Circulating strains of variant infectious bursal disease virus may pose a challenge for antibiotic-free chicken farming in Canada. (October 2016)

• Record Type: Journal Article
• Authors: Kurukulsuriya, Shanika; Ahmed, Khawaja Ashfaque; Ojkic, Davor; Gunawardana, Thushari; Gupta, Ashish; Goonewardene, Kalhari; Karunaratne, Ruwani; Popowich, Shelly; Willson, Philip; Tikoo, Suresh K.; Gomis, Susantha
• Is Part Of: Research in veterinary science. Volume 108(2016)
• Page Start: 54
• Page End: 59
• Publication Date: 2016-10
• Subjects: BBW bursal weight to body weight ratio -- CCS cumulative clinical score -- E. coli Escherichia coli -- EID50 embryo infective dose 50 -- TCID50 tissue culture infective dose 50 -- GM geometric mean -- H&E hematoxylin and eosin -- IBDV infectious bursal disease virus -- MAb maternal antibody -- SD standard deviation -- SPF specific pathogen free -- cIBDV classical IBDV -- vIBDV variant IBDV -- VP viral protein; VP2 hyper-variable domain -- Broiler chickens -- Bursal atrophy -- Hyper-immunization -- Immunosuppression -- Maternal antibodies; Veterinary medicine -- Periodicals; Veterinary Medicine -- Periodicals; Médecine vétérinaire -- Périodiques; Médecine vétérinaire -- Recherche -- Périodiques; Diergeneeskunde; 636.089
• DOI: 10.1016/j.rvsc.2016.08.002
• Languages: English
• ISSNs: 0034-5288

Abstract

Abstract: Antibiotic-free and safe animal products are most desirable among consumers. However, ensuring safe poultry products is a challenging task when the chicken immune system is compromised. Infectious bursal disease virus (IBDV) causes immunosuppression and predisposes chickens to secondary infections. Breeder vaccination against IBDV is routinely practiced for producing chicks with maternally-derived antibody (MAb) to prevent infection in newly hatched chicks. The majority of IBDV circulating in Canadian farms are variant strains (vIBDV). Whether circulating vIBDV strains are immunosuppressive in chicks or are amenable to current vaccine regimens has not previously been tested through challenge studies. In this study, one-day-old broiler chicks ( n = 240) carrying MAb were obtained from broiler breeders vaccinated with commercial IBDV vaccines. In the first set of experiments ( n = 40/group), at six days post-hatch, one group was challenged with a Canadian field isolate, vIBDV (strain-SK09) (3 × 10 3 EID50 ). The second and the third groups (controls) were inoculated with non-immunosuppressive IBDV D-78 (10 × 10 3 TCID50 ) and saline, respectively. Histopathological examination on days 14 and 30 post-challenge revealed that despite the high level of MAb, vIBDV (SK09) caused severe bursal damage in chicks. Another set of experiments with treatment groups as above, demonstrated that pre-exposure of chicks with vIBDV (SK09) caused immunosuppression resulting in significantly higher mortality and disease severity in chicks challenged with a virulent strain of Escherichia coli ( E. coli ). Our data provide evidence that IBDV strains circulating in Canada are immunosuppressive, not amenable to current anti-IBDV vaccination strategy, and a potential threat to antibiotic-free chicken farming. Highlights: Circulating vIBDV SK09 is pathogenic and causes severe bursal damage in chickens. vIBDV SK09 is an immunosuppressive strain. vIBDV SK09 is not amenable to currently available vaccines.