Vectors and Vector-borne Diseases Research Programme, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
Biotechnology Platform, Agricultural Research Council, Onderstepoort, Pretoria, South Africa.
Parasit Vectors. 2018 Jan 3;11(1):5. doi: 10.1186/s13071-017-2595-5.
Only a few studies have examined the presence of Anaplasma marginale and Anaplasma centrale in South Africa, and no studies have comprehensively examined these species across the whole country. To undertake this country-wide study we adapted a duplex quantitative real-time PCR (qPCR) assay for use in South Africa but found that one of the genes on which the assay was based was variable. Therefore, we sequenced a variety of field samples and tested the assay on the variants detected. We used the assay to screen 517 cattle samples sourced from all nine provinces of South Africa, and subsequently examined A. marginale positive samples for msp1α genotype to gauge strain diversity.
Although the A. marginale msp1β gene is variable, the qPCR functions at an acceptable efficiency. The A. centrale groEL gene was not variable within the qPCR assay region. Of the cattle samples screened using the assay, 57% and 17% were found to be positive for A. marginale and A. centrale, respectively. Approximately 15% of the cattle were co-infected. Msp1α genotyping revealed 36 novel repeat sequences. Together with data from previous studies, we analysed the Msp1a repeats from South Africa where a total of 99 repeats have been described that can be attributed to 190 msp1α genotypes. While 22% of these repeats are also found in other countries, only two South African genotypes are also found in other countries; otherwise, the genotypes are unique to South Africa.
Anaplasma marginale was prevalent in the Western Cape, KwaZulu-Natal and Mpumalanga and absent in the Northern Cape. Anaplasma centrale was prevalent in the Western Cape and KwaZulu-Natal and absent in the Northern Cape and Eastern Cape. None of the cattle in the study were known to be vaccinated with A. centrale, so finding positive cattle indicates that this organism appears to be naturally circulating in cattle. A diverse population of A. marginale strains are found in South Africa, with some msp1α genotypes widely distributed across the country, and others appearing only once in one province. This diversity should be taken into account in future vaccine development studies.
仅有少数研究检查了在南非的边缘无浆体和中央无浆体的存在，并且没有研究全面检查整个国家的这些物种。为了进行这项全国性的研究，我们改编了一种双定量实时 PCR（qPCR）检测方法在南非使用，但发现该检测方法所基于的一个基因是可变的。因此，我们对各种野外样本进行了测序，并在检测到的变体上测试了该检测方法。我们使用该检测方法筛选了来自南非所有 9 个省的 517 个牛样本，随后检查了 A. marginale 阳性样本的 msp1α 基因型，以评估菌株多样性。
尽管边缘无浆体的 msp1β 基因是可变的，但 qPCR 的功能效率是可以接受的。qPCR 检测区域内的中央无浆体 groEL 基因没有变异性。在使用该检测方法筛选的牛样本中，分别有 57%和 17%被检测为边缘无浆体和中央无浆体阳性。大约 15%的牛是混合感染。Msp1α 基因分型显示 36 个新的重复序列。结合以前研究的数据，我们分析了南非的 Msp1a 重复序列，总共描述了 99 个重复序列，可以归因于 190 个 msp1α 基因型。虽然其中 22%的重复序列也存在于其他国家，但只有两个南非基因型也存在于其他国家；否则，这些基因型是南非特有的。
边缘无浆体在西开普省、夸祖鲁-纳塔尔省和姆普马兰加省流行，而在北开普省则不存在。中央无浆体在西开普省和夸祖鲁-纳塔尔省流行，而在北开普省和东开普省则不存在。该研究中没有牛已知接种了中央无浆体，因此发现阳性牛表明该生物体似乎在牛群中自然循环。南非发现了多种边缘无浆体菌株，一些 msp1α 基因型在全国广泛分布，而另一些则仅在一个省份出现一次。在未来的疫苗开发研究中，应考虑到这种多样性。
