Experimental Evidence of the Diarrheal Activity of Sarcocystis sp. in Sika Deer (Cervus nippon)

Recently, the wild deer population has been increasing in Japan, causing serious feeding-related damage to the agricultural and forestry industries. In conjunction with the government's promotion of hunting for population control, the effective utilization of resources and promotion of the game meat industry as a sixth sector of industrialization are desired by local governments. However, several cases in which patients showed intestinal symptoms such as diarrhea due to the consumption of sika deer meat infected with protozoan Sarcocystis spp. have been reported, and the pathogenic microorganisms found in wild deer should be investigated. In this study, Sarcocystis sp. parasitized Kyushu sika deer (Cervus nippon nippon) in Nagasaki Prefecture, Japan, was examined for its enterotoxicity. A phylogenetic analysis based on the sequence of the 18S rRNA gene and cox1 showed that the species was highly homologous to Sarcocystis japonica and/or Sarcocystis sp. HM050622. We attempted to confirm the diarrhea-evoking toxicity of Sarcocystis sp. in sika deer meat, which has been previously reported in human case reports. A mouse ileal loop assay showed that Sarcocystis sp. in sika deer meat induced significant fluid accumulation in the loop at doses of ∼5 × 106 bradyzoites. Western blotting showed that these Sarcocystis parasites possess actin-depolymerizing factor, a diarrhea-evoking factor, similar to Sarcocystis fayeri, which exists in horsemeat. However, the pathogenic conditions of the ileal loop were different from those of similar experiments with S. fayeri. This study suggests that S. japonica parasitizing C. n. nippon may cause diarrhea via a different mechanism from that of S. fayeri.

The Relationship Between Epidemiological Factors and the Parasite Load of Sarcocystis in Yezo-Deer (Cervus nippon yesoensis) in Hokkaido, Japan

Several cases of gastrointestinal symptoms including diarrhea and vomiting due to the consumption of Sarcocystis-infected venison have been reported in Japan. However, the control of case incidence is difficult, as epidemiological information concerning Sarcocystis in venison in Japan is insufficient. We examined the prevalence and parasite load of Sarcocystis in 89 samples of Yezo-deer (Cervus nippon yesoensis) venison in Hokkaido by quantifying the copy numbers of the 18S rRNA gene of Sarcocystis, followed by a statistical analysis that considered the sampling area, age, and sex to clarify the parameters related to the parasite load. The copy numbers per gram of venison in samples ranged from 4.8 to 8.8 log. Wilcoxon rank-sum test, the one-way factorial analysis of variance (ANOVA), Steel-Dwass test, and a two-way factorial ANOVA showed significant differences in the copy numbers among sampling areas, not by age or sex, suggesting that the load of Sarcocystis in wild deer depended on the sampling area in Hokkaido. Notably, more than 80% of Hokkaido venison has a higher gene copy number than the meat that caused Sarcocystis fayeri-food poisoning. This information is expected to contribute to the establishment of hygiene standards for safe venison consumption and the control of gastrointestinal symptom cases due to consumption of Sarcocystis-infected venison.

Development of a new quantification method of Sarcocystis cruzi through detection of the acetyl-CoA synthetase gene

Sarcocystis cruzi is a member of the genus Sarcocystis, infecting bovine animals such as cattle and bison as intermediate hosts, and canids such as dogs and raccoon dogs as definitive hosts. Acute sarcocystosis of S. cruzi causes occasional symptoms in cattle, including weight loss, reduced milk production, abortions, and death, and similar to other Sarcocystis species can potentially cause food poisoning in humans when raw or undercooked infected cattle meat is consumed. Despite these issues, genetic information on S. cruzi is scarce, and there is no specific quantitative method for the detection and quantification of the parasite in infected cattle. In this study, we aimed to develop a method based on high-throughput sequencing of S. cruzi genome and transcriptome that specifically and quantitatively detects the S. cruzi acetyl-CoA synthetase gene (ScACS). Cardiac muscles were collected from slaughterhouses in Saitama Prefecture to obtain sarcocysts from which DNA and RNA were extracted for the high-throughput sequencing. Using the sequences, we developed a specific quantitative PCR assay which could distinguish S. cruzi ACS from that of Toxoplasma gondii by taking advantage of the differences in their exon/intron organizations and validated the assay with the microscopic counting of the S. cruzi bradyzoites. Thus, this assay will be useful for future studies of S. cruzi pathogenesis in cattle and for the surveillance of infected animals, thereby easing public health concerns.

Establishment of a Novel Molecular Detection Method for Sarcocystis in Venison

Recently, horse meat (basashi) contaminated with Sarcocystis spp. caused food poisoning in Japan. An official detection method provided by the Ministry of Health, Labour and Welfare (MHLW), Japan, was designed to detect Sarcocystis fayeri to diagnose and control outbreaks of basashi food poisoning. In 2011, Sarcocystis-contaminated venison also caused food poisoning. However, the official MHLW detection method was not adequate for detecting Sarcocystis spp. in venison. In this study, we established a novel PCR-based detection method that amplifies 18S rRNA gene based on the conserved region of the sequence in 32 species of Sarcocystis for screening and quantification. Fifty venison samples from three areas in Hokkaido were examined by the MHLW method and the novel detection method. All samples were Sarcocystis spp.-positive. A sequence analysis indicated the presence of a species of Sarcocystis specific to sika deer (Cervus nippon), and not to horses. Another primer pair was designed for a quantitative real-time PCR assay to determine the copy number of the Sarcocystis-18S rRNA gene in parasitized venison. The melting curve analysis revealed high specificity of this assay. The calculated curve demonstrated that this quantitative PCR assay showed R² value of 0.993 with 10-10⁶ copies. Using this quantitative real-time PCR assay, the gene copy numbers were determined in 50 venison samples. The copy numbers of each sample ranged from 10⁴ to 10⁷ per gram. The copy numbers differed according to the area in Hokkaido. This indicates that the density of Sarcocystis spp. that infect Sika deer in Hokkaido is affected by the area. The novel screening and quantitative PCR method for Sarcocystis in venison was useful for collecting epidemiological information on Sarcocystis in wild Japanese sika deer, which will contribute to improve the safety of venison products in Japan.

Presence of Sarcocystis sybillensis in Japanese sika deer (Cervus nippon) captured in its native territory and its phylogenetic relationship with Sarcocystis nipponi

The first study reporting the morphological characterization of Sarcocystis sybillensis was performed in 1983; however, without any molecular analysis. Sarcocystis nipponi has been recently described as a species synonymic to S. sybillensis. We reconfirmed the presence of S. sybillensis in Japanese sika deer (Cervus nippon) captured in its native territory; and performed its molecular and phylogenetic characterization. The morphological characteristics of the sarcocysts were consistent with those of S. nipponi and S. sybillensis described in the first report. However, the nucleotide sequence of 18S rRNA gene of S. sybillensis showed only 91.9% identity to that of S. nipponi, suggesting low homology among the concerned Sarcocystis spp. Accordingly, S. sybillensis was found to occupy a clade distinct from that of S. nipponi in a phylogenetic tree of Sarcocystis. Therefore, the present study provides essential information on 18S rRNA-based molecular characterization of S. sybillensis and disproves the existing notion of morphology-based species synonymity of S. sibillensis and S. nipponi. These results also suggest that S. sybillensis belongs to type 2 Sarcocystis.