Cutaneous migratory larvae. Diagnosis and treatment

An example from a medical history

The mother of an 18-month-old boy consulted a physician about an itchy rash on her child’s feet and buttocks. The doctor, who first examined the boy, misdiagnosed smooth skin dermatophytosis. Treatment with clotrimazole cream was unsuccessful. The child could not sleep because of the constant itching and was losing weight due to loss of appetite. He was admitted to the intensive care unit, where the attending physician found out that the family had returned from a trip to the Caribbean coast before his first visit to the doctor. The child had been playing on the beaches where the local dogs often ran in. The doctor recognized a serpiginous rash pattern of migrating cutaneous larvae and successfully treated the child with topical application of thiabendazole.

Prevalence (epidemiology)

• Common disease in travelers returning from tropical countries.
• The exact incidence in the U.S. is unknown because there are no records of the disease. A Centers for Disease Control review indicates that 35-52% of dogs in animal shelters are infected with worms that can cause disease in humans. Cutaneous migratory maggot is the second most common worm infection.
• In our country, the infection is predominantly found in Florida and the Gulf Coast.
• Children are sicker than adults.

Etiology (causes), pathogenesis (pathology)

• Caused by blood-sucking nematodes present in dogs and cats, e.g. Ancylostorna braziliense, Ancylostoma caniurri.
• Worm eggs are transmitted with dog and cat feces.
• The larvae hatch in moist, warm sand/soil.
• During the infection stage, the larvae penetrate the skin.

Clinic

The diagnosis of cutaneous migratory larvae is made on the basis of history and clinical picture.

• Serpiginous or linear reddish-brown passages 1-5 cm long are elevated above the surface.
• Severe itching.
• Symptoms may last for weeks or months.

Typical localization on the body

Lower extremities, particularly feet (73%), buttocks (13-18%), and abdomen (16%)

Tests for the disease

Not indicated. In rare cases, blood tests show eosinophilia or increased levels of immunoglobulin E.

Differential diagnosis of cutaneous migratory larvae

In cases of cutaneous migratory maggot infections, the following diseases are often mistakenly assumed:

• Cutaneous fungal infections. The lesions are characteristically flaky plaques and ring-shaped spots with resolution in the center. If the serpiginous course of cutaneous migratory larvae is annular in shape, dermatophytosis is often incorrectly assumed.
• Contact dermatitis. The difference lies in the location of the foci, the presence of vesicles, and the absence of classic serpiginous passages.
• Erythema migrans in Lyme disease. The lesions are usually ring-shaped spots or plaques but are not serpiginous and are not elevated above the skin surface.
• Phytophotodermatitis. In the acute phase, phytophotodermatitis is manifested by edema and vesicles, with later foci of postinflammatory hyperpigmentation. Such lesions may occur after a visit to the beach, but they are not caused by grub-infected sand but by the preparation of drinks with lime juice.

Treatment of cutaneous migratory maggot infestations

Oral thiabendazole is the only drug approved by the Federal Drug Administration for the treatment of patients with cutaneous migratory larvae. A water-soluble topical cream (15%) can be prepared from 500 mg tablets. Trials of the efficacy of the systemic and topical dosage forms have been few and far back in the 1960s. Cream is a good choice for children who cannot swallow a tablet.

• Recommended dose for oral administration is 25 mg/kg every 12 hours for 2-5 days (dose should not exceed 3 g per day). The cream is applied topically 2-3 times a day for five days to larval passages with 2-3 cm of skin over the lesions.
• Efficacy is 75-89% for systemic therapy and 96-98% for topical treatment.
• Systemic therapy was slightly worse tolerated; adverse reactions included nausea (49%), vomiting (16%), and headache (7%). No side effects have been reported for topical medications.

Ivermectin (Stromectol) (not approved by the Federal Drug Administration for this use).

• A single dose of 0.2 mg/kg (12-24 mg) is recommended.
• Efficacy at a single dose is 100%.
• No side effects were noted in a series of six trials.
• Many experts consider it the drug of choice.

Albendazole has been successfully prescribed for over 25 years, but is also not approved by the Federal Drug Administration for this use.

• The recommended dose is 400-800 mg daily for 3-5 days.
• The efficacy is over 92%.
• A dose of 800 mg daily for three days or more is used; gastrointestinal side effects may occur in 27% of patients.

Cryotherapy is ineffective and even harmful and should be avoided.

• Antihistamines can relieve itching.
• If there is a secondary infection, antibiotics should be prescribed.

Counseling by a physician to the patient

• Wearing shoes is recommended on beaches where animals are allowed.
• Children’s sandpits must be closed off from animals.
• For pet owners: Keep pets away from beaches, treat them for worms if necessary and clean up excrement properly.

Observation of the patient by a physician.

Surveillance is necessary for persistent lesions.