Give Chiggers the Brush

Enlarge Image Image Gallery Don't let these nasty little bugs make you a prisoner in your home. COURTESY NATIONAL CHIGGER COLLECTION

It’s summer again, the season when chiggers make cowards of us all. Wouldn’t it be great to skip through fields of wildflowers and roll around in cool grass like the people in allergy medicine commercials do? Anyone that reckless either doesn’t get out much or is too young to know better. Call the rest of us “once bitten, twice shy” because meadows and lush grass often are guarded by chiggers — tiny “red bugs” that leave small and terribly itchy wounds on human hosts in the most delicate and unmentionable places.

Ounce for ounce, the almost-microscopic chigger may cause more irritation than any other critter. Yet contrary to popular belief, chiggers don’t suck blood or burrow under the skin. They eat skin cells, which they dissolve with digestive enzymes. The human immune system defends bitten areas by forming a hard wall of cells, called a stylostome. Conveniently for the chigger, these stylostomes double as strawlike feeding tubes. And there’s the rub — and the scratch — it’s your own immune system’s response that causes the intense itching.

Undercover Chiggers

Chiggers are not true insects — they actually are immature mites — though they do scamper around on six legs in their troublesome larval stage. Like their parasitic tick cousins, chigger larvae attach themselves to hosts to feed by inserting minute mouthparts into skin, usually at hair follicles. Chiggers are found worldwide. In the United States, they are most common in the Southeast and Midwest because they thrive in humid weather amid thick vegetation.

Science seldom turns its microscope on chiggers because, as annoying as they may be, chiggers don’t destroy crops or otherwise cause catastrophes worthy of big research bucks. But the U.S. Army considers chiggers enemies well worth studying. Servicemen in World War II never knew they had been bitten until they came down with scrub typhus, a disease covertly spread by tropical Asian chiggers that causes fever, headaches and swollen lymph glands. Bill Wildman, an environmental health officer at Irwin Army Community Hospital in Fort Riley, Kan., notes the species found in North America do not spread diseases.

Humans are accidental victims of chiggers because most of these mites evolved to feed on reptiles and birds, says M. Lee Goff, curator of the National Chigger Collection, housed at the University of Hawaii at Manoa. He and his predecessors have accumulated about 25,000 specimens representing 1,800 identified chigger species. Goff, who also is the forensics science program chairman at Chaminade University in Hawaii, says chigger species in Southeast Asia evolved to feed on mammals and can spread disease because the human immune system does not reject their enzymes and the chigger bites don’t itch.