Mites are a subclass of arachnids. Some species can cause disease in humans.
What are mites?
The term mites (Acari) is used to describe a subclass of arachnids (Arachnida). They belong to the phylum of arthropods. The total of 546 mite families includes about 50,000 known species. This makes the mites the most species-rich group among the arachnids. It is assumed that there are still several unknown species. The mites have six orders, which are grouped into two superorders. These are named Acariformes and Parasitiformes. The superorder Acariformes consists of the orders Trombidiformes and Sarcoptiformes, while the superorder Parasitiformes is divided into the orders Ticks (Ixodida), Opilioacarida, Holothyrida, and Mesostigmata. There are a variety of different mite species. Among the best known are the house dust mite, anthrax mite, cheese mite, hair follicle mite, spider mite, flour mite, water mite, and the burrowing mite.
Occurrence, distribution and characteristics
Mites occur in a wide variety of habitats because they have a distinct ecological potency. About half of the mite species settle in the soil. In suitable soils, up to 100,000 specimens of the arachnids can be found on each square meter of surface. Of importance to humans are mites that settle in their bodies. For example, the hair roots of the eyelashes serve as their habitat. They are also found in animals such as monkeys in their lungs or birds in their nostrils. They are also found in insects in their tracheal exits. There are mite species that feed on plants or fungi, as well as carnivorous species whose diet consists of dead tissue or carrion. A large number of mites lead a parasitic lifestyle. The size of the arachnids varies from 0.1 millimeters to 3 centimeters. The largest mite species are the ticks, whose females can reach up to 3 centimeters. Just like web spiders, mites are equipped with eight legs. However, in the larval stage they have only six legs. Mites do not move very fast. For this reason, other animals such as insects serve as their means of locomotion, allowing them to cover greater distances. Some mite species also suck the bodily fluids of the affected host in the process. One of the most powerful mites is the tropical horn mite, which reaches a body size of 0.8 millimeters. It is thus capable of lifting 1200 times its own body weight. Numerous mite species are blind, so they do not have the central eyes of arachnids. However, some species have one to five eyes and are equipped with a sense of sight, which they use for hunting. Particularly well known and relevant to humans are the house dust mites. The eight-legged creatures reach a size of between 0.2 and 0.4 millimeters, which means that they cannot be seen with the naked eye. They prefer a humidity of 70 to 80 percent and temperatures between 15 and 32 degrees Celsius. Their lifespan is between two and four months. Dust mites form a natural part of the ecosystem of human dwellings. In the home, they prefer places where they can have food, warmth, moisture and darkness. Their nutrition consists of human skin scales. The dust mite finds the best living conditions in the human bed. There it can accumulate in the mattress, the bedspread and the pillows. Via the house dust it penetrates into the floors, carpets, armchairs and curtains. The mites begin to multiply in spring, reaching their highest population numbers in midsummer and autumn. With the onset of the heating season, most dust mites die off.
Diseases and complaints
Some mite species have a harmful effect on human health. Medical professionals refer to diseases caused by mites as acariosis. Among the most common adverse health effects are house dust allergies, which are caused by dust mite excretions such as droppings and protein particles. Without treatment, sufferers are at risk of bronchial asthma over time. Another disease caused by mites is scabies. This is an allergic reaction on the human skin caused by the excretions of the parasites.The term scabies goes back to “having to scratch”. The reason for this is the almost unbearable itching that patients suffer from the parasites. Scabies symptoms usually appear 2 to 5 weeks after the first infection. If a further infection occurs, the symptoms set in after only a few days. Scabies is particularly widespread in developing countries, where up to 30 percent of the population suffer from it. In Central European countries, scabies is rare and occurs there mainly in communal facilities such as day care centers for children or homes for the elderly. The disease is caused by the mite species Sarcoptes scabiei variatio Hominis, which reaches a size of 0.3 to 0.5 millimeters. Harvest scabies is a special form of scabies. It is caused by the harvest mite, also known as autumn mite, which belongs to the family of running mites. In addition to humans, it can also infest dogs, cats and mice. Those affected suffer from reddening of the skin and itchy wheals that resemble mosquito bites. However, the symptoms subside after 10 to 14 days.
