Mycoplasmosis in poultry
Mycoplasma gallisepticum, M. synoviae, M. meleagridis, (M. iowae)
Mycoplasma infections in poultry and birds are caused by different Mycoplasma species, mainly Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS), and in turkeys especially Mycoplasma meleagridis (MM). The aforementioned mycoplasmas show high specificity for poultry and birds and usually do not cause symptoms in mammals. Infection with MG, MS or MM can cause high losses in production in chickens, turkeys and other avian species mainly due to secondary bacterial or viral infections.
The pathogens are introduced into flocks by infected animals and via animate and inanimate vectors; animals in a flock are infected by dust and aerosols via the respiratory tract. The transmission of the pathogens from infected parents via the hatching egg is of great importance for the spread of the infection.
Situation in Austria
Mycoplasma gallisepticum (MG) and Mycoplasma meleagridis (MM) have been suppressed in Austria through consistent control by monitoring the breeding flocks. The occurrence of MG or MM in breeding poultry is notifiable. Mycoplasma synoviae (MS) occurs in Austria in laying birds and in small flocks and is treated with antibiotics, although freedom from the pathogen in the flock often cannot be achieved permanently.
Poultry pathogenic mycoplasmas belong to the genus Mollicutes, order Mycoplasmatales, family Mycoplasmataceae, which can occur intracellularly and extracellularly as cell-wallowing Gram-negative, coccoid-pleomorphic bacteria. Infections in poultry and birds are caused by different Mycoplasma species, mainly Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS), or in turkeys especially Mycoplasma meleagridis (MM) and rarely Mycoplasma iowae. These mycoplasmas occur worldwide and cause high losses in poultry production with high morbidity but low mortality. They are resistant to many antibiotics due to the lack of a cell wall, but are sensitive to commercial disinfectants and environmental exposure.
Infections are often chronic or subclinical, presenting with symptoms of the upper respiratory tract, conjunctiva, air sacs, and ovarian tract only when stressors are encountered in the poultry flock. Animals may be latently infected and transmit mycoplasma vertically through the hatching egg, resulting in poor hatch rates, increased chick mortality, and weak-living chicks. Infection with MG, MS, or MM can cause high production losses in chickens, turkeys, and other avian species primarily due to secondary bacterial (e.g., E. coli, Pasteurella sp., ORT) or viral infections (e.g., IBV, NDV, ART) or other stressors preferentially during the laying phase. These animals show a general decrease in performance (fattening or laying performance) and catarrhal or fibrinous exudates on the mucous membranes of the respiratory tract. Rhinitis, sneezing, nasal and ocular discharge, as well as rales breathing and consequent poor feed intake show up due to sinusitis, conjunctivitis to highly swollen eyelids, bronchitis and aerosacculitis. Especially in MS infections, immobility or lameness is possible due to joint inflammation with marked swelling and visible eggshell deformities.
Turkeys are particularly susceptible to mycoplasmas and show severe symptomatology, which may be expressed as torticollis and opisthotonus when infecting the nervous system.
The above mycoplasmas show high specificity for poultry and birds and usually do not cause symptoms in mammals. Turkeys and chickens are particularly susceptible. Cases in pheasants, peacocks, pigeons, quail, ducks, geese, and parrot birds have been reported.
PCR methods for antigen detection are available for individual animal diagnostics. PCR methods and serological tests are used for flock testing, which is carried out in accordance with the Poultry Hygiene Ordinance (2007) or in self-monitoring programs of the Poultry Health Service (QGV) in breeding animals. Serum rapid agglutination and elisa techniques are the main serological screening methods used.
Bacteriological diagnosis by means of culturing mycoplasmas requires swabs from the respiratory tract of diseased animals, freshly dead animals, or animals frozen immediately after death. Bacteriological culture is usually only possible in special laboratories due to the high demands of the pathogens on the culture media and the resulting complexity of culture medium preparation.
Last updated: 10.10.2023