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.
Velogenic Viscerotropic Newcastle Disease
This form is characterized by acute onset with up to 100% flock morbidity and rapidly ascending high mortality (20% in 2 days, 50% in 3 days, 80% in 5 days) accompanied by respiratory and nervous signs. In susceptible commercial egg production flocks and breeders, peracute cessation of production occurs with the presence of shell-less eggs due to premature oviposition. Exposure of immunized flocks results in variable decline in production.
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.
Infectious Bursal Disease is a major restraint to productivity and profitability in the poultry industries of both industrialized and developing nations.