The disease affects immature chickens world wide. Acute infection with classic mild or variant strains results in up to 5% mortality. The variants are more immunosuppressive than the classic strains. Very virulent (vvIBD) virus may kill up to 50% of susceptible flocks.
Avibirnaviruses are immunosuppressive and predispose flocks to intercurrent viral pathogens and secondary bacterial infection.
Infectious Bursal Disease is a major restraint to productivity and profitability in the poultry industries of both industrialized and developing nations.
Flocks are affected acutely and show variable morbidity (5-50%) and rapidly ascending mortality (5-50%), depending upon the pathogenicity of the IBDV strain and the susceptibility of the flock. Affected birds are depressed and show recumbency, ruffled plumage and white diarrhea. There are no characteristic signs specific to IBD.
Pasteurella multocida serotypes (including 1, 3, & 4) which vary in pathogenicity.
Occurrence and Economic Significance
World-wide in distribution, pasteurellosis is encountered as an endemic infection in many intensive poultry producing areas and frequently persists as an infection in specific integrations or farms. Mortality occurs in floor housed replacement commercial laying and breeding stock and extends into mature flocks. Acute outbreaks associated with environmental or managemental stress, may result in depression in egg production. In breeders, reduced mating activity lowers fertility and depresses productivity of flocks as measured by the number of chicks produced by each hen placed.
Infection occurs following direct contact between susceptible birds and clinically affected or recovered carriers. Environmental contamination, rodents, and wild birds are sources of indirect infection. Contaminated feed bags, equipment, and the clothing of personnel may introduce infection onto farms or into integrations. Intra flock transmission is enhanced by handling birds for vaccination and weighing and by open watering systems such as troughs and bell drinkers.
Morbidity and mortality rates depend on the pathogenicity of the strain and the susceptibility of the flock. Newly introduced infections may result in up to 10% mortality. Prodromal signs are not observed in peracute cases. Chronic infection may be recognized by enlargement of the wattles, lameness caused by arthritis and torticollis (twisted necks) due to otitis interna (infection of the inner ear).
Acute cases show enlargement of the spleen and liver with punctate
hemorrhages of the viscera including the heart. Subacute cases may show
gray granulomatous foci in the liver. Caseous cellulitis of the wattles and
seropurulent arthritis may be present in chronic cases.
Laboratory examination is required to isolate and identify P. multocida from specimens of heart blood, liver, and spleen. In acute cases, characteristic bipolar organisms may be observed in Giemsa-stained smears of heart blood.
Tetracycline incorporated into feed at a level of 200 – 400 g/ton or in water at 250 – 500 mg/l will suppress clinical signs and reduce mortality.
Stringent biosecurity procedures are necessary to prevent introduction of infection. Eradication of rodents is critical to reducing the exposure of flocks to P. multocida.
Immunization of flocks in endemic areas is recommended. Routine vaccination is essential on farms where previous cases have occurred.
Live-attenuated P. multocida vaccines (CU; PM-1; PM-9 strains) are administered by wing-web stab twice during the rearing period, at approximately 10 and 14 weeks of age. Breeder males or flocks subjected to environmental stress may be vaccinated with the relatively milder PM-1 and PM-9 strains in place of the CU strain to avoid adverse vaccine reaction. Antibiotics should not be administered one week before and one week after administration of a live attenuated vaccine.
Inactivated vaccines can be used to protect flocks if an undesirable reaction to a live vaccine occurs. It is emphasized that for effective control of pasteurellosis inactivated bacterins must be homologous with the endemic strains of P. multocida. In some areas or integrations, autogenous, inactivated vaccines are required.
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.
IBD is the reason for great economic loss of poultry in bangladessh