There are numerous mites that are capable of invading our homes. A variety of mites are known to bite humans and cause irritation, itchy papules and rashes. Most of these mites are actually parasites of other animals not humans, but will bite humans when their normal hosts are not present. These mites are mostly nest parasites of birds, rodents and other animals that blood-feed on their normal hosts and then return to the host�s nest. They do not remain on the animal or human that they feed on.
Mite bites cause red papules, and these bites can be extremely itchy. The free-living mites tend to bite in areas where clothing rubs. Scabies mites tend to occur most frequently on the hands and wrists, armpits and groin area.
Mites can easily enter a home through tiny entrance points around windows, doors or any other space large enough for them to squeeze through. Other mites that originate from plants do not migrate as well as other mites but they can enter our homes by hitching a ride on anyone that works in gardens, hot houses, nurseries or even children playing outdoors. Most plant mites do not bite but they can be an annoyance when their numbers are high. These mites can also cause an allergic reaction in some people.
Facts About Mites
“Mite” is a term commonly used to refer to a group of insect-like organisms, some of which bite or cause irritation to humans. While some mites parasitize animals, including man, others are scavengers, some feed on plants, and many prey on insects and other arthropods. In fact, there are nearly as many different types of mites as there are insects. Like their relatives, the ticks, mites pass through four stages of development: egg to larva to nymph to adult. All stages have eight legs except the six-legged larva.
Most mites never come in contact with humans, but some that do can affect a person’s health. Yet, in many situations where mites or other “invisible” arthropods are believed to be biting or “attacking” people, no causative organism is present. The irritation may be real or imagined: real, due to mechanical, chemical or other inanimate irritants, or imagined due to a psychological disorder.
While mites rarely transmit disease to humans in the United States, they definitely impact health in ways that range from simply being a nuisance when they enter homes in large numbers, to inflicting severe skin irritation that can cause intense itching. The most commonly encountered mites, including those that can adversely affect human health, are listed below.
CLOVER MITES (Bryobia spp.)
This mite sometimes enters homes and other buildings by the thousands, causing panic among residents. Though they do not bite or cause health-related problems, clover mites can be a nuisance. If smashed when they crawl over carpets and drapery, the mites leave a red stain. Clover mites can be red, green or brown, and have front legs that are about twice as long as their other legs. They feed on clover, ivy, grasses, fruit trees and other plants. Well-fertilized lawns are favored. Clover mites enter homes when their food plants are removed or dry up. They are most active in fall, and will seek refuge in structures as colder weather approaches, when molting (shedding skin) and when laying eggs. Typical of many mite species, all clover mites are females capable of laying viable eggs without fertilization. They have no need for male mites!
HOUSE DUST MITES (Dermatophagoides spp.)
Much information (and misinformation) has appeared in recent years about house dust mites. Virtually invisible to the naked eye, house dust mites are nevertheless real. It has been shown that, like cockroaches, dust mites and their feces can become airborne and are one of the most common indoor allergens. That is, most persons diagnosed as being allergic to “house dust” are actually allergic to the dust mites whose bodies and feces are major components of dust. Roaches and dust mites have also been implicated in triggering asthma attacks. But, unlike rodent mites, itch mites and chiggers, skin irritation is rarely caused by exposure to dust mites. Although they may “hitchhike” on clothing, dust mites do not live on people. They feed primarily on dander, flakes of dead skin that fall from people and animals. Upholstered furniture, pillows and mattresses typically harbor more dust mites than carpeting.
STRAW ITCH MITES (Pyemotes tritici)
These mites are parasites of insects. Many infest stored products. Humans are bitten when they come in contact with straw, hay, grasses, leaves, seeds or similar materials harboring the mites. When they become separated from their insect hosts or their hosts become scarce, itch mites may bite other animals including humans. A person who is severely infested may have thousands of bites from itch mites that cannot be detected by the naked eye. Fortunately, the mites cannot live on humans and do not remain long. Females, swollen with eggs, resemble tiny pearls and appear to bear live young.
RODENT and BIRD MITES (Liponyssoides sanguineus, Laelaps echidnina, Ornithonyssus spp., Dermanyssus gallinae, Cheyletiella spp.)
Rodent and bird mites may bite people when their hosts die or abandon their nests. Three types of rodent mites readily bite humans: the house mouse mite (Liponyssoides saguineus), spiny rat mite (Laelaps echidnina) and tropical rat mite (Ornithonyssus bacoti). The house mouse mite prefers to suck the blood of mice, but also will bite rats and people, often causing a rash around the bite. They prefer warm places (e.g., around pipes and furnaces) where rodents live. The spiny rat mite feeds on rats at night and hides by day in cracks and crevices around rat nests and resting places. The tropical rat mite’s bite is painful and causes skin irritation and itching.
Mites that normally infest birds also bite people. The northern fowl mite (Ornithonyssus sylviarum) and chicken mite (Dermanyssus gallinae) primarily infest chickens, but also pigeons, starlings and sparrows. The northern fowl mite cannot survive for more than a month off its host, while the chicken mite hides in cracks and crevices near bird nests during the day and feeds by night. Cheyletiella mites infest both birds and mammals. They may prey on other mites and insects living on the host’s skin. They can cause a mange-like condition in pets, and itching in people who handle infested pets. They do not stay long on humans.
CHIGGERS (Eutrombicula spp.)
Two species of chigger mites attack humans and other mammals, birds and reptiles. The nymph and adult stages prey on insects. It is the six-legged larval stage that typically feeds on rodents or ground dwelling birds but will bite people when they are available. Chigger larvae are red to yellow in color and appear as scarcely visible specks. When they detect the carbon dioxide exhaled by an animal, they climb on soil or vegetation and wave their front legs to contact it, then grasp it with their mouthparts. They do not suck blood but cut into the skin, inject skin-digesting saliva and suck up the liquefied skin. If not dislodged, the chigger will feed for several days. The bite becomes inflamed, hardens and itches. Chiggers spend most of their lives in cracks in the soil. They are typically found in rural, less disturbed areas, but can persist for years on soil in new subdivisions.
SCABIES MITES (Sarcoptes scabiei)
Sarcoptes scabiei are mites that infest mammals, including man. Most human infestations result from person-to-person contact. Although they can transfer from animals to humans and vice versa, several types of scabies mites exist, each having a preferred host species on which it reproduces. In dogs, scabies mites cause mange. Scabies is the most common and important condition resulting from mite infestation of humans. Unlike other mites, scabies mites actually burrow up to 3cm into the skin to lay eggs. The mites are believed to feed on skin and secretions. The entire life cycle (10-17 days for human-infesting scabies mites) is spent on their host. Without a host, they survive only a few days. In previously unexposed individuals, a scabies infestation may go unnoticed for more than a month. Then, severe irritation and itching develops, especially at night.
Tips for controlling Mites
The first (and most important) step in eliminating biting mites from your home is to eliminate all possible sources. If you know exactly which mite has infested your home, the task would be simple. Identifying the pest is the real trick. This arachnids (who are related to spiders more than than insects) are so small that either a hands lends or microscope must be used in identification. Even with proper viewing device, a professional or entomologist is usually required to make a correct identification.
For the average person, identification of a particular mite is too difficult. Instead of squinting through a hands lens at a bug that is as small as a speck of dust or as large as a tiny tick, your time is better spent looking for possible sources of the infestation. In many cases this task is simple because certain animals have been seen in the area. Common sources of biting mites are birds, raccoons, rats, mice or other animals that nest in, below or very near the home. Other annoying mites have plants as natural hosts. Once an animal dies or leaves its nest, the mites left behind in the nesting material (or immediate area) will begin to move about as they search for another host. Many of the biting mites can live for a couple of weeks without a blood meal, which makes it easier for them to migrate to another warm blooded host. Ridding your home of rodent infestations and cleaning up or destroying all possible nesting materials will go a long way in reducing the mite populations. Inspect beneath eaves and other over hangs, window ledges, fireplaces, chimneys, attics and crawl spaces. You might be surprised to find evidence of birds, rodents or other wildlife. If no evidence of birds or animals are found, you should inspect plants around the home before starting a spray program. Sprays are indeed a great help but you need to know which type to use for safe and adequate control of the mite infestation. Once you have made a thorough inspection but failed to find any sort of wildlife evidence in your home, turn your attention to shrubs, grasses and other plants that are near your home. If you find evidence of mites on plants or see damage from mites or their possible predators (lacewings are an example) you should treat the plants with an approved miticide. For vegetables or edible crops, take care as to which product you spray. These types of mite and insect sprays will be discussed in the chemical control section of this article. Many people who discover mites in their homes (or just suspect mites, due to itching, scratching) will jump the gun, spraying and fogging everything in site - and usually with poor results! As in any integrated pest management program, certain steps should be followed to safely rid your home of pests using the holistic approach: identify the pest; locate its source and eliminate if possible; reduce conditions that contribute to the migration, feeding and reproduction of the pest; use chemicals as a last resort; choose correct chemical for the job
The first step in determining the true cause of irritations that may involve mites is to thoroughly inspect the premises and identify any organisms discovered. The simple fact that all mites are tiny creatures, some so small they can be seen only with magnification, often makes inspection and identification difficult. Likewise, mites that affect humans are a diverse group, each with very different habits, all of which investigators should be aware.
Seek medical attention when exposure to mites is suspected as the cause of skin irritation. This is certainly true in the case of scabies infestations that will require medication. In addition, bedding and clothing of scabies-infected persons should be washed regularly. Information on the treatment of scabies can be found at www.idph.state.il.us/public/hb/hbscab.htm.
When mites have been identified, appropriate control measures can be employed. A vacuum sweeper can be a valuable weapon in the mite control arsenal. Infestations of clover mites, rodent and bird mites in and around structures can sometimes be eliminated by vacuuming alone. Vacuuming may be less effective, but still of value, in controlling various food mites, straw itch mites and dust mites. Note that dust mites are not prevalent in ductwork; therefore, duct cleaning is not recommended for dust mite control. However, a high-efficiency particulate air (HEPA) filter can be installed to help prevent airborne allergens, including dust mite particles.
Moisture control also can be important. Mites transfer air and water through their body walls and are subject to desiccation at low humidity. Dust mite populations, for example, suffer when a relative humidity of 50 percent or less is maintained. On the other hand, high humidity can cause mite populations to increase exponentially.
Well-ventilated homes in dry climates contain few dust mites. Homes with a relative humidity that consistently rises above 50 percent can contain more than 100 dust mites per gram of dust. To reduce dust mite numbers, a relative humidity of less than 50 percent must be maintained for several weeks. Any fluctuation in humidity, however brief, seems sufficient for dust mites to remain and reproduce. Daily activities such as air-conditioning and showering, will cause humidity levels to fluctuate in portions of the home. Thus, other means of controlling dust mites should be employed in addition to humidity control.
For dust mites, Steri-Fab Disinfectant can provide control when applied to flooring and floor coverings. Bedding, draperies, floor coverings and furniture should be cleaned regularly. Pillows, mattresses and upholstered furniture can be discarded or sealed in plastic covers to help prevent dust mite infestation, and to reduce ongoing infestations and their associated allergens. Persons suffering from allergic reactions or asthma should consult a physician.
Exclusion methods also can be used for certain mites, e.g., clover mites. Structural entry points, e.g., gaps in and around foundations, doors, windows, vents, utility lines, etc., should be sealed. This will help to keep clover mites outdoors along with rats, mice, birds -- and the mites these pests bring when they are allowed to nest in structures. If nests are found, they should be removed and the area around them vacuumed. Other non-chemical methods include maintaining a plant-free border around foundations and reducing the amount of fertilizer applied to lawns – both of which help to keep clover mites away from structures.
Pesticides labeled for use against mites, can be effective against clover mites and chiggers in grassy areas. For chiggers, however, insect repellents containing 7 percent to 30 percent “DEET” should be used as the first line of defense. To dislodge any chiggers that may have attached, take a hot, soapy bath or shower immediately after visiting natural areas where chiggers are present.