EXPERIMENTAL-INFECTION OF TURKEYS WITH MYCOPLASMA-GALLISEPTICUM OF LOW VIRULENCE, TRANSMISSIBILITY, AND IMMUNOGENICITY

Three-week-old turkeys were inoculated intranasally with approximately 10(6) colony-forming units (CFU) of putative variant Mycoplasma gallisepticum (MG) strains M876, M35, or the virulent S6 reference strain. Uninoculated turkeys in each group served as contact sentinels. The hemagglutination-inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA) were used to determine serologic responses. MG was isolated from 100% and 92% of S6- and M876-inoculated turkeys, respectively, on day 7 PI. However, culture-positive rates among M876-inoculated turkeys declined more rapidly, transmission to contact sentinels took longer and occurred at lower rates, and serologic responses measured by HI and ELISA were lower than in S6-infected turkeys. Testing sera from inoculated turkeys for antibodies to MG in homologous and heterologous ELISA systems indicated that strain M876 was significantly (P < 0.05) less immunogenic than S6 (days 62 and 95 PI), and that the homologous ELISA was more sensitive (P < 0.005). MG strain M35 failed to infect turkeys in three attempts, even though the inocula used were viable on culture media.