30/09/2020
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Poultry disease part (3)
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3. Infectious Coryza
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Synonyms
Infectious Coryza is also known as
✔fowl coryza,
✔roup,
✔contagious or infectious catarrh and ✔umcomplicated coryza.
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Introduction
Infectious Coryza is an infection of chickens
it has been under diagnosed or mistakenly diagnosed as Mycoplasma gallisepticum for which there is a simple blood test. However, combination infections with both organisms would be expected to cause more severe clinical signs.
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Etiology
Avibacterium paragallinarum formerly known ✔Haempholius paragallinarum.
This is a Gram-negative, non-motile, non -spore forming, rod or coccobacilli shaped bacterium.
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Host
Only chickens but it can cause disease in all ages of bird. It is more severe in older birds. It has not been possible to experimentally infect, ducks, pigeons or turkeys.
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Transmission
✔This is a highly contagious infection that spreads horizontally from bird to bird,
✔It is a disease of the upper respiratory tract.
✔The primary source of infection is respiratory exudates from either clinically affected or carrier birds.
✔Infection from drinking water contaminated with a few bacteria or as an aerosol over short distances is possible.
✔Vertical transmission does not occur.
✔Mechanical spread of infection in respiratory exudates may also occur.
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Clinical signs
The disease has a
✔short incubation period, 1 – 3 days,
✔and will spread rapidly through a flock of susceptible birds in 7 to 10 days.
The initial signs will include
✔watery discharges (seromucoid) from the nostril and eyes with
✔swelling of the face with a marked morbidity in the flock but low mortality. ✔Conjunctivitis,
✔closed eyes,
✔open mouthed breathing,
✔lethargy and drops in feed and water consumption.
This can result in egg production drops,
✔failure to grow and in the presence of secondary infections severe mortality.
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Pathology
✔Subcutaneous oedema of the face and wattles,
✔inflammation of the nasal passage, ✔infraorbital sinus and conjunctiva with excess catarrhal to fibrinopurulent mucus. When secondary complications are present, there may be a
✔tracheitis progressing to airsacculitis and pnuemonia.
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Differential diagnoses
✔Avian metapneumovirus (ART),
✔Infectious Bronchitis (IBV) with secondary E.coli,
✔Infectious Laryngotracheitis (ILT), ✔Mycoplasma gallisepticum (Mg),
✔virulent E.coli and
✔subcutaneous infections following mechanical damage following fighting or mating.
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Treatment
Antibiotic treatment, e.g.
✔doxycycline and
✔fluroquinolones, can alleviate the worst of the clinical signs but will not eliminate infection from the flock. Return to nornal egg production takes longer than clinical recovery following treatment.
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