Synonyms
Infectious roop, infectious catarrh.
Aetiology
The disease is caused by Haemophilus gallinarum, a non motile gram negative bacteria that appear as rods or coccibacilli.
Age/host range
Chickens, guinea fowls and turkeys are affected and occasionally pheasants. All ages of birds are susceptible but chickens 14 weeks of age and older are most susceptible and the severity of the infection increases with age.
Transmission
The source of the infection is from carriers and infected birds by direct and indirect contact with nasal and ocular secretions that contaminate feed and water during coughing and sneezing episodes. Recovered birds remain carriers and a source of infection.
Clinical signs
The disease develops within 24-48 hours and runs a course for 2-3 weeks. Morbidity is low to moderate up to 30% but high when there is intercurrent infection like Newcastle disease, mycoplasma, infectious bronchitis and infectious laryngotracheitis. Mortality is usually low(less than 5%) except in complicated cases.
Clinical signs include
Facial swelling
Swollen wattles
Lacrimation
Purulent ocular and nasal discharge
Conjunctivitis
Tracheal rales
Sneezing
Dyspnea
Inappetence
Loss in condition
Drop in egg production of 10-40%.
Post-mortem lesions
Catarrhal inflammation of nasal passages and sinuses.
Catarrhal conjunctivitis
Eyelid adherence
Air sacculitis
Caseous material in conjunctiva/sinus
Tracheitis
Pericarditis
Perihepatitis.
Diagnosis
A presumptive diagnosis may be made based on clinical signs and post-mortem lesion. Positive diagnosis is based on recognition and isolation of the bacteria.
Serology: Haemagglutination inhibition, Immunoflorescent and slide agglutination have all been utilized but are not routine.
Differential diagnosis
Mycoplasmosis, infectious laryngotracheitis, chronic or localized pasteurellosis, aspergillosis and vitamin A deficiency.
Treatment
Sulphonamides, Streptomycin, dihydrostreptomycin, , erythromycin, fluoroquinolones and tylosin are bactericidal and might prevent carriers.
Prevention
Coryza-free birds should be stocked on an all-in/all-out production policy.
Vaccinations
Live attenuated vaccines have been used. Commercial bacterins may not fully protect against all field strains but reduce the severity of infections.