Mycoplasma gallisepticum (MG) is a bacterial pathogen that primarily impacts poultry, causing a respiratory disease. The disease can lead to considerable economic losses in commercial poultry operations due to its effects on bird health and productivity.
Understanding Mycoplasma gallisepticum
Mycoplasma gallisepticum most commonly affects chickens and turkeys, but it can also infect other avian species such as pheasants, quail, and various wild birds. Once birds are infected, they often become chronic carriers of the bacterium. The incubation period can vary from 6 to 21 days, though birds may remain asymptomatic for longer periods until stressed.
Transmission of Mycoplasma gallisepticum occurs through several pathways. Vertical transmission happens when infected hens pass the bacterium directly to their offspring through the egg. Horizontal transmission is also common, occurring through direct bird-to-bird contact via infectious aerosols, such as respiratory droplets. Indirect transmission can occur through contaminated feed, water, or the environment, as well as via fomites like shoes, clothing, or equipment.
Recognizable Signs in Poultry
Mycoplasma gallisepticum infection manifests primarily through respiratory signs in poultry. Birds may exhibit sneezing, coughing, and rales, which are rattling or crackling sounds heard during breathing. Nasal discharge can also be present, often appearing as clear fluid.
Ocular signs are also frequently observed in infected birds. These include foamy eyes or swollen eyelids, which can be quite noticeable. Beyond respiratory and ocular symptoms, general signs of illness include reduced feed intake, leading to poor growth rates in younger birds. Laying hens may experience a noticeable decrease in egg production, and egg quality can also be affected.
Identifying and Managing Infections
Identifying Mycoplasma gallisepticum infections in poultry involves specific diagnostic tests. Serological tests, such as the rapid serum agglutination (RSA) test or enzyme-linked immunosorbent assay (ELISA), detect antibodies produced by the bird’s immune system in response to the bacterium. A positive serological test indicates exposure to MG, but it does not confirm an active infection.
For definitive diagnosis, molecular tests like Polymerase Chain Reaction (PCR) are frequently used. PCR tests detect the genetic material of the bacterium directly from samples, such as tracheal or choanal swabs, providing a highly accurate confirmation of infection.
Once an infection is confirmed, managing the flock often involves the use of antibiotics. Certain antibiotics, such as tylosin, tetracyclines, or enrofloxacin, can help reduce the clinical signs and lessen the severity of the disease. However, antibiotics do not eliminate the Mycoplasma gallisepticum infection from the birds; they primarily reduce bacterial shedding and mitigate symptoms, helping to prevent secondary bacterial infections. In situations with severe disease outbreaks or in breeding flocks where eradication is desired, culling of infected birds may be considered to prevent further spread of the bacterium.
Preventing Outbreaks
Preventing Mycoplasma gallisepticum outbreaks relies heavily on implementing robust biosecurity measures. A fundamental practice is quarantining any new birds introduced to an existing flock for at least 30 days to monitor for signs of disease before integration. During this time, new birds should be housed separately with dedicated equipment to avoid cross-contamination.
Maintaining strict hygiene for coops and equipment is also important. Regularly cleaning and disinfecting all housing, feeders, and waterers helps to eliminate potential bacterial reservoirs. Limiting access for wild birds to poultry areas is important, as they can carry and transmit Mycoplasma gallisepticum without showing symptoms. Using netting or secure fencing can help deter wild birds from interacting with domestic poultry.
Controlling visitor traffic to the poultry area is another practical step. Limiting who enters the coop and requiring visitors to wear clean footwear and clothing or use footbaths can significantly reduce the risk of indirect transmission. Sourcing birds from Mycoplasma gallisepticum-free flocks is a primary prevention method, as this ensures that new additions are not carriers. While vaccines are available, they reduce the severity of symptoms and the amount of bacteria shed by infected birds, thereby reducing disease transmission within a flock. Early detection of sick birds and their prompt isolation from the rest of the flock can also help contain an outbreak and prevent widespread infection.