Mycoplasmas are the smallest known bacteria also called as Mollicutes. Mollicutes is derived from two Latin words Mollis and cutes meaning soft body. Mycoplasmas don’t have cell wall, they are wall less bacteria. Their size ranges from to equal to the size of Pox virus. Their key feature is absence of cell wall and due to the absence of cell wall they are naturally resistance to penicillin and other Beta – Lactams. They have cholesterol in plasma membrane. Most of the Mycoplasmas move by gliding movement.

Mycoplasma gallisepticum

Mycoplasma gallisepticum is a pathogen of avian species and it does not cause disease in humans. Even eating infected eggs don’t harm humans. But don’t use antibiotics treated eggs.

History

Respiratory disease in chickens was firstly described in 1905 but the causative agent of the disease remains undiscovered for more than 50 years after the discovery of disease. After 50 years the Mycoplasma gallisepticum was isolated and cultivated from chickens. In 1980 it was isolated in turkey in American states. It was due to the close contact between domestic poultry and wild turkey. In 1994 the Mycoplasma gallisepticum was also isolated from household finches suffering from mycoplasmal conjunctivitis.

Taxonomy

Mycoplasma gallisepticum is an important pathogen in avian species. It causes disease in chickens, turkey, pigeons and other birds too. Its classification is as follows;

Physiology

Mycoplasmas are obligate parasites. They are dependent on external cholesterol source for the synthesis of their plasma membrane. So they need their host for the synthesis of plasma membrane and growth. They are dependent on host for getting most of their compounds. They require especial growth requirements and hence special media for their growth. 5 to 10 % of Carbon dioxide is required for their growth.

Diseases

Mycoplasma gallisepticum is mainly involved in causing chronic respiratory disease in birds. Following are the diseases caused by Mycoplasma gallisepticum in following birds.

Turkeys:

Mycoplasma gallisepticum cause respiratory infection in turkeys which includes sinusitis, airsacculitis and pneumonia. The birds have symptoms of coughing, sneezing, nasal discharge, ocular discharge, inability to breathe, swelling of sinuses, weight loss and impaired vision.

Chickens:

In chickens the respiratory disease includes coughing, sneezing, difficulties in breathing, ocular and nasal discharge, poor productivity and retard growth, reduce hatchability and abnormal growth of feathers in chickens.

House finches:

Mycoplasma gallisepticum is also involved in causing conjunctivitis in house finches. The bird have impaired vision, nasal and ocular discharge, swelling of periocular membrane, weight loss and depression. Birds feel irritation in eyes and start rubbing their eyes to the feathers of other birds causing a spread in disease.

• Mycoplasma gallisepticum also cause diseases in quail, geese, gamebirs, ducks, peafowl, pigeons and other avian species.

Transmission

Mycoplasma gallisepticum can only survive for few days without a host. Its transmission is from infected poultry to their offsprings through eggs. Disease can also transmit by breeding with an infected partner. Disease can also be spread through the body secretions of sick and even recovered birds. Cages, coops, tools, equipments and people working with live poultry can also spread disease through their clothing, footwear and equipments used.

Pathology

Mycoplasmas are surface parasites. They attaches to the surface of respiratory tract. Major adhesion protein named as P1 attaches to the sialoglycolipids receptors. Mycoplasma gallisepticum causes oxidative damage by producing hydrogen peroxide and superoxide redicals. Resulting in that there is an immune response causing inflammation.

Signs and Symptoms

Mycoplasma gallisepticum is involved in causing chronic respiratory disease in birds. Following are the signs and symptoms associated with the disease:

• Nasal discharge
• Ocular discharge
• Coughing and sneezing
• Difficulties in breathing
• Foamy eyes
• Slow growth and less productivity
• Stunting
• Reduce hatching of eggs and less viability of chickens
• Post-mortem lesions on respiratory tract
• Airsacculitis
• Pericarditis
• Nasal passages, Trachea, bronchi having catarrhal inflammation

Disease can be more severe in the presence of E. coli, bronchitis and Newcastle disease. If the level of dust ammonia is high the disease can be more severe.

Further complications

In chickens Mycoplasma gallisepticum can further cause tracheitis, airsacculitis and mild catarrhal sinusitis. Encephalalitic form of disease is also observed in turkeys. Mycoplasma gallisepticum mainly affects respiratory tract, eyes and sinuses. Bird could also be died if there is a presence of a secondary infection.

Diagnosis

Typical respiratory lesions and other signs and symptoms help in detection of disease. The tissue swab samples are taken from sinus, trachea and inner eyelids. Then following diagnosis tests can be done.

Culturing:

After taking sample culturing is done in Mycoplasma free embryos or it can be done in Mycoplasma broth. After that it is cultured on Mycoplasma agar and then isolation and identification is done.

Serology:

Serum plate agglutination (SPA) test is done as standard screening test for Mycoplasma gallisepticum. For primary screening test ELISA is done. For confirmatory test haemagglutination inhibition (HI) test is done. More commonly and preferable test for diagnosis is serum plate agglutination test.

Molecular testing:

DNA based special PCR kits are available. If we want to know the flock status urgently PCR could be done for that purpose.

Treatment

Birds having Mycoplasma gallisepticum once remain the carrier of the disease throughout their life. Antibiotics treatment is given to teat the disease. Usually tetracyclines, fluoroquinolones, tylosin, spiramycin can be given to reduce the infection. Even after treatment the bird can spread the disease more efforts should be done in prevention of secondary infection.

Prevention

To prevent Mycoplasma gallisepticum infection following preventive measures should be taken so that there should be reduction or absence of the disease.

• Routine monitoring of flock with the help of serological testing.
• Infected bird should be slaughter immediately to prevent the spread of Mycoplasma gallisepticum to the flock.
• Fertile hatching eggs should be checked for the absence of Mycoplasma.
• Inactivated bacterins are proving to be effective in prevention of respiratory lesions in birds.
• A proper dust ammonia removal setup should be present.
• Proper cleaning and disinfection of poultry house should be done.
• Live attenuated or natural mild strains can be used as vaccines.