Managing the health of your herd is paramount to ensure the profitability and efficiency of your operations. Among the myriad challenges you face, controlling internal parasitic worms in pigs is crucial. These parasites not only compromise the health and growth of your pigs but also impact overall farm productivity. Understanding the different types of worms that can affect your swine, their life cycles, and the problems they cause is the first step towards effective management. This article provides a comprehensive overview of worm infestations in swine, highlighting practical strategies for diagnosis, treatment, and prevention to help you maintain a healthy and productive herd.
Types of common worms in swine
The following are some of the most prevalent types1:
- Large Roundworm (Ascaris suum): One of the most common and harmful worms, Ascaris suum grow to a considerable size, typically 6 to 12 inches in length. They are stout and pinkish, sometimes with curved tails, making them easily noticeable during a necropsy. Pigs acquire infections by ingesting infective eggs from the environment, which is a particular concern in areas with intensive farming practices.
- Whipworm (Trichuris suis): Found in the large intestine, whipworms are a major cause of diarrhea and anemia in pigs. Whipworms have a distinctive slender shape that tapers into a fine, whip-like front end. Adults usually measure about 2 to 2.5 inches long. They are generally thinner and smaller than roundworms, with their heads embedded deeply into the intestinal wall. Whipworms are especially resilient in soil, making outdoor rearing systems a higher risk for this type of infection.
- Threadworm (Strongyloides ransomi): These worms are notably smaller and thinner compared to other species, making them less visible to the naked eye. Common in warmer climates, they predominantly affect piglets, causing severe diarrhoea and potentially fatal dehydration if not managed properly. The transmission can occur through contaminated soil or, more critically, through infected sows to their newborns.
- Nodular worm (Oesophagostomum spp.): Nodular worms are less than 1 inch in length. They typically reside in the large intestine and are known for causing visible nodules in the intestinal walls, which are detectable during a necropsy. They are common in both indoor and outdoor rearing systems and can survive in the soil for extended periods, posing a recurring risk.
- Lungworm (Metastrongylus spp.): Lungworms are usually between 1 and 2 inches in length and are primarily a problem in pigs with access to pastures where earthworms, which act as intermediate hosts, are present. They are slender and white, often found in clusters deep within the respiratory tract of infected pigs.
The life cycle of worms in swine
Having identified the common types of worms that affect swine, it is useful to delve deeper into their lifecycle and prepatent period. The prepatent period, which is the interval between the initial infection and the point at which the parasite can be detected, varies significantly among different worm species. This knowledge allows for more precise timing in implementing control measures and treatments.
Large roundworm life cycle
- Egg stage: Adult female worms in the small intestine of pigs produce eggs, which are excreted in the faeces. These eggs become infective after 3-4 weeks under optimal conditions.
- Larval migration: Infectious eggs are ingested by pigs. Larvae hatch in the small intestine, migrate through the liver and lungs, then return to the intestine. The prepatent period is approximately 7 to 8 weeks2.
- Adult stage: Mature worms reside in the small intestine, where they produce new eggs.
Whipworm life cycle
- Egg stage: Adult female whipworms residing in the large intestine of pigs produce eggs, which are then excreted in the faeces. These eggs contain an infective first-stage larva and require about 10-12 weeks under optimal environmental conditions to become infective.
- Larval migration: After ingestion, larvae hatch in the small intestine and migrate to the caecum and large intestine. The prepatent period is about 6 to 8 weeks3.
- Adult stage: Adult worms embed their heads into the intestinal lining, causing inflammation and bleeding. Their lifespan is usually around 4-5 months.
Threadworm life cycle
- Egg stage: Adult female threadworms produce small, thin-shelled eggs that are excreted in the faeces.
- Larval migration: Larvae can infect pigs by either penetrating the skin or through the milk of lactating sows. The prepatent period is very short: 7-9 days, or just 4-5 days via milk transmission4.
- Adult stage: Larve mature into adult females in the small intestine, where they burrow and lay eggs.
Nodular worm life cycle
- Egg stage: Adult nodular worms in the large intestine produce eggs, which are excreted in the faeces. These eggs hatch into infective third-stage larvae (L3) within one week.
- Larval migration: Pigs ingest the L3 larvae, which penetrate the intestinal mucosa and return to the lumen in 6-20 days. The prepatent period is approximately 3 to 6 weeks5.
- Adult stage: Mature worms reside in the large intestine and produce new eggs.
Lungworm life cycle
- Egg stage: Adult lungworms produce eggs that are coughed up from the lungs swallowed, and excreted in the faeces. These eggs are then ingested by earthworms, which act as intermediate hosts.
- Larval migration: The larvae migrate from the mesenteric lymph nodes to the right heart and then to the lungs. The prepatent period is approximately 28 days6.
- Adult stage: Mature worms reside in the large intestine and produce new eggs.
General signs and symptoms of worm infestations in swine
Worm infestations in swine can lead to several common symptoms that significantly impact animal health and farm productivity. General symptoms include:
- Diarrhoea: Often severe and potentially bloody, affecting nutrient absorption and overall health.
- Poor growth and reduced weight gain: Chronic infections impair nutrient uptake, leading to stunted growth and poor feed efficiency.
- Respiratory distress: Manifests as laboured breathing, coughing, and thumping, particularly in lung-related parasitic infections.
Specific symptoms of worm infestations
Following are specific clinical signs related to particular worm types:
Signs of large roundworm (Ascaris suum)
"Milk Spot" Liver: As the larvae of Ascaris suum migrate through the liver, they cause haemorrhagic foci, which heal into white fibrotic lesions known as "milk spots". These lesions are often grounds for the condemnation of the liver during meat inspections due to their impact on liver function and appearance7.
Verminous Pneumonia: In a critical phase of their lifecycle, Ascaris suum larvae migrate through the lungs, causing verminous pneumonia. This condition manifests as laboured breathing, an asthmatic cough, and difficulty in breathing, which can be severe enough to result in death, especially in young or heavily infested pigs7.
Signs of whipworm (Trichuris suis
In many cases, whipworm infestations are relatively mild and may not present any noticeable clinical signs. Such light infections typically go undetected unless specifically looked for during routine faecal examinations3.
More severe infestations can cause significant inflammatory lesions in the caecum and the large intestine. These heavy infections are often accompanied by symptoms such as diarrhoea and unthriftiness, particularly impacting the overall health and growth rates of the pigs3.
Signs of threadworm (Strongyloides ransomi)
In most cases of light and moderate infestations, pigs show no clinical signs, making it difficult to detect the presence of threadworms without specific testing. Nevertheless, heavy infestations, especially in piglets up to three months old, can cause severe symptoms including diarrhoea, anaemia, and emaciation. In the most vulnerable groups, particularly piglets less than two weeks old, the severity of these symptoms can lead to death. The high susceptibility of young piglets is attributed to their underdeveloped immune systems, which are not yet capable of effectively combatting the parasite4.
Signs of nodular worm (Oesophagostomum spp.)
Typically, adults of Oesophagostomum spp. cause little to no damage to the intestinal mucosa, making mild to moderate infections often asymptomatic. This low symptom profile can make nodular worm infestations difficult to detect without specific diagnostic procedures5.
In cases of heavy infestation, clinical signs become more apparent and can significantly impact the health of the pigs. Symptoms may include anorexia, emaciation, and various gastrointestinal disturbances such as diarrhoea or constipation. These symptoms result from the formation of nodules in the wall of the intestine, which can disrupt normal digestive processes5.
Signs of lungworm (Metastrongylus spp.)
Pigs infected with lungworms often exhibit respiratory distress. Common symptoms include laboured breathing and a persistent cough that may worsen over time as the infestation progresses. Lungworm infections often lead to pneumonia, which can exacerbate the symptoms of respiratory distress. A characteristic sign in pigs with severe lungworm infection is "thumping"8,1, which refers to an audible, heavy breathing pattern. This symptom is particularly noticeable in younger or more severely affected animals and is indicative of respiratory discomfort or difficulty.
Diagnosis of worm infestations in swine
Effective diagnosis of worm infestations is critical to managing and controlling these parasites efficiently. Early and accurate identification not only helps in treating affected pigs but also in preventing the spread of infestations throughout the herd. Here are key diagnostic methods that can be used.
Effective worm management in swine herds relies on a combination of several diagnostic techniques that help veterinarians and farmers detect and confirm the presence of parasitic worms.
Clinical observation
It involves the regular monitoring of the herd for signs that suggest a worm infestation, such as diarrhoea, poor growth, coughing, and general unthriftiness1. These observations are crucial as they can indicate the severity of an infestation and the potential need for immediate treatment. Veterinarians use these signs, along with the history and physical examination, to guide further diagnostic and treatment actions.
Faecal examination
A fundamental diagnostic tool where faecal samples are collected and microscopically examined9. Techniques like flotation or sedimentation are used to isolate and visualise worm eggs, making this a critical first step in diagnosing worm infestations. Regular faecal exams are essential for ongoing health monitoring and early detection of parasites.
Necropsy
It is performed in cases where pigs have died or are euthanised due to severe health issues. This examination of the intestines and other organs allows for direct observation of worms or lesions caused by worms9. For instance, liver spots from migrating Ascaris suum larvae can be identified, providing definitive evidence of specific infections.
PCR-Test
PCR, or Polymerase Chain Reaction, is a sophisticated technique used to identify worm DNA in faecal samples10. This method is especially useful for accurately determining the species of worms when visual identification through microscopy is challenging. PCR can distinguish between worm species that produce similar eggs, offering precise diagnosis that can guide targeted treatment strategies.
Treatment options for worm infestations in pigs
Once a diagnosis confirms the presence of worms, implementing an appropriate treatment strategy becomes paramount to managing the health and productivity of the herd. Treatment typically begins with choosing the right anthelmintic, which varies based on the type of worm and the extent of the infestation:
- Benzimidazoles: Effective against a wide range of worms11, these compounds, including flubendazole, disrupt the energy metabolism of the worms, leading to their elimination. Flubenol is particularly recommended for treating roundworms and other common intestinal worms. It's available in formulations that can be easily mixed with feed, making administration straightforward even for large herds.
- Macrocyclic Lactones: These are vital in the fight against both internal and external parasites. By paralysing the parasites, these drugs ensure they can no longer cling to the host's tissues, thus being expelled from the animal's body. This group includes ivermectin, which is effective for treating not only worms but also mites and lice12.
- Imidazothiazoles: Another class used to target specific worms, known for their fast-acting nature13.
Given the effectiveness of benzimidazoles in disrupting worm metabolism, a particular product within this class stands out for comprehensive worm control in swine:
Flubenol™: A broad-spectrum treatment tool
Flubenol™, containing the active ingredient flubendazole, exemplifies the efficacy of benzimidazoles with its broad-spectrum capability. It is highly effective against all life stages of common parasitic worms in swime: Ascaris suum, Hyostrongylus rubidis, Oesophagostomum dentatum, and Metastrongylus apri. The ability of Flubenol to target these parasites from eggs through to adult worms makes it an invaluable component of any comprehensive worm control strategy. Its wide-reaching impact is instrumental in not only treating infestations but also in preventing the development of significant health issues in the herd, thereby supporting optimal growth and productivity.
Administration and dosage of Flubenol
For general treatment: Flubenol is administered through feed at a dosage of 600g per tonne of feed, equivalent to 30g of flubendazole, over a period of 10 consecutive days. This ensures thorough coverage and effectiveness across the herd.
For individual treatment: In breeding pigs, a targeted dose of 5 mg of flubendazole per kg of body weight is mixed into the feed. Precise mixing is crucial to ensure even distribution and optimal efficacy.
Tailoring your worm control strategy
To maximise the effectiveness of your deworming efforts, also consider the following:
Regular faecal checks: Keep track of worm burdens by conducting regular faecal examinations. This will help you adjust your deworming strategy as needed and prevent overuse of medications.
Rotate dewormers: To avoid the development of resistance, rotate between classes of anthelmintics annually or as recommended by your veterinarian.
Integrated management: Combine chemical treatments with good sanitation and biosecurity measures (more about this in the next section). Regularly clean pens and rotate pastures to disrupt the life cycles of parasites.
The importance of a regular worming schedule
Prevention is the best treatment. For this reason, it is essential that you develop a regular worming schedule in consultation with a veterinarian. The ideal frequency depends on the specific of your herd and local parasite conditions, but as a general rule, it is recommended to carry out a routine worming treatment of your adult pigs at least once every six months14. Moreover, a strategic deworming routine should be combined with other essential aspects for prevention:
Enhanced biosecurity15: To prevent new infections, establish strict quarantine protocols for new arrivals and maintain high standards of cleanliness for all equipment and vehicles entering the farm. Educating everyone on production about the importance of these measures will help enforce compliance and effectiveness.
Environmental management: Proper manure management is critical. Regularly remove and appropriately dispose of manure to minimise the risk of parasite spread. Implement pasture rotation and manage stocking densities to prevent overgrazing and reduce environmental contamination with worm eggs and larvae.
Nutritional support: Ensure that pigs receive a balanced diet to support a strong immune system, making them less vulnerable to severe infestations. Regular health checks and a systematic approach to monitoring for signs of worm infestations will allow for early detection and intervention.
These strategies, when combined, provide a robust defense against worm infestations and enhance the efficiency and sustainability of your farm.
Overall, managing worm infestations is an essential aspect of swine production that cannot be overlooked. As outlined in this article, understanding the types of worms that may affect your pigs, recognising the signs and symptoms of infestation, and accurately diagnosing the presence of these parasites form the foundation of effective worm control. Implementing appropriate treatment strategies, including the use of proven anthelmintics like Flubenol, is critical for maintaining the health of your pigs and the profitability of your operations.
Always read and follow the label directions.
Flubenol™ oral wormer for pigs and chickens contains 50 mg/g flubendazole. Flubenol™, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. ©2025 Elanco or its affiliates. EM-AU-25-0018.
- Corwin, Robert M., "Common Internal Parasites of Swine," University of Missouri Extension, November 2018. Available at: https://extension.missouri.edu/publications/g2430
- Available at https://vetmed.iastate.edu/vdpam/FSVD/swine/index-diseases/ascariasis
- Ballweber, R., "Trichuris suum in Pigs," MSD Veterinary Manual, February 2022. Available at: https://www.msdvetmanual.com/digestive-system/gastrointestinal-parasites-of-pigs/trichuris-sp-in-pigs
- Ballweber, R., "Stongyloides sp in Pigs," MSD Veterinary Manual, February 2022. Available at: https://www.msdvetmanual.com/digestive-system/gastrointestinal-parasites-of-pigs/strongyloides-sp-in-pigs
- Ballweber, R., "Oesophagostomum spp in Pigs," MSD Veterinary Manual, February 2022. Available at: https://www.msdvetmanual.com/digestive-system/gastrointestinal-parasites-of-pigs/oesophagostomum-spp-in-pigs
- Kristi L. Helke DVM, PhD, DACVP, ... M. Michael Swindle DVM, DACLAM, DECLAM, in Laboratory Animal Medicine (Third Edition), 2015. Available at: https://www.sciencedirect.com/science/article/pii/B978012409527400016X
- Ballweber, R., “Ascaris suum in Pigs”, MSD Veterinary Manual, February 2022. Available at: https://www.msdvetmanual.com/digestive-system/gastrointestinal-parasites-of-pigs/ascaris-suum-in-pigs
- "Internal Parasites of Pigs", NSW Department of Primary Industries, August 2017, Primefact 1149 second edition. Available at: https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0019/433018/Internal-parasites-of-pigs.pdf
- Ballweber, R., "Stomach Worms in Pigs," MSD Veterinary Manual, February 2022. Available at: https://www.msdvetmanual.com/digestive-system/gastrointestinal-parasites-of-pigs/stomach-worms-in-pigs
- “Specialized Diagnostics: Polymerase Chain Reaction (PCR) and Nucleic Acid Sequencing”, University of Saskatchewan, June 2021. Available at: https://wcvm.usask.ca/learnaboutparasites/diagnostics/specialized-diagnostics-pcr-nucleic-acid-sequencing.php
- Vercruysse J., Claerebout E., “Benzimidazoles”, MERCK Veterinary Manual. Available at: https://www.merckvetmanual.com/pharmacology/anthelmintics/benzimidazoles
- Vercruysse J., Claerebout E., “Macrolytic Lactones”, MERCK Veterinary Manual. Available at: https://www.merckvetmanual.com/pharmacology/anthelmintics/macrocyclic-lactones
- Vercruysse J., Claerebout E., “Imidazothiazoles”, MERCK Veterinary Manual. Available at: https://www.merckvetmanual.com/pharmacology/anthelmintics/imidazothiazoles
- Available at: https://www.pigadvocates.com/vaccinationsparasite-control.html
- “Biosecurity plans and worm testing program”, Agriculture Victoria, November 2023. Available at: https://agriculture.vic.gov.au/livestock-and-animals/pigs/biosecurity-plans-and-worm-testing-program
