Avian MycoplasmosisDisease Overview

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Introduction

Avian mycoplasmosis is caused byseveral pathogenic mycoplasmas,the most common are;1. Mycoplasma gallisepticum (MG)

2. M. synoviae (MS)

They are the only strains listed bythe OIE.

Cont. …

MG causes chronic respiratory disease CRD of domesticpoultry, especially in the presence of management stressesand/or other respiratory pathogens.

MS may cause respiratory disease, synovitis, or may result ina silent infection.

Importance

Mycoplasma gallisepticum is the most economicallysignificant mycoplasma pathogen of poultry.

Mycoplasma gallisepticum infections causes significanteconomic 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.

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Etiology

Class mollicutes

Order mycoplasmatales

Family mycoplasmataceae including:

1. M. gallisepticum

2. M. Synoviae

3. M. meleagridis

4. M. iowae.

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.

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Species Affected

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Geographic Distribution

Geographic Distribution

In the United States, this organism has been eradicated frommost commercial chicken and turkey breeding flocks, butremains present in other poultry operations.

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Transmission

Horizontal

M. gallisepticum is transmittedduring close contact between birds.

Aerosol spread occurs over shortdistances and can be responsiblefor transmission within a flock.

Cont. …

Vertical

M. gallisepticum is also transmittedvertically in eggs.

Egg transmission is more frequent inbirds infected during laying than inbirds infected before they mature.

Infected birds carry M. gallisepticumfor life, and can remain asymptomaticuntil they are stressed.

Incubation Period

Experimentally infected poultry develop symptoms after 6 -21days.

In natural infections, the incubation period is variable;infected birds may be asymptomatic for days or months untilstressed.

Cont. …

Stressors such as:

1. Viral infections

2. Vaccination with live viruses

3. Cold weather

4. Crowding

Can trigger disease outbreaks in infected flocks.

Morbidity and Mortality

In chickens with uncomplicated infections, the morbidity rateis high and the mortality rate low.

More severe disease occurs if the birds are concurrentlyinfected with other viruses or bacteria.

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Clinical Signs

M. gallisepticum infections vary from asymptomatic to severe,depending on the infecting strain and other factors, such asthe infection with other respiratory pathogen;

1. NDV

2. IBV

3. E. coli

Cont. …

Infected chickens usually develop respiratory symptoms thatmay include:

1. Depression

2. Rales

3. Coughing

4. Sneezing

5. Nasal discharges

6. Dyspnea

7. Decreased weight gain, feed efficiency and egg production

Depression

Conjunctivitis Corneal opacity

Conjunctivitis, edema (eyelid, periorbital)

Conjunctivitis Sinusitis

Drop in egg production

Drop in Egg Production

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Post Mortem Lesions

In uncomplicated cases in chickens, the lesions typicallyinclude:

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

Eyelid, Infraorbital sinus, nares

Trachea

Trachea

BronchiTrachea

Lungs

Air sac

Keel, Pectoral muscles

Air sac

Air sac

Heart

Embryo

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

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, becausethe flocks are still infected.

In broilers, at the first 4 days of life, then at 19th day for 2successive days.

In breeders, following any respiratory vaccination, especiallyND for 2 successive days.

As soon as one stops the medication the disease increasesagain

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 themeantime other control systems have to be developed.

Treatment – Egg Transmission

If a flock proves to be positive for M.G. there are severalpossibilities to prevent vertical transmission to the broiler flocks:

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 thetemperature-difference method or the pressure differencemethod.

4. Egg-heating method (yoder) eggs are heated, before setting,at 46 C during 12-14 hours. This system is not very reliable.

Plan of talk

Introduction

Etiology

Species affected

Geographical distribution

Transmission

Clinical signs

Post mortem lesions

Treatment

Prevention

Biosecurity

Very strict hygienic system is essential to keep a flock free:

1. Limit visitors and movement of vehicles between farms to theabsolute minimum.

2. Make sure that all visitors change clothes and footwear on theentrance of the farm and disinfect their hands.

3. Showering is even better, and certainly recommended for GrandParent Farms.

4. As most Mycoplasma’s are killed within two days, we keep two daysas a minimum safety period between visiting possibly infected farmand visiting a M.G. clean farm.

5. Staff should not be allowed to have any contact with poultryoutside their work. Otherwise, the same period of two days counts.

Cont. …

On multi-age farms, it is difficult to control M.G..

On a single-age farm, M.G. control mainly means control ofmovement of staff and material.

Vaccination

Various vaccines are used:

1. Live vaccines

2. Killed vaccines

Vaccination - Live vaccines

F-strain (Avipro MGF, LAH)

Can produce immunity.

Profits in such flocks are less than in unvaccinated flocks thatmaintained 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 plateagglutination test.

Vaccination - Killed Vaccines

Killed vaccines are safe to use and give generally a reasonableprotection.

They should be given by injection and are rather expensive.