Four Mycoplasma species are recognised as pathogens of avian hosts, although more than 23 different Mycoplasma species have been recovered from birds. Mycoplasma gallisepticum is the pathogen addressed in this datasheet, but Mycoplasma synoviae may be seen in chickens and turkeys in association with synovitis and/or airsacculitis; Mycoplasma iowae may occur in several hosts but it is normally asso
ciated with mortality of turkey embryos but can give rise to joint and bone abnormalities and occasional airsacculitis; Mycoplasma meleagridis is usually found in turkeys causing airsacculitis, poor growth and skeletal abnormalities in progeny, and it has been associated with poor hatchability. gallisepticum causes chronic respiratory disease of domestic poultry, especially in the presence of management stresses and/or other respiratory pathogens. Disease is characterised by coryza, conjunctivitis, sneezing, and by sinusitis, particularly in turkeys and game birds. It can result in loss of production and downgrading of meat-type birds, and loss of egg production. Mycoplasma gallisepticum and Mycoplasma synoviae are on the World Organisation for Animal Health (OIE) list of economically important diseases and infections are notifiable to them. The EU Directive 2009/198 includes Mycoplasma gallisepticum and Mycoplasma meleagridis and relates to animal health conditions governing intra-Community trade and imports from third countries of poultry and hatching eggs. Mycoplasma gallisepticum (Mg) is the most economically significant mycoplasma pathogen of poultry and has a world-wide distribution (Levisohn and Kleven, 2000). Infection with Mg may manifest in different ways but chronic respiratory disease (CRD) and downgrading of carcasses in meat-type birds is probably the most severe forms. Mg is often one of the aetiological agents in a multi-factorial disease complex, which may include respiratory viruses, Escherichia coli, Haemophilusparagallinarum and other bacteria. Loss of egg production in laying birds may occur and is usually most marked at peak laying times. Conjunctivitis and sinusitis may occur with severe infections causing inflammation of the tissues around the eyes resulting in a swollen distorted face. Mg is transmitted both vertically from hen to progeny through the egg (in ovo), through the semen of infected roosters; and horizontally by the respiratory route. Mg has been reported in wild birds, particularly as a cause of conjunctivitis in house finches (Carpodacus mexicanus) in North America where the disease emerged in 1994 (Ley et al., 2006). Antimicrobial treatment may reduce the impact of the disease, but can not be relied upon to eliminate the disease. Good biosecurity and obtaining birds from Mg free stock is a good way of preventing diseases. Some live attenuated vaccines are available, but some questions about their effectiveness and ability to cause disease still need to be addressed. The Mycoplasma species that occur in avian host species are not zoonotic.
