Prepare for the bite of the itch mite

Itch mites grabbed public attention in 2004 after an outbreak of bites from the tiny parasites befell several members of the Pittsburgh State University and Western State College of Colorado football teams.

The two teams were having a picnic in a park on campus in Pittsburgh, Kan., when some of the players were bitten by itch mites.

It wasn’t long before Pittsburgh residents found themselves suffering from mite bites.

Soon after the Pittsburgh State outbreak, itch mites were affecting residents of Manhattan, Kan.; Lincoln, Neb.; and the Missouri cities of Joplin and St. Louis.

MU entomologist Richard Houseman said the type of itch mite that caused the bites was not recognized in the United States before 2004. There were other cases in the previous 10 years that were suspected to be itch mites but were not confirmed. Most of the reported itch-mites calls that Houseman received since 2004 were from western Missouri and eastern Kansas, he said.

Itch mites were particularly active last year in Columbia and other parts of Missouri.

“Last summer, we received a lot of calls from people complaining about itch mites,” said John George, an entomologist for the Missouri Department of Conservation. People often confuse an itch-mite bite for a chigger bite. Chiggers tend to attack people on the lower legs and along the belt line, where clothing is tight against the body, while bites from itch mites usually appear on the shoulders and neck, which reflects the fact that itch mites fall from pin oak trees, Houseman said. Most people are bitten while standing under pin oak trees or raking leaves in the fall.

The bites look different, too. “A chigger bite would get a hard cap on it; if you scratch, it oozes a clear liquid,” Houseman said, adding that itch-mite bites do not ooze any fluid. After an itch mite bite, “what’s left on your skin are many local swellings that look like an itchy rash,” Houseman said.

Some people get a fever if they’re allergic to itch mites or get a lot of bites, Houseman said. For treatment, entomologists advise using calamine lotion, an antihistamine cream, such as Benadryl, or a hydrocortisone cream.

“A change of clothing and a hot, soapy shower after working outdoors, especially around oak trees, should help reduce the incidence of bites,” Broce said. Entomologists also advise using a DEET repellent when working under pin oak trees.

Alberto Broce, a Kansas State University entomologist, said the initial mite bites do not cause pain. Most victims are unaware that they have been bitten until the next day, when quarter-sized reddened welts appear with a pimple in the center.

Houseman said he thinks itch mites attracted so much attention in 2004 because their numbers increased. This was probably the result of an increased number of gall midges, the insects on which itch mites typically feed.

“Probably the rapid build-up of this prey population happened over years and the number of itch mites just followed and became so numerous that they started ending up on people,” he said. After that, an increased number of reports might have been the result of entomologists’ increased awareness of itch mites, he said.

Before they mate and find a host, the parasitic itch mites have a cigar-shaped body and measure a mere hundredth of an inch. But once they mate and find an insect host, they grow to one-twentieth of an inch and become visible. “They look like a perfectly round ball, with legs and head sticking out,” Houseman said. “Kind of like a pumpkin.”

Itch mites cannot feed on human blood and end up on people when they fall from oak trees or get carried by the wind.

“When they’re searching for an insect host, they’ll taste anything they get on,” Houseman said, by sticking their mouth part into human skin to see whether it’s the host they’re looking for. “When they discover we’re not, they don’t keep feeding on us,” Houseman said.

Jim Kalisch, an entomologist from the University of Nebraska at Lincoln, said itch mites are arthropods that prey on the larvae of the gall midge, a small fly that causes “leaf edge” galls in pin oak trees. Fully developed midge larvae, or maggots, begin to fall from leaf galls from late August through mid-September — and the itch mites fall with them.

“Most of the mites disperse in the evening, when there’s more humidity and temperatures are moderate,” Kalisch said.

The number of itch mites that end up on people reaches its peak in October and November, Kalisch said, and many people get bitten while raking leaves in the fall. In an experiment performed at the University of Nebraska last October, entomologists caught an estimated 250,000 itch mites in one day on sticky traps.

Robert Hall, former head of the Entomology Department at MU, said itch mites are particularly resistant to temperature changes because they primarily depend on the insulation level of their host. “As long as your host is alive, you’re going to be OK. When your host dies, you’ve had it. So outside temperatures shouldn’t have much of an impact.”

Entomologists don’t know for certain how itch mites survive the winter, Broce said. Like MU’s Houseman, Broce suspects the mites find protected areas on soil and grass where it’s warm. As an itch mite, “all you have to do is crawl from one warm-blooded host to another,” Hall said, explaining why cold weather and temperature changes don’t have a major effect on the number of itch mites from year to year.

“It’s a big mystery for us where they overwinter,” Kalisch said.

Kalisch said Nebraska entomologists are performing insecticide trials that are designed to kill the gall midges that emerge in mid-April. Several formulations of insecticides are being applied onto lawns of cooperators in a Lincoln, Neb., neighborhood that has been plagued by mite bites for three years.

“We are trying to eliminate the source of food for itch mites,” he said. “The most convenient goal is targeting adult midges in spring to greatly reduce galls, and then pray we won’t have that many itch mites in the summer.”