Kala-azar is a slow progressing indigenous disease caused by a protozoan parasite of genus Leishmania. Kala-azar also known as black fever and Dumdum fever. It is most severe form of leishmaniosis.
It is parasitic infection transmitted by sand fly (Leishmania donovani), a blood-sucking pest, which is found in moist (humid) mud and sand and in close proximity to livestock. It signs and symptoms include fever, weight loss, fatigue, anemia, and substantial swelling of liver and spleen.
Recently, Scientists have found that parasite called Leptomonas seymouri hosting virus called Lepsey NLV1 may be also responsible for spread of kala-azar. Earlier it was believed that parasite Leishmanial donovani (sand fly) alone is responsible for spread of the dreaded infection.