Ascaris suum is the small intestinal roundworm of pigs whose eggs and life cycle closely resembles ascarids of other veterinary species, including Toxocara spp. of dogs and cats and Parascaris equorum of horses. The eggs are thick-shelled, brown, and mammillated, and are very hardy in the environment (can survive up to nine years).
Ascariasis is the most common parasite in swine worldwide. More common in swine with access to the outdoors due to environmental contamination and earthworms and dung beetles act as paratenic hosts.
After ingestion, eggs hatch in the intestine and larvae penetrate the intestinal wall and enter the portal circulation. Migration through the liver to the lungs causes classic “milk spot lesions” (indicating recent infection).
In the lungs they can cause or worsen respiratory signs and lead to general ill-thrift, depending on parasite burden. They are coughed up from the bronchial tree, swallowed, and then mature to adults in the small intestine with a prepotent period of 6-7 weeks.
Prevention (deworming sows before farrowing, all-in-all-out, pasture rotation) is better than Tx. Many available effective dewormers (e.g., piperazine, hygromycin, benzimidazoles and probenzimidazoles, dichlorvos, ivermectin, doramectin, and pyrantel) for patent infections but larval stages are more difficult to Tx.
A. suum is zoonotic and can infect not only people (occasionally causing visceral or intestinal ascariasis) but other mammals, birds.
Image courtesy of Strongyle.
