Notes from the field: Ascariasis from pigs!
During the 3 year period from April 2010 to March 2013, health officials in Maine received reports of ascariasis from health-care providers, veterinarians, and patients. All patients reported contact with pig farms during that time. Human infections by Ascaris lumbricoides represents the most significant human roundworm infection worldwide with approximately 1 billion infections, however precise numbers for infection are not known as it is not a reportable disease in the US. Ascaris is a soil-dwelling nematode or roundworm that enters the body when fertilized eggs are ingested. The eggs hatch in the small intestine, and larvae penetrate the lining of the intestine to the bloodstream, where they migrate to the pulmonary circulation. The larvae mature in the lungs, and then penetrate through the alveolar wall and migrate up the bronchial tree, where they are then swallowed and go back to the intestines to develop into adult worms. Female adult worms can grow up to 30 cm in length and lay 200,000 eggs per day which leave the body via the feces to continue the cycle of infection. Disease due to Ascaris infection is typically not serious, although intestinal blockage due to the presence of masses of worms may occur. Allergy-like symptoms may also occur, due to inflammatory responses as the worms move through the body. Treatment for roundworm infections in humans is very effective, and is accomplished by a brief dose of an antihelminthic medicine such as ivermectin.
The CDC’s Morbidity and Mortality Weekly Report details the current outbreak of Ascaris infection among several farms in Maine. A total of 14 patients from 7 farms were identified. Confirmation of Ascaris from human samples was done by reference laboratories, and the link to pig farming was strengthened by the realization that previous pig-human transmission of roundworms had been seen in the medical literature. Health officials noted that each of the farms grew either organic or conventional crops, in addition to livestock. Recommendations to the farmers included improving handwashing hygiene, growing vegetables away from areas where pigs are penned, thoroughly washing all produce, and finally discontinuing the use of pig manure as a fertilizer. The CDC notes that transmission from animal reservoirs into human populations in the United States holds significant implications for foodborne disease transmission in “small-scale” farming practices, and runs somewhat counter to the notion that local farming is safer or healthier than large scale factory farming. Regardless of the ultimate type of farming used to produce our food, all consumers should practice good personal hygiene in order to prevent acquiring a foodborne disease.