Mycoplasma gallinarum infection associated with apparent Mycoplasma meleagridis seropositivity in breeder turkey flocks

Abstract

Monitored EU-wide, mycoplasmosis is a significant poultry disease caused by bacteria of the genus Mycoplasma, among which M. gallisepticum, M. synoviae, M. meleagridis and M. iowae are of major importance. Infection can lead to clinical disease and economic losses. Serological assays can give false positive results because of antigenic cross-reactivity among Mycoplasma species. Molecular diagnostics provide greater specificity and reliability. This study investigated suspected cases of Mycoplasma meleagridis infection in turkeys and assessed whether the observed serological reactivity was by cross- reactive antibodies rather than a sign of M. meleagridis infection. Material and Methods: One case in a breeder turkey flock was investigated during the rearing period, and another case in a similar flock was explored in the laying period. Both flocks had serology results positive for M. meleagridis. The rearing flock was monitored with ELISA, PCR and sequencing for extended time after a single positive result, whereas the laying flock was testing using rapid plate agglutination (RPA) in addition because mortality was higher and egg production lower. In both cases, swab and blood samples were taken to verify the initial serological findings and assess the potential presence of M. meleagridis. Results: In the breeding flock, ELISA detected a single positive reaction against M. meleagridis in one of three houses. However, a PCR did not confirm the presence of M. meleagridis DNA, although Mycoplasma spp. DNA was detected at low/inconclusive levels. In the laying flock, the RPA test gave several seropositive reactions against M. meleagridis, whereas a PCR did not confirm its presence. Microbiological culture, 16S rRNA PCR and Sanger sequencing identified M. gallinarum in both flocks. Conclusion: The results highlight the limited specificity of serological assays and the necessity of molecular confirmation for accurate diagnosis.