Q&A on the Paper of Kurukulasuriya et al. (2017) on IBD Vaccine Efficacy Against a Canadian Variant IBDV Strain in Broiler Chickens

Abstract

Kurukulasuriya, et al. (2017) are reporting the efficacy of two IBD vaccines against an early (6 days post-hatch) challenge with a variant Canadian IBDV strain in broilers. A modified live vaccine(UNIVAX BD) administered by SQ route at 1 dayof-age delayed infection whereas an HVT-IBD vector vaccine (VAXXITEK HVT+IBD) administered in ovodid not protect. Furthermore, the authors suggested that the HVT-IBD vector induced immunosuppression responsible for an earlier IBDV challenge strain replication in the bursa. The data presented in the paper showed no evidence of VAXXITEK HVT+IBD vaccine take since the mean IBD ELISA antibody titer at D35 in the vaccinated/non-challenged group was not significantly different from that of the non-vaccinated group. It wasmuch lower than the expected one based on previous studies performed in the same conditions : in ovo vaccination of broilers [1,2]. Since there is no evidence of vaccine take, the other potential effects (immunosuppression and earlier IBDV replication in the bursa) observed in that group cannot be attributed to the vaccine. Since its launch in 2006 in Brazil, VAXXITEK HVT+IBD has been licensed in more than 75 countries and more than 80 billion birds have been vaccinated. VAXXITEK HVT+IBD is protecting against a wide variety of IBDV strains including the classical, the very virulent and different variant strains. To our knowledge, noabsence of efficacy nor bursa depletions have been so far officially reported as long as the vaccine has been administered properlyto healthy embryonated eggs or to healthy one-day-old chicks.