Leishmaniasis is a parasitic disease caused by Leishmania spp. This disease is rare in the United States, but is occasionally found in dogs. Leishmaniasis can have different forms. The most two common forms are cutaneous (cue-TAY-knee-us) leishmaniasis, which causes skin sores, and visceral (VIS-er-al) leishmaniasis, which affects some of the internal organs of the body (for example, spleen, liver, bone marrow).

Cause

Leishmaniasis is transmitted by infected sand flies in areas outside the United States. Sand flies become infected when they bite animals, such as dogs, that are sick with leishmaniasis. The infected flies then bite other animals (including people) and pass leishmaniasis to them. Because sand flies are smaller than other flies and do not make any noise when they are flying, people may not know sand flies are around them.

Risk Factors

People of all ages are at risk for leishmaniasis if they live or travel where leishmaniasis is found. Leishmaniasis usually is more common in rural than urban areas; but it is found in the outskirts of some cities. The risk for leishmaniasis is highest from dusk to dawn because this is when sand flies are the most active. All it takes to get infected is to be bitten by one infected sand fly. This is more likely to happen the more people are bitten, that is, the more time they spend outside in rural areas from dusk to dawn. Adventure travelers, Peace Corps volunteers, missionaries, ornithologists (people who study birds), other people who do research outdoors at night, and soldiers are examples of people who may have an increased risk for leishmaniasis (especially cutaneous leishmaniasis).

Symptoms

People who get the skin form of leishmaniasis may have symptoms that start several weeks or months after the germ enters the body. One or more sores form on the skin and can change over time to look like volcanoes, with a raised edge and central crater. These sores may be painful or painless and may have scabs covering them. Sometimes, people have swollen glands near the sores. If this form of leishmaniasis is not treated, the sores can last for years and cause permanent scars.

People who get the form that affects the internal organs have symptoms that start even later, usually several months after getting leishmaniasis. The spleen and liver, both organs in the stomach area, may become swollen. Swollen glands and changes to the blood are also symptoms of this form of leishmaniasis. This form can be very serious if not treated and may lead to death.

Diagnosis

The first step is to find out if you have traveled to a part of the world where leishmaniasis is found. Your health care provider will ask you about any signs or symptoms of leishmaniasis you may have, such as skin sores that have not healed. If you have skin sores, your health care provider will likely want to take some samples directly from the sores. These samples can be examined for the parasite under a microscope, in cultures, and through other means. A blood test for detecting antibody (immune response) to the parasite can be helpful, particularly for cases of visceral leishmaniasis.

Treatment

Most people who have cutaneous leishmaniasis do not need to be hospitalized during their treatment.

Prevention

The best way for travelers to prevent leishmaniasis is by protecting themselves from sand fly bites. Vaccines and drugs for preventing infection are not yet available. To decrease their risk of being bitten, travelers should:

• Stay in well-screened or air-conditioned areas as much as possible. Avoid outdoor activities, especially from dusk to dawn, when sand flies are the most active.

• When outside, wear long-sleeved shirts, long pants, and socks. Tuck your shirt into your pants.

• Apply insect repellent on uncovered skin and under the ends of sleeves and pant legs. Follow the instructions on the label of the repellent. The most effective repellents are those that contain the chemical DEET (N,N-diethylmetatoluamide). The concentration of DEET varies among repellents. Repellents with DEET concentrations of 30-35% are quite effective, and the effect should last about 4 hours. Lower concentrations should be used for children (no more than 10% DEET). Repellents with DEET should be used sparingly on children from 2 to 6 years old and not at all on children less than 2 years old.

• Spray clothing with permethrin-containing insecticides. The insecticide should be reapplied after every five washings.

• Spray living and sleeping areas with an insecticide to kill insects.

• If you are not sleeping in an area that is well screened or air-conditioned, use a bed net and tuck it under your mattress. If possible, use a bed net that has been soaked in or sprayed with permethrin. The permethrin will be effective for several months if the bed net is not washed. Keep in mind that sand flies are much smaller than mosquitoes and therefore can get through smaller holes. Fine-mesh netting (at least 18 holes to the inch; some sources say even finer) is needed for an effective barrier against sand flies. This is particularly important if the bed net has not been treated with permethrin. However, it may be uncomfortable to sleep under such a closely woven bed net when it is hot.

References

Herwaldt BL. Leishmaniasis. Lancet 1999;354:1191-9.

Herwaldt BL, Stokes SL, Juranek DD. American cutaneous leishmaniasis in U.S. travelers. Ann Intern Med 1993;118:779-84.

Berman JD. Human leishmaniasis: clinical, diagnostic, and chemotherapeutic developments in the last 10 years. Clin Infect Dis 1997;24:684-703.

Desjeux P. Leishmaniasis: public health aspects and control. Clin Dermatol 1996;14:417-23.

CDC