Abstract: Leishmania donovani, causes Visceral Leishmaniasis (VL), which is very serious disease and endemic in warmer part of the world covering almost 88 countries. It is most prevalent in India, Bangladesh, southern Sudan, Nepal and northeast Brazil. VL is transmitted by an insect vector i.e. Sand fly (Phelobotomus argentipus) that lives in warmer places (cervics, tree hole, dung and domestic wastes) where humidity and temperature both are present at regular intervals in a day (humidity during night and temperature at day time). These conditions are essential / necessary for the survival of vector, parasite development and for their distribution. But now a day, due to global climate changes and temperature increases, which support the high degree of sand fly growth, the transmission of disease has increased manifold. The flooding also increase the transmission of larvae from one place to another place thus also increases the distribution of disease.