- The Phlebotomus sandfly is the primary vector responsible for the transmission of kala-azar (visceral leishmaniasis).
- It transmits the protozoan parasite Leishmania donovani during blood feeding.
- The parasite invades the reticuloendothelial system, causing systemic infection characterized by fever, hepatosplenomegaly, and pancytopenia.
- The disease is endemic in areas where the sandfly thrives, and control measures target reducing sandfly exposure. Other listed vectors do not transmit Leishmania spp. responsible for kala-azar.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Tropical Medicine, Page 840.