Cross-Transmission of Ascaris Infection from Pigs to Humans at an Organic Farm-Coastal Maine, 2012

BACKGROUND:  Human infection with Ascaris, a soil-transmitted roundworm, is rare in the United States but common globally. Adult worms live in the small intestine and can cause intestinal blockages. Pig and human ascarids, Ascaris suum and Ascaris lumbricoides, respectively, are indistinguishable morphologically. The role of Ascaris cross-transmission from pigs to humans is undetermined. In September 2012, Ascarisinfections were reported in two U.S.-born female apprentices working on an organic vegetable farm. We investigated to confirm the cases and determine whether cross-transmission had occurred.

METHODS:  We visited the farm, interviewed the apprentices, inspected pig-farming practices, and collected pooled pig feces and worms from pigs and one apprentice for analysis.

RESULTS:  Farm apprentices had direct daily contact with the farm’s 10 pigs, beginning May 2012, and had onset of nausea and malaise in September. Both women had excreted multiple worms and received anthelminthic treatment; only one apprentice provided a worm for testing. Farm pigs were treated with dewormer in July; however, the September pooled fecal sample contained Ascarisova, and when the 10 pigs were slaughtered in October worms were recovered from half of the pigs. Molecular speciation of the apprentice’s and pigs’ worms is pending.  Farm practices reflected industry standards. Dirt was noted on the apprentices’ hands, neither wore gloves during pig contact, and pig manure might have been used for vegetable compost.

CONCLUSIONS:  The timing of illness at this farm suggests that cross-transmission from pigs to humans probably occurred. To prevent further human Ascaris infections, we recommended better hand hygiene, excluding pig manure from compost, growing vegetables away from areas where pigs are penned, and thorough washing of vegetables possibly contaminated by Ascaris ova.