Evaluation of the potential influence of the disinfection cycle on the efficacy of strain F Mycoplasma gallisepticum vaccine administered by in ovo injection to layer hatching eggs

Authors: ELLIOTT, KEC - Mississippi State University; Branton, Scott; Evans, Jeffrey - Jeff; PEEBLES, E - Mississippi State University

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2020
Publication Date: 9/15/2020
Citation: Elliott, K., Branton, S.L., Evans, J.D., Peebles, E.D. 2020. Evaluation of the potential influence of the disinfection cycle on the efficacy of strain F Mycoplasma gallisepticum vaccine administered by in ovo injection to layer hatching eggs. Journal of Applied Poultry Research. 29(3):673-683. https://doi.org/10.1016/j.japr.2020.05.001.
DOI: https://doi.org/10.1016/j.japr.2020.05.001

Interpretive Summary: Strain F of Mycoplasma gallisepticum (FMG) is a live attenuated vaccine normally administered via eyedrop to pullets between 9-14 weeks of age which provides protection against field strains of MG for the life of the hen. Delivering the FMG vaccine in ovo has the potential to save labor and reduce stress on birds as compared to the handling of each pullet when administering eyedrop vaccinations. In ovo vaccination of a live-attenuated FMG vaccine has proven to be a promising alternative vaccination route for layer chickens to combat MG infections although practicality has been uncertain at it employs a disinfection step after each injection. The objective of this study was to determine the ability of FMG to survive the in ovo disinfection step and to subsequently elicit a post-hatch immune response. To that end, two trials were conducted in which layer chicken eggs were in ovo vaccinated with or without the disinfection step between injections utilizing an Embrex® Inovoject® machine. Treatments included non-injected eggs, diluent-injected eggs with or without a disinfection step, and eggs vaccinated with an FMG vaccine with or without a disinfection step. Ninety hatched chicks per treatment in both trials were raised to 6 wk of age and swabbed from the choanal cleft for FMG detection via Polymerase Chain Reaction (PCR) test and were also bled for IgM (Immunoglubulin M, Serum plate agglutination) and IgG (Immunoglobulin E, Enzyme Linked Immunosorbent Assay [ELISA]) testing for detection of antibody production against MG. Percentages of birds having FMG detected at 6 wk of age were similar between both FMG vaccination treatments in both trials (overall 89.4% without and 91.6% with disinfectant step). Layer chickens vaccinated with FMG also developed antibody responses regardless of employment of the disinfection step (overall >60% IgM and >30% IgG). These results indicate that FMG survives the disinfection step employed by commercial machines and could be readily applied to current commercial procedures of in ovo vaccination with no detriment to vaccine efficacy thereby reducing costs associated with handling of live birds while also providing a longer duration between FMG vaccination and potential exposure to wild strains of MG.

Technical Abstract: In ovo vaccination of a live-attenuated F-strain Mycoplasma gallisepticum vaccine (FMG) has proven to be a promising alternative vaccination route for layer chickens to combat Mycoplasma gallisepticum (MG) infections. Its practical application within current in ovo vaccination procedures, employing a disinfection step after each injection, was uncertain. The objective of this experiment was to determine the ability of FMG to survive the in ovo disinfection step to elicit a post-hatch immune response. Two trials were conducted in which layer eggs were in ovo vaccinated with or without the disinfection step between injections utilizing an Embrex® Inovoject® machine. Treatments included non-injected eggs, diluent-injected eggs with or without a disinfection step, and eggs vaccinated with an FMG vaccine with or without a disinfection step. Ninety hatched chicks per treatment in both trials were raised to 6 wk of age and swabbed in the choanal cleft for FMG detection via PCR and were bled for IgM (Serum plate agglutination) and IgG (ELISA) testing for detection of antibody production against MG. Percentages of birds having FMG detected at 6 wk of age were similar among both FMG vaccination treatments in both trials (overall 89.4% without and 91.6% with disinfectant step). Birds vaccinated with FMG also developed antibody responses regardless of employment of the disinfection step (overall >60% IgM and >30% IgG). These results indicate that FMG survives the disinfection step employed by commercial machines and could be readily applied to current commercial procedures of in ovo vaccination with no detriment to vaccine efficacy.