1. MYCOPLASMA GALLISEPTICUM Dr. Salah M
MYCOPLASMA GALLISEPTICUM Dr. Salah M. Hassan, MSc, PhD College of Veterinary Medicine University of Mosul

2. Common Names
Mycoplasma gallisepticum infection, MG, Mycoplasmosis, Chronic Respiratory Disease (CRD), PPLO Infection, Airsaculitis.

3. Definition A contagious disease primarily of
chickens and turkeys, characterized
by respiratory signs and lesions and a
prolonged course in the flock

4. 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

5. Etiology (Continued)
2) MG seldom survives for more than a few days outside the chicken. Carrier birds are required for survival.

6. Transmission
1) Vertically (transovarian). MG is transmitted in some eggs laid by
inapparent carriers.

7. Transmission (Continued)
2) Horizontally. Infected chickens transmit MG through:
aerosols
contaminated feed and water
other avian species, domestic and wild

8. Transmission (Continued)
3) Mechanically. MG is spread by contact with contaminated equipment, on shoes and fomites (feed sacks, crates, etc.).

9. 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.

10. Occurrence MG is of worldwide incidence and is of
considerable economic importance to
all segments of the commercial
poultry industry.

11. Occurrence MG causes: Breeders-decreased egg production
Fertile Eggs-reduced hatchability due to late embryo mortality
Chicks- reduced livability

12. 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

13. Occurrence Laying Hens
The main problem associated with MG infection is a 5-10% drop in egg production.

14. 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.
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Avian Diseases 25: , 1984

15. Occurrence Effect on egg production (quantity and quality) depends on:
virulence of the strain of MG
degree of stress placed on birds.

16. Occurrence
Increased medication costs and poor feed conversions are additional factors that make this one the costliest disease problems confronting the poultry industry.

17. 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

18. 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

19. Clinical Signs (Continued)
Broilers
feed intake and growth rates reduced
male birds more severely affected
illness more pronounced during winter- ammonia, dust,...

20. 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)

21. 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

22. 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

23. Lesions (Continued)
MG infection alone only slightly detectable lesions
complicated cases of MG- fibrinous perihepatitis, pericarditis, and severe airsaculitis

24. 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

25. Diagnosis
1) Tentative diagnosis of MG made based on history, clinical signs,
and lesions.

26. 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

27. Diagnosis (Continued)
3) A definitive diagnosis would include isolation and identification of MG (often is difficult and time consuming)

28. 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)

29. Diagnosis (Continued)
Causes of false positive SPA results:
Serum from MS infected chickens
Contaminated serum
Freezing of serum
Freezing of SPA antigen

30. 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

31. Differential Diagnosis
MG infection- differentiated
from other common respiratory
diseases of chickens, including NDV,
IBV, infectious coryza, fowl cholera,
TRT, ORT, and MS

32. Prevention and Control
Biosecurity
Strict isolation to prevent introduction of MG into a clean flock

33. Prevention and Control (Continued)
Prevention of MG in commercial layers is difficult because hens are commonly maintained on multiple-age farms

34. Prevention and Control (Continued)
Preferred method for eliminating MG infection- depopulation of infected flocks
Complete depopulation of MG (+) farms is necessary to eradicate infection

35. 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

36. 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

37. Prevention and Control (Continued)
In multiple-age farms where depopulation and disinfection are impractical, options include:
Medication
Vaccination

38. General Comments
Pullets raised MG (-) often become infected when placed in MG (+) multiple-age laying operations
When beginning production and reaching peak production

39. 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.

40. Medication
Commonly used antibiotics include tylosin, gallimycin, tetracyclines, Baytril, Pulmotil, others
Treatment will partially alleviate symptoms, lesions, and egg production losses

41. Medication Disadvantages: Cost of antibiotics
Development of antibiotic-resistant MG organisms
MG infection not eliminated
MG shed continues

42. Vaccination Vaccine types: F-strain MG - live product
Mycovac-L - strain 6/85 of MG
TS-11
MG bacterin - inactivated product

43. 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

44. 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

45. 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

46. 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