Experimental Chlamydia psittaci Infection of Japanese Quail

Japanese quail were used for the infection model of avian chlamydiosis. One‐day‐old Japanese quail were highly susceptible to lethal infection by a Chlamydia psittaci strain of budgerigar origin upon inoculation via the air sac route with 10 4.1 FFU of the organism, showing an acute and lethal course with chlamydial propagation. In contrast, 7‐day‐old quail developed resistance to the infection as shown by the lack of lethal effect with the same dose. The resistance of 7‐day‐old birds was abolished by immunosuppressive treatment with cyclophosphamide. Upon inoculation with a sublethal dose of 10 2.1 FFU, latent infection was established in 1‐day‐old birds with a minimum number of the organism. The latent infection in the birds was converted to the lethal form by treatment with cyclophosphamide along with chlamydial propagation and suppression of antibody production.