Protection Against Mycoplasma gallisepticum in Layers Immunized with Recombinant Fowl Poxvirus Vaccine Followed by Live F Strain Vaccine

Abstract

Generally, one administration of either a recombinant fowl poxvirus-Mycoplasma gallisepticum (rFPV-MG) or a live F strain (FMG) vaccine is recommended in layer flocks. This study aimed to assess MG protection when the rFPV-MG and FMG vaccines were given to layers as opposed to a single vaccination with FMG vaccine. One hundred 8-week-old layer chickens were divided into 4 groups as follows: group 1 received FMG at 11 weeks of age, group 2 received rFPV-MG at 8 weeks of age and FMG at 11 weeks of age, groups 3 and 4 served as positive and negative controls, respectively. At 14 weeks of age, groups 1-3 were challenged with a Thai MG strain. The protection was monitored by evaluating body weight gain, thoracic air sac and tracheal lesions and MG detection. Sera of 8- to 18-week-old layer chickens were collected and tested for MG-antibody response. During 12-16 weeks of age, five birds in each group were necropsied to evaluate gross thoracic air sac lesion and histopathologic tracheal lesion. At 16 and 17 weeks of age, MG were re-isolated and identified by using RAPD PCR assay to differentiate strains. Results revealed that during 14-18 weeks of age, the birds receiving rFPV-MG and FMG vaccines had a superior body weight gain and prevented colonization of the MG challenge strain. In conclusion, the birds receiving rFPV-MG and FMG vaccines provided appropriate performance compared with the other MG-challenged groups. The combination of rFPV-MG and FMG vaccination program could be used for MG protection in MG endemic area.