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Visceral leishmaniasis is a life-threatening disease caused by the leishmania parasite. The symptoms of infection include anemia, fever, enlarged liver, enlarged spleen and weight loss. This disease is often fatal if left untreated.
Infested sandflies carry the leishmania parasites inside their intestines. The parasites multiply rapidly inside the sandfly and eventually migrate toward the throat, where they clog the insect's esophagus. The fly, which feeds on blood, clears its throat by expelling the parasites into a human host while feeding. The pathogens then multiply inside the human host and cause infection.
Leishmaniasis infections can occur in three different forms. Visceral leishmaniasis is the most serious form of the disease and causes death in the majority of its victims. Cutaneous leishmaniasis, which is characterized by multiple ulcerations on the skin, causes severe scarring. Mucocutaneous leishmaniasis permanently disfigures individuals by attacking and destroying the tissues around the nose and throat.
Visceral leishmaniasis is most common in Brazil, India, Nepal, Bangladesh and parts of Africa. Individuals who suffer from acquired immune deficiency syndrome (AIDS) are at significantly higher risk than the general population. Men and children are more likely to develop visceral leishmaniasis than adult women. Malnourished and diseased people also are at risk of infection.
A single bite from a sandfly can inject enough parasites into the bloodstream to infect a human. Some of the symptoms of infection include fever, weight loss and anemia. People in India call the disease kala azar, or black disease, because the skin of infected patients darkens in color.
As the disease progresses, patients often develop an enlarged liver and spleen, and they might have distorted or extended abdomens. Some people experience internal bleeding. Patients sometimes hemorrhage to death or die of secondary infections because their immune systems are weakened by the disease.
A medical practitioner can perform a bone marrow biopsy or a blood test to look for leishmania parasites. He or she might also other run other tests, such as enzyme-linked immunosorbent assay, indirect fluorescent antibody or liver function tests, to confirm the diagnosis. The doctor treats the disease with anti-fungal medications such as amphotericin B. He or she might also prescribe antibiotics for infections or administer blood transfusions if the patient is bleeding internally.
People who live in or visit high-risk areas should limit the time they spend outdoors after dark, which is when sandflies are most active. Insect repellents and protective clothing can help prevent sandflies from biting. Individuals who survive an attack of visceral leishmaniasis are immune to reinfection.