# Cross-sectional study of Mycoplasma hyopharyngis, Mycoplasma hyopneumoniae, Mycoplasma hyorhinis and Mycoplasma hyosynoviae in the tonsils of fattening pigs from Central-Eastern Europe

## TL;DR

This study examined the presence of four mycoplasma species in pig tonsils across Central-Eastern Europe and developed a new test for one of them.

## Contribution

A novel qPCR assay for detecting Mycoplasma hyopharyngis was developed and validated.

## Key findings

- M. hyopharyngis was detected in 92.67% of herds, with successful isolation from 20 herds.
- M. hyorhinis was found in all 150 herds tested and isolated from 107 herds.
- The new qPCR assay for M. hyopharyngis proved reliable and sensitive for detection.

## Abstract

Mycoplasma (M.) hyopharyngis, M. hyopneumoniae, M. hyorhinis, and M. hyosynoviae can all be transiently present in the swine tonsils without causing any clinical signs or lesions. M. hyopharyngis is considered a commensal bacterium, however, our knowledge about its prevalence and pathogenic capabilities is lacking. M. hyopneumoniae, M. hyorhinis and M. hyosynoviae are widespread pathogens, responsible for significant economic losses. M. hyopneumoniae is known as the causative agent of porcine enzootic pneumonia, while M. hyorhinis and M. hyosynoviae are associated with arthritis and polyserositis. The objective of this study was to evaluate the detection rates of these mycoplasmas in Central-Eastern Europe (Croatia, the Czech Republic, Hungary, and Slovakia) through a cross-sectional investigation. In parallel, a novel quantitative polymerase chain reaction (qPCR) assay was designed targeting M. hyopharyngis to facilitate the identification of this bacterium.

Tonsils of 15 animals per herd were sampled from six-month-old fattening pigs, and a total of 150 herds were examined. Tonsils form each herd were divided into three pools, each comprising five tonsils. The samples were submitted for species-specific TaqMan assay and isolation. M. hyopharyngis was identified in 92.67% (139/150, 95% confidence interval: 87.35–95.86%) of the stocks, with successful isolation from 20 herds. Besides, M. hyopneumoniae was detected in 51.33% (77/150, 95% confidence interval: 43.40-59.19%) of the stocks. Additionally, M. hyorhinis was identified in all herds (100.00%; 150/150, 95% confidence interval: 97.50–100.00%) by qPCR examination and was successfully isolated from 107 stocks. Regarding the occurrence of M. hyosynoviae, 88.00% (132/150, 95% confidence interval: 81.83–92.27) of the herds showed positive PCR results, and the pathogen was successfully isolated in 122 cases. Moreover, the newly developed M. hyopharyngis qPCR assay proved to be a reliable and sensitive method.

This study determined the detection rates of several porcine mycoplasmas (M. hyopharyngis, M. hyopneumoniae, M. hyorhinis, and M. hyosynoviae) in fattening pigs in Central-Eastern Europe. Additionally, the developed M. hyopharyngis qPCR assay may facilitate future prevalence studies and diagnostic procedures concerning this neglected bacterium.

The online version contains supplementary material available at 10.1186/s40813-025-00429-6.