AVMS

Mites that Bug People
 

MITES THAT "BUG" PEOPLE

On a world-wide basis, mites are important nuisance pests and some are capable of transmitting disease agents. Fortunately, the mites we commonly encounter in North Carolina do not transmit disease agents that affect people. The majority of mites are free- living, but thousands of species are parasites of animals and plants. Most of these are external parasites, but some species inhabit the ear canals, lungs, intestine and bladder of vertebrates, particularly domestic animals Their biting and bloodsucking behavior causes considerable discomfort to and a few species also cause serious allergic reactions, such as asthma, in people.

Mite Biology

Mites are not insects; they are more closely related to ticks and spiders. Most mites are visible to the unaided eye and usually measure 1/8" or less in length. Their life cycle has four basic stages: egg, larva, nymph and adult. The egg hatches into a larval stage, which is followed by two to three nymphal stages, then the adult. Mites, like ticks, have three pairs of legs as larvae and four pairs of legs as nymphs and adults. The life histories of some common mites associated with people are described in the rest of this document.

Scabies Mites

Sarcoptes scabiei, commonly known as the scabies, mange or itch mite, is a parasite of humans and other animals. Scabies mites are host-specific. The varieties of scabies that infest domestic animals can penetrate the skin of humans and cause the typical itching and rash, but they cannot complete their life cycles there. The adult female burrows into the outer layer of the skin (epidermis) where she feeds on tissue fluids and lays eggs that she cements to the floor of the burrow. Females lay eggs at a rate of up to 3 per day for a period of 8 weeks, producing about 200 eggs over her lifetime. These eggs hatch in 3-4 days and the newly-hatched larvae emerge from the burrows onto the surface of the skin and molt to form the first nymphal stage.

The rash and intense itching associated with scabies occurs when the nymphs burrow into the skin and begin feeding. These symptoms usually appear several weeks to a month after the initial infestation. The majority of mites are found in lesions in folds of skin between the fingers, on the sides of the feet, on the wrists and genitals, and in the bends of the knees and elbows. After feeding on tissue fluids, the nymphs molt to become adults. The life cycle, from egg to adult, can be completed in about two weeks. Scabies mites are readily transmitted within families and within institutions such as nursing homes. Personal contact, particularly holding or shaking the hands of an infested person, is a principal method by which the mites are spread. Intimate contact and sleeping with an infected person can also spread the mites.

Proper treatment and control of a scabies problem requires:

• Positive diagnosis of the problem by a physician. Scabies mites are extremely small; females measure about 1/60th inch. In the case of both scabies and straw itch mites, the rash or bites associated with these mites is the primary diagnostic characteristic.
• Application of an insecticide-containing prescription lotion to the body. Because there is time lag between the initial mite infestation and the appearance of symptoms, family members or people coming in close contact with infested persons may require treatment.
• Sanitation is extremely critical to successful control. An infested person's undergarments and bed linen should be washed regularly in hot, soapy water.
  NOTE: Human scabies mites cannot survive off a host for more than about 24 hours. Therefore, insecticide foggers ("bug bombs") and sprays do not help eliminate the problem.

Chigger (Red Bug)

Eutombicula alfreddugesi are very small, reddish mites that feed,only in the larval stage, on humans and other animals, particularly rodents. The red color of the larvae is not blood but a natural red pigment. On animals, chigger larvae remain attached to the skin for several days but on humans, they are usually dislodged within several hours of attachment. Unlike scabies mites, chiggers do not burrow into the skin. They feed at the base of a hair follicle or in a pore. Chiggers generally attach to those areas of the body where clothing fits tightly, such as at the sock line and waistline. Larvae ingest lymph and partially digested cells after the chigger attaches. The bites commonly cause itching in about 3 to 6 hours and dermatitis develops in about 10 to 16 hours. Some people experience allergic reactions to the bites and develop blister-like lesions. Chiggers do not transmit any disease agents to people. The adults and nymphs are free-living predators of insects. In the South, chiggers are active virtually year round. They are commonly encountered at the woodland borders, along the periphery of swamps, and in shrub thickets and unmowed areas of lawn. Areas that contain thick layers of pine straw, leaf litter or thatch are suitable habitats for chiggers and their prey. Treating chigger-infested areas with a pesticidal spray will provide some control. Ground cover in these areas should be wetted down to the soil surface. Excessive treatments that can lead to pesticidal runoff into creeks and streams should be avoided. For personal protection, apply insect repellent to clothing and exposed skin. Repellents should be used in moderation by children and pregnant women. For more information about repellents, see

Straw Itch Mites

Pyemotes tritici commonly breed in stored grain, dried beans and peas, wheat straw, hay and other dried grasses . They are actually beneficial because they parasitize insects that feed on stored grain and similar materials. People who handle mite-infested materials will be attacked. The bites of straw itch mites are characteristically found on the trunk of the body.

The best control strategy is to eliminate the mite's host insects. Surface sprays of malathion may be used in some storage areas. If necessary, stored commodities can be fumigated to disinfest them. Fumigation should be performed by persons holding the appropriate state pesticide applicator's license or certification.

Bird Mites

Ornithonyssus sylviarum, the northern fowl mite (NFM), is a common pest of domestic fowl, pigeons, starlings, house sparrows and other wild birds commonly associated with people. Mite populations build up rapidly and a generation can be completed in 5 to 12 days. Several generations occur each year. Northern fowl mite spends virtually its entire life on the host bird. It can survive off a host for about a week or so. Mites that fall off host birds may be found wandering indoors. In poultry houses, they are sometimes found in the litter or on eggs, crates and cages.

Dermanyssus gallinae, the chicken mite (or red mite of poultry), is similar to the fowl mite in its host preferences. Unlike NFM, the chicken mite spends much of its time off the host bird, hiding in cracks and crevices during the day and feeding at night. They can survive for extended periods (as much as 8 months) off a host. It can be a serious problem to workers who handle birds. Around residences and other structures, mite problems tend to be more sporadic. Bird nests are often located in chimneys and tucked under eaves or window-mounted air conditioners. In the spring, nestling birds may be parasitized by thousands of mites. When the nestlings mature and leave their nest, large numbers of mites may invade buildings in search of alternate hosts.

In some areas of the state, bird mite problems may continue year round because hosts, such as pigeons, are constantly present. The key to reducing bird mite problems is to prevent the birds from nesting on structures and to remove abandoned nests quickly. Mites that find their way indoors are easily removed by vacuuming or can be killed with an aerosol insecticide.

House Dust Mites

Dermatophagoides pteronyssinus and D. farinae are the most common species of house dust mites. These tiny mites are most abundant in warm, humid areas. Contrary to popular belief, house dust mites do not bite or sting. They feed on shed human skin scales that collect in the dust on furniture, particularly mattresses, and on carpeting below beds. House dust mites are important medically because they produce allergens in their secretions and excrement. Inhalation of dust containing mite feces and cast skins is a common cause of asthma in young children.

Only one insecticide (Acarasan®) is registered for use against house dust mites. Its use should be considered only for severe infestations. The real solution to reducing a house dust mite problem is sanitation:

• Vacuuming frequently and thoroughly will remove mites and the organic debris on which they feed. Target critical areas, such as:
  • mattresses and bed frames
  • rugs and carpets (especially under beds)
  • overstuffed furniture (and the area underneath)

• Routine maintenance of air conditioner filters and lowering humidity indoors will reduce conditions that favor to mite growth.
• Encasing mattresses and pillows in plastic covers and frequent changing of bed linen also help prevent mite populations from building up.

Clover Mites

Bryobia praetiosa is a small (1/32") mite easily recognized because of its reddish-brown color and long pair of front legs. Clover mites do not bite. They are a nuisance because large numbers of them often invade homes. Hot dry weather in the summer will cause clover mites to migrate indoors. In the fall, the mites may also migrate indoors seeking shelter from low winter temperatures. In attempting to remove the mites, homeowners often crush them, leaving red stains on furniture and drapes. Mite invasions are most common from vigorously-growing lawns and other vegetation surrounding homes, especially if shrubs are close to or touching the walls.

A simple, non-chemical control method involves leaving a strip (12-18 ") of bare soil around foundation walls. This plant-free zone discourages mites from migrating onto the walls and provides an area that is easily treated if needed. If mites become a problem, application of a miticide to nearby foliage and lawns may help. Insecticides applied to foundation walls, door thresholds and window ledges make an excellent barrier. Indoors, the mites are easily killed with aerosol insecticide sprays, but vacuuming is a preferable alternative. Dursban®, diazinon and malathion are examples of pesticides currenly labeled for such use. Read the pesticide label carefully and select products appropriate for use indoors or outdoors as needed.

"Paper Mites" and "Cable Mites"

Complaints about bites and rashes for which a cause can not be found are often attributed to these fictitious pests. Although mites are extremely small, they are usually detectable with the unaided eye. In the case of scabies and straw itch mites, the rash or bites that these mites leave allows them to be readily identified as the cause of the problem. Cable and paper mites are often used as reasons to justify pesticide treatments in dwellings. Pesticide applications made without first identifying a target pest are usually ineffective and repeated applications are potentially hazardous. The cause of a problem should be identified before resorting to pesticide sprays.

Relieving the Itch of Mite Bites

When mites attach to skin, the saliva they secrete causes the intense itch that may be felt for several days after the mite is no longer attached. As soon as possible after walking through chigger-infested areas or being exposed to other mites, you should bathe in hot, soapy water and scrub down with a wash cloth. Oral antihistamines and the application of a hydrocortisone cream to bites may help to relieve itching. If a severe reaction develops then consult your physician.

 

Prepared by
Charles S. Apperson and Michael Waldvogel
Entomology Extension Specialists

References used in preparing this publication:

Axtell, R. C., and J. J. Arends. 1990. Ecology and management of arthropod pests of poultry. Annual Review of Entomology. 35: 101-126.

Fine, Robert M., and Harold G. Scott. 1965. Straw itch mite dermatitis caused by Pyemotes ventricosus: comparative aspects. Journal of the Southern Medical Association. Vol. 58, No. 4., pages 416-420.

Goddard, Jerome. 1993. Physician's Guide to Arthropods of Medical Importance. CRC Press.

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2008 Alabama Vector Management Society
Last modified: 02/04/08