Infectious Bursal Disease
Causative Agent – IBDV is a member of Birnaviriidae family
SIGNS
Earliest sign of infection in the flock is the tendency of the birds to pack their own vent.
Whitish or watery diarrhea.
Anorexia, depression and ruffled feathers.
Trembling, severe prostration and death.
Mortality may vary depending upon the susceptibility of the flock and the virulence of virus.
LESIONS
Pectoral muscles appear dark and dehydrated
Haemorrhages in thigh and pectoral muscles. (Fig-14.6 and 14.7)
Increased mucus in intestine.
Renal changes are prominent. (Fig-14.9)
The cloacal bursa is the prime target of the virus. Post infection changes seen are gelatinous yellowish transudate covering the serosal surface. (Fig-14.1)
Third day post infection shows enlarged bursa with oedema and hyperemia. (Fig-14.2 and 14.3)
Atrophy of bursa on 5th day of infection.
Bursa often showsnecrotic foci and petechial or ecchymotic haemorrhages on mucosal surface. (Fig-14.4)
Occasionally haemorrhages throughout the bursa are noted. Such birds void blood in droppings. (Fig-14.5)
Sometimes spleen may be enlarged with small gray foci, uniformly dispersed on the surface
Occasionally haemorrhages are seen in the mucosa at the juncture of pr9oventriculus and gizzard. (Fig-14.8)
HISTOPATHOLOGY
Bursa – hyperemia, oedema, infiltration of heterophils accompanied by lymphoid cell necrosis. (Fig-14.10)
Bursa – hyperplasia of reticuloendothelial cells and interfollicular tissue. (Fig-14.11)
Bursa – with the decline of acute inflammatory response, the corticomedullary epithelium proliferates and cystic cavities are seen in the medullary areas of the follicles. (Fig-14.12 and 14.13)
Liver – congestion and mononuclear cell infiltration. (Fig-14.15)
Kidney-show presence of homogenous cast with cellular infiltration. (Fig-14.16)
Flocks recovered with IBD will show higher susceptibility to secondary infections like Coccidiosis, Newcastle disease, Marek’s disease, salmonellosis and Pasteurellosis.
Occasionally other diseases seen are
Gangrenous beaks. (Fig-14.17)
Gangrenous dermatitis. (Fig-14.18, 14.20 and 14.21
Swollen heads. (Fig-14.22)
Gangrenous tips of the comb. (Fig-14.19)
Diagnosis
By gross lesions.
Isolation and identification of causative agent from bursa and the spleen.
ELISA—for evaluation of I.B.D. antibody titres in the flock.
