The effects of infectious bronchitis superimposed on latent M. gallisepticum infection in adult chickens

Mycoplasmas in the etiology of multifactorial respiratory disease

The avian mycoplasmas pathogenic for commercial poultry, Mycoplasma gallisepticum and Mycoplasma synoviae in chickens and turkeys, and Mycoplasma meleagridis and Mycoplasma iowae in turkeys are egg-transmitted infections and exhibit wide variations in clinical manifestations. Mycoplasma gallisepticum strains vary widely in virulence, tissue tropism, and antigenic makeup and have the ability to alter the expression of major surface antigenic proteins. Although less well studied, strains of M. synoviae, M. meleagridis, and M. iowae appear to exhibit similar variability. Intraspecies variability among mycoplasma strains and their ability to interact with other disease-producing factors explain the wide variability of clinical manifestations, difficulties in diagnosis, their ability to persist within the host for long periods of time, and many of the difficulties involved in control and eradication programs. Mycoplasmas are also well known for their interactions with other infectious agents and environmental factors in producing clinical disease. Control of the clinical manifestations of Mycoplasma infections is simplified when concurrent infections are minimized and optimum environmental conditions are provided.

Avian mycoplasma infections: prototype of mixed infections with mycoplasmas, bacteria and viruses

Mixed infections involving mycoplasmas, viruses and bacteria are well recognized in chickens. Synergism has been demonstrated between Mycoplasma gallisepticum and the viruses of Newcastle disease and infectious bronchitis and Escherichia coli, although the outcome of infection is influenced by many factors associated with the host and the organisms. Airsacculitis in broilers due to M. synoviae or M. gallinarum may be precipitated by concurrent respiratory virus infections including vaccine strains. Turkeys, geese and ducks have been less well studied, but similar interactions seem to occur. Such observations may give an indication as to the likely interactions between mycoplasmas, viruses and bacteria in other host species.

Isolation and identification of avian mycoplasmas in Singapore

Two hundred and forty batches of chickens with chronic respiratory syndrome were tested for mycoplasmas. One hundred and five batches (43.8%) were found to have mycoplasmosis. A total of 110 isolates of mycoplasma was cultured, of which nine isolates were identified as Mycoplasma gallisepticum, 48 avian sero-group D, 45 M. gallinarum, one M. iners and seven unclassified. 2. Identification of the mycoplasmas isolated was carried out by biochemical and serological tests (disc growth inhibition and agar gel diffusion tests). A modified agar gel diffusion test using solubilised antigens with sodium deoxycholate-glucose solution was developed for serotying of mycoplasmas.

[Respiratory diseases of the fowl:principles of histopathological diagnosis]

Groups of specific pathogen free chickens were inoculated with five strains of Newcastle disease virus, one strain of adenovirus, four strains of infectious bronchitis virus, one strain of Mycoplasma gallisepticum and with infectious bronchitis virus together with Mycoplasma gallisepticum. Lungs and tracheas were taken at regular intervals for histopathological examination. A diagnosis could be based on tracheal lesions at different periods of their development. Newcastle disease was distinguished by a necrotic and haemorrhagic tracheitis. Adenovirus infection caused epithelial degeneration with basophil intranuclear inclusion bodies and discrete infiltration of the lamina propria by lymphocytes and histiocytes. Infectious bronchitis was characterised by a strong hyperplasia of epithelial cells and Mycoplasmosis by a massive infiltration of the lamina propria by lymphocytes and histiocytes. Epithelial hyperplasia and cellular infiltration of tracheal mucosa were typical of mixed infection with infectious bronchitis virus and mycoplasma.