Some epidemiological consequences of the evolutionary fit between Leishmaniae and their phlebotomine vectors

There is a more or less close fit between Leishmania species and their vectors with the proven vector of one parasite often unable to support the full development of another. This fit is presumably a result of coevolution of vector and parasite and it is notable that, if a Leishmania has different invertebrate hosts in different parts of its range, the vectors are often closely related. The epidemiological consequences of this restriction are, firstly, that the spread of the cutaneous leishmaniases of the Old World and, to a lesser degree, that of visceral leishmaniasis is restricted by the distribution of suitable vectors and, secondly, that secondary vectors are of less importance on the epidemiology of the leishmaniases than they are in malaria.