By: Josh Schaeffer, University of Missouri

Regardless of how pigs are raised, they are inherently at risk for health concerns, including several diseases and conditions. Pigs raised in a traditional extensive manner, or what has been termed “transitional swine,” have higher risks for exposure to certain diseases and conditions in comparison to pigs raised in confinement. This guide will provide information on some of the more notable diseases and conditions of greater risk to transitional swine. Further reading and conversations with your herd veterinarian are encouraged for more complete coverage of the topic. To promote swine health and welfare, become acquainted with a swine veterinarian when you first purchase pigs, and employ a veterinarian in the diagnosis and treatment of ill pigs and in the development of disease control and prevention programs.

Temperature Extremes
During cold months, production will often decline as the body requires more of the energy consumed to maintain an appropriate body temperature. Younger pigs are most at risk of chilling or hypothermia because they have a higher and narrower range of thermal comfort than adult pigs (e.g., see thermal comfort ranges for young versus adult pigs at When the pig becomes cold, its body systems, including the immune system, have the potential to become compromised. This can lead to increased susceptibility to disease and even death. To prevent unfavorable effects from cold weather, shelter that provides protection from wind, rain, and snow should be provided. Absorbent bedding, such as straw or wood shavings, should be placed in the shelter to offer additional insulation from adverse temperatures.

Hot months also pose a threat to swine health. Pigs experiencing heat stress will often be inactive and can have reduced feed intake. As the body temperature rises, heat stress may lead to embryonic and fetal mortality, abortions, infertility, and even sudden death. Pigs housed outdoors, regardless of skin color, are at risk of sunburn. Sunburn in pigs is often very painful and can make pigs reluctant to move. Covering the affected skin with a bland oil, such as mineral oil, and moving sunburnt pigs indoors can provide relief. To protect pigs from the heat and sun, adequate shade should be provided. Shelter structures should be open-ended to allow for appropriate air flow. Access to wallows, or shallow mud pits, provides cooling as well as protection from the sun.

Photosensitization may also be seen in pigs housed outdoors. This condition occurs when pigs are exposed to photodynamic agents which intensify the effects of the sunlight. Photodynamic agents are present in some plants, such as St. John’s wort and rape. Some pharmaceuticals, such as tetracyclines and sulfonamides, can act as photodynamic agents. Pigs suffering from photosensitization will initially appear as severely sunburnt. The affected skin will become thickened, and the pig will be itchy. As the condition progresses, strips of skin, and sometimes the ears and tail, may start to slough, or fall off. Control this condition by preventing exposure to photodynamic agents or by grazing only at night. If photosensitization becomes a concern, consult a veterinarian for a more complete list of potential photodynamic agents.

Care should be taken to minimize or eliminate risks of injury. Poorly maintained housing, fencing, and equipment, such as fences, feeders and waterers, can cause penetrating or cutting wounds. With access to pasture, transitional swine are also at risk to predation from other animals, such as foxes, coyotes, raptors and dogs. In addition, birds have been known to peck holes in the backs of pigs on pasture. Care should be taken to minimize exposure to other animals that pose a health risk. Pigs are also at risk of injury from fighting with each other. If this occurs, measures should be taken to separate the fighting pigs. Traumatic injuries can range from minor cuts to life-threatening deep wounds. If kept clean, minor cuts and abrasions will usually heal without further intervention, but it is important to note that any open wound can become an entry point for infection.
Inappropriate footing in the pasture can predispose transitional swine to lameness.  Lameness can be caused by injuries such as a sprain, or even a fracture, but also by hoof disease, such as an abscess. All injuries and lamenesses should be evaluated quickly, and a veterinarian consulted if there is a question about the severity of the condition.

Because of increased potential for environmental exposure, transitional swine have an elevated risk for parasitic infection. Parasite loads can severely affect productivity of boars and sows in the natural setting, where they need to be highly durable. Information is provided below about some of the more common and clinically significant parasites of pigs. A veterinarian should consulted to aid in developing a parasite control program, and integrated pest management may be part of that program. When using parasiticides or dewormers, be sure to follow label directions for administration and meat withdrawals.

Scabies, or sarcoptic mange, is caused by a mite, Sarcoptes scabei var. suis. Pigs that come in contact with the mite usually begin to develop clinical signs approximately 3 weeks later. The most notable clinical sign is extreme itchiness. Affected pigs may have crusting around the eyes, ears, and snout. The skin of the back, flank, and rump will often be reddened with small raised areas, or papules. Chronically infected pigs often have thickened, scaly skin and hair loss and can suffer substantial losses in growth and feed efficiency. Scabies is extremely contagious from pig to pig. The best prevention is protecting a clean herd from carriers of the disease.

Toxoplasmosis is caused by the protozoan, Toxoplasma gondii. Based on the life cycle of T. gondii, only cats can pass the infective form of the protozoa in their feces. Pigs ingest the infective form (sporulated oocyst) through contaminated feed, water, or soil. Because the pig is not the natural host, T. gondii forms cysts in the muscles of the pig. Most pigs do not show any clinical signs. However, the disease is of public health importance because humans can get toxoplasmosis from the consumption of undercooked infected pork. Control is best maintained by limiting exposure to cat feces.

Gastrointestinal parasites
There are many gastrointestinal parasites of pigs. The major route of transmission is through ingestion of infective feces. It is important to provide appropriate manure management to control these parasites. Appropriately timed pasture rotation is one form of manure management. For brevity, only large roundworms and whipworms will be discussed here. In general, control principles will be similar; if more information is needed, please contact a veterinarian.

The large roundworm of pigs is Ascaris suum. Pigs ingest Ascaris suum in the feces of an infected pig, and the larvae migrate through the gut wall and to the liver. This causes what is known as milk spots, which are seen in the liver when the pig is processed. If there is enough larval migration, severe liver disease may result. Next the larvae migrate into the lungs, where they are coughed up, and swallowed. High numbers of larvae in the lungs can cause pneumonia to develop. After the larvae are swallowed, they mature into adults and begin to create infective eggs, which are shed in the feces to begin the cycle again. Most pigs become naturally resistant at about 6 months of age. If other animals, such as cattle, become infected with Ascaris suum, the larvae often have prolonged migration within the lungs and may die there. This results in a severe, possibly life threatening, pneumonia.

Pigs become infected with the swine whipworm, Trichuris suis, by ingesting infective feces. The whipworm embeds itself into the wall of the large intestine. Infected pigs often develop diarrhea that contains blood and mucous. This will often slow or stunt their growth. Severe infestation may result in death.

Lungworms of pigs belong to the genus Metostrongylus. Infected pigs cough up eggs, swallow them, and then pass the eggs in the feces. The eggs are then ingested by earthworms. The eggs hatch inside the earthworm, which is then eaten by a pig. The larvae then migrate through the gut wall and to the lungs. Once in the lungs, the larvae mature into adults and begin producing eggs. Migration of the lungworm through the lungs can cause pneumonia, especially if secondary bacterial infection occurs.

Pork Measles
Cysticercosis, pork measles, is caused by the human tapeworm, Taenia solium. Humans infected with adult T. solium shed proglottids (egg sacs) in their feces. A pig becomes infected by eating human feces. The eggs hatch within the pig’s gut and the organism penetrates through the small intestine and is carried throughout the pig’s body. The parasite develops into a cysticeri (fluid filled cyst) within the muscles of the pig. Humans can then become infected by eating undercooked pork containing these cysts, or “pork measles.” Cysticercosis can be prevented by eliminating pig exposure to human feces, in particular waste lagoons, and use of proper cooking techniques for pork products.

Diarrhea is an important health concern for all groups of pigs. There are many causes of diarrhea in the pig (Table 1), and reporting the age group(s) affected, the percentage of sick pigs, and the characteristics of the diarrhea (blood, mucous, watery, tarry, etc.) can help the herd veterinarian narrow down the potential causes and prescribe a more efficacious treatment and control plan. Use of proper farm biosecurity is an important preventive measure.
The treatment for diarrhea is mostly supportive care. This includes ensuring that the affected pigs are receiving enough to eat and drink. For suckling pigs, bottle or eye-dropper feeding may be required as the pigs are often too weak to latch on to the sow. Older pigs may be enticed to drink by flavoring the water with fruit juice or flavored drink powders. Diarrhea often causes the pig to become low in salt, so having available salt blocks may aid the pig to maintain its own salt levels. Some sports drink powders contain salts and may help the pig maintain salt levels. Depending on the cause of the diarrhea, antibiotics and anti-inflammatories may need to be administered under the guidance of a veterinarian.

Table 1. Common causes of diarrhea in the pig, age groups affected and clinical signs

Common Causes of Diarrhea Age Group(s) Affected Clinical Signs
E. Coli
  • Most common cause of diarrhea in pigs <5 days old
  • Can be seen at weaning
  • Watery diarrhea
  • May see edema (swelling) of eyelids
Clostridial Enteritis
  • Preweaning pigs
  • Bloody diarrhea
  • Sudden death
  • Chronic poor doer
Transmissible Gastroenteritis
  • All age groups
  • If endemic to herd, may only see clinical signs in recently weaned pigs
  • Vomiting
  • Diarrhea
  • May see high mortality in young pigs
Porcine Epidemic Diarrhea
  • All age groups
  • Vomiting
  • Diarrhea
  • High mortality in young pigs
Proliferative Ileitis
  • Grow/Finish
  • Adult
  • Dark, tarry diarrhea
  • Sudden death
  • Chronic poor doer
Swine Dysentery
  • Grow/Finish
  • Adult
  • Bloody diarrhea with mucous
  • Usually nearly entire pen affected
  • Grow/Finish (often shortly after mixing pigs from multiple sources)
  • Adult
  • Variable signs
  • Fever
  • Diarrhea
  • Septicemia (purple ears, systemically ill)
  • Pigs that recover may develop rectal strictures that inhibit the ability to defecate.

Erysipelas is caused by the bacterium, Erysipelothrix rhusiopathiae, and is a disease of all swine, regardless of housing. Outdoor pigs are at an increased risk because the infective spores can survive for extended periods of time in the soil. Acutely infected pigs will often have red, diamond-shaped lesions on the skin. This is due to vasculitis, or inflammation of the blood vessels, which causes the vessels to become leaky. Prolonged infection or exposure to the spores can lead to more chronic clinical signs, including arthritis, heart infection, and sloughing of large portions of the skin. The chronic skin lesions may be difficult to differentiate from chronic sarcoptic mange or photosensitization. Control of Erysipelas should be considered within the vaccination program developed by your herd veterinarian.

Only the more frequently occurring conditions that can affect transitional swine have been identified in this guide. It is important to remember that pigs raised outdoors may be more susceptible to these diseases and conditions than indoor swine. These include many bacteria and viruses that cause diarrheal disease, respiratory disease, and reproductive failure. To ensure animal health, production, and welfare, it is vital for any swine operation to develop proper biosecurity measures to protect the health of herd. Herd managers should work with a veterinarian to develop a herd health plan for the prevention, diagnosis, treatment, and control of disease.

When a pig does require treatment for a disease or condition, it is important to keep a careful record of the treatment. Records (e.g., Table 2) help ensure that pigs are not marketed before the appropriate withdrawal period has been fulfilled. In addition, good records allow for the tracking of diseases within a herd. This will aid the herd veterinarian in identifying risk factors and establishing a more effective herd health plan. Detailed record keeping can help to identify bloodlines or breeds that are more susceptible to disease, and can also help to pinpoint the effectiveness of management techniques.

Table 2. Sample treatment record template

Date Animal ID Reason for Treatment Product Name Amount Given Route Given By Withdrawal Time

For more information about diseases in pigs, check out these links:Queensland Australia Department of Agriculture and Fisheries, Common pig diseases:
Pork Information Gateway:
The Pig Site Quick Disease guide:
Center for Food Security & Public Health, Swine Diseases and Resources: