Outcomes and Clinicopathological Findings in Vaccinated and Unvaccinated Dogs with Leptospirosis-Associated Acute Kidney Injury Admitted to Intensive Care

Background: Canine leptospirosis is a significant clinical challenge in intensive care. This retrospective study evaluated prognostic factors and clinicopathological findings in dogs with leptospirosis-associated acute kidney injury (AKI), focusing on age and vaccination status. Methods: In 63 dogs admitted to two referral intensive care units (2020–2025), mortality was analysed by age class, vaccination status (unvaccinated, L2, L4), and presumptive infecting serogroup using the chi-square or Fisher’s exact test, a linear-by-linear trend test, and multivariable logistic regression. We compared 27 haematological and biochemical parameters among vaccination groups with the Kruskal–Wallis test, applying Bonferroni correction for multiple comparisons, and between survivors and non-survivors with the Mann–Whitney U test. Results: Overall mortality was 56% (35/63) and increased with age (31% in dogs ≤1 year, 59% in dogs 2–6 years, 67% in dogs ≥7 years; p = 0.028). Age was independently associated with death in multivariable analysis (odds ratio 1.16 per year, 95% CI 1.02–1.32; p = 0.023). Mortality did not differ significantly by vaccination status (OR 0.35, 95% CI 0.12–1.07; p = 0.067). Only the platelet count differed significantly among vaccination groups (p = 0.040), with the lowest values in L4-vaccinated dogs. No hematologic or biochemical parameter differed between survivors and non-survivors after correction for multiple comparisons. Conclusions: Advanced age was associated with mortality in canine leptospirosis, although this association was attenuated in a sensitivity analysis excluding euthanised dogs. In this critical-care cohort, vaccination status was not significantly associated with outcome; the study describes vaccine breakthrough cases requiring intensive care and, by design, cannot establish vaccine efficacy.