LEISHMANIASIS

Most cases of leishmaniasis occur in tropical and sub-tropical countries.

• 12 million people infected
• 400,000 new cases per year

The incidence of the disease is believed to be increasing in many areas as forest clearing, resettlement programs, and other planned and unplanned population movements expose more people to the infection.

Transmission Cycle

The three main forms of leishmaniasis--visceral, cutaneous and mucocutaneous--are caused by protozoan parasites of the genus Leishmania.

Leishmaniasis is transmitted by phlebotomine sand flies. Domestic dogs serve as reservoirs for visceral leishmaniasis in North Africa, the Middle East, USSR, China and Brazil. In India, there appears to be no reservoir but humans. Rodents are the main reservoirs of the other forms of the disease.

Visceral Leishmaniasis

Visceral leishmaniasis, or kala-azar, occurs in epidemic form in villages and urban slums. It is caused by Leishmania multiplying in the spleen, liver and bone marrow. An acute disease marked by fever, enlarged spleen and liver, it is the most deadly form of leishmaniasis and is usually fatal without treatment.

Cutaneous Leishmaniasis

Cutaneous leishmaniasis (chiclero ulcer, oriental sore or uta) occurs as one or more skin lesions, which are usually self-healing but can be can be seriously disfiguring. Cutaneous leishmaniasis is often endemic, but outbreaks may occur when susceptible people move into infected areas.

Mucocutaneous Leishmaniasis

Mucocutaneous leishmaniasis, a New World form, occurs when Leishmania invade the mouth, nose and throat, causing severe destruction and permanent disfiguration of the nose, lips and larynx.

Child Survival

Visceral leishmaniasis is a significant threat to child survival. In some areas, it is predominately a disease of children. For example, more than 90 percent of the 3,000 to 10,000 cases seen annually in Iraq are in children younger than four. Leishmanisis is also most likely to be misdiagnosed in children. Most deaths from visceral leishmaniasis in Central America occur in children.

Vaccination

Successful vaccination programs have been achieved only for Old World cutaneous leishmaniasis, using crude but often effective preparations. Several new vaccines being developed and tested.

Treatment

Pentavalent antimonials administered for a minimum of 20 days are the most effective treatment available for leishmaniasis.

Before the introduction of antimonial treatment, acute visceral leishmaniasis caused death in 95 percent of all cases. Today, five to 10 percent of treated patients die from the disease.

Leishmaniasis Control

House spraying with residual insecticides has probably been the most effective vector control measure. Successful control of sand flies has been an incidental bonus of insecticide spraying for malaria control in several countries. Spraying combined with solid waste disposal can control visceral leishmaniasis in village and urban settings.