B311 - MYCOPLASMOSIS (M. GALLISEPTICUM)

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B311 - MYCOPLASMOSIS (M. GALLISEPTICUM)

Nature of the disease
Mycoplasmosis due to M. gallisepticum (MG) is a chronic respiratory disease of birds.
Classification
OIE, List B disease
Susceptible species
Chicken, turkeys, pheasants, peafowl, guinea fowl, quail, ducks, pigeons and wide range of wild birds.
Distribution
Worldwide, in the Pacific Region it is identified or suspected in most places.
Clinical signs 
The incubation period varies between 1 to 3 weeks. Clinical signs include:
  • Nasal discharge,
  • Foamy or bubbly condition of the eyes
  • Persistent hacking cough, sneezing and sniffing, and tracheal rales. 
  • Poor physical condition and loss of weight 
  • In broilers, the onset of signs are severe and include severe reduced growth rate and feed intake. 
  • In layers there is a marked drop in egg production and feed consumption. Production may continue at a lower level.

Morbidity is high and mortality is low, excepting for turkeys where mortality is very high.

Post-mortem findings 
Sinusitis, tracheitis and air-sacculitis. The mucous membranes are thickened, hyperplasic and necrotic.
Differential diagnosis 
Specimens required for diagnosis
Culture of MG is difficult but it can be attempted from aspirates from the infraorbital sinuses or joint cavities and from yolk or embryos and from swabs or organs. Antigen detection and DNA detection more commonly used.
Transmission   
In poultry, transmission occurs by direct contact, air-borne respiratory droplets, dust (dried faecal material), contaminated equipment and via eggs.
Risk of introduction   
MG could be introduced by importation of live birds, hatching eggs and day-old birds. Migratory birds could also introduce the disease.  
Control / vaccines  
Control of the disease is done by strict Isolation of infected flocks, destruction and burial of animals, disinfection of premises.

Vaccines are available but when possible, the disease should be eradicated. 

References
  • Mycoplasma Gallisepticum Infection, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p. 1928-1929
  • Office International des Epizooties, 2002