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Itch Mites Associated with Gall Insects

October 20, 2004

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, although we have not heard of it occurring in Illinois.

The Pyemotes mite is preying on small fly maggots that cause the “leaf edge” galls on pin oak leaves. 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.

Although the galls are harmless, 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. 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. Bites of this type are usually caused by fleas, pirate bugs, chiggers, and mosquitoes; but this year, itch mites are also involved.

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

Nebraska authorities are recommending that people keep windows closed and limit outdoor activity until the problem subsides, which should occur in the next 7 to 10 days. After working outside, it is recommended to take a hot shower, lathering generously. Also, be sure to launder clothing after wearing and not wear the same clothing for more than one day.

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. Avoid scratching the intensely itchy bites because 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 appear. The red spots vary in size from 1/4 to 1 inch in diameter. In the middle of the red spot is a small, raised “pimple” or blister. The itch mite bites may occur in clusters, forming a rash that may last for several days. 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, the bites are not confined to ankles, feet, legs and the belt line.

Author: Phil Nixon David Keith, University of Nebraska


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