Flashcards in Final Exam - Birnaviridae Deck (12):
Family: Birnaviridae; Genus: Avibirnavirus
Infectious bursal disease virus
Family: Birnaviridae; Genus: Aquabirnavirus
Infectious pancreatic necrosis virus (IPNV). A viral disease of salmonid fish. Severe disease in young ones (
Infectious bursal disease (IBD)
Infectious bursal disease (IBD) is an acute, highly contagious viral infection of young chickens that has lymphoid tissue as its primary target with a special predilection for the bursa of fabricius (cloacal bursa).
IBD - Serotype 1
Pathogenic to chickens. 3 antigenic subgroups: Variant viruses (no mortality). Classic or standard viruses (10-50% mortality). Very virulent viruses ( 50-100% mortality).
IBD - Serotype 2
Asymptomatic infections in chicken and turkeys
IBD - Transmission
Contact, fecal-oral transmission. Virus excreted by infected birds. Detected in water and feed even after 52 days.
Pathogenesis of IBDV
Oral infection. Replication of the virus in gut associated macrophages and lymphocytes in the ceca and small intestine. Liver. Blood stream. The target organ of IBDV is the bursa of fabricius at its maximum development, which is a specific source for mature B lymphoid cells due to both necrosis and apoptosis. Highest susceptibility is between 3 and 6 weeks. Secondary viremia. Localization in other tissues, including other lymphoid tissues. IBDV trigger both indirect (T-cell activation) and direct (macrophage activation) pathways to induce a "cytokine storm" in acute phase of the disease, mortality.
In recovered birds or subclinical cases, diminished antibody response and increased susceptibility to a wide range of opportunistic infectious agents.
IBDV Clinical Signs
Distress, depression, ruffled feathers, diarrhea, anorexia, dehydration, swollen bursa fabricius with hemorrhages. Subcutaneous and intracmuscular hemorrhages.
Clinical signs and PM lesions. Virus neutralization (VN) test. Agar gel immunodiffusion (AGID) test. Antigen-capture ELISA. Identification by immunofluorescence. RT-PCR.
IBD - Vaccination
Live IBD vaccines are produced from filly or partially attenuated strains of virus, known as "mild", "intermediate" or "intermediate plus" (hot), respectively. Mild vaccine strains that cause no bursal lesions cannot be used effectively in chicks with maternal-derived antibodies (MDA) until about 4 weeks of age as they are neutralized. Intermediate and hot vaccine strains that are less affected by MDA can be given with some success at earlier stages, depending upon MDA titres.