A plague of tiny-yet-highly-annoying itch mites is sweeping across the state of Illinois as thousands of the microscopic arachnids gorge themselves on eggs left by a historic cicada emergence.
This year's cicada boom, an event triggered by the rare synchronization of two distinct broods—one that surfaces every 13 years and another every 17 years—brought billions of the large, hummingbird-sized insects to the eastern United States. Such an event happens only once every 221 years.
And although most of the cicadas have now died, the eggs they have left behind are harboring oak leaf itch mites, leading to a spate of rashes across the area.
The mites are less than half a millimeter in length and imperceptible to the human eye. Yet their presence is felt by anyone unfortunate enough to find themselves in the midst of the mites, which are small enough to be carried on the wind.
"The mites do not take blood," Jennifer Rydzewski, an ecologist at the Forest Preserve District of DuPage County, told Newsweek. Instead, she explained, "They inject saliva into the top layer of skin and slurp up the liquid.
"The resulting inflammatory response to the mite bites can develop into small, blister-like bumps with large red circles around them that can resemble a skin rash, typically on the upper torso."
The phenomenon of itch mite outbreaks in the U.S. is not new. The mites were first documented in 2004, with over 19,000 cases of rashes reported in Kansas alone, according to urban entomologist Steven Jacobs in an article for Penn State.
Since then, the pests have spread to other states, including Illinois, Missouri, Nebraska, Ohio, Oklahoma, Pennsylvania, Tennessee and Texas.
Subsequent investigations revealed that the mites had been feeding on the larvae of oak gall midges—hence the name oak leaf itch mite—a type of fly that lays eggs on oak trees, before turning to humans as their food supply dwindled.
Following an earlier outbreak in 2007, the Illinois Department of Public Health confirmed that while oak leaf itch mites primarily feed on oak gall midges, they are opportunistic predators capable of preying on a wide range of insects.
"The oak leaf itch mite has also been reported [in] stored products and grains where they feed on various stored products pests and from the galleries of wood boring beetles in the families Scolytidae and Anobiidae," Jacobs wrote.
When their populations surge and their food sources are exhausted, they turn to biting humans.
"During the last Chicago-area periodical cicada emergence in 2007, there was a spike in area residents reporting itchy welts due to increased itch mite populations," Rydzewski said.
Victims of oak leaf itch mite bites typically develop an itchy rash characterized by small, raised, pimple-like bumps. These red welts appear 10 to 16 hours after exposure and can persist for up to two weeks.
"Other signs can include localized redness, swelling, itching and pain," Rydzewski said, adding that, "fortunately, the mites cannot live on humans, do not survive indoors, and are not known to transmit disease."
In order to prevent being mauled by the mites, Rydzewski recommends using insect repellents, avoiding oak trees if possible, wearing clothing that covers as much skin as possible, showering after exposure to wooded areas and keeping windows closed if you live in an area with high mite populations.
For relieving symptoms, she suggests washing the area with soapy water, applying ice to reduce swelling, avoiding scratching where possible to prevent secondary infection, applying recommended topical products and taking oral antihistamines.
"One additional idea I'll add is that fogging or spraying with pesticides is not an effective way to get rid of the itch mites, and it could harm many more beneficial invertebrate species," Rydzewski said.
"By October, when the weather cools, the populations should decrease."
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