Leishmaniasis Life Cycle
Leishmaniasis is a disease caused by infection of the Leishmania parasite. The parasite is transmitted through the bite of an infected sand fly. There are two common forms of the disease, one that causes skin sores and another that infects the organs, including the spleen, liver and bone marrow. It is estimated by the Centers for Disease Control that there are about 2 million new cases of leishmaniasis in the world each year. Most cases occur in Mexico, Central America, South American and some parts of Asia, the Middle East, Africa and southern Europe. There are 21 species of the parasite that cause infection in people.
Bite
The life cycle of the disease begins when an infected female sand fly bites a person. Female sand flies must have blood for the development of their eggs, so it is common for them to seek a human to supply this meal. When the bite occurs, the sand fly injects the promastigotes, or the infective stage of the Leishmania parasite, into the person.
Infection
Through binary fission, reproduction starts to take place and the infection spreads. In the form of the disease that infects internal organs, the parasite then begins infection there and enters into the circulation system of their host.
Reproduction
At this point, if a sand fly chooses the infected human as the source of a blood meal, it will again ingest the parasite. Within the sand fly's body, the parasite -- now in its promastigote stage again -- will reproduce. The parasite will stay inside the sand fly for four to 25 days.
Completion
As the parasite protozoa reproduce within the sand fly, they migrate toward the insect's pharynx, creating a blockage in its esophagus. When the sand fly gets ready to feed, it cleans out its esophagus -- containing the promastigotes -- by injecting the leishmaniae into the skin of the person or animal from which it is preparing to feed. The life cycle of leishmaniasis is now full circle.
Treatment
Bringing the life cycle to an end through treatment depends upon what form of the disease has occurred. For the disease that infects the skin, topical paromycin is often used. If the lesions caused by the disease are more invasive, sodium stibogluconate, meglumine antimoniate or pentamidine may be prescribed. In the form of the disease known as mucosal, pentavalent antimony is often prescribed over a four-week course. For the leishmaniasis disease that infects organs, pentavalent antimony compound is the most common treatment protocol.
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