Mycoplasma in Chickens – A Review

Mycoplasma infects chickens all around the world, responsible for enormous economic losses in poultry farming. Mycoplasma infections are problematic as they lack a cell wall and certain metabolic pathways, as well as being small in size and having the smallest genome of any self-replicating organism. As aresult, they are fastidious microorganisms, making it difficult to control.

The primary illness issues have been respiratory diseases and the synergistic impact of mycoplasma on other respiratory infections makes it more complex. In other cases, particularly with certain mycoplasma strains, the consequences might be systemic (infectious synovitis caused by MS or even MG), reproductive (EAA), neurological (S6 strain of MG in turkeys), or causing peritonitis with E coli and other coliforms at the start of lay.

It is more expensive than merely the clinical signs as subclinical costs from lowering egg production, mortality, hatchability, body weight, early chick mortality, embryo mortality, and decreased egg production efficiency are significant. Even if infections do not create issues in one generation, vertical transmission of mycoplasma to the next generation can be problematic and costly.

The fundamental concern is stress

Mycoplasma gallisepticum causes chronic respiratory disease (CRD), whereas Mycoplasma synoviae causes synovitis. Both spread vertically (through certain eggs) from infected breeders to progeny, as well as horizontally via infectious aerosols and contamination of feed, water, and the environment, as well as by human activity on foot (shoes, equipment, etc.). Infection can remain latent in certain birds for days to months, but when they are exposed to cold temperatures, poor air quality, crowding, concurrent infections, and some live virus immunizations can all cause stress, which makes the bird vulnerable to infection. Mycoplasma infections are frequent in multi-age layer flocks and may contribute to lower output. Individuals or flocks once infected become carriers or reservoirs for the rest of their lives. Direct or indirect contact via movement of birds, people, or animals facilitates flock-to-flock transmission.

Uncomplicated and Complicated Mycoplasma

Uncomplicated M. gallisepticum infections in chickens result in relatively mild catarrhal sinusitis, tracheitis, and air sacullitis. Respiratory distress with slight to marked rales, difficulty in breathing, coughing, and/or sneezing. Nasal discharge and conjunctivitis with frothiness around the eyes may be present. Morbidity is high and mortality is low in uncomplicated cases, but poor feeding efficiency and weight gain are economic concerns.

M. gallisepticum infections are frequently complicated by E. coli infections, which cause severe air sac thickening and turbidity with exudative accumulations, pericarditis, and fibrinous perihepatitis.

Mycoplasma synoviae is more serious than Mycoplasma gallisepticum

In comparison to M. gallisepticum infection, clinical implications of M. synoviae infection are more severe and associated with joint problems. The earliest indicators of synovitis are pale-bluish head parts and lameness in many birds which make them to sit for most of the time. Although minor rales may be present in birds with M. synoviae respiratory infection, no further symptoms are normally observed in field conditions which makes it difficult to diagnose at initial stages.

Concurrent Infections

Birds that are stressed or having concurrent infections are more prone to develop clinical symptoms. Birds which are severely infected are depressed and can be spotted resting at feeders and waterers with swollen hocks and footpads, as well as sternal bursitis (breast blisters). Morbidity is high, with a mortality rate ranging from 1% to 10%. When birds are stressed due to poor air quality or are infected with Newcastle disease or infectious bronchitis, they may develop moderate mucoid tracheitis or sinusitis with air sacullitis. The initial stage of infectious synovitis causes a creamy to viscous yellow-grey exudate in most synovial structures, most commonly seen in hock joints and wing joints. This fluid may become inspissated/thickened in chronic cases; swollen liver and occasionally appear green; the spleen and kidneys get pale and enlarged; and birds may be weak and underweight with breast blisters due to sternal recumbency.

Mycoplasma-related losses are more than they appear

Mycoplasma infections in poultry clearly cost more than just the clinical symptoms. Subclinical costs are significant because of reduced egg production and lower production efficiency.

Breeders & Commercial Layers:

Production loss 5-20%; Synovitis morbidity 2-75%; Egg breakage & downgrading; Eggshell apex abnormalities (EAA Concept); Increase embryo mortality 5-10%; Reduced hatchability 5-7%

Commercial Broilers:

Reduced body weight 10 – 20%; Lower FCR 5-15%; Increased mortality 2-7%


Tentative diagnosis based on Flock History, clinical signs, gross lesions.

Swab samples of infraorbital sinuses, nasal turbinates, choanal cleft, trachea, air sacs, lungs, or conjunctiva and joints.

Primary isolation is made in mycoplasma media containing 10%–15% serum.  Colony identification by immunofluorescence with species-specific antibodies. Typical fried-egg appearance.

Confirmatory Test via Hemagglutination-inhibition as nonspecific false agglutination reactions may occur, especially after injection of inactivated oil-emulsion vaccines or infection with M synoviae.

Surveillance via Serology by Agglutination and ELISA

Differential diagnosisMycoplasma gallisepticum – Infections such as E. coli infection, Newcastle disease, avian influenza, infectious bronchitis should be considered.

Mycoplasma synoviae – Skeletal abnormalities and trauma must be eliminated as the causes of lameness. Viral tenosynovitis, staphylococcal and other bacterial joint infections should be rules out.

Real-time PCR-based diagnostic kits, on the other hand, are rapidly being used on most farms nowadays. This produces a result in 70 minutes.

An effective anti-mycoplasma strategy

The most effective strategy for prevention is to develop mycoplasma-free breeder flocks that are managed and maintained under high biosecurity to avoid invasions. To ensure infection-free status, serological examinations must be performed on a regular basis. Mycoplasma-free chickens are desired; however, infection is a problem in commercial multiple-age setups where depopulation is not feasible. As a result, to protect chicks from infections caused by vertical transmission, the first three days of life must be aided with an appropriate antibiotic. Also, a week before administering live or killed vaccines, clean-out programmes are carried out using appropriate antibiotics.

Mycoplasma infection may re-emergebecause of operational or production stress. Hence, provide your birds with a stress-free environment and give them immunity boosters. Also, a once-every-four-week metaphylactic approach with suitable antibiotics has been found to be beneficial in the field conditions.Antibiotics such as Tylvalosin,Tiamulinand Tilmicosin are effective against M. gallisepticum and M. synoviae, but those that act on the cell wall are ineffective, such as penicillins. Tylvalosin is a new generation or advanced macrolide that is widely used nowadays to minimize egg transmission, as a metaphylactic or treatment approach against mycoplasma induced infections.                 

Conflict of Interest: No conflict of interest

For more information please contact Alivira technical desk –

Dr. Balasaheb Vighane, Technical Manager

Dr. Kirankumar Madpathi, Product Manager