Prof. Dr./ Wafaa Abd El-ghany

Professor of Poultry Dis.,

Fac. Vet. Med., Cairo Univ.

Definition

It is a contagious bacterialdisease affects turkeys andchickens characterized byrespiratory signs, variablemortality, and decrease in eggproduction with change in eggquality.

Economic losses

High mortality.

High condemnation rate.

Decrease in egg quantityand quality.

Growth retardation.

The causeORT organism is Gram negative, highly

polymorphic, non motile, non spore formingshort rod.

Microaerophilic growth at 37C for 48 hr on 5-10% sheep blood agar or tryptose soya agar.The organism not grows on MacConkey.

Colonies are very small, non hemolytic,circular, gray to gray white in color.

Serotypes using boiled extract antigens andmonovalent antiserum using AGP or ELISA.

There are 18 serotype (A-R). Serotype A isthe most prevalent in chickens and turkeys.

ORT showing highly pleomorphic nature in Gram staining.

Mode of infection and transmission

The infection occurred bythe horizontal routes bycontact through aerosol ordrinking water.

The vertical transmissionoccurs by transovarian andoviduct.

Clinical signsIn Chickens:

A. Broilers:

Birds aged 3-4 weeks show mortality 2-10%.

General signs.

Respiratory signs including transient nasaldischarge, sneezing followed by facial edema.

Sudden death can be occurred withoutrespiratory signs due to brain and skull infection.

B. Broiler breeder and layer:

The infection occurred mostly at peak of eggproduction.

decrease in egg production and changes in eggquality.

Clinical signsIn turkeys:

A. Poults:

Turkey poults aged 2-8 weeks showmortality up to 50%.

Respiratory signs: coughing , sneezing,nasal discharge and sinusitis.

Decrease in feed and water intake.

B. Breeders:

Decrease in egg production.

Increase in the number of unhatchedeggs.

Post mortem lesions

• Uni or bilateral pneumonia.

• Profuse, foamy white to yellow(Yoghurt like) airsaculitis.

• Pleuritris.

• Subcutaneous edema of the head.

• Encephalitis in chickens.

• Enlarged liver and spleen withdegeneration of heart musclesare additionally seen in turkeys.

Thickened, opaque air sacs with

profuse, foamy white to yellow, “yogurt-

like” exudate in broiler chickens.

Pneumonia and pleuritis in turkeys

Diagnosis & differential diagnosis

• The diagnosis depends mainly onisolation and identification of theorganism.

• ORT must be differentiated fromcauses of sudden death andrespiratory signs (E.colisepticeamia, fowl cholera ,infectious coryza and chlamydiosis).

Prevention1) Application of good sanitary

measures especially separation ofdifferent ages and species.

2) Vaccination:

There are two types of vaccines:

a. Inactivated vaccine considered asserotype specific vaccine.

b. Live vaccine can induce crossprotection between someserotypes.

ControlAmoxicillin and chlortetracycline in

water.

Tetracycline and penicillins byinjection.

The use of antibiotic is of limitedvalue as the organism has variablesusceptibility to antibiotics andcan acquire drug resistance.