Tropical Diseases

Another disease spread by insects is leishmaniasis, a sickness caused by several types of protozoa carried by sand flies. In the mid 1990s, the disease was infecting about 12 million people worldwide, killing about 1,000 annually. It is spread when sand flies draw blood from individuals who already are infected. Hosts can be humans, dogs, or other mammals.

Each of the four major clinical syndromes of the disease have a long incubation period that ranges from three months to 24 months. The disease is marked by one or more skin lesions and varies in severity depending on the type. Kala Azar, one of the types, is commonly found in East Africa and the Sahara. Kala Azar causes fever, diarrhea, enlarged liver, and anemia. Another type, Old World leishmaniasis, usually heals on its own and is marked by multiple lesions.

Treatment depends on the type of leishmaniasis and may include the use of drug therapy and transfusions for several weeks. The need for extended medical care makes treatment of leishmaniasis impossible for many poor individuals in developing countries, raising the mortality rate of the disease.