Infectious Bronchitis Virus (IBV) causes drop in egg production
Mechanisms of Production Drop
The IBV leads to production problems through two main scenarios:
1. Infection during the laying period:
Direct Damage to Oviduct Tissues: The virus replicates in the epithelial cells of the oviduct, causing inflammation (oviductitis) and lesions. This interferes with the normal physiological process of egg formation.
Impaired Albumen and Shell Formation: Specific parts of the oviduct are responsible for adding different components of the egg.
Damage to the magnum (where albumen is produced) leads to a reduction in albumen protein synthesis, resulting in watery whites (low Haugh unit values).
Damage to the uterus/shell gland interferes with the deposition of shell membranes, calcium, and pigments, leading to misshapen, thin, soft, wrinkled, or pale/colorless shells.
Temporary or Permanent Production Loss: While some flocks may see a return to normal production after 6-8 weeks, the drop can be as high as 70% during the acute phase. In some cases, the damage is permanent, resulting in a consistently lower production rate.
2. Infection at a young age (chicks/pullets):
Permanent Oviduct Damage: Infection in very young birds (especially in the first two weeks of life) can cause irreversible developmental problems in the oviduct, such as cystic dilation or atrophy.
"False Layer" Syndrome: Birds with permanent oviduct damage may have normally functioning ovaries but are physically unable to form or lay eggs properly. They are sometimes referred to as "false layers" or "blind layers".
Other Contributing Factors
Respiratory Distress: IBV initially affects the respiratory tract, and severe cases can indirectly impact the bird's overall health and appetite, further compromising egg production.
Kidney Damage: Some IBV strains are nephropathogenic, causing severe kidney damage (nephritis) which can increase mortality and stress on the birds, indirectly affecting productivity.
Secondary Infections: The virus can compromise the immune system and damage epithelial linings, making the birds more susceptible to secondary bacterial infections (like E. coli), which complicate the disease and worsen production losses.
In summary, the production drop is a direct result of the virus's ability to replicate in and cause pathological lesions in the reproductive organs, particularly the oviduct.
