Leishmaniasis

Overview :

Protozoa are considered to be the most simple organisms in the animal kingdom. They are all single-celled. The types of protozoa that cause leishmaniasis are carried by the blood-sucking sandfly. The sandfly is referred to as the disease vector, simply meaning that the infectious agent (the protozoan) is carried by the sandfly and passed on to other animals or humans in whom the protozoan will set up residence and cause disease. The animal or human in which the protozoan then resides is referred to as the host. Once the protozoan is within the human host, the human's immune system is activated to try to combat the invader. Specialized immune cells called macrophages work to swallow up the protozoa. Usually, this technique kills a foreign invader, but these protozoa can survive and flourish within macrophages. The protozoa multiply within the macrophages, ultimately causing the macrophage to burst open. The protozoa are released, and take up residence within other neighboring cells. At this point, the course of the disease caused by the protozoa is dependent on the specific type of protozoa, and on the type of reaction the protozoa elicits from the immune system. There are several types of protozoa that cause leishmaniasis, and they cause different patterns of disease progression. At any one time, about 20 million people throughout the world are infected with leishmaniasis. Between one million and one and one-half million cases of cutaenous leishmaniasis are reported yearly worldwide. While leishmaniasis exists as a disease in 88 countries on five continents, some countries are hit harder than others. These include Bangladesh, India, Nepal, Sudan, Afghanistan, Brazil, Iran, Peru, Saudi Arabia, and Syria. Other areas that harbor the causative protozoa include China, many countries throughout Africa, Mexico, Central and South America, Turkey, and Greece. Although less frequent, cases have occurred in the United States, in Texas. As Americans travel to these countries, they will come in contact the protozoa that cause forms of leishmaniasis. Also, physicians were advised in 2004 to suspect cutaneous leishmaniasis in military personnel who were deployed to areas where the infection is present. From August 2002 to February 2004, staff from the U.S. Department of Defense identified 522 confirmed cases of the disease in American military personnel. In some areas of southern Europe, leishmaniasis is becoming an important disease that infects people with weakened immune systems. In particular, individuals with acquired immunodeficiency syndrome (AIDS) are at great risk of this infection.