Leishmaniasis is a disease caused by infestation with parasitic protozoans called Leishmania. The disease occurs in parts of southern Europe, the tropics, and the subtropics. It is a type of parasitic infection.
Definition & Facts
Leishmaniasis occurs on every continent except Australia and Antarctica. It has been reported in over 90 countries. It is not clear how many new cases occur per year, and the estimates vary widely. For example, the most common type, cutaneous leishmaniasis is believed to cause anywhere from 0.7 to 1.2 million new cases per year. Visceral leishmaniasis is estimated to cause 0.2 to 0.4 million new cases per year.
Leishmaniasis is an infection that takes several different forms. The most common type of leishmaniasis is cutaneous leishmaniasis which affects the skin. Visceral leishmaniasis, which is also known as systemic leishmaniasis or kala azar affects the internal organs. Mucosal leishmaniasis is one of the less common types. It most commonly develops in people with cutaneous leishmaniasis and affects the mucous membranes.
Most cases of leishmaniasis that develop in the United States involve patients who had traveled somewhere leishmaniasis is prevalent. Since the disease has a long incubation period, the patient generally does not develop symptoms until they have returned home. There have been a few cases of cutaneous leishmaniasis caused by sand fly bites in Texas or Oklahoma; so far, there have been no cases of visceral leishmaniasis that have originated in the United States.
Symptoms & Complaints
These sores eventually develop into ulcers that have a raised edge and depressed center and look like a miniature volcano. The ulcers are sometimes covered with crusts or scabs. They are usually painless.
Visceral leishmaniasis most commonly involves the bone marrow, spleen, and liver. This type of leishmaniasis can be fatal. Visceral leishmaniasis generally develops months or years after the original bite.
The patient with visceral leishmaniasis suffers weight loss, fever, and swelling of the liver (hepatitis) and swelling of the spleen. Damage to the bone marrow causes several types of low blood counts: thrombocytopenia (platelets), leukopenia (white blood cells), and anemia (red blood cells).
Leishmaniasis is caused by the bite of a sand fly that transmits parasitic protozoa. Over 20 species of the Leishmania parasite can cause the disease in humans. Over 30 species of sand fly can carry the parasite, and certain species of sand fly transmit certain parasite species.
In some regions, the parasites use only humans as hosts. In such places, the flies need to bite humans in order to pick up or transmit the protozoa. In other places, the parasite can infect other mammals like dogs or rats.
Some species of Leishmania parasites can also be spread by sharing contaminated needles or through blood transfusions. There have also been cases of the parasites being transmitted from a pregnant woman to her child.
Leishmaniasis is most common in rural areas. The parasites can infect anybody of any age and of either gender. Since the sand flies are active mainly from dusk to dawn, the parasites primarily infect people who are active outdoors at night. High-risk occupations include soldiers, ornithologists, Peace Corps volunteers, ecotourists, missionaries, and adventure travelers.
Diagnosis & Tests
If a person suspects they have contracted leishmaniasis, they need to see their doctor. They should inform their doctor of their travels within at least the past year, so the doctor can determine if they were in a region where leishmaniasis occurs.
The various tests used for diagnosis involve looking for the parasites and/or an immune system response to the parasites. For example, if the patient might have cutaneous leishmaniasis, the doctor will take a biopsy or tissue sample from a suspicious-looking ulcer. They will then examine the sample under a microscope to look for the parasites.
If the doctor is looking for visceral leishmaniasis, they will start by performing a physical examination to look for symptoms like an enlarged spleen (splenomegaly) or liver (hepatomegaly). If they find such symptoms, they will take a blood sample for a blood test and/or bone marrow biopsy to examine under a microscope.
In some cases, the doctor will have to grow a culture before examining the sample. The doctor will put the sample in a medium to encourage a small number of parasites to grow to a detectable level. If the doctor does have to grow a culture, it can take two to four weeks for them to make a diagnosis.
Treatment & Therapy
Cutaneous leishmaniasis sometimes goes away on its own, and the ulcers heal without treatment. The sores can leave disfiguring scars, however. The other two types of leishmaniasis always require treatment. Visceral leishmaniasis, in particular, is often fatal if not treated.
The patient should be given antiparasitic drugs like amphotericin B that will kill the parasite. In cases of cutaneous leishmaniasis, they should be treated to speed healing and reduce scarring. Photodynamic therapy, for example, can help heal the sores. If the patient has severe scars, especially on their face, they may opt for plastic surgery.
Mucosal leishmaniasis is most commonly treated with paromomycin and liposomal amphotericin B. Most of the drugs used to treat leishmaniasis are administered through injection. A new drug, miltefosine, which is used to treat visceral leishmaniasis, is the first oral treatment to be developed.
Prevention & Prophylaxis
If travel to such regions is unavoidable, people should do the following:
- Avoid being outdoors from dusk to dawn, for sand flies are usually most active at night
- Wear long-sleeved clothes that have been treated with insecticide
- Spray insecticide or insect repellant in living or sleeping areas
- Stay in air-conditioned or well-screened areas
- If screens and air conditioning aren’t available, use a mosquito net coated with insecticide
- Apply insect repellent to any exposed skin and under the ends of pants legs and sleeves