Sand flies play significant role in spreading kala-azar because they

• suck blood only from the patients suffering from kala-azar

• convert amastigote into promastigote

• engulf amastigote at the time of blood sucking from the infected persons

• inject promastigote into the body of non-infected persons at the time of blood sucking

B.

convert amastigote into promastigote

C.

engulf amastigote at the time of blood sucking from the infected persons

D.

inject promastigote into the body of non-infected persons at the time of blood sucking

Kala-azar is a slow progressing indigenous disease caused by a protozoan parasite of genus Leishmania end spread by the bite of certain types of sandflies.

Sandfly takes a blood meal from the patient of kala-azar and injects its macrophages infected with amastigotes. In sandfly midgut these amastigotes gets transformed into promastigote multiply differentiate into metacyclic promastigotes and migrate to proboscis. Amastigotes again get transferred into the skin of host (non-infected person) at the time of blood sucking.