Canine leishmaniosis is expanding northward in Italy, new incidence mapping shows

Canine leishmaniosis is no longer confined to Italy’s traditional endemic areas in the south. A new nationwide analysis shows marked geographic expansion into central and northern regions, with particularly high incidence proxies still concentrated in southern Italy and Sicily but new hotspots also emerging in the northwest.

The study analysed routine diagnostic data from 2022–2023 and developed a provincial incidence proxy by combining newly diagnosed canine leishmaniosis cases with estimated dog population denominators. Rates were expressed as cases per 10,000 dogs and provinces were grouped into five operational risk categories.

Nearly one quarter of provinces were moderate to very high risk

Incidence estimates ranged from 0 to almost 500 cases per 10,000 dogs.

Among Italian provinces:

• 49 provinces (45.4%) were classified as minimal risk

• 30 (27.8%) as low risk

• 21 (19.4%) as moderate risk

• 4 (3.7%) as high risk

• 4 (3.7%) as very high risk.

Most minimal- and low-risk provinces were located in northern and central Italy, whereas higher-risk categories were concentrated in the south and Sicily. However, the study identified an important exception: Imperia and Savona, in Liguria, were classified among the very-high-risk provinces, reinforcing evidence that Leishmania infantum transmission is moving beyond its historical Mediterranean distribution.

From prevalence to incidence

The authors argue that traditional prevalence estimates can be difficult to compare because diagnostic submissions are influenced by clinical suspicion, sampling strategy and test performance. Their incidence-based approach instead focuses on newly diagnosed cases relative to the estimated canine population, providing a tool for identifying areas where transmission pressure may be changing.

The estimates were tested using several alternative dog-population assumptions (including dog-to-human ratios of 1:4, 1:5 and 1:6) and through comparisons with regions covered by Italy’s SINAC dog registry. Although absolute incidence values changed with the denominator used, the broad geographic ranking remained relatively stable.

Dogs as sentinels in a One Health framework

Because dogs are the principal domestic reservoir of Leishmania infantum, changes in canine infection can provide an early indication of changing human exposure risk.

The authors therefore propose incidence mapping as a complement to prevalence surveillance, particularly for spatial prioritisation, prevention and risk communication.

The findings reinforce a broader epidemiological shift already observed across Europe: climatic and ecological changes affecting sand-fly vectors are helping canine leishmaniosis expand into regions previously considered marginal or non-endemic.