Electron-Beam-Killed Staphylococcus Vaccine Reduced Lameness in Broiler Chickens

Abstract

Broiler chicken lameness caused by bacterial chondronecrosis with osteomyelitis (BCO) is presently amongst the most important economic and animal welfare issues faced by the poultry industry, and the estimated economic loss is around USD 150 million. BCO lameness is associated with multiple opportunistic bacterial pathogens inhabiting the respiratory and gastrointestinal tracts. In cases of immune deficiency resulting from stress, injury, or inflammation of the tissue, opportunistic pathogens, mainly Staphylococcus spp., can infiltrate the respiratory or gastrointestinal mucosa and migrate through the bloodstream to eventually colonize the growth plates of long bones, causing necrosis that leads to lameness. This is the first report of developing a Staphylococcus vaccine against BCO lameness disease in broiler chickens. Electron beam (eBeam) technology causes irreparable DNA damage, preventing bacterial multiplication, while keeping the epitopes of the cell membrane intact, helping the immune system generate a more effective response. Our results show a 50% reduction of lameness incidence in the eBeam-vaccinated chicken group compared to the control. Additionally, the eBeam-vaccinated chickens present higher titer of anti-Staphylococcus IgA, signifying the development of an efficient and more specific humoral immune response. Our data establish the eBeam-killed Staphylococcus vaccine as an effective approach to reducing the incidence of lameness in broiler chickens.

Keywords: Staphylococcus agnetis; Staphylococcus aureus; lame; lameness prevention; vaccination.

Figure 1

eBeam vaccine prevents lameness in broiler chickens. (A) Lameness trial experimental strategy. (B) Table shows percentages of cumulative lameness and lameness prevention of Formalin and eBeam groups compared to Control group and representative graph of lameness prevention. (C) Kaplan–Meier lameness-free curve for broiler chickens. (D) Population plot estimates of probability of lameness with 95% confidence interval (blue line). (E) Plot of the odds ratios for treatment versus control with 95% confidence interval (blue line) and OR = 1 (black line—indicates no difference). n represents the number of chickens evaluated. ** p-value < 0.01.

Figure 2

Leukocyte populations in broiler chickens were similar between the three experimental groups. (A) Representative flow cytometry gating strategy for stains 1, 2, and 3. (B) Quantification of absolute cell number of leukocytes (CD45⁺CD41/61⁻ cells), CD4⁺T cells (CD45⁺CD4⁺CD8⁻TCRγδ⁻), CD8⁺T cells (CD45⁺CD4⁻CD8⁺TCRγδ⁻), γδ T cells (CD45⁺CD4⁻CD8^+or−TCRγδ⁺), B cells (CD45⁺Bu1⁺KUL01⁻), monocytes (CD45⁺Bu1⁻KUL01⁺), and heterophils (CD45⁺Bu1⁻KUL01⁻SCC^hi) at day 11 (control n = 4; formalin n = 5; eBeam n = 6), day 33 (n = 6), and day 56 (n = 10). n represents the number of chickens evaluated; graphs show means ± SD.

Figure 3

eBeam vaccine developed a more specific immune response compared to other treatments. Quantification of the relative concentration of IgM, IgY, and IgA antibodies in the serum of broiler chickens of the three treatments at days 11 (A), 33 (B), and 56 (C). n represents the number of chickens evaluated; graphs show means ± SD; ns p-value > 0.05, * p-value < 0.05, ** p-value < 0.01.