Feral Swine Disease Risks to Domestic Swine 

Why should I worry about feral swine? 

Animal and Plant Health Inspection Service

Feral swine and domestic swine are both the same species (Sus scrofa) meaning they 

can be infected with the same diseases. Pasture-raised pigs, non-confined domestic 

swine, and other outdoor swine practices can increase the risk of feral swine transmitting 

pathogens and parasites. Since feral swine roam freely, they can also contaminate 

accessible feed and water sources meant for domestic pigs.

Swine are social animals; domestic swine may interact with feral swine in pastures or through fences. 

Feral boar will even breed with domestic sows if they can access them. These interactions can result 

in transmission of pathogens not usually found in domestic swine. Infections can result in reduced 

productivity, abortions, reduced number of piglets, or even death. Pasture-raised pigs are also 

susceptible to acquiring parasites from feral swine, which can result in consumer health concerns 

and market losses. 

Disease Routes of Transmission Symptoms

Brucellosis (Brucella 

species bacteria)

Direct contact with aborted fetuses, afterbirth, or 

vaginal discharges. Ingestion of contaminated feed, 

water, or tissues. 

Infertility, abortion, vaginal discharge, 

lameness, and swollen testicles. 

Pseudorabies (Aujeszky’s 

disease or “mad itch”) 

Nose-to-nose or sexual contact. Ingestion of 

contaminated water, feed, or infected tissues. 

Through contaminated equipment or clothing or by 

airborne virus. 

Abortions, infertility, fever, sneezing, 

coughing, pneumonia, incoordination; 

stillbirth, abortion, piglet mortality. 

Porcine Reproductive 

and Respiratory

Syndrome 

Direct contact with nasal discharge, feces, urine, 

saliva or through sexual contact. Contaminated 

feed, water, or equipment or by airborne virus. 

Lack of appetite, lethargy, coughing, 

pneumonia, skin discoloration, stillbirth, 

weak piglets, and reduced milk production. 

Porcine Circovirus 

Type 2 

Direct contact with infected animals, through nasal 

discharge, feces, urine, or saliva. 

Weight loss, jaundice, diarrhea, respiratory 

distress, and swollen lymph nodes. 

Giant Kidney Worm Ingestion of larvae, penetration through the skin, or

through infected earthworms.

Loss of appetite, weight loss, blood in urine. 

Porcine Epidemic 

Diarrhea Virus 

Contact with infected feces directly or through 

contaminated, feed, water, soil, or surfaces. Acute watery diarrhea and vomiting. 

Trichinellosis Ingestion of muscle tissue infected with the 

encysted larval stage of the parasite. 

Vomiting and diarrhea, larvae may migrate 

and form cysts in muscle tissue. 

Toxoplasmosis

Ingestion of tissue cysts in undercooked or raw 

meat, or of food and water contaminated with 

oocysts. Also, the consumption of rodents. 

Clinical signs are uncommon in adults but 

may cause an increase in stillbirths or 

premature, weak piglets. Diarrhea may occur. 

Salmonellosis Ingestion of contaminated feces, food or water. Fever, lethargy, lack of appetite, and rancid, 

watery or bloody diarrhea. 

Disease impacts to domestic swine production 

Diseases of concern for domestic swine production 
Feral Swine Disease Risks to Domestic Swine

The United States is the second largest producer of pork in the world, 

generating $34 billion of revenue in the United States per year. An increasing 

amount of pork producers in the United States, nearly 37%, are located in 

regions where feral swine are common. Disease introductions from feral swine 

could have a huge financial impact on your farm through losses in 

productivity and trade. It is important to protect your livestock by reducing 

any potential for exposure to feral swine.

Take additional precautions to prevent interactions with your pigs if feral swine are found in your area. 

See the map to determine where feral swine currently exist.

Store feed in barns or prevent feral 

swine from accessing feed.

Avoid feeding in troughs or on the 

ground which can increase the risk 

of pathogen transmission since feral 

swine can easily access the feed. 

Prevent direct contact between 

feral swine and domestic swine by 

maintaining fences and keeping 

pigs confined, especially at night.

Prevent feral swine access to water 

sources used by domestic swine.

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What is at risk?

How can I protect my domestic swine from becoming infected? 

Want to learn more?

Call Wildlife Services, a program within the U.S. Department of Agriculture's 

(USDA) Animal and Plant Health Inspection Service, at 1-866-4-USDA-WS or visit 

www.aphis.usda.gov/wildlife-damage/stopferalswine to learn more about 

the problems caused by this invasive animal, as well as to seek advice and 

assistance in dealing with feral swine.