Mycoplasma gallisepticum causes chronic respiratory disease (CRD) in chickens. The incubation period is 1-3 weeks. In young birds, the disease is less severe than adults and the predisposing factors are concurrent bacterial (E.coli) and viral (Reovirus) infections. The disease is characterized by nasal discharge, shaking of head, coughing, tracheal rales and swelling of infraorbital sinuses. The affected birds suffer from loss of condition, reduced egg production and lowered fertility. The infection passes to next generation through eggs. Hence, it is absolutely essential to use Mycoplasma free embryos for production of vaccines. Ideally, it is preferable to use specific pathogen free (SPF) embryos.
The diagnosis of the disease is carried out by observing symptoms, lesions and using serological tests like rapid serum plate agglutination, tube agglutination, and haemagglutination inhibition tests. The diseased birds should be destroyed and egg transmission can be prevented by dipping the eggs in antibiotic solutions like tylosin and erythromycin, before hatching.
The other species M. synoviae causes infectious synovitis in chicken and turkey poults. It is characterized by swollen joints, bursitis and splenomegaly and more common in young birds of 4-12 weeks of age than adults. M. melagridis is responsible for air sacculitis in turkeys. Since turkey farming is coming up in India, it is necessary to look for these organisms. M. gallinarum is isolated from respiratory tract of chicken and turkeys of all age. On experimental inoculation, the organism causes air sacculitis