Mycoplasma is the most common disease in backyard chickens and turkeys and predisposes to other diseases. It is carried by wild birds and is very contagious, so quarantining new stock is vital.

Disease background

Mycoplasma in poultry is not a new disease. There is mention in the old books of similar symptoms from about 100 ago but it has generally been called roup or a common cold. Treatment tended to be culling only.

The disease acquired the name mycoplasma once the causative organism has been discovered. Mainly the respiratory system in poultry is affected. The incubation period before clinical signs appear can be as little as a few days - it is very infectious. It appears to thrive in the bird when other pathogens are present, such as E.coli or infectious bronchiti. Debilitating factors include nutritional deficiency, excessive environmental ammonia and dust and stressors such as changes in the pecking order or exhibitions.

Cause and clinical signs

The organism is neither a bacterium nor a virus in size, but partway between, having no cell wall but with a plasma membrane. Four out of the know 17 species of mycoplasma are pathogenic in poultry:

• Mycoplasma galliseptum: signs can include foamy eyes, sneezing, nasal discharge, swollen eyelids and sinuses, reduced egg production and gasping in chickens, turkeys and pheasants, swollen sinuses in waterfowl. This one is the main culprit in back yard flocks.
• Mycoplasma synoviae: signs include swollen and hot joints in chickens and turkeys and/ or respiratory signs as above. Egg shells become weak ar the broad end.
• Mycoplasma meleagridis: signs include poor growth in turkey poults and lowered hatchability in turkey breeders.
• Mycoplasma iowae: signs include reduced hatchability in turkey breeders, twisted legs in turkey poults. When nasal discharge is evident, feathers become stained with this as the bird tries to clean its eyes and nostrils. There is a distinctive sweet smell associated with this discharge which to the sensitive nose is immediately apparent when entering a hen house.

Transmission

Nasal discharge and cool temperatures are protective of the organism so any sneezing will deposit droplets which will remain infective for several days. Transmission is also through the egg, plus carried on the clothes and hands of people tending the birds.

Economic impact

Reduced egg production and reduced weight gain in chickens, turkeys, waterfowl and pheasants. Poor welfare.

Treatment

Antibiotic treatment will not completely cure the disease but will reduce the incidence to a tolerably low level. Tylan Soluble is licensed for the treatment of mycoplasma, Baytril Oral should not be used in laying hens. Tylan Soluble can be given to new stock in quarantine if mycoplasma had been diagnosed on the premises. With chronically infected birds, if breathing is still noisy after treatment, the bird must be culled as the organism will be too deeply entrenched within the airsacs and hollow bones to be removed, the bird remaining a carrier which will infect others.

Prevention

• Keep stressors to a minimum or if a known stressor such as a show is imminent, give vitamin supplementation. There are several useful products on the market which contain probiotics and/ or vitamins, administered in the water.
• Use a suitable disinfectant for both huts and equipment such as Virkon or F10.
• Keep dust and ammonia levels low. Ammonia paralyses the small hairs which act like an escalator to move normal mucus up the trachea before being swallowed. Pathogens love mucus.
• Feed high quality commercial food for the stage of growth and the species of the bird.
• Monitor weather changes and take steps to minimise any effects.
• When attending to the stock, begin with the youngest at the start of the day (i.e with clean clothes),
• Quarantine new stock for 2-3 weeks, treat with Tylan Soluble as soon as the birds are obtained if there has been mycoplasma in your flock.
• Do not buy from auctions.
• If adult stock are kept symptom free the risk of passing mycoplasma on through the egg is reduced.
• If young stock happen to be exposed to a mild bout of mycoplasma they will acquire a certain amount of immunity as long as there are no other pathogens (such as E.coli) present.
• Biosecurity

Vaccination

There is a mycoplasma vaccine marketed by MSD but it is recommended not to use it in breeding chickens. This appears to be because the manufacturers do not know how long the vaccine is effective.

By Victoria Roberts BVSc MRCVS