What is leishmaniasis?

Causes and Symptoms

Leishmaniasis, also known as kala-azar in its visceral form, is a parasitic disease that strikes nearly two million persons each year. At least 350 million persons, from more than ninety subtropical and tropical countries around the world, are at risk of contracting the disease. Leishmaniasis has received more attention among United States’ medical authorities because of the risk of contracting the disease faced by US military personnel in Southwest Asia, including Iraq, and Central Asia, including Afghanistan. Leishmaniasis may be a contributor to the complex of illnesses called Gulf War
syndrome reported from veterans of the first Persian Gulf War in 1991.

Leishmaniasis is caused by any of more than twenty species of the protozoan
parasite
Leishmania. They are transmitted by the bites of sandflies, small bloodsucking insects in the subfamily Phlebotominae. The parasite may also be transmitted by blood transfusion, sharing of needles by intravenous drug abusers, and other modes not requiring the bite of a sandfly. Humans are one of many mammalian hosts of these parasites. Infection can cause skin disease, called cutaneous leishmaniasis. Leishmania can also affect the mucous membranes, frequently resulting in ulcers, or cause systemic disease called visceral leishmaniasis, which is often fatal. Infection in children is usually sudden, with symptoms including vomiting, fever, abdominal discomfort, diarrhea, weight loss, and cough. Adults suffer from similar symptoms, but they may be accompanied by nonspecific symptoms such as fatigue, weakness, and loss of appetite. The skin may become darker, dry, and flaky, and
the hair may begin to thin. Other signs include an enlarged spleen, liver, and lymph nodes.

Diagnosis is based on demonstration of the organism in spleen pulp, lymph nodes, liver, or peripheral blood. Species of Leishmania cannot be differentiated morphologically. They are distinguished on the basis of the disease produced, the host and its immune response, and geographical distribution.

Treatment and Therapy

Compounds containing the mineral antimony are the principal medications used to treat leishmaniasis. These compounds include meglumine antimonite and sodium stibogluconate. When these drugs are ineffective, other antiprotozoan medications may be utilized, including amphotericin B, pentamidine, flagyl, and allopurinol. With mucocutaneous leishmaniasis, plastic surgery may be needed to correct the disfigurement caused by destructive facial lesions. Removal of the spleen may be required in drug-resistant cases of visceral leishmaniasis. Relapse may occur and infection may persist despite treatment.

Perspective and Prospects

Cases of infection by Leishmania have been reported on all the continents except Australia. In the Americas, Leishmania can be found from southern Mexico into the South American continent. The disease is widespread in the tropics. In the United States, cases have been reported in dogs, cats, and humans in Texas, Ohio, and Oklahoma.

The prognosis for leishmaniasis is quite variable and depends on the specific strain of infecting protozoan, as well as on the individual patient’s immune system response to infection. Cure rates are high with antimony compounds. There are no preventive vaccines. Preventing sandfly bites is the most immediate form of protection. Insect repellent, appropriate clothing, screening of windows, and fine mesh netting will reduce exposure.

Bibliography

Centers for Disease Control and Prevention. "Parasites—Leishmaniasis." Centers for Disease Control and Prevention, January 10, 2013.

Chang, K.-P., and R. S. Bray, eds. Leishmaniasis. New York: Elsevier, 1985.

Hide, G., et al. Trypanosomiasis and Leishmaniasis: Biology and Control. Wallingford, Oxon, England: CAB International, 1997.

Lane, R. P. “Sandflies (Phlebotominae).” In Medical Insects and Arachnids, edited by Richard P. Lane and Roger W. Crosskey. New York: Chapman & Hall, 1993.

MedlinePlus. "Leishmaniasis." MedlinePlus, April 5, 2013.

Raghunath, D., and R. Nayak, eds. Trends and Research in Leishmaniasis: With Particular Reference to Kala Azar. New York: Tata/McGraw-Hill, 2005.

Ryan, Kenneth J., and C. George Ray, eds. Sherris Medical Microbiology: An Introduction to Infectious Diseases. 4th ed. New York: McGraw-Hill, 2004.