Occurrence of infections in dogs receiving ciclosporin in a single‐centre UK referral population

OBJECTIVES: The study aimed (a) to describe the occurrence and nature of new infections in dogs receiving oral ciclosporin and (b) to identify any risk factors associated with the development of a new infection whilst receiving ciclosporin. MATERIALS AND METHODS: In this retrospective cohort study, medical records of dogs presented to a private UK referral hospital between March 2015 and September 2022 that received ciclosporin were evaluated. The development of a new infection was classified as confirmed or suspected, based on available data, and the infection was further characterised by causative agent (bacterial, fungal and parasitic) and location (integument, urogenital, hepatobiliary, cardiorespiratory, musculoskeletal and miscellaneous). Risk factors for the development of an infection were assessed using binary logistic regression analysis. RESULTS: Our cohort consisted of 265 dogs with 281 prescribed courses of ciclosporin. Of the included dogs, 33.2% (88/265) developed one or more new infections over the study period. When separated into aetiological groups, 26.0% of dogs (69/265) developed bacterial infections, 4.5% of dogs (12/265) developed fungal infections, 1.1% of dogs (3/265) developed parasitic infections, and 5.6% of dogs (15/265) developed unknown infections. Heavier dogs (increasing body weight OR 1.04, 95% CI 1.01 to 1.07), use of an additional third immunosuppressive agent (OR 1.96, 95% CI 1.09 to 3.51) and those receiving higher daily doses of ciclosporin (>8 mg/kg/day OR 3.01, 95% CI 1.41 to 6.46) were more likely to develop infections. The risk of infection was particularly increased with concurrent use of mycophenolate mofetil (OR 3.43; 95% CI 1.47 to 7.99). The most common locations for infection to occur in were the integument and urogenital systems. CLINICAL SIGNIFICANCE: Increasing body weight, higher doses of ciclosporin and concurrent use of an additional third immunosuppressive agent, particularly mycophenolate, were risk factors for developing novel infections. The risks of ciclosporin treatment must be considered by the clinician and discussed with owners prior to use.