<i>Sarcocystis sinensis</i> is the most prevalent thick-walled <i>Sarcocystis</i> species in beef on sale for consumers in Germany

Abstract

Bovines are intermediate hosts of <i>Sarcocystis cruzi</i>, <i>Sarcocystis hirsuta</i>, and <i>Sarcocystis hominis</i>, which use canids, felids, or primates as definitive hosts, respectively. Cattle represent also intermediate hosts of <i>Sarcocystis sinensis</i>, but the definitive hosts of this parasite are not yet known. Sarcocystosis in cattle is frequently asymptomatic. The infection is characterized by the presence of thin-walled (<i>S. cruzi</i>) or thick-walled muscle cysts or sarcocysts (<i>S. hominis</i>, <i>S. sinensis</i>, and <i>S. hirsuta</i>). Recent reports suggest high prevalence of the zoonotic <i>S. hominis</i> in beef in Europe. We therefore aimed at differentiating Sarcocystis spp. in beef offered to consumers in Germany using molecular and microscopical methods, focusing on those species producing thick-walled sarcocysts. A total of 257 beef samples were obtained from different butcheries and supermarkets in Germany and processed by conventional and multiplex real-time PCR. In addition, 130 of these samples were processed by light microscopy and in 24.6 % thick-walled cysts were detected. Transmission electron microscopical analysis of six of these samples revealed an ultrastructural cyst wall pattern compatible with <i>S. sinensis</i> in five samples and with <i>S. hominis</i> in one sample. PCR-amplified 18S ribosomal DNA (rDNA) fragments of 28 individual thick-walled cysts were sequenced, and sequence identities of ≥98 % with <i>S. sinensis</i> (n = 22), <i>S. hominis</i> (n = 5) and <i>S. hirsuta</i> (n = 1) were observed. Moreover, nine Sarcocystis sp. 18S rDNA full length gene sequences were obtained, five of <i>S. sinensis</i>, three of <i>S. hominis</i>, and one of <i>S. hirsuta</i>. Out of all samples (n = 257), 174 (67.7 %) tested positive by conventional PCR and 179 (69.6 %) by multiplex real-time PCR for Sarcocystis spp. Regarding individual species, 134 (52 %), 95 (37 %), 17 (6.6 %), and 16 (6.2 %) were positive for <i>S. cruzi</i>, <i>S. sinensis</i>, <i>S. hirsuta</i>, and <i>S. hominis</i>, respectively. In conclusion, <i>S. sinensis</i> is the most prevalent thick-walled Sarcocystis species in beef offered for consumption in Germany. Further studies are needed to identify the final host of <i>S. sinensis</i> as well as the potential role of this protozoan as a differential diagnosis to the zoonotic species <i>S. hominis</i>.