Monitoring and detection of new endemic foci of canine leishmaniosis in northern continental Italy: An update from a study involving five regions (2018–2019)

Canine leishmaniosis (CanL) is an emerging zoonosis caused by Leishmania infantum and transmitted in southern Europe by phlebotomine sand flies of the subgenus Phlebotomus (Larroussius). Endemic foci of CanL have been recorded in northern continental Italy since early 1990s and attributed to the northward expansion of vector populations due to climatic changes in association with travelling/relocated infected dogs from the southern Mediterranean littoral. In this study, further spread of endemic Leishmania foci was monitored during 2018–2019 in five regions (Aosta Valley, Piedmont, Lombardy, Veneto and Friuli-Venezia Giulia), with focus to territories where investigations were not performed, or they have been inconclusive. Clinical cases of CanL identified by local veterinary practitioners and confirmed by reference diagnosis centers were regarded as autochthonous if their origin from, or travel to, areas endemic for CanL were excluded in the previous ≥2 years. Around these index cases, i) serosurveys for L infantum were carried out where indicated, ii) sampling from potential autochthonous cases in healthy or clinically-suspected resident dogs was intensified by collaborating veterinary practitioners, and iii) suitable sites were investigated for the presence of competent phlebotomine vectors. Fifty-seven municipalities whose enzootic status of CanL was unreported before 2018, were identified as endemic. The stability of 27 foci recorded over the past decade, was also confirmed. Competent phlebotomine vectors, mainly Phlebotomus perniciosus, were collected for the first time in 23 municipalities. The newly recorded endemic municipalities appear to be distributed over a west-to-east decreasing gradient: 30 in Piedmont, 21 in Lombardy, 4 in Veneto and 2 in Friuli-Venezia Giulia. As regards Veneto, it should be noted that a relatively restricted territory was investigated as several municipalities of the region had already been surveyed and detected as endemic for CanL in the past. Cold climate conditions of the easternmost region of Friuli-Venezia Giulia bordering non-endemic territories of Slovenia, are probably less favorable to L infantum transmission.