Life cycle of LEISHMANIA DONOVANI

Leishmania Donovani has two stages in its life cycle –

    A .. Leishmanial form in the Mammallam host –

i)                    Man , dog or a wild rodent may be infected .

ii)                  During the blood meal , the infected sandfly introduces the leptomonad form of L.D body . The leptomonad forms are taken up by macrophages and change into leishmanial forms

iii)                In the human beings , the leishmanial forms will reside in the cells of reticulo endothelial system  . these will multiply by binary fission .

iv)                When the cells become packed with the parasite , the macrophages will enlarged and ultimately rupture . Then the parasite enter into circulation and are engulfed by new macrophages and cycle is repeated . Ultimately the entire R.E system becomes infected . This leishmanial form may be engulfed by neutrophils and monocytes .

    B.. Leptomonad form in female sandfly –

i)                    During blood meal , a sandfly may be infected . The sandfly will draw blood along with the leishmanial forms which are present within the monocytes of an infected person .

ii)                  In midgut of sandfly , the leisshmanial form will change into leptomonad form on the third day of blood meal . Then there will be multiplication and this process will continue upto seven days .

iii)                The flagellates or leptomonad forms then enter to pharynx and buccal cavity of the sandfly . The oesophagus will be completely blocked by flagelets and this will occur between 6^th and 9^th day of blood meal of sandfly . But salivary gland will not be affected .