Specific strains of an avian coronavirus.
Occurrence and Economic Significance
Infectious bronchitis (IB) occurs world wide and is responsible for depressed egg production and shell quality in susceptible commercial and breeder flocks. Infection of immature chickens causes a mild respiratory disease which may affect live ability and growth if exacerbated by adverse managemental, climatic stress or intercurrent mycoplasmosis.
The virus can be transmitted from clinically affected birds to susceptible
flocks either by direct contact or indirectly by fomites.
Moderate morbidity and low flock mortality associated with respiratory rales (gurgling and snicking) and ocular discharge. Mature flocks show reduced egg production with malformed shells.
Hyperemia (red discoloration) of the trachea and accumulation of mucus
in the nasal cavity. Chronic cases, complicated by secondary E. coli
infection show airsacculitis.
RT-PCR is used to rapidly diagnose IB.
Retrospective diagnosis is possible by demonstrating a significant rise in
circulating antibody in paired acute and recovery-phase sera applying
ELISA or SN assay.
Vaccinated with a mild attenuated product (H-120, Massachusetts, Connecticut strains
or their combination) at 7 days in drinking water or by aerosol
vaccination is repeated at 30-40 days. The initial live vaccine should always
be administered to susceptible breeder and layer flocks before 12 weeks
of age to avoid possible damage to the developing reproductive tract of the pullet. Immunity in commercial layers can be boosted by administration
of live attenuated vaccine either in drinking water or as a coarse spray
during the production period. Potential breeder flocks receive inactivated
IB vaccine as a booster, usually in the form of an injectable multivalent
emulsion at the end of the rearing period and then at mid-cycle, as
considered necessary, to maintain adequate maternal antibody transfer to
Fowl cholera is a contagious, bacterial disease that affects domestic and wild birds worldwide. It usually occurs as a septicemia of sudden onset with high morbidity and mortality, but chronic and asymptomatic infections also occur.
Newcastle disease is an infection of domestic poultry and other bird species with virulent Newcastle disease virus (NDV). It is a worldwide problem that presents primarily as an acute respiratory disease, but depression, nervous manifestations, or diarrhea may be the predominant clinical form. Severity depends on the virulence of the infecting virus and host susceptibility. Occurrence of the disease is reportable and may result in trade restrictions.
Fowl cholera is the reason for great economic loss of poultry in bangladessh