In case you need a break from all the discussion about H5N1 influenza and the multitude of species it now seems to be able to infect, there’s nothing like a good zoonotic parasite story to make your skin (or pants in this case) crawl. (I promise that this will be a normal-length blog post… ahem.)

There was a recent research letter in Emerging Infectious Diseases (Hobbs et al. 2024) that caught my eye – particularly because it includes a picture/video which you should definitely check out.  The letter was about the finding of a sizable – and motile – adult roundworm in the diaper of a 2-year-old girl in Mississippi (now that’s got to be uncomfortable…).  The worm was identified from the video taken by the child’s mother (before she disposed of both worm and diaper – can’t say I blame her) as Ascaris lumbricoides.  That may not sound terribly noteworthy, as A. lumbricoides is the primary species involved in human roundworm infections globally, but it is usually spread by ingestion of eggs from human feces in areas where the is very poor sanitary infrastructure (e.g.  where human feces are more likely to be found in the general environment due to “promiscuous defection”) – but not in a region like northern rural Mississippi, on a farm with two flush toilets.  However, pigs have a very closely related roundworm that was previously known as Ascaris suum, that was more recently determined to actually be the same species as the human roundworm, A. lumbricoides.  Ascariasis is not uncommon in some farmed pigs even in the US, particularly those raised outdoors. In this case, no one in the family had traveled outside the US, and there was no reason to suspect there was human fecal contamination in the environment, but there were pigs on the property.  The two young kids were also reported to occasionally eat dirt from house plants, which has to make one wonder if they may have eaten other “dirt” on the farm as well (along with some pig feces and the parasite eggs therein).  Unfortunately by the time the Department of Health conducted their field visit, the family’s pigs had all been sent to slaughter, so it was not possible to confirm that the pigs were carrying the same parasite, but the story all fits together (admittedly it would have been nice to have some more definitive proof).

Fortunately the child was treated promptly by her pediatrician, and did not expel any additional worms, and suffered no further ill effects.  A fecal sample collected within 24 hours was negative for any parasite eggs, so they suspect there was only one adult worm present (I’m sure finding that once in the girl’s diaper was quite enough!). 

One more reason not to eat poop (from any species!) and wash your hands and veggies (or at least do the best you can, if you’re two years old :p).