Abstract
BackgroundMycoplasma synoviae (MS) is a major poultry pathogen which causes severe economic losses in all the productive sectors. The prevalence of MS in European countries has increased in the last few years, leading to greater attention to the available methods to prevent its spread. The main strategy currently applied for its containment is the development and maintenance of MS-free breeder flocks. A live MS vaccine (MS-H) obtained by mutagenizing an Australian field strain has recently been introduced in Italy. The aim of the present study was to evaluate the vaccine behaviour in broiler breeder groups at different production stages and the effectiveness of the available laboratory tests in discriminating the MS-H from a field strain.ResultsThe vaccine diffused extensively through the population, shown by the wide serological response (over 80% of positive samples in RSA and 85% in ELISA), the high serological titres, the positivity of all the tracheal samples collected during the production phase by MS PCR and the positivity by cultivation from tracheal swabs at the end-point (55 weeks after vaccination). In contrast, only one swab from a sternal bursa was positive in MS PCR, while all the joint and oviduct samples were negative. There was no evidence of vertical transmission. Different genotyping techniques were used to achieve a clear classification of the MS positive samples. The vlhA and the obg gene analysis showed that most of the strains were homologous with the vaccine, but some ambiguous samples were further investigated with the multi locus sequence typing (MLST) scheme which confirmed the homology.ConclusionsThe development of a multi-technique approach to monitor vaccinated avian flocks, based both on serological and biomolecular methods, is advised as well as the use of effective genotyping techniques to analyse the MS strains circulating in high densely populated poultry areas.
Highlights
Mycoplasma synoviae (MS) is a major poultry pathogen which causes severe economic losses in all the productive sectors
The laboratory findings of the present study suggest that there was no vertical spread of the MS vaccine, but further large scale studies should be carried out in view of the recent reports of Mycoplasma gallisepticum (MG) vaccine transmission in the USA [28]
It is interesting to report that the mutation in position 629 was not confirmed in each barn at every sampling time; for example in barn 4 the point mutation was not recovered until the end of the trial. These results suggest that the 2 vaccine types (MS-H ts + and reisolate ts-) could be present together in the population
Summary
Mycoplasma synoviae (MS) is a major poultry pathogen which causes severe economic losses in all the productive sectors. The main strategy currently applied for its containment is the development and maintenance of MS-free breeder flocks. The aim of the present study was to evaluate the vaccine behaviour in broiler breeder groups at different production stages and the effectiveness of the available laboratory tests in discriminating the MS-H from a field strain. MS infection often leads to severe economic losses due to reduced body weight, poor feed conversion rate, high carcasses condemnation and increased antibiotic treatment; in case of EAA it can involve increased. The most effective control strategies are focused on the development and maintenance of MS-free breeder flocks, but in case of infection the interruption of the vertical transmission represents an important goal for the practitioner. The production of a MS-positive offspring could have even worse economic consequences than those arising from the culling of breeder groups
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