Avian mycoplasmosis is an economically significant poultry disease caused primarily by Mycoplasma gallisepticum and Mycoplasma synoviae, leading to chronic respiratory issues and economic losses due to decreased production. The disease is transmitted both horizontally through close contact and aerosol spread, and vertically via eggs, with clinical signs varying from asymptomatic to severe respiratory distress. Effective management includes treatment options and strict biosecurity measures, along with vaccination to minimize disease spread within flocks.

1. Avian Mycoplasmosis
Disease Overview

2. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

3. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

4. Introduction
 Avian mycoplasmosis is caused by
several pathogenic mycoplasmas,
the most common are;
1. Mycoplasma gallisepticum (MG)
2. M. synoviae (MS)
 They are the only strains listed by
the OIE.

5. Cont. …
 MG causes chronic respiratory disease CRD of domestic
poultry, especially in the presence of management stresses
and/or other respiratory pathogens.
 MS may cause respiratory disease, synovitis, or may result in
a silent infection.

6. Importance
 Mycoplasma gallisepticum is the most economically
significant mycoplasma pathogen of poultry.
 Mycoplasma gallisepticum infections causes significant
economic losses on poultry farms from:
1. Chronic respiratory disease (CRD).
2. Reduced feed efficiency.
3. Decreased growth rate.
4. Decreased egg production.
5. Carcasses downgrades.

7. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

8. Etiology
Class mollicutes
Order mycoplasmatales
Family mycoplasmataceae including:
1. M. gallisepticum
2. M. Synoviae
3. M. meleagridis
4. M. iowae.

9. Cont. …
 M. gallisepticum infections are also known as:
1. Chronic respiratory disease (CRD) of chickens.
2. Infectious sinusitis of turkeys.
 Several strains of M. gallisepticum have been reported,
including the R strain in poultry.

10. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

11. Species Affected

12. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

13. Geographic Distribution

14. Geographic Distribution
In the United States, this organism has been eradicated from
most commercial chicken and turkey breeding flocks, but
remains present in other poultry operations.

15. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

16. Transmission
Horizontal
 M. gallisepticum is transmitted
during close contact between birds.
 Aerosol spread occurs over short
distances and can be responsible
for transmission within a flock.

17. Cont. …
Vertical
 M. gallisepticum is also transmitted
vertically in eggs.
 Egg transmission is more frequent in
birds infected during laying than in
birds infected before they mature.
 Infected birds carry M. gallisepticum
for life, and can remain asymptomatic
until they are stressed.

18. Incubation Period
 Experimentally infected poultry develop symptoms after 6 -21
days.
 In natural infections, the incubation period is variable;
infected birds may be asymptomatic for days or months until
stressed.

19. Cont. …
Stressors such as:
1. Viral infections
2. Vaccination with live viruses
3. Cold weather
4. Crowding
Can trigger disease outbreaks in infected flocks.

20. Morbidity and Mortality
 In chickens with uncomplicated infections, the morbidity rate
is high and the mortality rate low.
 More severe disease occurs if the birds are concurrently
infected with other viruses or bacteria.

21. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

22. Clinical Signs
 M. gallisepticum infections vary from asymptomatic to severe,
depending on the infecting strain and other factors, such as
the infection with other respiratory pathogen;
1. NDV
2. IBV
3. E. coli

23. Cont. …
Infected chickens usually develop respiratory symptoms that
may include:
1. Depression
2. Rales
3. Coughing
4. Sneezing
5. Nasal discharges
6. Dyspnea
7. Decreased weight gain, feed efficiency and egg production

24. Depression

25. Conjunctivitis
Corneal opacity

26. Conjunctivitis, edema
(eyelid, periorbital)

27. Conjunctivitis
Sinusitis

28. Drop in egg production

29. Drop in Egg Production

30. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

31. Post Mortem Lesions
In uncomplicated cases in chickens, the lesions typically
include:
1. Mild sinusitis
2. Tracheitis
3. Airsacculitis
If chicken is infected concurrently with E. coli:
1. Thickening and turbidity of the air sacs
2. Exudative accumulations
3. Fibrinopurulent pericarditis
4. Perihepatitis

32. Eyelid,
Infraorbital sinus, nares

33. Trachea

34. Trachea

35. Bronchi
Trachea

36. Lungs

37. Air sac

38. Keel,
Pectoral muscles

39. Air sac

40. Air sac

41. Heart

42. Embryo

46. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

47. Treatment – Live Bird
 The (semi) permanent use of antibiotics (Tylan ®,
Lincospectin®, Baytril®) can reduce the damage of a M.G.
infection, but it will never really solve the problem, because
the flocks are still infected.
 In broilers, at the first 4 days of life, then at 19th day for 2
successive days.
 In breeders, following any respiratory vaccination, especially
ND for 2 successive days.
 As soon as one stops the medication the disease increases
again

48. Cont. …
Limitations of treatment:
1. Mycoplasma develops resistance against the antibiotics
2. Expensive
3. Medication can not fully prevent an infection.
4. It is useful for a relatively short period of time, but in the
meantime other control systems have to be developed.

49. Treatment – Egg Transmission
If a flock proves to be positive for M.G. there are several
possibilities to prevent vertical transmission to the broiler flocks:

50. Cont. …
1. The P.S. Flock can be killed.
– This is the only completely safe procedure to prevent further spread of
the disease, but of course it is not always practical.
2. Treatment of the hatching egg with tylan® (or baytril®):
– Injection into the hatching eggs with 0.2 mg tylosine by hand or
automatic.
3. Egg dipping in a 2500 ppm containing tylan solution, using the
temperature-difference method or the pressure difference
method.
4. Egg-heating method (yoder) eggs are heated, before setting,
at 46 C during 12-14 hours. This system is not very reliable.

51. Plan of talk
 Introduction
 Etiology
 Species affected
 Geographical distribution
 Transmission
 Clinical signs
 Post mortem lesions
 Treatment
 Prevention

52. Biosecurity
Very strict hygienic system is essential to keep a flock free:
1. Limit visitors and movement of vehicles between farms to the
absolute minimum.
2. Make sure that all visitors change clothes and footwear on the
entrance of the farm and disinfect their hands.
3. Showering is even better, and certainly recommended for Grand
Parent Farms.
4. As most Mycoplasma’s are killed within two days, we keep two days
as a minimum safety period between visiting possibly infected farm
and visiting a M.G. clean farm.
5. Staff should not be allowed to have any contact with poultry
outside their work. Otherwise, the same period of two days counts.

53. Cont. …
 On multi-age farms, it is difficult to control M.G..
 On a single-age farm, M.G. control mainly means control of
movement of staff and material.

54. Vaccination
Various vaccines are used:
1. Live vaccines
2. Killed vaccines

55. Vaccination - Live vaccines
F-strain (Avipro MGF, LAH)
 Can produce immunity.
 Profits in such flocks are less than in unvaccinated flocks that
maintained their freedom from M.G.
 The vaccine can spread up to 8 weeks after vaccination.
6/85 strain (Mycovac-L, Intervet)
 Is not spreading and safe.
 It can be differentiated from field strains by plate
agglutination test.

56. Vaccination - Killed Vaccines
 Killed vaccines are safe to use and give generally a reasonable
protection.
 They should be given by injection and are rather expensive.