Avian Mycoplasmosis (Mycoplasma gallisepticum)

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Avian Mycoplasmosis (Mycoplasma gallisepticum)

“Pleuropneumonia–like Organism (PPLO) Infection, Chronic Respiratory Disease,

Infectious Sinusitis, House Finch Conjunctivitis”

      Importance

  

                              Mycoplasma gallisepticum is the most economically significant mycoplasmal pathogen of poultry. M. gallisepticum infections can cause significant economic losses on poultry farms from chronic respiratory disease reduced feed efficiency, decreased growth and decreased egg production. The carcasses of birds sent to slaughter may also be downgraded. M. gallisepticum infections are also notifies by to the World Organization for Animal Health (OIE). This organism has been eradicated from most commercial chicken and turkey breeding flocks in the United States; however, it remains endemic in many other poultry operations

              Etiology

                     Avian mycoplasmosis is be caused by several speciesof Mycoplasma

                           “class Mollicutes, order Mycoplasmatales, family Mycoplasmataceae’

                Mycoplasma gallisepticum, M. synoviae, M. meleagridis and M. iowae. M. gallisepticum”

“M. gallisepticum infections are also known as chronic respiratory disease (CRD) of chickens, infectious sinusitis of turkeys and house finch conjunctivitis.”

                         Several strains of M. gallisepticum have been reported, including the R (poultry), 

    P (psittacine) and house finch strains. Strains may vary greatly in their pathogenicity for 

    different species of birds.

    Transmission

M. gallisepticum is transmitted

•   During close contact between birds as well as on fomites.
• Aerosol spread occurs over short distances.
•  Can be responsible for transmission within a flock.

                 M. gallisepticum is also transmitted vertically in eggs.                                     

  Incubation Period

• Experimentally infected poultry develop symptoms after 6 to 21 days.
• In natural infections, the incubation period is variable; infected birds may be asymptomatic for   days          or months until stressed.
•   In finches, incubation periods from 4 to 14 days have been reported

  Clinical Signs

“M. gallisepticum infections vary from asymptomatic to severe, depending on the infecting strain and other factors. More severe infections are seen when the birds are infected concurrently with Newcastle disease virus, infectious bronchitis virus, Escherichia coli or other pathogens. “

 Infected chickens usually develop respiratory symptoms that may include

•   Rales,  
•  Coughing,
•  Sneezing,          
• Nasal discharges
•  Dark or black comb 
• Dyspnea

          Postmortem Lesions

In uncomplicated cases in chickens, the lesions typically include

•       mild sinusitis
•      tracheitis and airsacculitis.

If the chicken is infected concurrently with E. coli

•     Thickening and turbidity of the air sacs
•    Exudative accumulations
•  Fibrinopurulent pericarditis and perihepatitis may be seen.
•  In turkeys, severe mucopurulent sinusitis may be found, with variably severe tracheitis and airsacculitis.
•   The eyelids may be swollen and inflamed, and a clear to cloudy, thickened ocular discharge may be noted.
•   There may also be drainage from the nares.

Morbidity and Mortality

M. gallisepticum has been eradicated from most primary and multiplier poultry breeding flocks, but this organism can be endemic in large, multiple-age commercial egg laying flocks. Outbreaks also occur in meat flocks. Clinical cases tend to occur in large commercial operations during the winter. Stressors such as viral infections, vaccination with live viruses, cold weather or crowding can trigger disease outbreaks in infected flocks. In chickens with uncomplicated infections, the morbidity rate is high and the mortality rate low; however, more severe disease occurs if the birds are concurrently infected with other viruses or bacteria. Mortality rates can be high in turkeys.

In wild songbirds, the impact of the disease is complicated by other factors. Under controlled experimental conditions, house finches exhibited morbidity rates approaching 100%, but low mortality rates of approximately 5% or less. However, the mortality rate can be high in wild house finches, probably due to environmental factors such as cold, predation and difficulty locating food and water. American goldfinches are also highly susceptible to experimental infection; however, in the wild, the morbidity rate is reported to be 2-3% in this species, compared to a 20-27% morbidity rate in free-living house finches. The cause of this discrepancy is unknown.

          Diagnosis

    Clinical

M. gallisepticum infections should be considered in poultry or game birds with upper respiratory disease and wild house finches with conjunctivitisPresumptive – History; signs; lesions

•     Definitive
•   Antibody detection-serology
• Serum plate agglutination (SPA)
• Hemagglutination inhibition (HI)
• Enzyme-linked immunosorbent assay (ELISA) 

On filed rapid plate test (RPT) may be help full which later may be confirmed by ELISA and PCR test at lab.

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Differential diagnosis

•  infectious bronchitis
• Mild Newcastle disease
• Avian influenza.
• Hemophilus  paragallinarum
• Pasteurella multocida
• Mycoplasma synoviae

Prevention and Control

             Biosecurity   is the key for Mycoplasma Prevention

M. gallisepticum can be introduced into a flock by live birds or hatching eggs, as well as the movement of people and fomites. Subclinically infected small backyard flocks can be a source of infection for commercial poultry. Lateral transmission is the most common means of introduction, as the disease has been eradicated from most primary and multiplier breeding flocks.- M. gallisepticum–negative breeding stock can be identified and maintained by serologic testing. Biosecurity measures are important in preventing transmission on fomites. Wild or pet birds can also carry M. gallisepticum, and should be excluded from poultry operations. Infections can be eliminated from a farm by depopulation of the flock, followed by thorough cleaning and disinfection of the premises. Most commonly used disinfectants are thought to be effective for M. gallisepticum. Recommended disinfectants for buildings and equipment include phenolic or cresylic acid disinfectants, hypochlorite, and 0.1% glutaraldehyde. Mycoplasmas are typically fragile and only survive in the environment for a few days; birds can be re–introduced after 2 weeks.

Note : Please follow the strict 

Cleaning and Disinfection Program for Breeder Flocks

 Treatment:

• Treatment does not eliminate carrier state; it only suppresses the level of Mycoplasma.
• Positive Breeders should have a consistent Mycoplasma reduction program
•  Continuous Monthly treatments with suitable antibiotic like Tylosin ,Tilmycosin etc.
•  Good biosecurity practices in Positive Farms are very critical