Serological and Molecular Evaluation of Leishmania infantum Infection in Stray Cats in a Nonendemic Area in Northern Italy

Infection by Leishmania species is increasing worldwide. It was hypothesized recently that cats act as a secondary reservoir for Leishmania infection. The aim of the present study was to assess the prevalence of Leishmania infantum antibodies and DNA in blood samples collected in a sample of stray cats in metropolitan area of Milan in northern Italy, which is a nonendemic area for leishmaniasis. An indirect immunofluorescence antibody test for L. infantum showed that 59 of 233 cats (25.3%) were seroreactive, 38 samples (16.3%) had antibody titers of 1？:？40, 15 (6.4%) had antibody titers of 1？:？80, and 6 (2.6%) had antibody titers of 1？:？160. Feline immunodeficiency virus (FIV) seropositive status was statistically associated with seroreactivity to L. infantum ( ) as shown by univariate and multivariate logistic regression ( ; OR？=？7.34). All blood samples that were tested using real-time PCR were negative for parasite DNA. These results were surprising, since no autochthonous human or canine cases of leishmaniasis have ever been reported in this region of northern Italy. It is possible that this high seroreactivity to L. infantum could be due to cross-reaction with antigens from other parasites. Additional studies that include parasite isolation are needed to clarify our findings on feline leishmaniasis in this region. 1. Introduction Leishmaniasis in the Old World is caused by the protozoa Leishmania infantum. It is prevalent in countries in the Mediterranean basin, and dogs are the main reservoir of the parasite in that region [1]. In recent years, autochthonous cases of human and canine disease have been recorded at higher latitudes, namely, in Germany [2, 3], The Netherlands [4], and North America [5]. Infections have also been reported in species other than dogs and humans, including horses [6] and cows [7]. There have been numerous reports of feline leishmaniasis (FeL), mostly in cats living in known endemic areas [8–10]; some of the cats had concurrent immunosuppressive infections [9–11]. In countries in southern Europe, where canine leishmaniasis (CanL) is endemic, serological investigations of feline populations have revealed seroprevalence rates ranging from less than 1% to more than 60% [9–21]. Given the diffusion of Leishmania infection and the lack of information regarding infection rates in cats in the Milan metropolitan area in northern Italy, the aim of the present study was to assess the prevalence of leishmaniasis in a large representative sample of stray cats from this nonendemic area. A secondary aim was to analyze the results