The application of molecular techniques to the surveillance and control of leishmaniasis in Italy: the facts and doubts

Abstract

Leishmaniases are parasitic diseases caused by various species of the protozoan Leishmania. In Italy human visceral and cutaneous leishmaniases are caused by Leishmania infantum, which has the dog as domestic reservoir, and different Phlebotominae species as the vector. Several molecular techniques are currently used with success for a rapid, very sensitive and non‐invasive detection of Leishmania organisms in specimens of infected organs. The high sensitivity, however, may raise doubts on the significance of target DNA detection, which may represent either an established infection—with or without epidemiological importance—or just a trace of parasite–host contacts. Three examples of the application of nested PCR technique using rDNA sequence primers on different biological samples, are reported here: (a) five different bioptic samples were examined from 153 dogs of an endemic focus of canine leishmaniasis (CanL) (Salina Island, Sicily), giving a Leishmania prevalence of 82.8%, in contrast with 31.4% seroprevalence; (b) in a new CanL focus of Rome province; 60/127 Phlebotomus perniciosus (45.7,0%) were found positive by nested PCR, in contrast with 1.4% microscopically positive; and (c) leishmanial DNA was detected in a natural case of leishmaniasis in a novel mammal host, a domestic ferret (Mustela putorius furo). These results raise the following doubts, respectively: (a) Does the high “infection” prevalence detected in dogs correspond to the “infectiveness‐to‐the vector” prevalence? (b) Can the positive sandflies transmit infective promastigotes? and (c) Can an infected domestic ferret play a role as parasite reservoir?