Comparison of "Pathotypes" Among Chlamydial (Psittacosis) Strains Recovered From Diseased Birds and Mammals

¹ National Animal Disease Laboratory, Animal Disease and Parasite Research Division, Agricultural Research Service, United States Department of Agriculture, Ames, Iowa

Studies of the pathogenicity for laboratory animals of organisms of the genus Chlamydia (psittacosis-LGV-trachoma group) recovered from diseased birds and mammals were extended to include three strains isolated from cows which had a history of encephalomyelitis or abortion. Each of the strains was titrated or passaged in chicken embryos, mice, guinea pigs, pigeons, turkeys, sparrows, parakeets and sheep. In terms of pathogenicity for these animals, one of the bovine abortion strains was identical to a previously studied pigeon strain in that it produced severe systemic disease indistinguishable from psittacosis in mice, pigeons, sparrows, parakeets and turkeys, while not affecting sheep or guinea pigs. The second abortion strain produced lesions in mice and chicken embryos only. The encephalomyelitis strain caused death and severe lesions in guinea pigs and dwarfing of chicken embryos but otherwise failed to affect the other test species. The "pathotype" determination may reveal significant epizootiologic relationships and may be useful in identifying the source of chlamydiae to domestic animals or in recognizing mutants with new pathogenic capabilities.