Carrier State Studies of Infectious Bronchitis Virus in Asymptomatic Layer in Pakistan

Abstract: Isolation of infectious bronchitis virus (IBV) was conducted in asymptomatic layer flocks with a history of IB or IB vaccination at least from 5 to 20 weeks before the day of sampling. A trypsin-induced hemagglutination (THA) assay to detect IBV in allantoic fluid of embryonated eggs was used. Detection of IBV through THA showed that group A [5 wks post-inoculation (PI)] was 100%, group B (10 wks PI) was 86%, group C (15 wks PI) was 74 % and group D (20 wks PI) was 28 % positive for IBV. Virus titre was found negatively correlated with the PI duration. Key words: Infectious bronchitis virus, layer, allantoic flui