Demodex mites belong to the group of mites (Acari), which is a vast and incredibly diverse group of arachnids, comprising over 55,000 described species. Among them are free-living forms (predators, saprophages, herbivores, fungivores) as well as symbionts, including commensals and parasites. In terms of their lifestyle, the latter are divided into external parasites (called ectoparasites) and internal parasites (called endoparasites).
The family Demodecidae encompasses mites that are exclusively obligatory and permanent parasites of mammals. They are associated with nearly all modern orders of these animals. So far, about 120 species of Demodex mites have been described and classified into seven genera. However, it is estimated that the currently known diversity within the family Demodecidae is just the tip of the iceberg, considering the number of potential hosts for Demodex mites (around 5,000 species of mammals).
Demodex mites in humans!
Mites from the Demodex genus in humans pose an important and growing ophthalmic problem. Demodex mites play a role in the pathogenesis of eye diseases, especially in aging populations, causing chronic inflammation of the eyelids (blepharitis or acaricidal blepharitis – from Acari, the mite order) and conjunctiva (conjunctivitis). The areas around the eyes can be infested by both species of Demodex mites, with D. folliculorum primarily inhabiting the eyelash follicles, while D. brevis occurs within the sebaceous glands and Meibomian glands.
The activity of Demodex mites in the Meibomian glands can lead to their dysfunction, causing conditions such as dry eye syndrome. They can also affect the quantity and quality of gland secretions. Additionally, the presence of mites in hair follicles can induce swelling and inflammatory states in the tissues. D. folliculorum typically causes chronic anterior blepharitis, while D. brevis is responsible for posterior blepharitis (see clinical symptoms). Infected eyelids become red, and there may be a deficiency in the lipid layer of the tear film. By damaging the hair follicles, Demodex mites can directly contribute to the loss of eyebrows and eyelashes. Furthermore, their feeding within the hair follicles can promote secondary fungal and/or bacterial infections (mostly Gram-positive bacteria such as Staphylococcus aureus and Streptococcus pyogenes), altering the pH of the tear film. The penetration of antigens into the superficial layers of the conjunctival epithelium triggers an immune response and the secretion of pro-inflammatory cytokines.
Currently, the diagnosis of Demodex mites relies on visual examination performed by an ophthalmologist, as well as the collection of a few eyelashes from both eyes of the patient, followed by microscopic examination. In response to the need for more effective and less invasive Demodex diagnostics, the company Demox was established.