Large roundworm of pigs
Ascaris suum (Large Roundworm)
Common name: Large Roundworm
Morphology: Eggs: ovoid, golden brown, thick-shelled, bumpy appearance on surface of egg
Adults: up to 40 cm
Life cycle can be direct or indirect with paratenic hosts. The pig ingests the egg with an L2 larvae inside. The larvae undergo hepatic migration, molt to the L3 form, then to migrate to the lungs. Larvae enter the alveoli, are coughed up and then swallowed. This process is known as hepato-tracheal migration. They then molt two times and become adults.
Paratenic hosts ingest the eggs and the L2 larvae remains in the tissues of the paratenic host until a pig eats it. These may include beetles and earthworms.
Clinical signs include coughing, rapid shallow breathing called "thumps", unthriftiness, colic, weight loss or reduced weight gain.
It is diagnosed by finding eggs in the feces by fecal floatation and clinical signs.
In Canada in 1970, a postgraduate student tainted his roommates' food with the parasite Ascaris lumbricoides. Four of the victims became seriously ill; two of these suffered acute respiratory failure.
1James A. Phills et al., Pulmonary Infiltrates, Asthma and Eosinophilia due to Ascaris Suum Infestation in Man, 286 New England Journal of Medicine 965-70 (1972).
2FDA/CFSAN Risk Assessment for Food Terrorism and Other Food Safety Concerns http://www.cfsan.fda.gov/~dms/rabtact.html