Leishmania donovani, L. tropica, L. braziliensis are flagellate pathogenic parasitic protozoa. The organism is transmitted by blood-sucking sandflies of the genus Phlebotomus. Infection of the blood cells is obtained by using carbohydrates from the host’s body fluids. It is seen most often in tropic and subtropic regions. Leishmaniasis was the parasitic disease found in the returning troops after Desert Storm. They were prevented from donating blood for this reason. In 1990, there were twelve million cases of leishmaniasis worldwide, killing hundreds of thousands of people in India, China, North Africa, and Brazil. The number of cases continues to grow.
After the sandfly bites, and the organism has entered the bloodstream, special white blood cells called macrophages engulf the invader, but cannot kill it. Instead, it is carried throughout the body hidden in the white blood cell. The organism is capable of producing two types of disease. One consists of ulcerated skin or mucosal lesions, known as cutaneous leishmaniasis. The other is a more serious infection, known as visceral leishmaniasis, involving such internal organs as the lymph nodes, liver, bone marrow, and spleen. It can also dissolve the brain. This type is more common in Africa, Latin America, India, and the Middle East.
Cutaneous leishmaniasis generally appears on an extremity or the face. It begins as a small itchy pimple that enlarges over time, forming an ulcer. This is often accompanied by swollen lymph glands. Other lesions may form around the edge and fuse with the primary one. Usually, the ulcers come to a head in three to six months, and, if left alone, leaves a pitted depigmented scar. Sometimes the lesions fail to heal, particularly on the ear, leading to progressive destruction of the external part of the ear. If the protozoa lodges in the nose, it causes a disfiguring disease called espundia, where the nasal septum is destroyed, collapsing the nasal structure. The palate is sometimes perforated, and the upper lip becomes so grossly swollen that the patient is unable to eat and virtually starves to death.
Visceral leishmaniasis generally causes fever, weight loss, spleen and liver enlargments, and anemia. This disease can be annoyingly difficult to diagnose, and, if not properly treated, can be fatal. Advanced lesions are difficult to treat, sometimes taking up to a year and a half for healing. The most deadly form of the disease is called Kala-azar. Diagnosis involves tests of the blood, bone marrow, liver, spleen, or lymph nodes for microscopic examination or cultures for the organism in WBC’s. This type of leishmaniasis has a mortality rate of 90% if untreated, but even with treatment, about 10% will still succumb to the disease.
Symptoms appear two to eight weeks after a bite, but the incubation period can last as long as two years. These include high fever with chills, weakness, watery diarrhea, abdominal pain, headaches, and a chronic irritating cough. The disease recurs in epidemic form at twenty-year intervals, when a new generation of the non-immune enters the community. The cause of the disease is determined by the species of parasite and the immune response of the host. There are also types of leishmania that come from Central and South America, as well as from Mexico. These are known as L. mexicana or L. braziliensis.