Updating the epidemiology of canine leishmaniosis in the United Kingdom through the use of electronic health data

Dogs infected with Leishmania infantum have been increasingly reported in the UK mostly related to imported/travelled dogs. Up-to-date epidemiologic data are essential for a better control of this zoonotic disease in such emerging areas. This study aimed for the first time, to estimate the percentage and temporal variation of dog and cat samples testing positive for L. infantum infection at commercial diagnostic laboratories, and to describe the travel history of positive dogs and cats positive to leishmaniosis in a network of UK veterinary practices. Leishmania infantum serology and PCR data were collected by the Small Animal Veterinary Surveillance Network (SAVSNET) from five UK national veterinary diagnostic laboratories between 2010 and 2022 and were analysed. In addition, electronic health records (EHRs) were collected from 251 veterinary practices across the UK between March 2014 and September 2022. Text mining tools were used to identify cases compatible with clinical leishmaniosis as recorded in the clinical narratives; these were subsequently manually validated. Data from a total of 25,327 diagnostic samples (25,201 from dogs and 126 from cats) were analysed including 20,517 sera tested by either quantitative ELISA or IFAT, and 4810 by PCR. Leishmania infantum antibodies were detected in 39.7 % of tested dog samples and 1.07 % of cat samples. In dogs, seropositivity increased from 2013 to 2022. Leishmania DNA was only detected by PCR in samples from dogs (11.8 %). A total of 368 dogs with canine leishmaniosis (CanL) were identified from clinical narratives. Of these, 189 had either visited, or were rescued/imported from, Spain, Greece, Cyprus and other southern European countries. Among factors associated with CanL in the UK canine population, dogs between 3 and 6 years of age were 4.71 times more likely to have CanL than those two years or younger. In addition, there was an increased risk of having recorded CanL clinical cases from 2017 to 2022, compared to 2014. Southeast of England was the UK region that accounted for the highest number of CanL cases (34.51 %). This study provides recent trends in Leishmania infection in dogs in the UK, identifies risk factors and countries likely associated with imported cases, and provides important insights to help plan and monitor national intervention strategies.