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MYCOPLASMA GALLISEPTICUM Dr. Salah M
MYCOPLASMA GALLISEPTICUM Dr. Salah M. Hassan, MSc, PhD College of Veterinary Medicine University of Mosul
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Common Names Mycoplasma gallisepticum infection, MG, Mycoplasmosis, Chronic Respiratory Disease (CRD), PPLO Infection, Airsaculitis.
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Definition A contagious disease primarily of
chickens and turkeys, characterized by respiratory signs and lesions and a prolonged course in the flock
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Etiology 1) Mycoplasma gallisepticum is the causal agent. Mycoplasma are the smallest free-living organisms (smaller than the bacteria). They do not possess cell walls and grow rather slowly
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Etiology (Continued) 2) MG seldom survives for more than a few days outside the chicken. Carrier birds are required for survival.
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Transmission 1) Vertically (transovarian). MG is transmitted in some eggs laid by inapparent carriers.
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Transmission (Continued)
2) Horizontally. Infected chickens transmit MG through: aerosols contaminated feed and water other avian species, domestic and wild
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Transmission (Continued)
3) Mechanically. MG is spread by contact with contaminated equipment, on shoes and fomites (feed sacks, crates, etc.).
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Transmission (Continued)
The MG organism infects poultry which often become long term carriers. These chickens then contaminate the farm and infect other MG free birds.
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Occurrence MG is of worldwide incidence and is of
considerable economic importance to all segments of the commercial poultry industry.
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Occurrence MG causes: Breeders-decreased egg production
Fertile Eggs-reduced hatchability due to late embryo mortality Chicks- reduced livability
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Occurrence MG plays a role in the respiratory complex of diseases resulting in downgrading of carcasses MG + E. Coli + IBD Immunosuppression + IB and ND Vaccine/Field Viruses
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Occurrence Laying Hens
The main problem associated with MG infection is a 5-10% drop in egg production.
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Production Losses MG free hens laid 15.7 more eggs per hen
housed than unvaccinated MG infected birds over a 45 week laying period. MG infected layers, vaccinated with F-strain or bacterin, produced 7 more eggs per hen housed as compared to unvaccinated group. _____________ Avian Diseases 25: , 1984
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Occurrence Effect on egg production (quantity and quality) depends on:
virulence of the strain of MG degree of stress placed on birds.
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Occurrence Increased medication costs and poor feed conversions are additional factors that make this one the costliest disease problems confronting the poultry industry.
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Clinical Signs Commercial Layers tracheal rales
ocular and nasal discharge coughing feed intake reduced weight loss egg production drops, usually maintained at a lower level
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Clinical Signs Broilers usually between 3 and 8 weeks of age
more pronounced than in adult birds severe cases frequently associated with stress factors-poor ventilation, concurrent diseases, vaccine reactions
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Clinical Signs (Continued)
Broilers feed intake and growth rates reduced male birds more severely affected illness more pronounced during winter- ammonia, dust,...
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Clinical Signs(Continued)
MG infection may be dormant in infected chickens and cause no disease until triggered by stress (poor husbandry, dust, ammonia, temperatures extremes, disease challenge, vaccine reactions, immunosuppression, etc)
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Clinical Signs (Continued)
MG is often associated with the following pathogens: IBV and NDV (field and vaccine viruses), E. coli, H. paragallinarum, making the condition more severe
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Lesions Primarily catarrhal exudate in nasal passages, trachea, and bronchi early- air sac exudate has a “soap suds” or “beaded” appearance later- exudate becomes caseous and yellow
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Lesions (Continued) MG infection alone only slightly detectable lesions complicated cases of MG- fibrinous perihepatitis, pericarditis, and severe airsaculitis
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Mortality adult flocks- negligable
broilers - low in uncomplicated cases up to 30% if poor management and other stress factors mortality may be low, but cull rate high
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Diagnosis 1) Tentative diagnosis of MG made based on history, clinical signs, and lesions.
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Diagnosis (Continued)
2) Serology Positive plate test for MG from suspect flock strengthens diagnosis False positive reactions may occur with plate test, confirm suspicious results with HI or ELISA test
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Diagnosis (Continued)
3) A definitive diagnosis would include isolation and identification of MG (often is difficult and time consuming)
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Diagnosis(Continued)
Serum Plate Agglutination (SPA): Detects IgM class of antibodies Detects antibodies within 7 days of infection Test is easy to perform, rapid, inexpensive, and sensitive Test is prone to false positive reactions (screening test)
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Diagnosis (Continued)
Causes of false positive SPA results: Serum from MS infected chickens Contaminated serum Freezing of serum Freezing of SPA antigen
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Diagnosis (Continued)
Causes of false positive SPA results: Prolonged storage of serum at 4 C Infection of chickens with S .aureus Vaccination with inactivated oil- emulsion vaccines, 2-8 weeks post vaccination
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Differential Diagnosis
MG infection- differentiated from other common respiratory diseases of chickens, including NDV, IBV, infectious coryza, fowl cholera, TRT, ORT, and MS
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Prevention and Control
Biosecurity Strict isolation to prevent introduction of MG into a clean flock
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Prevention and Control (Continued)
Prevention of MG in commercial layers is difficult because hens are commonly maintained on multiple-age farms
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Prevention and Control (Continued)
Preferred method for eliminating MG infection- depopulation of infected flocks Complete depopulation of MG (+) farms is necessary to eradicate infection
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Prevention and Control (Continued)
The MG organism is fragile and lives only a short time outside the chicken A house can be easily freed of MG by cleaning and disinfecting between flocks after all chickens are gone
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Prevention and Control (Continued)
Avoid multiple age farms All in & all-out grow-out programs Careful traffic control and good sanitation Maintain biosecurity on single age farms
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Prevention and Control (Continued)
In multiple-age farms where depopulation and disinfection are impractical, options include: Medication Vaccination
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General Comments Pullets raised MG (-) often become infected when placed in MG (+) multiple-age laying operations When beginning production and reaching peak production
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General Comments (Continued)
Flocks may have serologic evidence of infection with no clinical signs, especially if infected at an early age. These birds may have some immunity, but remain carriers and transmit the disease to susceptible chickens by contact or egg transmission, especially after a stressor.
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Medication Commonly used antibiotics include tylosin, gallimycin, tetracyclines, Baytril, Pulmotil, others Treatment will partially alleviate symptoms, lesions, and egg production losses
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Medication Disadvantages: Cost of antibiotics
Development of antibiotic-resistant MG organisms MG infection not eliminated MG shed continues
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Vaccination Vaccine types: F-strain MG - live product
Mycovac-L - strain 6/85 of MG TS-11 MG bacterin - inactivated product
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Vaccination F- strain MG: Non-pathogenic in pullets
Administered by spray, water, eyedrop Administered at 10 to 16 weeks of age Chickens remain infected and shed organism throughout laying cycle
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Vaccination (Continued)
F-Strain MG: Must vaccinate prior to field infection Does not prevent field strain MG infection Protects against drops in production Is pathogenic to turkeys May replace field MG strain
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Vaccination (Continued)
6/85 Strain MG: Does not spread well, no vertical transmission Biologically stable Non-pathogenic for turkeys Vaccinate chickens at 6+ weeks of age Minimal seroconversion Must be administered prior to field infection
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Vaccination MG Bacterin: Does not prevent field strain MG infection
Protects against drops in production Does not spread to other poultry Non-pathogenic (killed product) Administered by injection (SQ or IM) Must be administered prior to field infection
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