First molecular characterisation of Sarcocystis miescheriana in a pig carcass condemned during routine meat inspection in Poland

Introduction: This article presents the fourth detection of macroscopic cystic lesions due to sarcocystosis in domestic pigs during routine meat inspection worldwide, and the first molecular detection of Sarcocystis miescheriana in a domestic pig in Poland. Pigs can become intermediate hosts for S. miescheriana by accidental ingestion of oocysts or sporocysts present in food or water contaminated by the faeces of canids (definitive hosts). Material and Methods: The affected swine showed no clinical symptoms such as weight loss, dermatitis or dyspnoea suggesting sarcocystosis. The presence of grossly visible cyst-like lesions was noticed by veterinary inspectors during post-mortem meat inspection of pig carcasses at a slaughterhouse located in central Poland. Ten rice-grain-shaped white lesions were isolated from the muscle tissue for molecular analysis, and four other macroscopic cyst-like lesions were also isolated for histopathological and microscopy analysis. The molecular characterisation included amplification and sequencing of the cytochrome C oxidase subunit 1 mitochondrial gene. Results: The cyst-like structures were whitish, calcified, 1 cm long and 3 mm wide. The presence of S. miescheriana DNA was confirmed in all ten grossly visible cyst-like lesions. Conclusion: This study shows that Sarcocystis spp. may be present in swine muscle tissue and cause lesions leading to carcass discard. Further analyses are needed to fully recognise the prevalence and impact of Sarcocystis spp. on animal and human health, especially taking into account the possible presence of the zoonotic S. suihominis.