Occurrence of horizontal transmission in layer chickens after administration of an in ovo strain F Mycoplasma gallisepticum vaccine

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

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2019
Publication Date: 10/12/2019
Citation: Elliott, K., Branton, S.L., Evans, J.D., Peebles, E.D. 2019. Occurrence of horizontal transmission in layer chickens after administration of an in ovo strain F Mycoplasma gallisepticum vaccine. Poultry Science. 98(10):4492-4497. https://doi.org/10.3382/ps/pez306.
DOI: https://doi.org/10.3382/ps/pez306

Interpretive Summary: While Mycoplasma gallisepticum (MG) is known to be transmitted from infected birds to non-infected birds, it is not known whether transmission can occur to non-vaccinated pen mates from chicks that were in ovo-vaccinated with F strain MG. Embryonated chicken eggs were either not injected or administered a dilution of an FMG vaccine: high (1X resuspended vaccine), medium (10-2), low (10-4), or very low dose (10-6 dilution). Subsequent to hatching, ten non-injected, sentinel birds, and one in ovo-vaccinated chick were placed in each of 32 isolation units and at 6 weeks of age (woa), birds that had been injected in ovo were removed while sentinel (non-vaccinated birds) were maintained through 12 woa. Results of this study indicate that the percentages of MG positive sentinel birds and sentinel birds with antibody production against MG at 12 wk from each unit were not different between all MG dosages with the conclusion being that layer chickens in ovo-vaccinated with a live attenuated FMG vaccine are able to transmit FMG to other chicks with which they are in direct contact.

Technical Abstract: Mycoplasma gallisepticum (MG) is known to be transmitted from infected birds to non-infected. This study was performed to determine the transmissibility of live attenuated strain F MG (FMG) from chicks having been in ovo-vaccinated with FMG to non-vaccinated pen mates. Eggs from an MG clean flock were incubated together for 18 days, at which point all live embryonated eggs were either not injected or administered a dilution of an FMG vaccine: high (1X resuspended vaccine), medium (10-2), low (10-4), or very low dose (10-6 dilution). Non-injected eggs were hatched in a separate incubator. Ten non-injected, sentinel birds, and one in ovo-vaccinated chick each placed in each of 32 isolation units located in 2 replicate rooms (8 replicates per dose). At 6 weeks of age, birds that had been injected in ovo were removed, swabbed for FMG detection by PCR, and bled for serum plate agglutination (SPA) and ELISA testing for the presence of antibodies against MG. At 12 weeks of age, the remaining sentinel birds were likewise sampled. No sentinel birds died and out of the in ovo-vaccinated chicks, 1 high, 2 medium, 6 low, and all 8 very low dose treated chicks survived through week 6. The in ovo-vaccinated birds that survived to 6 wk were serologically positive except for 5 birds in the very low dose treatment. The percentages of MG positive sentinel birds and sentinel birds with antibody production against MG at 12 wk from each unit were not different between all MG dosages (P = 0.48, PCR; P = 0.77, SPA; P = 0.85, ELISA). Body weights of the in ovo vaccinated chicks at 6 weeks of age (P = 0.43) and the sentinel birds at 12 weeks of age (P = 0.95) were each not affected due to the FMG treatment. These findings indicate that layer chickens in ovo-vaccinated with a live attenuated FMG vaccine were able to transmit FMG to other chicks with which they were in direct contact.