Ostrovskii Alexandr, Kadyrova Madina, Yerzhanova Nurdina, Kamalova Dinara, Kassen Amirkhan, Tursunbay Nailya, Shevtsov Alexandr, Bauer Christian, Mukanov Kassym
National Center for Biotechnology, 01000, Astana, Kazakhstan.
Institute of Parasitology, Justus Liebig University Giessen, 35392, Giessen, Germany.
Vet World. 2025 Jan;18(1):67-75. doi: 10.14202/vetworld.2025.67-75. Epub 2025 Jan 9.
Anaplasmosis in small ruminants is a tick-borne infection caused mainly by the obligate intraerythrocytic bacterium . It is usually subclinical, with persistent infection in affected animals, but acute disease can occur, particularly in young animals. The pathogen is widespread in Central Asia and neighboring regions. In Kazakhstan, the infection was first detected in 1929. However, until now, diagnosis in the country has been based on traditional microscopic examination of blood smears. There were no reliable data on the prevalence and genetic diversity of spp. in sheep in Kazakhstan. This study aimed to determine the occurrence of spp. infection in sheep in southern Kazakhstan, a high-risk region for tick-borne diseases, using PCR and to identify the species by sequencing.
A cross-sectional study was conducted on apparently healthy adult ewes from 77 settlements in 34 districts of Kyzylorda, Turkistan, Zhambyl, Almaty, and Jetisu, southern Kazakhstan. A total of 2553 whole blood samples collected in midsummer 2022 and 2023 were analyzed for spp. using polymerase chain reaction targeting the 404 bp gene fragment. The amplification products from the 441 positive samples were sequenced using the Sanger sequencing method. Phylogenetic analysis of the obtained sequences was performed using the maximum likelihood model.
Overall, 1017/2553 (39.8%; 95% confidence interval: 37.9%-41.7%) ewes tested were positive for spp. Positive animals were found in 68/77 (88%) of the settlements from which samples were taken. The percentage of spp.-positive ewes varied significantly from 21.3% to 50.1% in the provinces. Altitude <500 m above sea level was identified as a risk factor for infection. All amplification products were identified as through sequencing. Phylogenetic analysis of the gene fragment sequences revealed the presence of two genotypes; one was 100% identical to sequences from isolates from China and the other was >99.5% identical to isolates from Africa, Cyprus, and China.
This first molecular study revealed a widespread of . infection in adult ewes in southern Kazakhstan. Altitude <500 m was identified as a risk factor. Therefore, clinical cases associated with are expected in this region, especially in young animals. Future studies are needed to determine the clinical and economic impact of anaplasmosis on sheep production in the country, to investigate seasonal patterns of infection, and to identify tick species or other arthropods that act as local vectors. This information is useful for developing possible control measures and evaluating their effectiveness.
小反刍兽无形体病是一种主要由专性红细胞内细菌引起的蜱传感染。该病通常为亚临床感染，患病动物会持续感染，但也可能发生急性疾病，尤其是在幼龄动物中。该病原体在中亚及周边地区广泛分布。在哈萨克斯坦，1929年首次检测到这种感染。然而，迄今为止，该国的诊断一直基于传统的血涂片显微镜检查。关于哈萨克斯坦绵羊中无形体属物种的流行情况和遗传多样性，尚无可靠数据。本研究旨在利用聚合酶链反应（PCR）确定哈萨克斯坦南部这一蜱传疾病高危地区绵羊中无形体属物种感染的发生情况，并通过测序鉴定其种类。
对来自哈萨克斯坦南部克孜勒奥尔达、突厥斯坦、江布尔、阿拉木图和杰特苏等34个区77个定居点的表面健康成年母羊进行了横断面研究。对2022年和2023年仲夏采集的共2553份全血样本，使用针对404 bp 基因片段的聚合酶链反应分析无形体属物种。对441份阳性样本的扩增产物采用桑格测序法进行测序。使用最大似然模型对获得的序列进行系统发育分析。
总体而言，检测的1017/2553（39.8%；95%置信区间：37.9%-41.7%）只母羊无形体属物种检测呈阳性。在采集样本的68/77（88%）个定居点中发现了阳性动物。各省无形体属物种阳性母羊的百分比在21.3%至50.1%之间有显著差异。海拔低于海平面500米被确定为无形体感染的一个风险因素。通过测序将所有扩增产物鉴定为无形体。对基因片段序列的系统发育分析显示存在两种无形体基因型；一种与来自中国分离株的序列100%相同，另一种与来自非洲、塞浦路斯和中国的分离株>99.5%相同。
这项首次分子研究揭示了哈萨克斯坦南部成年母羊中无形体感染广泛存在。海拔低于500米被确定为一个风险因素。因此，预计该地区会出现与无形体相关的临床病例，尤其是在幼龄动物中。未来需要开展研究以确定无形体病对该国绵羊生产的临床和经济影响，调查感染的季节性模式，并确定作为当地传播媒介的蜱种或其他节肢动物。这些信息对于制定可能的控制措施并评估其有效性很有用。
