David R. Haburchak, MD, FACP


August 19, 2004


My patient is a young, married, unemployed woman. She came for evaluation because she "spat out worms" while brushing her teeth. The lab confirmed the "worm" to be an insect larva. Her CBC is normal except that her hemoglobin is 13.2 g/dL. Her stools were normal. Could this be pica? She recently called to say she spat out some more worms and is coming back for another office visit. How does one approach this case?

K.V., MD

Response from David R. Haburchak, MD, FACP

This patient's complaint should at least initially be taken at face value, since she at least produced a real "worm," as opposed to patients with delusional parasitosis, who usually bring in pieces of string, mucus, skin fragments, and other debris for inspection.[1] The laboratory has identified the "worm" as an insect larva, most likely of the 2-winged fly variety (Diptera). This variety is easily identified by their tubular, segmented shape, tapered end, and bristles at their segments.

The 2 most prevalent types of flies associated with domestic animals and pests, and therefore, humans, are the bot fly and blowfly, including horseflies. It would be interesting to get more epidemiologic history from the patient, such as exotic travel and exposure to animals, especially horses.

Human oral, nasal, and tracheopulmonary myiasis is uncommon, due to the need for flies to deposit eggs in the mouth or respiratory tract.[2] Most human cases have actually been nosocomial, secondary to flies depositing eggs in fetid nasal and oral secretions of comatose or demented patients unable to protect themselves. A dramatic recent outbreak occurred in an American intensive care unit when a mouse investigation was inappropriately handled. Mice were killed when poisoned bait was placed in the walls of the hospital building, thus producing ample food for green blowflies. The blowflies subsequently proliferated and laid eggs in 2 comatose patients.[3]

Horses can apparently ingest eggs of the bot fly Gasterophilus pecorum, which can invade the mouth without much host reaction.[4] These larvae can subsequently molt and move to the intestine, or conceivably, if the horse brushed its teeth, be spit out. I suppose pica could be a possible cause if the patient's habits included visits to pastures with horses.

I suspect that a more likely scenario would be the infestation of the patient's toothbrush or toothbrush holder with eggs deposited by houseflies or horseflies. A close inspection of the toothbrush or holder might be helpful. Of course, the patient should be thoroughly examined for any oral or nasal pathology.

This case reminds me of a patient I saw a few years ago with a complaint of "worms" in her toilet. Apart from mild anxiety, she was asymptomatic and had a normal physical exam. Inspection of the "worm" also revealed insect larvae. In her case, flies were depositing eggs while feeding in the toilet bowl. More vigorous cleaning of the toilet and better screens on the house solved the problem.

I would therefore examine the patient, obtain more history of the possibility of flies in the house, and replace her toothbrush as first steps in management of the patient. Should this problem persist, you might want to talk with her husband.