Current questions of the control of Mycoplasma synoviae infection

Mycoplasma synoviae infection is widepread both abroad and in Hungary because of the variability of strains in this Mycoplasma species. Some strains have decreased virulence in layers. For this reason breeding companies do not lay stress on eradication of M. synoviae infection from their breeding stocks. On the other hand variant strains show a significant virulence for broiler chickens and broiler breeders, especially in combination with some virus infections (e. g. infectious bronchitis). Organotropism of variant strains has changed also in the last few years; M. synoviae infection causes no synovitis but respiratory disease. Variant strains have different antigen structure, they induce a weak and late serological response making serological detection of the infection difficult. It is more difficult Co culture the variant strains and to perform more modern methods, such as ELISA, DNA probes, PCR, Western blot. M synoviae strains have higher antibiotic resistance than other avian mycoplasmas, therefore it is more difficult to treat infected flocks successfully. To decrease the economical losses caused by M. synoviae it is important to diagnose the infection as soon as possible. Infected flocks should be treated in the framework of a systematic program to prevent decrease of egg production and spread of infection to their offspring. Broiler chicken flocks originating from infected parent flocks should be also treated with adequate antibiotics. Every effort should be made to import M. synoviae free flocks and to raise them free of Mycoplasma infection.