Comparison of some ovine Chlamydia psittaci isolates by indirect immunofluorescence

Four ovine abortion isolates, including the A22 vaccine isolate, and an isolate from a case of lamb arthritis, were compared by indirect immunofluorescence using antisera raised in chickens and mice. Cross titrations with homologous and heterologous antisera showed a one-way reaction between the single chlamydial isolate from a lamb with arthritis and the four isolates from cases of ovine enzootic abortion. The abortion isolates could not be distinguished.