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Itchy chiggers coming to lifeTexas As spring temperatures rise, so do chiggers, up the legs of unsuspecting humans who serve as accidental hosts for the tiny parasites that can leave itchy welts, an expert says. But there are ways to avoid and treat the wrath of chiggers without avoiding the outdoors, said Dr. Boris Castro, a Texas Cooperative Extension entomologist in Weslaco. "Chiggers are not insects," Castro said. "They are mites, and when they are in the larval, or baby stage of their lives, they are parasitic. And humans are actually accidental hosts. Chiggers prefer rodents, birds, toads or livestock. But if a human happens along, in lawns or maybe hiking in tall weeds, they'll hop on a human leg for the ride." In their larval stage, chiggers crawl to the end of vegetation, including weeds and blades of grass, lying in wait for a host, Castro said. When a human walks by, they will latch on and crawl up the leg of their new host until they come to a fold in the skin or an area where clothes bind the skin. "They feel protected in these areas, which would be where the elastic of a sock or underwear binds the skin, or in folds of skin like behind the knee, in the crotch or in the armpit," he said. Once chiggers find their human resting place, they begin to do their damage. "Contrary to popular belief, chiggers do not burrow into the skin or suck blood," Castro said. "Instead, they insert their claw-like mouth parts into the skin and release a digestive enzyme in their saliva which actually liquefies the skin. The liquefied skin, enzyme and saliva then harden into a sort of feeding tube from which the chigger draws nutrients. They feed on the digested skin cell material." Left unmolested, the chigger, which is so small as to be invisible to the naked eye, will continue feeding for about three days. "Usually we'll scratch the chigger off, or knock it off while bathing, but the enzyme is left behind and that's what causes the allergic reaction, the itching and the red welts," Castro said. Medical treatment is not usually necessary unless the chigger bites are so numerous as to be alarming, or if the allergic reaction is severe, he said. "The effects of chiggers on the skin can be bothersome, but shouldn't keep people indoors," Castro said. "Instead, consider avoidance, protection and treatment." Avoidance would include keeping lawns mowed and vegetation trimmed since manicured lawns are less preferred by chiggers, Castro said. "Consider treating lawns with pesticides labeled for such use," he said. "Insecticide sprays, such as those containing bifenthrin, cyfluthrin, esfenvalerate or permethrin can reduce chigger populations. Use of hose-end spray applicators may be the best way to apply liquid insecticide sprays to large lawn areas. Make sure to follow label directions carefully when using insecticides, and pets should not be allowed in treated areas until the spray residue is dry. Retreat every three weeks as needed." Protection would include wearing boots outdoors and tucking pant cuffs into your socks to prevent entry. Also, spray your footwear, lower pant legs or exposed leg areas with mosquito repellant that contains DEET, and reapply every three hours. Using sulfur powder is an option, but that can be smelly, Castro advised. "And immediately after being outdoors, bathe or shower in warm water, scrubbing your skin with a wash cloth. Wash clothes in warm water separate from bed linens, and treat any chigger welts with a topical, over-the-counter itch relief cream that contains an antibacterial. It will take the body a week to 10 days to repair the skin damage. Scratching will open a wound that could provide opportunity for a secondary infection of some other bacteria," he said. Chiggers are not active in cool weather, but once temperatures warm up, eggs hatch and chiggers begin looking for hosts. In North Texas, chiggers may be a problem only for a couple of generations that last 40 to 70 days. But in South Texas where warm temperatures last longer, chiggers may be a problem for up to four generations, Castro said. "Chiggers are a nuisance more than anything, but with a few common sense steps, it's possible to minimize their effects without sacrificing outdoor activities," he said. ------CUTLINE------ 1.) Humans serve as accidental hosts of chiggers in their larval stage which leave red, itchy welts but do not burrow into the skin or feed on blood. (Texas Cooperative Extension Photo by Dr. Michael Merchant.) 2.) Chiggers are so small they are not visible to the naked eye. They have claw-like mouth parts that feed on human skin liquefied by an enzyme in chigger saliva. (Illustration by Centers for Disease Control.) Date: 5/3/07
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