Comparison of efficacy and safety of preventive measures used against canine leishmaniasis in southern European countries: Longitudinal retrospective study in 1647 client-owned dogs (2012-2016).

The best preventive strategy for canine leishmaniasis is, to date, unknown. In the last few years, new preventive measures have become available in Europe, including vaccination against leishmaniasis and the use of domperidone. The objective of the present study was to evaluate the efficacy and safety of the different preventive measures available against leishmaniasis in client-owned dogs. A database search of medical records was carried out in 52 private veterinary practices located in endemic areas of canine leishmaniasis in Spain, Italy and Portugal. Healthy seronegative dogs were included in the study. Serology was repeated at least 6 months later, and was used to retrospectively classify dogs into healthy, infected or sick. A total of 1647 dogs were included in the study. The use of preventive measures in this population was widespread. The single most utilized measure was repellents alone in 45.7% of dogs, followed by the combination of repellents and vaccination in 23.0%, repellents and domperidone in 11.3%, vaccination alone in 4.2%, vaccination and domperidone in 2.7%, domperidone alone in 2.3%, and the combination of the three measures in 0.2% of dogs. No preventive measure was applied in 10.7% dogs. The incidence of clinical leishmaniasis in the group with no preventive treatment applied was 12.5%. In the groups where prevention was applied, the reported incidence was the following: 10.1% for the vaccination only group, 4.5% for repellents only group, 4.0% for repellents + vaccination group, and 0.5% for repellents + domperidone group. No dogs in the groups of domperidone, vaccination + domperidone, and combination of the three measures developed clinical leishmaniasis. All preventive measures resulted in a significantly lower incidence of leishmaniasis compared to not applying any measure, except for vaccination alone. The majority of preventive strategies used, with exception of vaccination alone, decreased the incidence of leishmaniasis significantly. Adverse events, mild and self-limiting in most of the cases, were reported in 5.2% of dogs and were significantly more common in dogs following vaccination. In conclusion, this is the first large-scale field study investigating the efficacy and safety of the preventive measures used routinely against leishmaniasis in client-owned dogs. Most preventive strategies used, with exception of vaccination alone, had some benefit over not applying any preventive. In this field study, the use of repellents showed a good degree of protection in dogs living in endemic areas of canine leishmaniasis. Although lower numbers of dogs are included, the use of domperidone appeared to provide additional protection. The role of vaccination and its combination with other preventive strategies needs further study.