Dermatology Online Journal

Parasitic infections of the nails
Bertrand Richert
Abstracts of the Fifth Meeting of the European Nail Society:DOJ 9(1): 17C

Department of Dermatology, University of Liège, Belgium

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About 3—10% of travellers may experience skin, hair or nail disorders. In a world where international business travel and vacationing may take anyone anywhere within a few hours, patients with exotic imported skin disorders may be knocking on your door.... So get ready!!

The aim of the following lines is to remind you of the clinical presentation of the most common imported parasitic skin diseases. But hopefully for nail doctors, the nail apparatus is rarely involved in such instances.

Crusted (Norwegian) scabies.—Crusted (Norwegian) scabies is a rare variant of scabies characterized by the presence of thick crusted lesions able to harbour millions of parasites responsible for its high infectivity. As a rule, the patient is immunodeficient, either due to HIV, the use of immunosuppressant, or any severe disease. Patients with neuropsychiatric (mental retardation or dementia) and neuromotor disorders are also prone to develop the condition. Pruritus is a variable symptom and may be absent, slight, moderate or severe. Crusted scabies may masquerade as hyperkeratotic eczema, psoriasis, Darier’s disease and contact dermatitis as well as on the skin as on the nails.

In the ordinary form of scabies, the nails are not involved but the distal subungual area may represent a reservoir of mites (collected from skin scratching), potential source for small epidemics. The lesions of the Norwegian scabies have a predilection for areas of pressure and are strikingly different from those of ordinary scabies. The characteristic of this condition is the existence of dystrophic nails which are hyperkeratotic and accompanied by large, psoriasis-like accumulations of scales under the nails. Even after successful treatment of the hyperkeratotic lesions on the skin, the dystrophic nails persist. The mites survive in the subungual material and are a source of reinfestation. Diagnosis is confirmed by microscopic examination of material scraped from the lesion (and from beneath the nails).

Treatment of the nails should include frequent trimming of the nails associated with scrubbing twice daily with topical scabicide or even chemical partial nail avulsion using 40 % urea ointment. Oral treatment with ivermectin is a treatment of choice : a single ivermectin dose (12 mg), may be sufficient to reach very high cure rate. This drug has been successfully demonstrated in HIV patients with crusted scabies. However, its effect on the nail involvement has not been mentioned.

Tungiasis.—Tungiasis is caused by the sand flea Tunga penetrans also known as the jigger or chigoe. Originally native of South America, its subsequently spread to Africa. A recent report show that it has reach South Europe. The larvae develop in dry, sandy soil. Humans become therefore infected between the toes, under the toenails and on the sole. Rarely, contamination may be observed on the buttocks, elbows, fingers or even on the penis.

The presence of the fleas causes intense irritation. At first, the site of penetration of the skin is visible only as a black dot, but soon an inflammatory nodule develops, giving rise to a white pea-sized nodule with a central black pit evoking a mistletoe. Secondary infection is common, and tetanus has often complicated tungiasis in the past.

Treatment consists in the removal of the flea with a sterile needle, curettage or application of turpentine, DDT, 4 % formaldehyde solution, or chloroform. Topical or systemic antibiotics are recommended after removal. Tetanus prophylaxis is mandatory.

Cutaneous larva migrans.—Cutaneous larva migrans is a clinical term for a cutaneous eruption that has numerous causes. The lesions creep or migrate due to the presence of moving parasites into the skin. Causes of creeping eruption may include Ancylostoma sp. (dog, cat), Bubostomum sp. (cow), Necator sp. (pork), Strongyloides stercoralis, Dirofilaria repens, Gnathosthoma sp. and Loa Loa.

Adult hookworms live in the intestines of the dog and cat and their ova are deposited in the animal's faeces. Humans become infected when resting on sandy, warm, moisted and shaded areas. The condition is common in all warm climates and may occur in Northern Europe during a hot summer.

The larvae penetrates the skin where it has been in contact in infected soil, usually the feet, hands or buttocks. They can lie quiet for weeks or months or immediately begin their creeping activity with the production of a thread-like line about 3 mm wide. This is exceedingly itchy, slightly raised and forms serpentine patterns. The larvae advance at a rate of several millimetres to a few centimetres daily. Along the line of tracks are often vesicle, and itching leads to secondary changes of dermatitis and bacterial infection. The disease is self-limiting and most larvae die in 4 weeks. However some species may persist for many months.

Treatment consist in cryotherapy of small lesions. Ivermectin in a single oral dose of 12 mg seems best. Albendazole 400 mg/d by mouth for three days is also effective. An alternative choice of treatment is the topical application of 10 % thiabendazole.

Myiasis.—Myiasis is the infestation of human body tissues by the larvae of Diptera. The various forms of myiasis are classified according to the part of the body affected. Cutaneous myiasis are divided into bloodsucking, creeping, furuncular and traumatic (wounds). A nasopharangeal, intestinal and urogenital form are also described.

Traumatic or wound myiasis has been a serious complication of war wounds in tropical areas and is sometimes observed in neglected ulcers : the eggs or larvae (maggots) can be seen, often in large numbers, in the suppurating tissues (Cochliomyia macellaria).

In the furuncular form, boil-like lesions develop gradually over a few days. Each lesion has a central punctum, which discharge serosanguinous fluid. The posterior end of the larva is usually visible in the punctum and its movements may be noticed by the patient. The lesions are often extremely painful. There is an inflammatory reaction around the lesions may be accompanied by lymphangitis or lymphadenopathy. These symptoms rapidely resolve after the larva has been removed. The flies causing furuncular myiasis in humans are Dermatobia hominis, Cuterebra, Cordylobia anthropophaga, Cordylobia rodhaini, Wohlfahrtia sp. and Hypoderma sp.

Another common clinical form is a creeping eruption. The larva lies ahead of the vesicle in apparently normal skin. This form of myiasis is produced by Gasterophilus larvae.

Two cases of subungual myiasis have been reported up to now.

Traditional treatment include obstruction the punctum with pork fat, mineral oil, petrolatum or butter. Surgical management is most frequently recommended : the punctum is enlarged by cruciate incisions and the larva removed with forceps. A successful treatment with topical ivermectin (1 % in propylene glycol solution) left on the affected area for 2 hours was recently reported. Another useful technique is a venom extractor.

Pediculosis.—An anecdotal case of pediculosis of the great toenail has been reported. Debridement of the great toe nail for onychomycosis exposed multiple cavities, housing 10 to 12 body lice. These quickly dispersed upon being disturbed, returning to the hallux nail within minutes and disappearing into the tunnels, which were present in the nail. One of the bugs was secured and placed in alcohol. Examination under the microscope confirmed the clinical impression of Pediculus humanus corporis. The infestation was apparently confined to the hallux nail.

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