Page 68 - Poultry-Punch April 2020 edition

POULTRY PUNCH ARTICLE

Transmission: In laying birds, ova can be congested and sometimes ruptured,
The virus is transmitted via the respiratory secretions, as well as with free yolk in the abdominal cavity. Desquamation of respiratory
faecal droplets from infected poultry. Contaminated objects and epithelium, edema, epithelial hyperplasia, mononuclear cell
utensils may aid transmission and spread of the virus from one infiltration of the submucosa, and regeneration occur in various
flock to another. Evidence of virus was shown in trachea, kidney, combinations. Repair processes begin after 6–10 days, and are
and Bursa of Fabricius 24 hrs following aerosol transmission. The complete in 14–21 days. Some virus strains affect the kidney,
nature of IBV persistence remains to be elucidated; however, causing interstitial nephritis.
detection of the virus in the caecal tonsils (up to 14 weeks) and Poor egg shall quality, rugged appearance, thin shells and
from faeces (20 weeks) after infection might suggest a role of faecal watery albumin. In hatching eggs curled and stunted embryos
shedding in viral transmission and persistence. are common

Incubation Period of IB
Generally the short incubation period for IBV varies with
infective dose and route of infection. For example, while infection
via the tracheal route may take a course as short as 18 hours, ocular
inoculation leads to an incubation period of 36 hours

Pathogenesis and Pathology
The virus replicates to high titer first in the respiratory tract
(ciliated epithelial cells); this is followed by viremia (within 1–2
days of infection), which distributes the virus to many organs. The
virus can cause extensive damage to the ovaries, oviduct, and the
kidneys, but this is dependent on the properties of individual virus
strains. The intestinal tract is another site of primary infection, but
damage usually is minimal.
The most frequent gross pathologic finding is mucosal thickening
within The upper and lower respiratory tract, with serous or
catarrhal exudate in the nasal passages, trachea, bronchi, and
airsacs. In very young chicks, the main bronchi may be blocked with
caseous yellow casts. Pneumonia and conjunctivitis occur in some
cases.

Fig: a).Chick gasping for breath,
b).inflammation of larynx and c) Nephritis
Clinical Signs of Infectious Bronchitis
l gasping
l coughing
l sneezing
l tracheal rales
l nasal discharge Shortening of oviduct in pullets causing “False Layers with normal
l wet eyes Ovary.Cystic oviduct distended with watery fluid

68 April, 2020