Avian mycoplasmosis :

               Mycoplasma causes respiratory infection ( chronic respiratory disease) in chicken, turkey and other avian sps.

• Morbidity is typically high and mortality is low in affected flocks in uncomplicated cases; signs are generally more severe in turkey.
• In Turkey, it frequently results in swollen infraorbital sinuses; thus called “infectious sinusitis”.

  Etiology :

1. gallisepticum ( most pathogenic avian mycoplasma )

    [ it is very small , lack cell wall so sensitized to antibiotic like           

                    penicillin ]

1. synoviae 🠞 causes infectious synovitis

 In experimental cases ; IP = 6-21 days

Naturally IP = variable ; infected birds maybe asymptomatic until they   

                            stressed

Transmission :

a. Horizontal transmission :

• Close contact between birds
• Aerosol spreads over short distances and can be responsible for transmission within a flock.
• Contamination of feed, water and environment .
• Fomites ( shoes, equipment)

b. Vertical transmission :

• Egg transmission occurs more frequent in birds infected during laying than n birds infected before they mature.
• Infected birds can be carriers and can remain asymptomatic until they are stressed .

• Stress condition :
• Infection ( bacterial , viral )
• Vaccination with live viruses
• Cold weather
• Crowding or poor air quality
• Concurrent infection ( newcastle disease , IBV , E. coli )

     Pathogenesis :

               When the organisms enter  into body through route of inhalation

                                   🠋

                They bind to mucosal surface of upper respiratory tract ( trachea , bronchi , sinus )

                                   🠋

                  Causes respiratory lesions

                       ( tracheitis , bronchitis , sinusitis )

                                   🠋

              Activates host immune system and killed or neutralized by activation of B-cell and T-cell

                              ( cell mediated immunity )

                            🠋

             Some of them remains unkilled and remains in URT of chicken and turkey for long time

                            🠋

               When there is stressed condition or concurrent infection with E. coli or NDV

                            🠋

                 Chronic respiratory lesions occurs

Clinical signs:

• Depression
• Slight to marked rales
• Coughing and sneezing
• Dyspnea
• Decrease weight gain , feed efficiency and egg production
• In turkey; swelling of infraorbital sinus
• In laying flocks; chronic increase in mortality and decrease in overall production rate

Postmortem lesions :

• In case of uncomplicated infection ; there is relatively mild catarrhal sinusitis, tracheitis and air sacculitis
• When E. coli infection occurs more concurrent ; there is severe air sac thickening and turbidity with exudative accumulation , adhesive pericarditis and fibrinous perihepatitis .

• Turkey ; severe mucopurulent sinusitis and varying degree of tracheitis and air sacculitis .

Microscopic lesions:

• Involved mucous membranes ( trachea , air sac ) are thickened, hyperplastic, necrotic , infiltrated with inflammatory cells, formation of lymphoid follicles.
• Mucosa lamina propria contain focal areas of lymphoid hyperplasia and germinal center formation
• Tubulo-alveolar elongation of tracheal glands
• Presence of lymphoid follicles in walls of air vesicles.

Diagnosis :

• History
• Clinical signs and lesions
• Isolation and identification of organism
• Serological test : HI test ( confirmatory test )

                           ELISA

• Molecular level test : Real Time- PCR ( RT-PCR )

                                [ due to its fastidious nature and difficulty in isolation ; it is method for                              

                                               detection and characterization ]

Fig : Photomicrograph of air sac showing severe mononuclear cell infiltration along with few PMN and congestion

  DDx :

• coli infection
• Newcastle disease
• Avian influenza
• Infectious bronchitis
• Fowl cholera