Cat on ciclosporin that develops fever and dyspnoea
4-year-old cat, a regular hunter, on ciclosporin for 6 weeks for feline atopic skin syndrome. He presents with fever, anorexia, dyspnoea with a diffuse interstitial-alveolar pattern, jaundice and raised ALT. Bronchoalveolar lavage shows Toxoplasma gondii tachyzoites. No serology was performed before treatment.
Which prior measure would have most reduced the risk of this picture?
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A. Prophylactic clindamycin throughout ciclosporin treatment
Routine antibiotic prophylaxis is not recommended: it exposes the cat to adverse effects and resistance and there is no evidence that it replaces avoiding exposure.
B. Use ciclosporin only in seronegative cats, which cannot reactivate cysts
It is the other way round: most fatal cases have been described in seronegative cats that become infected for the first time during treatment. Seropositive cats are unlikely to become ill.
C. Measure blood ciclosporin to keep it below the toxic range
Acute toxoplasmosis has been described at usual therapeutic concentrations; monitoring levels does not remove the risk of a primary infection.
D. Prior serology; if negative, no hunting or raw meat during treatment
Correct. The main risk is primary infection of an immunosuppressed seronegative cat, which can cause fatal disseminated toxoplasmosis (pneumonia, hepatitis). Knowing the serological status allows the owner to be warned and exposure to be limited.
lightbulb Key takeaway
Before ciclosporin or another immunosuppressant in a cat with outdoor access, run Toxoplasma serology. If it develops fever, dyspnoea or hepatopathy during treatment, suspect toxoplasmosis: stop the ciclosporin and start clindamycin.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.