Detection of M. synoviae infection in chickens and its differentiation from M. gallisepticum infection

The response of chickens to experimental infection 'em ovo' with Mycoplasma synoviae

Embryonated chicken eggs were inoculated at 18 days of incubation with a broth culture of Mycoplasma synoviae and the infected chicks were hatched and reared in isolation. Control chicks were hatched following inoculation of eggs with sterile mycoplasma broth. Both groups were closely observed for clinical signs and, at intervals up to 6 weeks infected and control chicks were killed and examined for gross lesions and for isolation of M. synoviae. Four of the 35 infected chicks developed synovitis but there were no other clinical signs. Airsacculitis was encountered in 44% of birds at postmortem examination but M. synoviae was not consistently isolated from affected air sacs. The organism was recovered most frequently from the trachea and lung but sporadic isolations were made from other sites including infraorbital sinus, heart, kidney, liver, spleen and blood. M. synoviae was also isolated consistently from the tracheas of 10 live infected birds until the end of the experiment at 23 weeks. However, the serum plate agglutination test, using a commercial antigen was positive for only half these birds up to ten weeks, and it was not until 15 and 23 weeks that 90% to 100% of the samples were positive.

A urease-ELISA for the detection of mycoplasma infections in poultry

An ELISA utilising a urease-antibody conjugate specific to chicken IgG was examined as an alternative to the serum agglutination and the haemagglutination inhibition tests in the diagnosis of Mycoplasma gallisepticum and M. synoviae infections in poultry. Use of a urease conjugate allowed the serum reactions to be appraised without the need for expensive photometric equipment. Non-specific binding of conjugate to antigen was eliminated by treatment of antigen coated microplates with 10% foetal calf serum in phosphate buffered saline. Some chicken serums produced non-specific reactions. These reactions were reduced without any loss of test sensitivity by making the initial 1:5 dilution of chicken serum in whole sheep serum rather than diluting buffer. Tests on serums from experimentally infected chickens showed that the urease ELISA was specific, and was as sensitive as the serum agglutination test but more sensitive than the haemagglutination inhibition test.