United States Department of Agriculture

Animal and Plant Health Inspection Service

Program Aid No. 2086

Feral Swine:

Damage and 

Disease Threats

Distribution of 

Feral Swine Over Time Knowing If 

Feral Swine 

Are in Your 

Area

Feral swine damage 

is often caused at 

night when the 

animals are most 

active. The best 

way to tell if feral 

swine are active in your area is to look for common 

signs of rooting, rubbing, wallowing, tracks, and trails. 

Reducing Feral Swine Damage

Experts with the U.S. Department of Agriculture 

(USDA), Animal and Plant Health Inspection Service 

(APHIS) are working in collaboration with State, local, 

and tribal officials to reduce the threats caused by feral 

swine to our country’s livestock, native ecosystems, 

and human and animal health. You can help be part 

of the solution.

Additional copies of this brochure are available 

at no charge from:

Publications Distribution

USDA/APHIS

4700 River Road, Unit 1

Riverdale, MD 20737-1229

Order online via: www.aphis.usda.gov/publications/

Photo Credits: All images in this brochure were taken by 

APHIS employees or are part of the APHIS image collection. 

USDA is an equal opportunity provider and employer.

This publication supersedes Agricultural Information Bulletin No. 799, 

“Feral/Wild Pigs: Potential Problems for Farmers and Hunters,” which was 

published in October 2005. 

Issued August 2011

To learn more about feral swine and the diseases 

they carry, visit these Web sites.

n APHIS 

www.aphis.usda.gov/wildlife_damage/

www.aphis.usda.gov/animal_health/animal_dis_spec/

swine/ 

n Centers for Disease Control and Prevention

www.bt.cdc.gov/agent/brucellosis/

www.cdc.gov/parasites/toxoplasmosis/ 

n National Feral Swine Mapping System, 

University of Georgia

http://128.192.20.53/nfsms/

1982

2004

2010

Feral Swine Identified

No Feral Swine

Feral swine are quickly spreading across the United 

States due to natural population growth, illegal 

movement by sports hunters, and escapes from 

domestic swine operations. Experts estimate their 

numbers at over 5 million animals nationwide.

Feral swine often forage alongside livestock and eat grains, mineral 

blocks, and other items intended for cattle. APHIS animal health 

experts are concerned that such close contact can result in the 

transmission of disease from feral swine to livestock and people. 

n Report feral swine activity to the proper 

wildlife and agriculture officials in your State. 

You may also call APHIS Wildlife Services toll 

free at 1-866-4USDA-WS (1-866-487-3297) 

for assistance in dealing with feral swine. 

n Do not relocate feral swine without the 

proper permits. It is illegal in most States to 

trap and move feral swine.

n If you raise domestic pigs, take adequate 

biosecurity measures at your facility to prevent the accidental release of domestic pigs 

or the interaction between feral swine and 

domestic pigs. 
illegal trapping and movement by 

hunters, and accidental releases 

from domestic swine operations. 

The expanding populations of feral 

swine are a significant concern 

to farmers, livestock producers, 

natural resource managers, and 

animal health officials. However, 

feral swine issues are not limited 

to natural areas and rural 

environments. Feral swine are 

highly adaptable and are becoming 

more common in suburban areas, 

rooting up lawns, gardens, golf 

courses, and city parks.

Free-ranging populations 

of feral swine (also called 

feral hogs and wild pigs) 

in the United States are located 

in at least 35 States. Some 

experts estimate their numbers 

at over 5 million, with the 

largest populations located in 

California, Florida, Oklahoma, 

and Texas. This species causes 

extensive damage and disease 

threats to public property, native 

ecosystems, livestock health, 

and human health. Feral swine 

populations will likely continue 

to spread across the country as a 

result of natural range expansion, 

An Invasive Species 

Feral swine are an invasive species. They are not native 

to the United States and should not be confused with the 

collared peccary (javelina), a native pig-like mammal of the 

Southwest. Today’s feral swine are descendants of domestic swine that were first introduced to the United States in 

1539 by Spanish explorers. Following their arrival, it was 

common practice for settlers to allow their domestic swine 

to roam freely. Many years later, sport hunters introduced 

true Eurasian wild boars into certain areas where their 

bloodlines mixed with domestic swine. Due to their extensive crossbreeding, feral swine often vary in appearance 

and can be mistaken for domestic pigs. 

The Cost of Feral Swine Damage

It is estimated that feral swine in the United States cause 

more than $1 billion in damages and control costs each 

year. For example, rooting and wallowing activities cause 

property damage and erosion to river banks. Feral swine 

eat and destroy field crops such as corn, milo, rice, watermelon, spinach, peanuts, hay, turf, and wheat. They are 

also efficient predators and, when given the opportunity, 

prey upon young livestock and other small animals, such 

as ground-nesting birds. 

In addition, their rooting activities allow invasive plants to 

re-vegetate damaged areas, reducing native plants and 

grasses. Their wallowing activities can contaminate water 

supplies and impact water quality. These animals have also 

been known to destroy livestock and game fences and consume livestock feed, minerals, and protein supplements. 

Disease and Feral Swine

Feral swine have been known to carry or transmit over 

30 diseases and 37 parasites that can be transmitted to 

livestock, people, pets, and wildlife. 

Feral swine can carry several diseases that affect domestic 

swine. If a foreign animal disease, such as classical swine 

fever or foot-and-mouth disease, were to enter the United 

States, feral swine could spread the disease to domestic 

swine or other susceptible animals. Once prevalent in feral 

swine populations, the disease would be extremely difficult to eradicate. Another 

concern is the potential for 

feral swine to reintroduce 

diseases that have been 

eradicated in U.S. livestock. 

For example, domestic 

swine are now free of pseudorabies and swine brucellosis. If reinfection through 

feral swine should occur, 

it would be economically 

devastating to the pork 

industry. 

Impacts to People and Pets

Though a rare occurrence, feral swine can directly 

infect people with diseases. For example, brucellosis 

(or undulant fever) can be transmitted to people when 

blood or other body fluid from an infected animal 

comes into contact with a person’s eyes, nose, mouth, 

or open wound. 

Feral swine can also carry harmful organisms and diseases such 

as toxoplasmosis, tularemia, 

trichinellosis, swine influenza, 

salmonella, E. coli, and a variety 

of bacterial diseases that can 

cause sickness and, in some 

cases, death to people who 

consume contaminated food 

products. If you feel ill after 

coming in contact with or consuming feral swine, contact 

your physician.

Pseudorabies can be transmitted from feral swine to some 

pets, such as dogs and cats, as 

well as cattle, sheep, and goats. 

Signs of illness include intense 

itching often followed by 

paralysis and death. Contact 

your veterinarian if your pets or 

livestock come in contact with 

feral swine and show any of the following clinical signs:

n Sudden change in behavior

n Excessive salivation

n Difficulty breathing

n Fever

n Vomiting

n Depression/reluctance to move

n Difficult walking/poor coordination

n Convulsions

n Intense itching or self mutilation

n Coma

n Sudden death

Some 

Diseases 

Carried by 

Feral Swine 

Pseudorabies 

Brucellosis

Porcine 

reproductive 

and respiratory 

syndrome

Swine influenza

Toxoplasmosis

Tularemia

Trichinellosis

Relocations of feral swine have resulted in extensive crossbreeding, producing variations in appearance. Some look like traditional wild boars, 

while others look more like domestic pigs in body shape and color. It is often difficult to distinguish feral swine from domestic swine based on 

appearance alone.

In just a few nights, feral swine can 

decimate lawns, native habitats, 

and pasturelands. Common feral 

swine damage includes wallowing, 

tree rubbing, and rooting.

APHIS wildlife disease 

biologists monitor feral swine 

for the presence of more than 

10 diseases that can affect 

livestock, people, and pets.