Early Lesions in Chicken and Turkey Embryos Inoculated with Mycoplasma gallisepticum Strain S6 at Various Stages of Incubation

Abstract

Much of the variability reported in earlier studies of the lesions induced in chick embryos by mycoplasma is probably referrable to the use of poorly characterized organisms. Another important discrepancy results from the use of dead and chilled embryos, which would also tend to cloud the histopathologic results. This study sought only to define the early lesions of Mycoplasma gallisepticum (Strain S6) infections in chicken and turkey embryos at various stages of incubation. The only previous embryo work with this strain of Mycoplasma is that of Casorso (1), who reported the failure of this organism to produce lesions in 7-day-old chicken embryos. No histopathologic studies seem to have been made of this infection in turkey embryos. The S6 strain of M. gallisepticum is a neurotropic strain isolated from a turkey brain which readily produces a severe cerebral arteritis when inoculated intravenously in poults aged 2 to 7 weeks (4,5,6). By this route it is much less pathogenic to chicks. Thomas et al. (6) found only a single case of very mild arteritis among 8 inoculated 3-day-old hatched chicks. However, they demonstrated that this organism produced a toxin that was probably responsible for the vascular changes. This strain, in addition to its neurotropic tendencies, will incite severe respiratory disease in turkeys and chickens, depending on the route of inoculation (9).