Explanation

Yersinia pestis (Pasturella pestis) is the causative agent of plauge. It is transmitted by rats and other rodents and its vector is a flea (Xenopsylla cheopis) which feeds on infected rodents and may bite man. Simalarly, Leishmania donovani (a protozoan) causes Kala-azar or visceral leishmaniasis and trasmitted by bite of sand fly-Phlebotomus.