Disease Background

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

The disease acquired the name mycoplasma once the causative organism had been discovered. Mainly the respiratory system in poultry is affected and the disease may be becoming more common, spreading with increased travelling of stock, or it may be that we are hearing about it more with improved communications.

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 bronchitis (IB is certainly now more common in free-range flocks) or if the birds are stressed or debilitated. Debilitating factors include nutritional deficiency, excessive environmental ammonia and dust and stressors such as changes in the pecking order or exhibitions.

Figure 1. Normal turkey head (note quite sunken appearance): Bourbon Red female

Cause and Clinical Signs

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

Mycoplasma gallisepticum: 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 backyard flocks.

Mycoplasma synoviae: signs include swollen and hot joints in chickens and turkeys and/or respiratory signs as above.

Mycoplasma meleagridis: signs include poor growth in turkey poults and lowered hatchability in turkey breeders.

Figure 2. Normal chicken head: Australorp female

Mycoplasma iowae: signs included 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 particular 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.

Figure 3. Nebraskan Spotted Turkey with Mycoplasma. Note swollen sinus (arrowed)

Economic Impact

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

Diagnosis

Diagnosis is on clinical signs, see above.

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, as is Baytril injection but this product does not cope with some field strains. Baytril Oral should not be used in laying hens. Tylan oral preparation (soluble) is effective in young stock but seems to be less effective in older stock. Tylan 200 injection (not licensed for poultry) is effective with 0.5ml in the breast muscle of an adult large fowl, 0.3ml for bantams, 0.75-1ml for adult turkeys, repeated 48 hours later if still sneezing. If still noisy after that 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.

The reason Tylan 200 is not licensed for poultry is because it harms muscle, which in a meat bird is disastrous but in backyard or fancy poultry which do not enter the food chain, it is not really an issue.

Figure 4. Swollen joint due to Mycoplasma

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.
• Feed high quality commercial food for the stage of growth and the species of 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).
• Either quarantine new stock for two to three weeks or inject once with Tylan 200 as soon as the birds are obtained if there has been mycoplasma in your flock.
• Some very conscientious breeders inject stock they sell and warn buyers of the disease risk.
• 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.

Figure 5. White Orpington with severely swollen sinuses and nasal discharge

Vaccination

There is a mycoplasma vaccine marketed by Intervet 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.

With vigilance, mycoplasma can be kept at a low level in backyard flocks thus increasing the welfare of the birds.

Further Reading

Find out more information on mycoplasmas in poultry by clicking here.

May 2013