New study reveals recent trends in canine leishmaniosis in the UK

11 December 2024

Dogs infected with Leishmania infantum have been increasingly reported in the UK, predominantly in imported or travelled dogs, and up-to-date epidemiologic data are essential to control the disease in emerging areas like the UK¹.

A new study, published in Veterinary Parasitology, used a novel approach based on large-scale electronic health record data from both diagnostic laboratories and veterinary practices to provide new insights into recent trends in Leishmania infection in UK dogs¹. The study used data collected by the Small Animal Veterinary Surveillance Network (SAVSNET) between 2010 and 2022 on leishmaniosis in pet dogs and cats from five national veterinary diagnostic laboratories and 251 veterinary practices, where clinical leishmaniosis cases were identified through text mining tools and subsequently manually validated.

From the diagnostic laboratories, a total of 25,327 diagnostic samples were analysed; 20,517 sera tested by either quantitative ELISA or IFAT, and 4,810 by PCR. Leishmania infantum antibodies were detected in 39.7% of dog samples tested – in 41% of samples tested by ELISA and 37% of samples by IFAT – whilst leishmania DNA was detected by PCR in only 12% of samples tested. Seropositivity increased in samples from 2013 to 2022, whilst there was a modest decrease in the proportion of PCR-positive samples from 2005 to 2022. Far fewer cat samples were tested; only 1% of these were seropositive by IFAT and there were no leishmania detections by PCR.

From clinical narratives from the veterinary practice data, 368 dogs with canine leishmaniosis were identified. Factors associated with a significantly increased risk of leishmaniosis were being neutered compared with entire; Pointing dogs and crossbreed dogs compared with Retrievers; and dogs aged 3-6 years compared to those 2 years or less. Most cases were recorded in the southeast of England (34%) and there was an increased risk of cases recorded from 2017 to 2022, compared to 2014.

Of the dogs with leishmania, half (51%) had been rescued or imported from, or had visited overseas, predominantly Spain, Greece, Cyprus and other southern European countries. For the remaining cases, no travel history was recorded, although none specified that the dog hadn’t travelled, so these cases could not be considered a result of autochthonous infection.

When presented for consultation, half (50%) of the dogs were sick, with the most common clinical signs reported being skin disorders, followed by poor general condition and lymphadenopathy, ocular disorders, articular disorders and disorders in the renal function. The most common treatment, in cases where this was recorded, was allopurinol either alone (75%) or in combination with miltefosine (16%), pentavalent antimonial drugs (3%) or domperidone (4%).

As SAVSNET doesn’t collect data from all veterinary practices or diagnostic laboratories, the total canine leishmaniosis cases are likely to be higher. However, because each sample tested could not be linked to an individual dog, it’s possible that samples from the same animal from different times may have been included in the analysis, giving an overestimation of seroprevalence.

Take home message

An increase in both the proportion of dog samples testing positive for Leishmania infantum infection and the number of dogs with leishmaniosis in the UK was found in this study, with an increased risk in neutered dogs, Pointing and crossbreed dogs; dogs aged 3-6 years and dogs in southeast England. This emphasises the spread of canine leishmaniosis via travelling dogs and the importance of testing clinically healthy dogs travelling to or from endemic areas. The findings of this study form a baseline for future patterns of canine leishmaniosis to be monitored against and identifies potential control points for the disease.

Reference

¹Checa R, Sánchez-Vizcaíno F, Miró G, Pinchbeck G, Jones H, Noble P-J & Radford AD (2024) Updating the epidemiology of canine leishmaniosis in the United Kingdom through the use of electronic health data. Veterinary Parasitology. doi.org/10.1016/j.vetpar.2024.110350.