A. Ballal  , A.E. Karrar  , A.M. ElHussein  , 
    Isolation and Characterization of Infectious Bronchitis Virus Strain 4/91 from Commercial Layer Chickens in the Sudan,
    Journal of Animal and Veterinary Advances,
    Volume 4,Issue 11,
    2005,
    Pages 910-912,
    ISSN 1680-5593,
    javaa.2005.910.912,
    (https://makhillpublications.co/view-article.php?doi=javaa.2005.910.912)
    Abstract: Outbreaks of suspected IB disease occurring in a number of commercial layer flocks at Khartoum and El Gazira states were studied during years (2000- 2001). Affected birds were of different breeds (Lohmann, Bovans Hisex). Their ages were from 5 / –7 months. The main clinical signs varied from mild respiratory signs to diarrhea sometimes yellowish in colour. Drop in egg production (up to 60%) was recorded in some flocks. IB virus was isolated from these outbreaks. Using virus neutralization (VN) and haemagglutination inhibition (HI) tests, three of these IB field isolates (M114/2000, K170/2000 and K158/2001) were antigenically similar to IB virus strain 4/91 (Neutralization index 4.4 to 4.8 and VN titer > 11(log ) were recorded). Isolate (K110/2000) on the other hand, was antigenically similar to IB virus Mass. (M41) strain (HI titer >11 log was recorded). This 2 is the first time to identify IB virus strain antigenically similar to IB virus strain 4/91 in Sudan.
    Keywords: Avian;infectious;bronchitis;strain;4/91