I have chosen to investigate the infectious disease Leishmaniasis, it is a disease that is strongly linked to poverty and as such is relatively unknown in the developed world. Leishmaniasis is a vector-borne parasitic disease caused by over 20 species of the protozoa Leishmania. Leishmaniasis is transmitted through the bite of an infected sand fly. The promasitgote form of the parasite is phagocytized by macrophages where it develops into the amastigote form, multiplies and infects other cells. It is possible for the more severe form of leishmaniasis, visceral leishmaniasis, to be transmitted through transfusions and needle sharing, congenital transmission appears to be very rare.
There are several forms of Leishmaniasis. Cutaneous leishmaniasis is the most common form of the disease; it is rarely fatal and involves skin sores which often resolve on their own without treatment. Mucocutaneous leishmaniasis is a possible complication of cutaneous leishmaniasis, usually due to L. braziliensis, which can cause destruction of mucosal structures such as the nasal septum and soft palate. My focus in this blog will be on the most deadly form of leishmaniasis which is visceral leishmaniasis, also known as kala-azar in parts of the world.
Leishmaniasis is found in 88 countries and as many as 12 million are currently infected. There are 1-2 million new cases each year. Of these 1-2 million new leishmaniasis cases a year and estimated 1.5 million are cutaneous leishmaniasis with the more severe visceral form accounting for about 500,000 new cases. Over 90% of visceral leishmaniasis cases occur in India, Bangladesh, Nepal, Sudan and Brazil. Visceral leishmaniasis is most often caused by L. donovani and L. infantum and without proper treatment it is fatal in >90% of cases. There have been several epidemics of visceral leishmaniasis. Malnutrition, displacement, poor housing and immunosuppresion are known risk factors and thus epidemics tend to occur in hard to reach places that are suffering from famine, war or mass population movements. In Southern Sudan a major epidemic occurring from 1984 to 1994 was estimated to have killed 100,000 in a population of about 300,000 in the upper Nile region. Most cases of leishmaniasis in the United States reflect individuals who were infected during travel or who immigrated to the U.S after they were infected. There have been a few cases of cutaneous leishmaniasis infections in Texas and Oklahoma but there have been no known cases of visceral leishmaniasis acquired in the United States.
There is no prophylactic medication to take if you are traveling to a part of the world where leishmaniasis is endemic. Disease prevention involves avoiding being bitten by the sand fly which hosts the Leishmania genus through use of bug spray, mosquito nets, clothing which covers extremities and avoiding being outside in the evening when the sand fly is most active.
For more information visit: www.cdc.gov
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