Ascarid Roundworm Infection in Pigs: Intestinal Worms and Poor Growth

Quick Answer
  • Ascarid roundworm infection in pigs is usually caused by the large roundworm Ascaris suum, a common intestinal parasite of young pigs.
  • Many pigs have mild infections, but heavier parasite burdens can lead to poor growth, rough hair coat, coughing during larval migration, pot-bellied appearance, and reduced feed efficiency.
  • Diagnosis often involves a fecal exam for eggs in longer-standing infections, plus your vet's exam and herd or housing history. Early infections may not show eggs yet.
  • Treatment usually includes a vet-guided deworming plan plus cleaning and manure management, because medication alone may not stop reinfection.
  • Typical US cost range is about $60-$180 for an exam and fecal testing for a pet pig, with deworming and follow-up often bringing total care to roughly $80-$300 depending on the plan.
Estimated cost: $80–$300

What Is Ascarid Roundworm Infection in Pigs?

Ascarid roundworm infection in pigs is a parasitic disease most often caused by Ascaris suum, sometimes called the large roundworm of swine. Adult worms live in the intestines and compete for nutrients, which can slow growth and reduce body condition, especially in young, growing pigs.

This parasite does more than stay in the gut. After a pig swallows infective eggs from a contaminated environment, larvae migrate through the liver and lungs before returning to the intestines to mature. That migration can cause liver scarring known as "milk spots" and may trigger coughing or a thumping breathing pattern in more heavily affected pigs.

Many pigs with light infections look fairly normal at first. Others show poor weight gain, a rough coat, reduced feed efficiency, or intermittent digestive upset. In rare heavy infections, adult worms can contribute to intestinal blockage. Because eggs can survive in the environment for long periods, reinfection is common if treatment is not paired with sanitation and housing management.

Symptoms of Ascarid Roundworm Infection in Pigs

  • Poor growth or failure to gain weight as expected
  • Reduced feed efficiency or slower finishing
  • Rough hair coat or unthrifty appearance
  • Pot-bellied look, especially in younger pigs
  • Intermittent cough or "thumps" during larval migration through the lungs
  • Mild diarrhea or inconsistent stool quality
  • Lower energy or reduced activity
  • Visible worms in feces or after deworming in some cases
  • Rarely, signs of intestinal blockage such as severe belly pain, vomiting, or sudden decline

Mild infections may cause only subtle poor growth. Heavier infections are more likely to cause coughing, poor body condition, and obvious lack of thrift. See your vet promptly if your pig is losing weight, breathing harder than normal, has repeated coughing, or seems uncomfortable after eating. See your vet immediately for severe abdominal pain, repeated vomiting, collapse, or signs of intestinal obstruction.

What Causes Ascarid Roundworm Infection in Pigs?

Pigs become infected when they swallow Ascaris suum eggs from contaminated soil, bedding, feed, water, or manure. The eggs are passed in feces by infected pigs and can remain infective in the environment for a long time, which makes contaminated pens and outdoor lots an important source of exposure.

Young pigs are affected most often because they have less acquired immunity than older animals. Crowding, poor manure removal, damp or dirty housing, and repeated use of the same contaminated areas all increase risk. Reinfection is common when pigs are treated but their environment is not cleaned well enough to reduce egg exposure.

In pet pigs and small backyard groups, infection may also happen when a new pig is introduced without quarantine or fecal screening. People handling pigs or raw pig manure should also use good hygiene, because A. suum has zoonotic potential.

How Is Ascarid Roundworm Infection in Pigs Diagnosed?

Your vet will usually start with a physical exam, weight and body condition review, and questions about housing, manure exposure, deworming history, and growth rate. In longer-standing infections, a fecal flotation can identify roundworm eggs. This is one of the most practical tests for pet pigs and small groups.

A normal fecal test does not always rule out early infection. During the first part of the parasite life cycle, larvae may be migrating through the liver and lungs before adult worms are producing eggs. That means pigs can have cough, poor growth, or liver lesions even when fecal testing is still negative.

If a pig dies or is examined after slaughter, adult worms in the intestine or characteristic liver "milk spots" can support the diagnosis. Your vet may also consider other causes of poor growth or cough, including pneumonia, other intestinal parasites, diet issues, and management stressors.

Treatment Options for Ascarid Roundworm Infection in Pigs

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$80–$180
Best for: Mild signs, stable pigs, and pet parents seeking evidence-based conservative care
  • Office or farm-call exam focused on parasite risk
  • Single fecal flotation or fecal parasite screen
  • Vet-directed deworming plan using an appropriate swine-safe product
  • Basic home sanitation steps such as prompt manure removal, feeder cleaning, and bedding changes
  • Monitoring weight, appetite, stool quality, and cough at home
Expected outcome: Often good when infection is mild and reinfection pressure is reduced.
Consider: Lower upfront cost, but a limited workup may miss other causes of poor growth or respiratory signs. Reinfection is more likely if environmental cleanup is incomplete.
Most Common

Recommended Standard Treatment

$150–$300
Best for: Most pigs with suspected or confirmed roundworms as a first-line approach
  • Full veterinary exam and review of housing and deworming history
  • Fecal testing, with repeat testing if timing suggests a prepatent infection
  • Targeted deworming and a scheduled repeat treatment when appropriate
  • Group or herd-level recommendations if other pigs share the same space
  • Written sanitation plan for manure handling, pen drying, and reducing exposure to contaminated soil or bedding
  • Follow-up recheck or fecal re-evaluation
Expected outcome: Good in many cases, especially when treatment is paired with environmental control and nutrition support.
Consider: Costs more than a minimal plan, but it gives better odds of controlling reinfection and identifying pigs that need additional care.

Advanced / Critical Care

$300–$900
Best for: Complex cases, severe illness, suspected obstruction, or pet parents wanting a more complete diagnostic plan
  • Expanded diagnostics for pigs with marked weight loss, respiratory disease, or poor response to initial treatment
  • Bloodwork or imaging if your vet is concerned about dehydration, obstruction, or another illness
  • Hospitalization or intensive supportive care for severe weakness, dehydration, or suspected intestinal blockage
  • Broader herd investigation and management review for repeated parasite problems
  • Postmortem evaluation in herd situations when diagnosis remains unclear
Expected outcome: Variable. Many pigs improve, but outcome depends on parasite burden, age, concurrent disease, and how quickly treatment starts.
Consider: Higher cost and more intensive care. This tier is most useful when signs are severe, diagnosis is uncertain, or previous treatment has not solved the problem.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Ascarid Roundworm Infection in Pigs

Bring these questions to your vet appointment to get the most out of your visit.

  1. Does my pig's age and housing setup make roundworms likely?
  2. Should we do a fecal test now, or repeat it later if this may be an early infection?
  3. Which deworming option is most appropriate for my pig's size, age, and intended use?
  4. Do any other pigs in the household or group need treatment at the same time?
  5. How should I clean bedding, feeders, and manure areas to lower reinfection risk?
  6. What signs would suggest a complication like pneumonia or intestinal blockage?
  7. When should we recheck a fecal sample or body weight after treatment?
  8. Are there any human health precautions my family should take while managing this infection?

How to Prevent Ascarid Roundworm Infection in Pigs

Prevention focuses on breaking the life cycle. Work with your vet on a parasite control plan that fits your pig's age, environment, and exposure risk. Strategic deworming can help, but medication works best when paired with manure removal and cleaner housing.

Clean pens regularly, remove feces promptly, keep feeders and waterers free of manure, and replace wet or heavily soiled bedding. If possible, avoid keeping pigs continuously on the same contaminated ground. Dry, well-managed housing lowers exposure better than relying on dewormers alone.

Quarantine new pigs before introducing them to the group, and ask your vet whether fecal testing or preventive treatment makes sense during that period. Good handwashing after handling pigs, bedding, or manure is also important, since pig ascarids can pose a risk to people in some situations.

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