WEDNESDAY, Dec. 19 (HealthDay News) -- Although Santa's reindeer deliver presents to kids around the world on Christmas Eve, they can also harbor fly larvae that cause skin problems and rare eye infections, so it might be best if your children stay tucked in their beds on the night of Dec. 24.
So suggests a case report by a Swedish infectious disease expert, published in the Dec. 20 issue of the New England Journal of Medicine.
A bumblebee-like fly -- Hypoderma tarandi -- attaches its eggs onto the hair of reindeer, also known as caribou. When the larvae hatch, they penetrate the skin, causing large bumps that can appear as long as three months after exposure, said Dr. Boris Kan, with Karolinska University Hospital, in Stockholm.
In rare cases, the infestations can develop in children's eyes, creating firm nodules that are likely caused by an immune reaction against dead larvae. When an eye is affected, surgery can be required and vision can be lost, according to the report.
The problem, broadly called myiasis, involves the infestation in the body of fly larvae that actually feed on the tissue.
Infestations among reindeer in Alaska, the Canadian Arctic and Greenland are common, and have also been found in muskoxen in Alaska and northern Quebec, Kan noted.
Kan said it's difficult to say how common the problem really is. "The Lapps of northern parts of Scandinavia, where reindeer are abundant, are not known to be frequent visitors to health care facilities," he explained. "And there is little knowledge about this fly among doctors and the public."
For example, one of Kan's patients had to visit about 10 physicians before his persistent mother sent tiny eggs she found in her son's scalp to an entomologist in Uppsala, Sweden. She was convinced the physicians' diagnosis of lice was wrong. The entomologist identified the parasites as H. tarandi, and the child was then treated with ivermectin (Stromectol), a broad-spectrum anti-parasitic medication.
Dr. Jean Tang, an assistant professor of dermatology at Stanford University, in Palo Alto, Calif., highlighted the importance of informing physicians of any exposure children or adults may have had to animals, including reindeer.
"If there's a rash, remember to tell the physician about any contact with animals," she said. "It's easy to forget that you've been doing something unusual."
Tang also emphasized the importance of monitoring the problem and going back to the physician if the prescribed treatment does not work. "Kids are more susceptible to rashes, and most will improve in a few weeks to a month. If they don't, keep on going back to the doctor," she advised.
Kan said it's also important to report your travel history to your physician if you end up with an unusual skin problem. "One should also know that you don't have to be close to animals -- and many of them don't want to get close to you -- but one can just be in the area where reindeers come about."
Kan said that since larval invasion starts with eggs deposited by flies in the back of one's head, wearing a baseball cap when you're around reindeer might also be a good idea.
As for Santa and his elves and all the time they spend with reindeer, there is no need to worry. After all, they typically wear tight-fitting caps.
Learn more about parasites and myiasis from the U.S. Centers for Disease Control and Prevention.