Delhi Boil also known as Cutaneous leishmaniasis is a skin related problem which is spread in different parts of the world and also this particular parasite is capbale of infecting human and scores of other species. Check here for further details-
http://en.wikipedia.org/wiki/Cutaneous_leishmaniasis
Much has already been said..adding on to what is already given here..When an individual is bitten by the sandfly, promastigotes are introduced into the skin and enter small blood vessels and macrophages around the affected area.