Biosciences Eastern and Central Africa - International Livestock Research Institute (BecA-ILRI) Hub, Nairobi, Kenya.
Molecular Parasitology and Entomology Unit, Department of Biochemistry, Faculty of Sciences, University of Dschang, Dschang, Cameroon.
Transbound Emerg Dis. 2020 Mar;67 Suppl 1(Suppl 1):68-78. doi: 10.1111/tbed.13425.
A major risk factor for the spread of livestock diseases and their vectors is the uncontrolled transboundary movement of live animals for trade and grazing. Such movements constrain effective control of tick-transmitted pathogens, including Theileria parva. Only limited studies have been undertaken to identify ticks and tick-borne diseases (TTBDs) affecting cattle in central African countries, including Cameroon. We hereby report the collection of baseline data on the prevalence of T. parva in Cameroon through a countrywide cross-sectional survey, conducted in 2016, involving collection of blood samples from cattle from 63 sites across the five agro-ecological zones (AEZs) of the country. ELISA-based surveillance of infected cattle was performed on 479 randomly selected samples and revealed specific antibodies to T. parva in 22.7% and T. mutans in 41.1% of cattle. Screening of 1,340 representative DNA samples for the presence of T. parva identified 25 (1.86%) positives using a p104 antigen gene-based nested PCR assay. The positives were distributed across agro-ecological zones I, II, III and V. None of the p104 positive cattle exhibited clinical symptoms of East Coast fever (ECF). Using reverse line blot (RLB), 58 (4.3%) and 1,139 (85%) of the samples reacted with the T. parva and T. mutans oligonucleotide probes, respectively. This represents the first report of T. parva from Cameroon. Surprisingly, no Rhipicephalus appendiculatus ticks, the main vector of T. parva, were identified in a parallel study involving comprehensive morphological and molecular survey of tick species present in the country. Only two of the 25 p104 positive cattle were PCR-positive for the CD8+ T-cell target schizont-expressed antigen gene Tp1. Cloning and sequencing of Tp1 amplicons revealed sequence identity with the reference T. parva Muguga. This new finding raises serious concerns of a potential spread of ECF into the central African region.
牲畜疾病及其传播媒介的主要传播风险因素是活体动物为贸易和放牧而不受控制的跨界移动。这种移动限制了对 tick 传播病原体的有效控制，包括 Theileria parva。只有有限的研究旨在确定影响中非国家（包括喀麦隆）牛的蜱和 tick 传播疾病（TTBD）。我们在此报告了通过 2016 年在全国范围内进行的横断面调查收集喀麦隆 T. parva 流行率的基线数据。该调查涉及从该国五个农业生态区（AEZ）的 63 个地点采集牛的血液样本。对 479 个随机选择的样本进行了基于 ELISA 的受感染牛的监测，结果显示在 22.7%的牛和 41.1%的牛中存在针对 T. parva 和 T. mutans 的特异性抗体。使用基于 p104 抗原基因的巢式 PCR 检测对 1340 个代表性 DNA 样本进行 T. parva 存在情况的筛查，结果发现 25 个（1.86%）为阳性。阳性样本分布在农业生态区 I、II、III 和 V。没有 p104 阳性牛表现出东海岸热（ECF）的临床症状。使用反向线印迹（RLB），分别有 58（4.3%）和 1139（85%）的样本与 T. parva 和 T. mutans 寡核苷酸探针反应。这是喀麦隆首次报告 T. parva。令人惊讶的是，在一项涉及该国 tick 物种全面形态和分子调查的平行研究中，没有发现 T. parva 的主要媒介 Rhipicephalus appendiculatus 蜱。25 只 p104 阳性牛中只有 2 只对 CD8+ T 细胞靶标裂殖子表达抗原基因 Tp1 呈 PCR 阳性。Tp1 扩增子的克隆和测序显示与参考 T. parva Muguga 的序列同一性。这一新发现引起了对 ECF 潜在传播到中非地区的严重关注。
