House dust mite

House dust mites (HDM, or simply dust mites) are various species of acariform mites belonging to the family Pyroglyphidae that are found in association with dust in dwellings. They are known for causing allergies.

Biology

Species

The currently known species are:

Dermatophagoides farinae (American house dust mite)
Dermatophagoides pteronyssinus (European house dust mite)
Dermatophagoides evansi
Dermatophagoides microceras
Dermatophagoides halterophilus
Dermatophagoides siboney
Dermatophagoides neotropicalis
Dermatophagoides alexfaini
Dermatophagoides anisopoda
Dermatophagoides chirovi
Dermatophagoides deanei
Dermatophagoides rwandae
Dermatophagoides scheremeteroskyi
Dermatophagoides scheremetewskyi
Dermatophagoides simplex
Euroglyphus maynei (Mayne's house dust mite)
Euroglyphus longior
Hirstia domicola
Malayoglyphus carmelitus
Malayoglyphus intermedius
Pyroglyphus africanus
Sturnophagoides brasiliensis
Blomia tropicalis

Taxonomy

The dust mites are cosmopolitan members of the mite family Pyroglyphidae.

Characteristics

House dust mites, due to their very small size and translucent bodies, are barely visible to the unaided eye. A typical house dust mite measures 0.2–0.3 mm in length. The body of the house dust mite has a striated cuticle.

House dust mite faecal pellets range from 10 to 40 µm.

Diet

They feed on skin flakes from humans and other animals, and on some mold. Dermatophagoides farinae fungal food choices in 16 tested species commonly found in homes was observed in vitro to be Alternaria alternata, Cladosporium sphaerospermum, and Wallemia sebi, and they disliked Penicillium chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum.

Predators

The predators of dust mites are other allergenic mites (Cheyletiella), silverfish and pseudoscorpions.

Reproduction

The average life cycle for a house dust mite is 65–100 days. A mated female house dust mite can live up to 70 days, laying 60 to 100 eggs in the last five weeks of her life. In a 10-week life span, a house dust mite will produce approximately 2,000 fecal particles and an even larger number of partially digested enzyme-covered dust particles.

Distribution

Dust mites are found worldwide, but are more common in humid regions. The species Blomia tropicalis is typically found only in tropical or subtropical regions. Detectable dust mite allergen was found in the beds of about 84% of surveyed United States homes. In Europe, detectable Der p 1 or Der f 1 allergen was found in 68% of surveyed homes.

Health issues

Asthma

House dust mite antigens are strongly associated with asthma development and severity; they are estimated to contribute to 60-90% of cases.

Allergies

Tropomyosin, the major allergen in dust mites, is also responsible for shellfish allergy.

Oral mite anaphylaxis

Dermatophagoides spp. can cause oral mite anaphylaxis (AKA pancake syndrome) when found in flour.