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Leishmaniasis

Leishmaniasis is a parasitic disease spread by the bite of infected sandflies. The disease is found in parts of about 88 countries on 4 continents. One of the most common forms of the disease is cutaneous leishmaniasis that occurs most commonly (over 90%) in Iran, Afghanistan, Syria, Saudi Arabia, Peru and Brazil. A form that affects some internal organs of the body, visceral leishmaniasis, mostly occurs in Bangladesh, India, Nepal, Brazil and Sudan. Parasites causing leishmaniasis are not found in New Zealand, Australia or the South Pacific.

Classification and causes

Leishmaniasis is divided into four main clinical forms and is caused by parasitic protozoa of the genus Leishmania. There are over 20 species and subspecies that infect humans via the bite of sandflies (subfamily phlebotominae) – tiny sand-coloured blood-feeding flies that breed in forest areas, caves and burrows in tropical and subtropical regions. The clinical features of the disease depend on the causative species and can range from simple, self-healing skin sores as found in cutaneous leishmaniasis (due to infection with Leishmania major), to severe, life-threatening disease of untreated visceral leishmaniasis caused by Leishmania donovani.

Clinical features

Leishmaniasis

Diagnosis

Diagnosis of cutaneous leishmaniasis is usually based on the appearance of the lesion. In over 70% of cases, skin biopsy can reveal the parasite. Skin biopsy is also used to establish mucocutaneous leishmaniasis and visceral leishmaniasis. Complete blood counts and liver function tests should also be performed in visceral leishmaniasis.

Treatment of leishmaniasis

Antiparasitic pentavalent antimonials, such as sodium stibogluconate or meglumine antimoniate, form the basis for all treatment of leishmaniasis. Long courses of these drugs are often required.

More recently liposomal amphotericin B has been found to be effective in treating visceral leishmaniasis and has a shorter course and lower toxicity than amphotericin B deoxycholate. However, cost issues prevent its use in most countries where leishmaniasis is prevalent. Secondary infections should be treated with appropriate antimicrobial therapy.

Most cases of cutaneous leishmaniasis resolve spontaneously without treatment, but this can take months or even years. Sores often leave unsightly scars. Treatment is recommended for:

• Chronic lesions – difficult-to-heal sores
• Cosmetically unacceptable lesions – large or multiple lesions
• Lesions over joints that may impair movement
• Mucosal lesions that may be irritating or impair function
• Lesions in immunosuppressed patients

Other treatments sometimes used for leishmaniasis include:

• Topical paromomycin (also known as aminosidine)
• Azole antifungal drugs: itraconazole, fluconazole, ketoconazole
• Zinc sulfate
• Cryotherapy

Prevention of insect bites

Infection can be prevented by avoidance of sandfly bites. Because there are currently no vaccines or drugs for preventing infection, travellers to areas where leishmaniasis is prevalent should decrease their risk of being bitten by adhering to the following precautionary measures.

• Avoid outdoor activities, especially from dusk to dawn when sandflies are the most active.
• Wear long-sleeved shirts, long pants, and socks. Tuck shirt into pants.
• Apply insect repellent on uncovered skin and under the ends of sleeves and pant legs. The most effective repellents are those that contain the chemical DEET (N,N-diethylmetatoluamide).
• Spray clothing, living and sleeping areas (including bed net) with permethrin-containing insecticides.