Ocular toxoplasmosis in cats: how to interpret serology
4-year-old cat with outdoor access and bilateral anterior uveitis with multifocal chorioretinitis. FeLV and FIV negative. Toxoplasma gondii serology shows low-titre positive IgG and negative IgM.
Which statement is correct?
chevron_right Show answer and explanation
A. Positive IgG confirms ocular toxoplasmosis
Many healthy cats with outdoor access are IgG positive from previous exposure. On its own it does not prove that the parasite is causing the uveitis.
B. Negative IgM rules out toxoplasmosis
IgM is transient and may be negative in reactivations or chronic infections, so it does not exclude disease.
C. All seropositive cats should be treated with clindamycin even without signs
Treating healthy seropositive cats is not indicated: it does not eliminate tissue cysts and gives no clinical benefit.
D. Diagnosis is presumptive: compatible serology, clinical signs, exclusion of other causes and response to clindamycin plus topical corticosteroid
Correct. There is no simple definitive test; diagnosis relies on IgM or rising IgG titres, ruling out FIP, FeLV, FIV and lymphoma, and response to treatment. The topical corticosteroid controls the anterior uveitis.
lightbulb Key takeaway
Toxoplasma serology in a cat with uveitis must be interpreted with caution: positive IgG only indicates exposure. Repeat serology after 2–3 weeks to look for a rising titre, and remember that chorioretinitis needs systemic treatment.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.