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'Itch Mites' are Mysterious Bug Bit Culprit

We have passed this article to several people concerned about mysterious itch

-- 'Itch Mites' are Mysterious Bug Bit Culprit
Sept. 20, 2004

LINCOLN, Neb. -- A tiny mite, aptly called an "itch mite," is responsible for the mysterious, itchy red bites reported by a number of eastern Nebraska residents recently, University of Nebraska entomologists say.

University entomologists worked with the Nebraska Department of Health and Human Services, Lincoln/Lancaster County Health Department, U.S. Department of Agriculture/Agricultural Research Service and entomologists from Kansas State University who are collaborating with the Centers for Disease Control and Prevention to identify the culprit, said David Keith, a university urban integrated pest management specialist.

The Pyemotes mite is preying on small fly maggots that cause the "leaf edge" galls on pin oak leaves, Keith said. The galls on pin oak leaves are unusually abundant this year and in many cases the maggots that caused the galls have matured and are emerging in the millions and dropping to the ground.

"These are harmless, but in examining empty galls, in which one or more maggots were killed, large numbers of the itch mites, a predator of the maggots, were found," the Institute of Agriculture and Natural Resources specialist said. "These microscopic mites, carried by the wind, are tiny enough to penetrate the mesh of a standard window screen and may be completely overlooked because of their very small size."

People sleeping with windows open could easily be bitten at night, giving the impression that something is infesting the bedroom.
"Every fall we seem to get complaints about insect and mite bites, but this year it is quite different," he said. "Although all the 'regulars' that we normally expect, such as cat fleas, pirate bugs, chiggers, mosquitoes and others are out there and doing their share, something else is involved this time."

The mites have been reported in several eastern Nebraska communities, but Lincoln seems to have been hardest hit. The mystery bites are being reported mostly by people who spend time outdoors, but also from others who remain indoors.

No one is seeing insects or associating them with these lesions, but several have reported they were working outdoors, and often standing in the shade of pin oak trees.

Keith recommends people keep windows closed and limit outdoor activity until the problem subsides, which should occur in the next seven to 10 days, he said.

"If you have to work outside, when you come back indoors, be sure to take a hot shower, lathering generously," he said.

Also, be sure to launder clothing after wearing -- "don't reuse yesterday's shirt," Keith said.

To reduce itching, apply calamine lotion, hydrocortisone cream or an antihistamine cream, such as Benadryl cream.

Also, wash the bites often with soap and use an antiseptic or antibiotic ointment to keep the wounds clean and promote healing.

"It's also important not to scratch," Keith said. "The bites are intensely itchy, but scratching provides little relief and actually causes pain and tenderness."

The bites don't hurt when they occur, but after a bite one or more red spots usually appears. The red spots vary in size from one-fourth to one inch in diameter. In the middle of the red spot is a small, raised "pimple" or blister, Keith said.

Most bites occur on the upper torso, abdomen, back and neck, shoulders and arms. With most people there are no apparent secondary effects, but some people have reported headache, fever, nausea or asthmatic symptoms.

Unlike chigger bites, these do not seem confined to ankles, feet, legs and the belt line, he said.

Some bites are quite small, but some may be as large as a quarter and each has a raised center which may take the form of a small watery blister.

The itch mite bites may occur in clusters, forming a rash which may last for several days.

Source: David Keith, Ph.D., Professor, UNL Dept. of Entomology, (402) 472-8918

Writer: Sandi S. Alswager, IANR News Service, (402) 472-3030

Images and Summary Information

Click each thumbnail for a larger image. 

Oak Leaf Margin Galls

In some areas of Nebraska and in the eastern Plains region, numerous pin oak trees have been infested with a gall gnat, Macrodiplosis sp. Pin oaks appear to be preferred, but infestations also occur in red oak. In the spring, adult female gnats deposit eggs on the edges of leaves. As the newly-hatched larvae (maggots) feed on the leaf tissue and continue to mature, hormonal secretions they produce cause the leaf edges to roll around them, thus protecting them from predaceous insects and extreme weather conditions. When the maggots mature in late summer (right image), they evacuate the galls, fall to the soil and pupate for the winter.  

Click each thumbnail for a larger image. 
"Itch Mites", Predators of Gall Gnat Larvae

One predaceous arthropod that has succeeded in preying upon the gall maggots is a mite in the genus Pyemotes. The species is yet to be determined. Able to easily invade the leaf margin galls because of its microscopic size, this mite has capitalized on this available food resource. The mites inject a highly-potent neurotoxic venom into their prey through their needle-like mouthparts and voraciously consume their prey. Adult females are unique among living animals in that they deposit their eggs into a pouch, or ovisac, formed at the tip of their abdomens. In this pouch, the food they consume nurtures their brood directly from the egg stage to adulthood (no nymphal stages). As many as 200-300 adults can develop in an ovisac! With a population doubling time of two days, Pyemotes mites can number in the millions in a short period of time. When numbers of the gall gnat larvae decline, either through predation or by evacuation from their galls, the hungry mites crawl about on foliage or bail out of the trees into wind currents to find other suitable hosts.  

Click each thumbnail for a larger image. 

Symptoms of Bites by "Itch Mites" 

Since late August, growing numbers of people in the urban areas of southeastern Nebraska have been complaining about bites mainly on the upper part of the body (neck, shoulders, arms and chest) that are intensely itchy. Initially a bite is characterized as a red patch that has a small blister in the center. Redness around the bite expands and becomes painful to the touch. Scratching breaks open the lesions, causes scabbing and invites secondary infections. More sensitive individuals have developed chills, fever, fatigue and nausea, or severe allergic skin reactions such as extreme itchiness and swelling.


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Best wishes to you Lo and your husband,

Best wishes,

George Manning

Consulting Entomologist
Chicago Pest Control and Exterminator
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