Isolation of Chlamydia psittaci from cats with conjunctivitis

Chlamydia psittaci was repeatedly demonstrated in stained smears of conjunctival scrapings from a group of cats in a single household and in 5 instances the organism was isolated by yolk sac inoculation of 6-day-old pathogen free, embryonated hen eggs. Thirteen of 15 cats in the cattery developed conjunctivitis at various times over a 9-month period. The outstanding features of the disease were its severity, chronicity and refractoriness to treatment. Prolonged (2 week) treatment with tetracycline was required to effect clinical recovery. Nine of 14 cats in the household developed significant complement-fixing (CF) antibody titres (greater than 128) to the chlamydia group antigen. A single serum from the owner had a titre of 32 although no associated illness was recognized. Of 134 serums collected from random source cats aged 1 month to 16 years, 17 (12.7%) also contained CF antibody to chlamydia group antigen. This is the first report of the isolation of chlamydia from cats with conjunctivitis outside North America and the first report to indicate general incidence figures for chlamydia infection of cats where vaccination is not used.