Canadian Wildlife Health Cooperative British Columbia, 1767 Angus Campbell Road, Abbotsford, British Columbia V3G 2M3, Canada.
Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada.
J Wildl Dis. 2021 Oct 1;57(4):856-864. doi: 10.7589/JWD-D-20-00225.
Sarcocystis spp. are protozoan parasites that cause a spectrum of lesions in various hosts. Hepatic sarcocystosis and encephalitis have been described in captive American black bears (Ursus americanus) and polar bears (Ursus maritimus), and in a free-ranging grizzly bear (Ursus arctos horribilis), but have not previously been reported in free-ranging American black bears. This study aimed to characterize the presence and lesions associated with Sarcocystis spp. in free-ranging bears in British Columbia, Canada from samples submitted to the provincial diagnostic laboratory. From 2007 to 2019, 102 free-ranging American black bear and grizzly bear tissues were examined postmortem for sarcocystosis using histopathology and follow-up molecular diagnostics. Sarcocystosis was confirmed in 41 (40%) free-ranging bears including 39 American black bears and two grizzly bears. Microscopic lesions included multifocal necrotizing hepatitis, nonsuppurative encephalitis, and/or intramuscular sarcocysts with or without associated inflammation. Sarcocystosis was considered the cause of death in eight (20%) of these bears, exclusively in cubs of the year (<1 yr old). Sarcocystis canis was identified in 22/32 (69%) cases where molecular characterization was performed and was the etiologic agent associated with bears that died of sarcocystosis. Confirmed cases were distributed widely across British Columbia. While there was an alternate proximate cause of death in the other confirmed bears, sarcocystosis may have contributed. Age was a significant risk factor, with yearlings presenting more often with fulminant lesions; however, there was a sampling bias toward juvenile bear submissions due to size and ease of transport. Further research is needed to understand the disease epidemiology and significance to population health.
肌肉内原虫病是由肉孢子虫属引起的，主要发生在各种宿主中，可引起一系列病变。在圈养的美洲黑熊（Ursus americanus）和北极熊（Ursus maritimus），以及自由放养的灰熊（Ursus arctos horribilis）中，已经描述了肝肉孢子虫病和脑炎，但在自由放养的美洲黑熊中尚未报道过。本研究旨在从提交给省级诊断实验室的样本中，描述不列颠哥伦比亚省自由放养的熊中存在的肉孢子虫属和与之相关的病变。2007 年至 2019 年，对 102 只自由放养的美洲黑熊和灰熊组织进行了死后剖检，通过组织病理学和后续分子诊断来检查肉孢子虫病。40%的自由放养熊（包括 39 只美洲黑熊和 2 只灰熊）被确诊患有肉孢子虫病。显微镜下的病变包括多灶性坏死性肝炎、非化脓性脑炎和/或肌内肉孢子虫，伴有或不伴有相关炎症。在这些熊中，有 8 只（20%）被认为死于肉孢子虫病，这些熊均为当年出生的幼熊（<1 岁）。在进行分子特征分析的 32 个病例中，有 22 个（69%）鉴定出犬肉孢子虫，是与死于肉孢子虫病的熊相关的病原体。确诊病例分布在不列颠哥伦比亚省各地。虽然在其他确诊的熊中还有其他的直接死因，但肉孢子虫病可能是导致其死亡的原因之一。年龄是一个重要的危险因素，当年幼的熊出现暴发性病变的频率更高；然而，由于熊的体型较小且易于运输，送检的熊多为幼年熊，存在采样偏倚。需要进一步研究以了解疾病的流行病学和对种群健康的意义。
