ntestinal parasites may not get the headlines that PRRS or ASF do, but they continue to be a hidden threat to swine productivity—especially in systems where pigs have outdoor access. Understanding who these parasites are, their life cycles, and how to effectively monitor and manage them is critical for maintaining herd health and profitability.
🪱 Who Are the Intestinal Parasites?
The most common intestinal parasites in pigs include:
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Ascaris suum (large roundworm): This is the most significant internal parasite in pigs globally. It migrates through the liver and lungs, impairing growth and carcass quality.
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Trichuris suis (whipworm): Causes diarrhea and inflammation in the large intestine.
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Oesophagostomum spp. (nodular worm): Common in pigs with outdoor access, these worms can cause intestinal nodules and inflammation.
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Strongyloides ransomi (threadworm): More concerning in piglets, this parasite can be passed from sow to piglet via milk.
Other occasional offenders include Metastrongylus spp. (lungworms), Eimeria and Isospora (coccidia), and Balantidium coli, a protozoan parasite.
🔍 Signs and Consequences of Infection
While infections are often subclinical, they may lead to:
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Poor growth performance
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Rough hair coats
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Diarrhea or digestive upset
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Reduced feed conversion
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Carcass condemnations (e.g., “milk spot liver” from Ascaris suum)
Economic losses due to parasites often go unnoticed, yet they can cost producers $4–$6 per pig in productivity losses and trimming at harvest.
🧪 Surveillance in Outdoor Access Systems
Pigs raised in outdoor or pasture systems are more likely to encounter parasites due to contact with contaminated soil, wildlife, or intermediate hosts (like earthworms for lungworms). As such, routine surveillance is vital.
Best Practices for Parasite Surveillance:
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Fecal Egg Counts (FEC): Take composite samples from pen groups or individual pigs to identify and quantify parasite burdens.
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Necropsy Monitoring: Inspect intestines and liver for worms or lesions during post-mortems.
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Pasture Rotation and Management: Allowing pastures to rest and using multi-species grazing can reduce environmental contamination.
💊 Deworming and Control Strategies
Routine, blanket deworming is no longer considered best practice due to resistance risks. Instead, targeted deworming based on surveillance data is encouraged. Common dewormers include:
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Fenbendazole
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Ivermectin
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Levamisole
Producers should rotate drug classes annually and focus on timing treatments to break parasite life cycles.
🌱 Environmental and Biosecurity Considerations
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Manure Management: Composting and removing old bedding help reduce parasite egg survival.
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Rodent and Wildlife Control: Essential to limit introduction of parasite eggs and intermediate hosts.
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Sanitation: Clean water and feed systems reduce transmission risk.
🧠 Final Word: Know Your Enemy
Parasites are persistent but manageable with awareness, regular monitoring, and targeted intervention. For producers embracing outdoor systems or niche pork markets, intestinal parasite control must be an active part of herd health protocols.
By integrating sound parasitology with good animal husbandry and pasture management, your pigs—and your bottom line—will thank you.
📚 Sources:
