A 32-year-old woman who visited a rural area outside of Moscow returned home with a surprising stowaway—in her face. And it was a restless one at that, according to a short report published this week in the New England Journal of Medicine (NEJM).
After her trip, she noticed an unusual lump on her cheek, below her left eye. Five days later it was gone, but another had formed just above her left eye. Ten days after that, a lump resurfaced on her upper lip, causing massive swelling.
To track the progress of her roving blemish, she took selfies. In reports to doctors, she said that the nodules caused some burning and itchiness but no other symptoms or problems. She also noted her recent trip and recalled being frequently bitten by mosquitoes.
The first nodule, under the left eye. Kartashev and Simon The nodule moved above the left eye. Kartashev and Simon The nodule later reappeared on the upper lip. Kartashev and Simon Doctors were able to extract the worm, a D. repens. Kartashev and Simon The life cycle: During a blood meal, an infected mosquito introduces larvae of Dirofilaria repens onto the skin of the canine definitive host (but also occasionally humans, especially in Europe), where they penetrate into the bite wound 1. In the definitive host, the larvae undergo two more molts into adults, which reside in subcutaneous tissues 2. Adult females are usually 100-170 mm long by 460-650 µm wide; males are usually 50-70 mm long by 370-450 µm wide. Adults can live for 5–10 years. In subcutaneous tissue, the female worms are capable of producing microfilariae in peripheral blood 3. A mosquito ingests the microfilariae during a blood meal 4-7. After ingestion, the microfilariae develop in the mosquitos midgut and 8. can infect another definitive host when the mosquito takes a blood meal 9. In humnans, D. repens usually manifests as either a wandering worm in the subcutaneous tissue or a granulomatous nodule, although there are reports of pulmonary dirofilariasis with this species. CDC
Doctors determined that the wandering wart was actually a marauding parasite, likely transmitted by a mosquito bite on her trip. Using forceps, they pinned it down and surgically removed the long, thin, yellowish stowaway. Subsequent genetic tests identified the worm as a Dirofilaria repens.
D. repens are parasitic worms that primarily prey on dogs and other carnivores and move around via mosquitoes—they only infect humans by accident. They tend to be found in parts of Europe, Asia, and Africa, where theyve been known to grow up to 170 millimeters long and live up to 10 years. The Centers for Disease Control and Prevention reports that D. repens are not found in the US, but the country does harbor relatives D. immitis, which cause heartworm disease in dogs, and D. tenuis, which affect raccoons.
In their preferred canine host, D. repens dwell in tissue under the skin, and the females release larvae into the blood stream. Those larvae then get picked up by biting mosquitoes, which incubate the mini mooches before transferring them to new hosts at their next blood meal. In humans, D. repens are caught crawling under the skin by victims noticing shifting subcutaneous nodules, as did the woman in the case report. Doctors sometimes call this “creeping eruption.” In rare cases, the worms can squirm into organs, such as lungs, breasts, male genitalia, and eyes.
The lead author of the report in NEJM, Vladimir Kartashev, an infectious disease expert at Rostov State Medical University in Rostov-na-Donu, Russia, told The Washington Post in an email that D. repens is an “emerging disease” in the western part of the former Soviet Union and certain parts of Europe. Since 1997, he said that there have been more than 4,000 cases in the region, particularly in Russia and Ukraine.
Luckily, the worms are easy to remove and, once yanked out, cause no lasting problems. The woman in the case in NEJM reportedly made a full recovery.
NEJM, 2018. DOI: 10.1056/NEJMicm1716138 (About DOIs).
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