not introduce wild pigs into herds or attempt to market wild-caught pigs.
2. Before transporting breeding swine, have blood tests performed according to State or Federal guidelines.
3. Blood-test all new stock before adding them to the existing herd.
4. Fence out wild pigs from areas with domestic hogs.
5. Do not butcher wild pigs on the farm or feed offal from dressed wild pigs to domestic swine.

Both State and Federal laws govern the control of swine brucellosis and pseudorabies. Relocating wild pigs without negative blood tests for these diseases violates the law. Individuals should contact their State veterinarian before moving wild pigs. Following the sanitary procedures outlined in this brochure is important to prevent human infection with swine brucellosis and to make sure that this disease and pseudorabies do not make their way onto farms from the wild.

Captions with JPG files

Map—From 500,000 to more than 1 million wild pigs roam the United States. This map depicts known populations as of 1988; many additional areas may also have wild pigs. Southeastern Cooperative
Wildlife Disease Study, Athens, GA.

Types of wild pigs: European wild boar (top left); wild pig with domestic appearance (bottom left); and javelina, or collared peccary (above), native to the Southwestern United States.

Photo credits: We gratefully acknowledge the help of the Southeastern Cooperative Wildlife Disease Study, Athens, GA, in providing a new photograph for the front cover of this brochure and a new image of a feral pig that resembles domestic swine (the bottom image on p. 4). The remaining shots are USDA file photographs.

Surveys have revealed swine brucellosis and/or pseudorabies infections in wild pigs in numerous States. The illegal relocation of infected wild pigs for hunting purposes can spread these diseases to new areas.

Before wild pigs are moved, they should be blood-tested by a veterinarian to certify that they are free from disease. JPG

Additional copies of this brochure are available at no charge from:

Publications Distribution
USDA, APHIS, ABS, PDMSC
4700 River Road, Unit 1
Riverdale, MD 20737–1229

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326–W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250–9410 or call (202) 720–5964 (voice and TDD). USDA is an equal opportunity provider and employer.

United States Department of Agriculture
Animal and Plant Health Inspection Service

Agriculture Information Bulletin No. 620
Issued July 1991 and
slightly revised June 1999

Click here for printable version (PDF)