Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald-Insel Riems, Germany.
Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Street 17, 10315, Berlin, Germany.
Parasit Vectors. 2021 Apr 14;14(1):201. doi: 10.1186/s13071-021-04697-3.
Besnoitia darlingi, B. neotomofelis and B. oryctofelisi are closely related coccidian parasites with felids as definitive hosts. These parasites use a variety of animal species as intermediate hosts. North American opossums (Didelphis virginiana), North American southern plains woodrats (Neotoma micropus) and South American domestic rabbits (Oryctolagus cuniculus) are intermediate hosts of B. darlingi, B. neotomofelis and B. oryctofelisi, respectively. Based on conserved regions in the internal transcribed spacer-1 (ITS1) sequence of the ribosomal DNA (rDNA), a real-time PCR for a sensitive detection of these Besnoitia spp. in tissues of intermediate hosts and faeces of definitive hosts has recently been established. Available sequence data suggest that species such as B. akodoni and B. jellisoni are also covered by this real-time PCR. It has been hypothesised that additional Besnoitia spp. exist worldwide that are closely related to B. darlingi or B. darlingi-like parasites (B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni). Also related, but not as closely, is B. besnoiti, the cause of bovine besnoitiosis.
Faecal samples from two free-ranging cheetahs (Acinonyx jubatus) from Namibia that had previously tested positive for coccidian parasites by coproscopy were used for this study. A conventional PCR verified the presence of coccidian parasite DNA. To clarify the identity of these coccidia, the faecal DNA samples were further characterised by species-specific PCRs and Sanger sequencing.
One of the samples tested positive for B. darlingi or B. darlingi-like parasites by real-time PCR, while no other coccidian parasites, including Toxoplasma gondii, Hammondia hammondi, H. heydorni, B. besnoiti and Neospora caninum, were detected in the two samples. The rDNA of the B. darlingi-like parasite was amplified and partially sequenced. Comparison with existing sequences in GenBank revealed a close relationship to other Besnoitia spp., but also showed clear divergences.
Our results suggest that a so far unknown Besnoitia species exists in Namibian wildlife, which is closely related to B. darlingi, B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni. The cheetah appears to be the definitive host of this newly discovered parasite, while prey species of the cheetah may act as intermediate hosts.
贝氏等孢球虫（Besnoitia darlingi）、新贝氏等孢球虫（B. neotomofelis）和奥氏等孢球虫（B. oryctofelisi）是亲缘关系密切的顶复门原虫，其终末宿主为猫科动物。这些寄生虫使用多种动物作为中间宿主。北美的负鼠（Didelphis virginiana）、北美南部平原林鼠（Neotoma micropus）和南美家兔（Oryctolagus cuniculus）分别是贝氏等孢球虫、新贝氏等孢球虫和奥氏等孢球虫的中间宿主。基于核糖体 DNA（rDNA）内转录间隔区 1（ITS1）序列的保守区域，最近建立了一种用于检测这些贝氏等孢球虫的实时 PCR，该方法可用于检测中间宿主组织和终末宿主粪便中的这些贝氏等孢球虫。现有序列数据表明，阿克多尼等孢球虫（B. akodoni）和杰利森等孢球虫（B. jellisoni）也被这种实时 PCR 所覆盖。据推测，全世界可能还存在与贝氏等孢球虫或类似贝氏等孢球虫（新贝氏等孢球虫、奥氏等孢球虫、阿克多尼等孢球虫或杰利森等孢球虫）亲缘关系密切的其他等孢球虫。此外，与贝氏等孢球虫亲缘关系较近但不密切的是引起牛贝氏等孢球虫病的牛贝氏等孢球虫（B. besnoiti）。
本研究使用了来自纳米比亚的两只自由放养的猎豹（Acinonyx jubatus）的粪便样本，这些猎豹此前通过粪便镜检检测到了顶复门原虫。常规 PCR 验证了顶复门原虫 DNA 的存在。为了阐明这些顶复门原虫的身份，进一步使用种特异性 PCR 和 Sanger 测序对粪便 DNA 样本进行了特征分析。
实时 PCR 检测到其中一个样本中存在贝氏等孢球虫或类似贝氏等孢球虫，而两个样本中均未检测到其他顶复门原虫，包括刚地弓形虫（Toxoplasma gondii）、哈氏巴贝斯虫（Hammondia hammondi）、H. heydorni、牛贝氏等孢球虫和犬新孢子虫（Neospora caninum）。贝氏等孢球虫类似物的 rDNA 被扩增并进行了部分测序。与 GenBank 中的现有序列进行比较显示，与其他贝氏等孢球虫密切相关，但也显示出明显的差异。
我们的研究结果表明，纳米比亚野生动物中存在一种迄今为止未知的贝氏等孢球虫，与贝氏等孢球虫、新贝氏等孢球虫、奥氏等孢球虫、阿克多尼等孢球虫或杰利森等孢球虫密切相关。猎豹似乎是这种新发现寄生虫的终末宿主，而猎豹的猎物可能是中间宿主。
