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Chiggers

Common Name Scientific Name

Chigger Trombicula alfreddugesi (Oudemans)

Jigger

Red Bug

Probably no creature on earth can cause as much torment for its size than thetiny chigger. Tiny six-legged chigger larvae attack campers, picnickers,hikers, bird watchers, berry pickers, fishermen, soldiers, and homeowners in

low, damp areas where vegetation is rank such as woodlands, berry patches,orchards, along lakes and streams, and even in drier places where vegetationis low such as lawns, golf courses, and parks. They are most numerous in earlysummer when grass, weeds and other vegetation are heaviest. Chiggers do notburrow into the skin, but insert their mouthparts in a skin bore or hairfollicle. Their bites produce small, reddish welts on the skin accompanied byintense itching as irritating as acute cases of poison ivory or poison sumac.These symptoms often are the only way of learning that anoutdoor area is infested since chiggers are so small that most cannot be seenwithout a magnifying glass. Chiggers feed on a wide variety of snakes,turtles, birds, and small mammals as well as humans.

Identification

Chigger mites are about 1/20 inch long, usually bright red, have hairybodies, and travel rapidly. The larval stage has three pairs of legs whereasthe nymph and adult stage have four pairs of legs. There is a markedconstriction in the front part of the body in the nymph and adult stage.Larvae are orange, yellow or light red and about 1/150 to 1/120 inch indiameter. Eggs are globular-shaped.

Life Cycle and Habits

Adult chiggers overwinter near or slightly below the soil and in otherprotected places. Females become active in the spring and lay up to 15 eggsper day in vegetation when soil temperatures are 60F. Eggs hatch into six-legged larvae, the only stage that attacks humans and animals (parasiticstage). After hatching, chigger larvae climb up onto vegetation from which

they can more readily snag a passing host. After engorgement, often requiringone to several days, larvae drop off the host and transform into eight-leggednymphs which mature to the adult stage. Nymphs and adults feed on eggs ofspringtails, isopods, and mosquitoes. The life cycle is about 50 to 70 days,with adult females living up to one year and producing offspring during thistime. Multiple generations occur in warmer climates, whereas only two to threedevelop each season in some northern states. Chiggers areusually encountered in late spring and summer in areas where weeds andbriars have overgrown. They lurk on grass stems, leaves, shrubbery,etc.,usually in damp, shaded spots near the top of different objects close tothe soil. Young chiggers attach themselves to the skin of people, domesticanimals, wild animals (including reptiles), poultry and birds. The preferredfeeding locations on people are parts of the body where clothing fits tightly

over the skin such as around the belt line, waistline, under girdles and undersocks, or where the flesh is thin, tender or wrinkled such as the ankles, inthe armpits, back of the knees, in front of the elbow, or in the groin.

Bites

Chigger larvae do not burrow into the skin, nor suck blood. They pierce theskin and inject into the host a salivary secretion containing powerful,digestive enzymes that break down skin cells that are ingested (tissues becomeliquefied and sucked up). Also, this digestive fluid causes surroundingtissues to harden, forming a straw-like feeding tube of hardened flesh(stylostome) from which further, partially-digested skin cells may be suckedout. After a larva is fully fed in four days, it drops from the host, leaving

a red welt with a white, hard central area on the skin that itches severelyand may later develop into dermatitis. Any welts, swelling, itching, or feverwill usually develop three to six hours after exposure andmay continue a week or longer. If nothing is done to relieve itching,

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symptoms may continue a week or more. Scratching a bite may break the skin,resulting in secondary infections. However, chiggers are not known to transmitany disease in this country.

Control Measures

Skin Care After returning from a chigger-infested area, launder the fieldclothes in soapy, hot water (125F.) for about half an hour. Infested clothesshould not be worn again until they are properly laundered and/or exposed tohot sunshine. Unlaundered clothes or those laundered in cool water will

contain the biting chiggers to again reinfest your skin. As soon as possible,take a good hot bath or shower and soap repeatedly. The chiggers may bedislodged,but you will still have the stylostomes, causing the severe itch. Scratchingdeep to remove stylostomes can cause secondary infections. For temporaryrelief of itching, apply ointments of benzocaine, hydrocortisone, calaminelotion, New Skin, After Bite, or others recommended by your pharmacist ormedical doctor. Some use Vaseline, cold cream, baby oil, or fingernail polish.(The sooner the treatment, the better the results.)

Prevention

Mowing of briars, weeds, and thick vegetation and close clipping of lawns,toeliminate shade and moisture, will reduce chigger populations, and permit

sunlight and air to circulate freely. Chigger larvae can penetrate many typesof clothing, but high boots and trousers of tightly woven fabric tucked intostockings or boots help deter them.

Before going into an area where chiggers may be present, protect yourself byusing a repellent such as deet (Off MGK, Muskol, Detamide, Metadelphene,Repel, Diethy-toluamide) or permethrin available at many drugstores orhardware stores. Deet-based repellents are effective for only a few hours,whereas permethrin-based repellents are for use only on clothing and effectivefor several days. Apply the repellent to both the skin and clothing,especially on hands, arms, or legs, if uncovered, and to clothing openings atcuffs, neck, waistband, and upper edges of socks. Follow label directionssince repellents may damage plastics, nail polish, and painted or varnished

surfaces. Do not use indiscriminately as severe human allergies can develop.Keep moving since the worst chigger infestations occur when sitting or layingdown in a sunny spot at midday with temperatures above60F. If possible, stick to roads and trails.

Insecticides

Treating known chigger trouble spots is quicker and less expensive thantreating an entire area. Place six-inch squares of black cardboard on edge inthe grass and observe for a few minutes. Any small, yellowish or pinkishchiggers present will climb rapidly to the top of the square and congregatethere. Make tests in 10 to 12 different spots such as grass, dead leaves,briars, weeds, etc. Unless the entire area is infested, treat only the spotswhere control is desired such as grass around picnic tables, lawn chairs, or

recreational equipment. Chiggers tend to concentrate in "mite islands" whilenearby spots are free of them. They become rather inactive at temperaturesbelow 60F.

Outdoor sprays of chlorpyrifos (Dursban), carbaryl (Sevin) or diazinon willgive control. Only the licensed pest control operator or applicator can usecertain formulations of propoxur (Baygon), cyfluthrin (Tempo), or fluvalinate(Marvik, Yardex). Treat the grass, shrubs, and trees in lawns, parks,campgrounds and golf courses, if needed, keeping humans and pets off treatedareas until dry. Retreatment may be needed after two to three weeks in heavychigger infestations. Before using any pesticide, always read thelabel and follow directions and safety precautions. Do not wear dog or catflea collars on your ankles or cattle ear tags on your shoes to ward off

chiggers. It is very dangerous resulting in chemicalskin burns and toxic effect to the wearers.