Strongyloidiasis in Pigs: Threadworm Infection in Young Piglets
- Strongyloidiasis is a threadworm infection caused by Strongyloides ransomi, and clinical illness is seen most often in nursing piglets.
- Many pigs carry light infections without obvious signs, but heavy infections in very young piglets can cause diarrhea, anemia, weight loss, dehydration, and sometimes death.
- Piglets are commonly infected through the sow's milk or from larvae in contaminated bedding or pens, especially where hygiene is poor and moisture is high.
- Diagnosis usually involves a fresh rectal fecal sample for parasite egg detection, because environmental contamination can confuse results.
- Treatment often includes deworming directed by your vet plus fluids, warmth, nursing support, and improved sanitation for the sow and litter.
What Is Strongyloidiasis in Pigs?
Strongyloidiasis is an intestinal parasite infection caused by Strongyloides ransomi, often called the pig threadworm. This parasite is found worldwide, although it is considered uncommon in much of the continental United States. When disease does happen, it is usually most important in nursing piglets, not healthy older pigs.
The adult female worms live in the small intestine, where they burrow into the intestinal lining. Mild infections may cause no obvious problems. Heavier infections can irritate the gut enough to trigger diarrhea, poor growth, weakness, and anemia. In the youngest piglets, especially those under 2 weeks old, severe disease can become life-threatening.
One reason this parasite matters is that newborn piglets can become infected very early in life. Larvae may pass through the skin from a contaminated environment, but transmission through the sow's milk is especially efficient. That means a litter can become infected before a pet parent notices any warning signs.
If your piglet has diarrhea, poor weight gain, or seems weaker than littermates, it is worth involving your vet early. Parasites are only one possible cause of illness in young pigs, and prompt evaluation helps your vet sort out what needs attention first.
Symptoms of Strongyloidiasis in Pigs
- Diarrhea, often in nursing piglets
- Poor weight gain or failure to thrive
- Thin body condition or emaciation in heavier infections
- Pale gums or weakness from anemia
- Dehydration, sunken eyes, or reduced nursing
- Sudden decline or death in piglets under 2 weeks old
Light infections may cause no visible signs at all. Clinical disease is more likely in young nursing piglets, especially when parasite exposure is heavy or the litter is already stressed by chilling, crowding, or other infections.
See your vet immediately if a piglet has profuse diarrhea, weakness, pale skin or gums, trouble nursing, marked weight loss, or signs of dehydration. These signs are not specific to threadworms, and newborn piglets can decline quickly from several causes of diarrhea.
What Causes Strongyloidiasis in Pigs?
Strongyloidiasis is caused by infection with the nematode Strongyloides ransomi. The parasite has an unusual life cycle because it can exist both inside the pig and as free-living stages in the environment. That makes damp, contaminated housing an important part of the problem.
Piglets can become infected in two main ways. First, infective larvae in bedding, soil, or manure can penetrate the skin and then migrate through the body before reaching the intestine. Second, and often more efficiently, larvae can be passed in the milk of lactating sows. Dormant larvae may persist in the sow and infect more than one litter over time.
Risk tends to rise when farrowing areas stay wet, dirty, and heavily contaminated with manure. Warm conditions help larvae survive and multiply. Crowding, poor sanitation between litters, and delayed manure removal can all increase exposure.
Older pigs usually develop stronger immunity, so they are less likely to show obvious illness. That is why threadworm disease is mainly a concern in young piglets, even when adult pigs on the property seem normal.
How Is Strongyloidiasis in Pigs Diagnosed?
Diagnosis usually starts with your vet reviewing the piglet's age, housing, litter history, and the pattern of diarrhea or poor growth. Because many causes of piglet diarrhea look similar, history matters. Your vet may ask whether the sow has had previous affected litters, whether the farrowing area stays damp, and how quickly signs appeared after birth.
The most common test is a fecal exam looking for the parasite's small, thin-shelled, embryonated eggs. A fresh sample collected directly from the rectum is preferred. That detail matters because manure on the ground can contain free-living worms from the environment, which may confuse interpretation. Cooling the sample promptly also helps prevent eggs from hatching before testing.
In some cases, your vet may recommend testing more than one piglet, especially if several littermates are affected. If a piglet dies, a necropsy can help confirm the diagnosis and rule out other serious causes of neonatal diarrhea. Postmortem testing may include intestinal scrapings or larval recovery techniques.
Because piglet diarrhea can also be caused by coccidia, E. coli, clostridial disease, rotavirus, coronavirus, and management problems, your vet may combine parasite testing with other diagnostics. That broader approach is often the fastest way to choose practical treatment options.
Treatment Options for Strongyloidiasis in Pigs
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Office or farm-call exam focused on affected piglets
- Fresh fecal flotation or basic parasite screening
- Targeted deworming plan from your vet for the sow, piglets, or both when appropriate
- Oral fluids, warmth, nursing support, and close weight monitoring
- Immediate pen cleanup, dry bedding changes, and manure control
Recommended Standard Treatment
- Complete veterinary exam and litter-level assessment
- Fecal testing on one or more piglets, with repeat testing if needed
- Vet-directed anthelmintic treatment such as ivermectin, doramectin, or a benzimidazole when appropriate for the case
- Supportive care for dehydration, weakness, and poor intake
- Treatment timing guidance for the sow around farrowing to reduce lactogenic transmission
- Written sanitation and farrowing-pen management plan
Advanced / Critical Care
- Urgent evaluation of severely affected or collapsing piglets
- Expanded diagnostics to rule out mixed infections or other neonatal disease
- Injectable or intensive supportive care directed by your vet
- Necropsy and laboratory submission if a piglet dies
- Litter and sow treatment strategy plus environmental control review
- Follow-up testing or herd-level consultation for recurrent outbreaks
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Strongyloidiasis in Pigs
Bring these questions to your vet appointment to get the most out of your visit.
- You can ask your vet whether my piglet's age and symptoms fit threadworm infection or whether other causes of piglet diarrhea are more likely.
- You can ask your vet which fecal test is most useful and whether the sample should be collected directly from the rectum.
- You can ask your vet whether the sow should be treated too, especially if this is not the first affected litter.
- You can ask your vet which deworming option makes sense for this piglet or litter and what timing is safest around farrowing and nursing.
- You can ask your vet how to tell if dehydration or anemia is becoming an emergency at home.
- You can ask your vet what cleaning and bedding changes will lower reinfection risk in the farrowing area.
- You can ask your vet whether other piglets in the litter should be checked or treated even if they still look normal.
- You can ask your vet what follow-up testing or monitoring is needed to make sure the infection is clearing.
How to Prevent Strongyloidiasis in Pigs
Prevention focuses on reducing exposure before piglets are born and while they are nursing. Good hygiene matters because Strongyloides larvae can develop in the environment, especially in moist, contaminated pens. Keeping farrowing areas clean, dry, and well-bedded lowers the chance that larvae will survive long enough to infect piglets.
Work with your vet on a sow and litter parasite-control plan. In herds with a history of threadworm problems, treatment of the sow before farrowing may help reduce larvae passed in milk. Your vet can help choose timing and products that fit the sow's stage, the litter's age, and your management setup.
Between litters, remove manure thoroughly, replace wet bedding, and clean and dry the farrowing space as completely as possible. Overcrowding and persistent dampness make reinfection more likely. If you keep multiple pigs, separating age groups and avoiding buildup of contaminated bedding can also help.
If one litter develops diarrhea, do not assume it is a one-time event. Early fecal testing, careful recordkeeping, and reviewing sanitation with your vet can help prevent repeat problems in future litters.