Molecular identification targeting cox1 and 18S genes confirms the high prevalence of Sarcocystis spp. in cattle in the Netherlands

Abstract

The reported prevalence of Sarcocystis infection in cattle in Europe ranges between 66 and 94%. Although in the Netherlands a prevalence of 100% was reported in 1993, this study aimed to develop a method for sensitive and specific molecular detection and species identification of Sarcocystis spp., in order to provide more recent data on the prevalence and identification of these protozoa in cattle meat intended for human consumption in the Netherlands. For this purpose, 104 cattle samples were obtained from Dutch slaughterhouses. Genomic DNA was extracted, and analysed by 18S and cox1 PCR. Magnetic capture was used to extract and amplify 18S-specific DNA. Sarcocystis DNA was detected in 82.7% of the samples. PCR amplicons of both targets were sequenced, and sequence identities of ≥97% were observed for Sarcocystis cruzi (65.4%), Sarcocystis hominis (12.5%), Sarcocystis bovifelis (8.7%), Sarcocystis hirsuta and Sarcocystis heydorni (both 1.0%). Mixed infections were observed in 17.3% of the samples. The magnetic capture was not significantly more sensitive compared with standard DNA extraction, but magnetic capture did add to the overall sensitivity. Using cox1 sequencing, all species are clearly distinguished, whereas for 18S the variation between species is limited, which particularly hampers reliable identification of thick walled Sarcocystis spp. Furthermore, the detection of 12.5% S. hominis and 1% S. heydorni points towards an established transmission route between cattle and humans in the Netherlands. The availability of four additional well-identified and well-referenced S. hominis cox1 sequences in public databases enables development of species-specific diagnostic PCRs targeting cox1, which in combination with magnetic capture could provide the means to determine the prevalence of human sarcocystosis.

Keywords: 18S; Cattle; Magnetic capture; Prevalence; Sarcocystis hominis; Sarcocystis spp.; The Netherlands; cox1.