title: Pathogenicity associated with coinfection with very virulent infectious bursal disease and Infectious bursal disease virus strains endemic in the United States.
abstract: The pathogenicity induced by co-challenge with the rB strain of very virulent Infectious bursal disease virus (vvIBDV) and IBDV pathotypes endemic in the United States was evaluated in specific pathogen-free chickens. Four- and 6-week-old birds were simultaneously challenged with a 10(5) 50% egg infectious dose (EID50) of rB mixed with a 10(5) EID50 of one of the following viruses: standard classic (STC), subclinical variant (Del-E), subclinical variant (T1), or avirulent serotype 2 (OH). Each challenge group consisted of 5 chickens. The severity of disease was assessed by comparing the 5-day mortality rates, bursal lesions (mean bursal lesion scores), and mean bursal-to-body weight ratios in each of the challenged groups. A mortality of 100% (10/10 and 5/5) was observed in birds inoculated with only the vvIBDV (rB) strain at 4 weeks and 6 weeks of age, respectively. Although the sample sizes were low, a significant reduction in mortality and severity of disease, based on mean bursal lesion scores, was observed in groups co-challenged with rB and the less virulent pathotypes Del-E, T1, or OH at 4 weeks of age. Co-challenge with rB and the antigenically similar STC strain did not result in a significant decrease in mortality compared to challenge with the pathogenic rB strain at 4 weeks of age, but a significant reduction in the mean bursa lesion score was observed. At 6 weeks of age, a significant decrease in mortality and mean bursa lesion score was observed in the rB groups co-challenged with STC, Del-E, or T1 but not OH.
authors.affiliation: Food Animal Health Research Program, Department of Veterinary Preventive Medicine, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA.
authors.forename: Simone T
authors.initials: ST
authors.lastname: Stoute
authors.forename: Daral J
authors.initials: DJ
authors.lastname: Jackwood
authors.forename: Susan E
authors.initials: SE
authors.lastname: Sommer-Wagner
authors.forename: Beate M
authors.initials: BM
authors.lastname: Crossley
authors.forename: Peter R
authors.initials: PR
authors.lastname: Woolcock
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Charlton
mesh_terms: D000818:Animals; D018175:Birnaviridae Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D002060:Bursa of Fabricius / Q000821:virology; D002645:Chickens; D019353:Endemic Diseases; D007243:Infectious bursal disease virus / Q000145:classification / Q000472:pathogenicity*; D011201:Poultry Diseases / Q000453:epidemiology / Q000821:virology*; D012367:RNA, Viral / Q000032:analysis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013047:Specific Pathogen-Free Organisms; D014774:Virulence
chemical_list: D012367:RNA, Viral
keywords: Chickens; co-challenge; pathogenicity; very virulent Infectious bursal disease virus