On a world-wide basis, mites are important nuisance pests and some are capable of transmitting disease agents. Fortunately, the mites that 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 or plants. Most of these are external parasites (i..e., they feed on the exterior of their hosts), 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 their hosts and a few species also cause serious allergic reactions, such as asthma, in people. Because of their relatively small size, mites are often the "suspects" of a whole range of biting/itching problems. Understanding mite biology and the symptoms associated with mite infestations can help determine if they are the actual cause of a particular problem.
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 inch or less in length. Their life cycle has four basic stages: egg, larva, nymph and adult. The egg hatches into a larval stage, which molts to the nymphal stage. After 1-2 more times, the nymph matures into an 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 below.
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 1⁄60 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 as well. Follow the directions for using these products carefully. Overuse of these lotions can cause skin reactions or sensitivity.
- 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 to furniture, carpeting or other areas do not help eliminate the problem and are unnecessary.
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 pesticide spray will provide some control. Ground cover in these areas should be wetted down to the soil surface. Avoid excess treatments that can lead to pesticide runoff into creeks, streams and storm sewers. For personal protection, use insect repellents. DEET or Permanone (permethrin) can be applied to clothing. DEET is appropriate to use on exposed skin. Repellents should be used in moderation by children and pregnant women. For more information about repellents, see Insect Repellent Prodcuts.
Note: Another red-colored mite often seen in the springtime and mistaken for a chigger is the clover mite which is a plant and nuisance pest (see below).
Pyemotes tritici commonly breed in stored grain, dried beans and peas, wheat straw, hay and other dried grasses. They are frequently a problem for people doing landscaping or feeding horses and other livestock. The mites are actually beneficial because they attack 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 and on the arms.
The best control strategy is to eliminate the mite's host insects. If possible, clean storage areas thoroughly and treat it with a pesticide, such as cyfluthrin. Treating the straw is difficult because the mites are inside the bales as well as on the surface and there is no way to treat the entire bale. Additionally, there are no insecticidal sprays labeled in North Carolina for application to hay that is use used as feed for animals. If necessary, stored commodities can be fumigated with Phostoxin® to disinfest them. Fumigation should be performed by persons holding the appropriate North Carolina F-phase structural pest control license or certification AND (more importantly) has the training to handle these products safely.
The northern fowl mite (NFM),Ornithonyssus sylviarum, 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 mites spend virtually their entire life on the host bird. They 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, 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. Mites that find their way indoors are easily removed by vacuuming or can be killed with an aerosol insecticide. The key to reducing bird mite problems is to prevent the birds from nesting on/in structures and to remove abandoned nests quickly. Although pigeons, starlings and sparrows can be removed readily, birds such as chimney swifts are protected under the 1918 Federal Migratory Bird Treaty Act and cannot be disturbed. The best approach is to install a screened chimney cap in the early spring or fall when the birds are not nesting.
Dermatophagoides pteronyssinus and D. farinae are the most common species of house dust mites in North Carolina. These tiny mites are most abundant in warm, humid areas. House dust mites do not bite or sting, but they may cause a skin reaction. They feed on "dander," shed human skin scales that collect in the dust on furniture, particularly mattresses and on carpeting below beds, couches, and chairs where people spend significant time. House dust mites are important medically because they produce allergens in their secretions and excrement. Inhaling airborne house dust containing mite feces and cast skins is a common cause of asthma in young children.
Products containing benzoyl benzoate and other ingredients are often used for severe infestations of house dust mites. Since dust mites can cause respiratory problems, avoid using insecticides that may further aggravate such conditions. The long-term solution to reducing a house dust mite problem is sanitation and environmental modifications:
- Vacuum (possibly with a HEPA-filtered vacuum cleaner) frequently and thoroughly to remove mites and the organic debris on which they feed. Target critical areas, such as:
- mattresses and bed frames
- rugs and carpets
- overstuffed furniture (and the area underneath)
- Replace or clean air conditioner filters frequently and maintain low (less than 50%) indoor humidity to reduce conditions favorable to dust mites.
- Encase mattresses and pillows in plastic covers and change bed linen frequently to help prevent mite populations from building up.
Bryobia praetiosa is a small (1/32 inch) mite easily recognized because of its reddish-brown color and long pair of front legs that are often mistaken for antennae. Clover mites do not bite. They are a nuisance because hot dry weather in the spring and early summer nay 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.
There is some anecdotal evidence that suggests that applying too much nitrogen fertilizer may worsen clover mite problems. A simple, non-chemical control method involves leaving a strip (12-18 inches) of bare soil or gravel mulch around foundation walls (Figure 1). 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. Sevin®, cyfluthrin, bifenthrin, and permethrin sold under a variety of brand names are examples of pesticides that are currently labeled for such use. Read the pesticide label carefully and select products appropriate for use indoors or outdoors as needed. For additional information about clover mites as a pest in turf, refer to Clover Mites in Home Lawns.
Complaints about bites and rashes for which a specific cause cannot be found are often attributed to so-called (and non-existent) "paper mites" or to one of the other mites mentioned above, particularly scabies and bird mites. Other biting/stinging pest such as fleas and bedbugs are easily seen and produce very noticeable and characteristic bites and other evidence of their feeding. Although mites are extremely small, they are usually detectable with the unaided eye (as in the case of bird mites) or by skin scrapings or biopsy or other samples collected and examined by a physician. In the case of scabies and straw itch mites, the rash or bites caused by these mites help in identifying them as the cause of the problem. However, bit marks (or presumed bite marks) are not entirely reliable on their own to confirm the cause of the problem.. Very often we unconsciously and repeatedly scratch irritated areas of the skin (particularly at night while sleeping) and this will only worsen the condition. Bird mites, "black pepper mites" and "paper mites" are often used as reasons to justify pesticide treatments in homes and offices. Pesticide applications made without first identifying a specific pest problem (and target application site) are usually ineffective and should not be used. More importantly, repeated and widespread pesticide applications are potentially hazardous to you and others around you. This includes constant (and multiple) applications of insect repellents and other insecticides to your skin (which can cause rashes and irritation) and to your clothing and / or bedding. You need to identify the cause of a problem before you resort to spraying any pesticides in your home.
Here are some tips for collecting specimens for identification.
- Repeated scraping or gouging into your skin with razors, knives or other items in order to collect samples or "relieve" the symptoms may actually worsen the problem and even result in a secondary infection. Specimens containing bodily fluids, skin tissue, etc. should be collected and examined by a medical professional.
- Never use adhesive ("Scotch") tape to “trap” specimens on your skin. Key features that are important for pest identification can easily be damaged or obscured.
- Use mouse glueboards, or cockroach sticky traps (available at most hardware stores) as monitors. Keep track of where and when you place each one. Such information may be critical if mites or insects are found.
- Brush/knock suspected specimens from your clothing or skin onto a light-colored piece of paper or cardboard.
- Use a fine artist paint brush to pick up the specimens. Place them carefully into a small prescription vial or bottle filled with alcohol (rubbing alcohol should work). Label the vial as to where you collected the specimen.
- Make sure that the vial/bottle is sealed tightly so that the contents do not leak.
- Take the specimen to your county Cooperative Extension center.
- Please note: Samples of bodily fluids excise (removed) skin, etc. will not be opened or handled by Cooperative Extension staff. Contact your personal physician for advice. Likewise, do not send vacuum cleaner bags filled with debris and possibly pesticide-laden dust. These items pose a potential hazard to the people handling them.
If no insects or mites can be found, then you need to keep a broad perspective and consider other possible non-arthropod (insects, mites, spiders, etc.) causes for your symptoms. A previously unidentified (or recently developed) allergy or sensitivity may a mimic biting sensation and bite-like marks or rashes. These allergies can include: certain foods, chemicals (including laundry detergents), dust, pollen, as well as interacitons among medications (and even medications with various health supplements). Even changes in your indoor environment (e.g., changes in humidity) and stressful situations can trigger skin reactions and sensitivities. Repeatedly using "natural" treatments or frequent (several times daily) bathing or showering can dry your skin too much and cause iteching or sensitivity. For that reason, you should consult your family physician or prefeably medical specialist such as a dermatologist or allergist.
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/or application of a hydrocortisone cream to bites may help to relieve itching. If you develop a severe reaction, then consult your physician.
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.
For assistance with a specific problem, contact your local Cooperative Extension center.
Publication date: June 1, 2015
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