Dr Andrew Tucker, CS Vet
Ascariosis is caused by the roundworm Ascaris suum. This worm has a direct life cycle in pigs starting with ingestion of the egg. The larvae hatch and enter the mucosa in the pig’s caecum. Six hours after being ingested these larvae have already migrated to the pig’s liver where they moult and then move on to the lungs. Here they moult again and are then coughed up and swallowed by the pig. They now move down to the small intestine where they mature and will start to produce eggs which then restart the life cycle.
How do you know if it’s on your farm?
Clinical signs are rarely observed even in heavy infections. The pig’s growth rate and feed conversion can be affected – up to ten percent lower growth rate and higher feed conversion is likely and dependant on the level of infection. Sometimes pigs will be heard coughing during the migration stage. Other rare but possible signs include jaundice and congested extremities.
Ascariosis is usually diagnosed on post mortem where the larvae’s migration through the liver leaves a characteristic lesion known as a milk spot. Lung lesions are also often present. In positive cases worms can be found in the small intestine. Diagnosis in live animals can be done by microscopy of the faeces where the worm eggs can be seen.
How do you treat or prevent it?
Treatment is effective and is possible via injection or in feed medication. Which stage to treat at and which pigs to treat depends on the level of infection on your farm. Proper washing, disinfection and drying of buildings is essential if ascaris is present. Control is made difficult by the nature of the ascaris egg, which can survive on the ground for up to five years.
Eradication is possible and has been done by herd medication as well as by depopulation and repopulation of the herd.
Pig Diseases – D.J. Taylor; Diseases of Swine – Straw, Zimmerman, D’Allaire, Taylor.