Dubey J P, Gupta A, Kothavale K, Calero-Bernal R, García-Gil M L, Cotey S R, Scimeca R C, Reichard M V, Rosenthal B M
J Parasitol. 2025 Aug 7;111(4):516-525. doi: 10.1645/25-25.
Sarcocystis infections are common in the muscles of herbivores but were, until recently, considered relatively rare in carnivores. Little is known of sarcocysts in the muscles of river otters in the United States. In a previous epidemiologic study of Toxoplasma gondii infections in North American river otters (Lontra canadensis) from Michigan in the 2018 and 2019 harvest season, Sarcocystis DNA was found in 34 (27.4%) of 124 otter muscles. Tongues from these 34 PCR-positive samples were further examined here for Sarcocystis species. An additional batch of frozen 62 samples collected at the end of the season was also tested for Sarcocystis herein. Morphologically, sarcocysts were studied in 23 otters (13 of 34 PCR-positive samples from the first batch and 10 of 62 samples of batch 2) in compression smears and paraffin-embedded histologic sections stained with hematoxylin and eosin. Morphologically, at least 2 different kinds of sarcocysts were identified, 1 with a smooth sarcocyst wall and the second with villar protrusions. By transmission electron microscopy, sarcocysts from 1 otter were similar to Sarcocystis caninum. Morphologically, sarcocysts from the river otter were different from the European otter (Lutra lutra). Sequencing amplification products from 18S rRNA, 28S rRNA, and cox1 genes, suggested S. caninum-like, Sarcocystis svanai-like, and Sarcocystis sp. We detected a third, potentially undescribed species, in 3 otters. Genetic markers for conclusive differentiation of Sarcocystis spp. from mustelids should be developed. The samples in the present study had degraded; better preserved samples are needed for further morphologic studies. This is the first report of S. caninum-like, S. svanai-like, and Sarcocystis sp. in the river otter in the United States.
肉孢子虫感染在食草动物肌肉中很常见，但直到最近，在食肉动物中仍被认为相对罕见。关于美国水獭肌肉中的肉孢子虫，人们了解甚少。在之前一项关于2018年和2019年收获季节密歇根州北美水獭（加拿大水獭）弓形虫感染的流行病学研究中，在124只水獭的肌肉中，有34只（27.4%）检测到肉孢子虫DNA。在此对这34份PCR阳性样本的舌头进行了肉孢子虫种类的进一步检测。本研究还对在季节结束时收集的另外一批62份冷冻样本进行了肉孢子虫检测。在形态学上，对23只水獭（第一批34份PCR阳性样本中的13只和第二批62份样本中的10只）的压缩涂片和苏木精-伊红染色的石蜡包埋组织切片中的肉孢子虫进行了研究。在形态学上，至少鉴定出2种不同类型的肉孢子虫，一种肉孢子虫壁光滑，另一种有绒毛状突起。通过透射电子显微镜观察，1只水獭的肉孢子虫与犬肉孢子虫相似。在形态学上，水獭的肉孢子虫与欧洲水獭（欧亚水獭）不同。对18S rRNA、28S rRNA和cox1基因的测序扩增产物表明，存在犬肉孢子虫样、斯氏肉孢子虫样和肉孢子虫属物种。我们在3只水獭中检测到了第三种可能未描述的物种。应开发用于从鼬科动物中明确区分肉孢子虫物种的遗传标记。本研究中的样本已经降解；需要保存更好的样本进行进一步的形态学研究。这是美国水獭中犬肉孢子虫样、斯氏肉孢子虫样和肉孢子虫属物种的首次报告。
