Demodex infestation – the eight-legged ectoparasite

The Demodex mite is an eight-legged (an arachnid) ectoparasite (living on the surface of the host) that can reside in our hair follicles and sebaceous glands. Of the 65 described Demodex species, only Demodex brevis and Demodex folliculorum are found on humans. Demodex is contracted and spread by either direct contact or dust containing eggs.
 Keratinization mixed with lipids produces the classical clear cylindrical dandruff that is associated with Demodex blepharitis.
Keratinization mixed with lipids produces the classical clear cylindrical dandruff that is associated with Demodex blepharitis.

The adult D. brevis mite is about 0.2 mm long and tends to live inside the lash’s sebaceous glands and in meibomian glands. It has been suggested that D. brevis can be associated with meibomian gland disease and subsequent tear lipid deficiency. D. folliculorum buries itself face down near the root of the eyelash and it is associated with anterior blepharitis.

D. folliculorum is longer, at about 0.4 mm in length, and has a more slender, tapered body than D. brevis. D. folliculorum often live in clusters, where D. brevis are more solitary.

Life cycle, survival of Demodex

The typical Demodex life cycle is usually 2 to 3 weeks. A female Demodex mite lays 15 to 20 eggs inside the hair follicle near the sebaceous glands. The eggs develop into larvae, which eventually become an adult eight-legged mite. The adult male Demodex mite will leave the follicle in search of a mate, while the adult female mite remains in the follicle. The mites are capable of walking approximately 10 mm/h and tend to be more active in the dark.

Multiple collarettes.
Multiple collarettes.

It is thought that both D. folliculorum and D. brevis consume epithelial cell cytoplasm by piercing through the cell membrane. D. folliculorum infestation causes follicular hyperplasia with subsequent increase in keratinization near the base of the eyelash. This keratinization mixed with lipids produces the classical clear cylindrical dandruff that is associated with Demodex blepharitis. This dandruff is thought to be a product of the mite’s claws scrapping around the follicle.

Eyelashes infested with Demodex often are brittle and are easily epilated. On about every tenth eyelash, one or more Demodex mites can be detected even in healthy asymptomatic patients.

Two Demodex attached to the hair follicle root.
Two Demodex attached to the hair follicle root.

Patients who suffer from Demodex infestation may complain of eyelid and eyebrow itching (especially in the morning), madarosis, a burning sensation and a foreign body sensation that seems to originate beneath their lids. Demodex blepharitis is observed equally in males and females and is age related. A study by Junemann showed that Demodex is found in 25% of 20-year-olds, 30% of 50-year-olds and 100% in patients older than 90 years.

Treatment regimen

Demodex blepharitis treatment goals include: eradicating the adult mites and their offspring, prevention of further mating, avoiding re-infestation and alleviating the patient’s symptoms. Understanding the mite’s life cycle and habits will help us design a logical treatment plan.

There are a number of published treatment regimens that report good results. This is one of them but they may alter from Optometrist to Optometrist.

First, therapy begins with educating the patient about their condition and showing them photos of the Demodex mites living in their hair follicles. Compliance is not an issue once the patient sees the crawling mites. I use a digital microscope that can take both photographs and video.

A treated eyelash.
A treated eyelash.

Initial treatment involves an in-office lid scrub/débridement. Start by instilling a drop or two of TetraVisc (tetracaine 0.5%, Cynacon/OcuSoft) or other long-lasting anesthetic. Then thoroughly débride the lashes and eyebrows with a cotton tip applicator soaked in 20% to 50% tea tree oil.

Tea tree oil also has excellent concentration-dependent Demodex-killing properties. Keep in mind that the readily available 100% tea tree oil solution is very irritating and, as such, should be diluted. One can prepare a mixture of 50% tea tree oil by diluting the tea tree oil in either macadamia or walnut oil.

For mild cases of cylindrical dandruff, a more commercially available tea tree oil can be used, 20% Desert Essence. This irritates the mites and stimulates them to come out of the follicle. Repeat this procedure in 10 minutes.

Next, apply an antibiotic/steroid ointment to help keep the mites from moving and possibly suffocate them. The steroid also helps calm down the inflammation secondary to the chemical and mechanical irritation of the in-office treatment, in addition to suppressing the possible inflammatory cascade associated with the decaying mites. The patient will return in 2 weeks for repeat office treatment.

Patient instructions

Send patients home with specific instructions. They should immediately wash sheets and pillow cases in hot water and dry with the “high” dryer setting and discard their pillows. They should not use makeup for at least 1 week and discard all old makeup. Recommend using tea tree soap on their face and consider tea tree hair shampoo as well. Make an appointment for the patient’s spouse to have an evaluation, as they are frequently also infested.

Ask the patient to purchase a supply of Ocusoft Plus Lid Scrub pads (Cynacon/Ocusoft). They should thoroughly scrub the lash margins, then work the eyelids and eyebrows. Do not rinse.

Allow the solution to dry, then apply a light film of antibiotic/steroid combination ointment over the lashes. In the morning, lids should be scrubbed again and rinsed well. The steroid/antibiotic ointment should be discontinued in a week and substituted with a bland ophthalmic ointment. This regimen should be continued for 3 more weeks (4 weeks total).

As a maintenance regimen, the patient should continue lid scrubs at least twice a week indefinitely. A follow-up appointment should be scheduled for 6 months.

 

If you would like to learn more or book an appointment at Labuschagne & Alberts Optometrists simply call: 018 468 8903 or come make a visit at 10 Rockwill Square Corner William & Austin Streets, Wilkoppies.

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