Introduction

African Animal Trypanosomiasis (AAT) or nagana in animals, is caused by the blood-borne parasitic protozoa called trypanosomes, and is potentially fatal. It is estimated that Africa loses $4‒5 billion annually due to the death of livestock to nagana in the tsetse belt.

Purpose

Although The Gambia lies within this belt, there is scanty data regarding the epizootiology of nagana in The Gambia. Here, records of reported cases of nagana for the period 2010–2019 at the International Trypanotolerance Centre (ITC) in The Gambia were analyzed retrospectively.

Methods

For insights into the current prevalence of AAT, blood samples of 384 cattle, 42 goats, and 59 sheep from the Central River Region (CRR) and Lower River Region (LRR) were analyzed microscopically for parasite identification. Furthermore, trypanosomes were characterized by polymerase chain reaction (PCR) using a panel of primers that identify trypanosomes to the level of the species and subspecies by targeting a portion of the internally transcribed spacer-one (ITS-1) of the ribosomal RNA.

Results

The retrospective study indicates that Trypanosoma vivax (66%) and T. congolense (33.4%) were the predominant species. Based on the archive records of ITC, the villages Touba, Misera, and Sambel Kunda all in the CRR of the Gambia are the most burdened with AAT. Microscopic examination of blood samples from cattle showed a prevalence of 1.56%, whereas the PCR-based analysis gave a higher prevalence of 12.5%. The molecular analysis revealed the presence of T. vivax (3.65%), T. congolense kilifi (2.6%), T. b. brucei (1.3%), T. congolense savannah/forest (0.52%), T. b. gambiense (0.52%). Interestingly, 4.43% of mixed infections i.e. multiple trypanosome species in individual animals were recorded. In 18% of the mixed infection cases, T. godfreyi, T. simiae were coinfecting cattle alongside T. congolense. The molecular identification including the phylogenetic analysis implicated T. congolense as the most predominant trypanosome species infecting animals in The Gambia.

Conclusion

The incidence of nagana in The Gambia is documented and the prevalent trypanosomes identified to be T. vivax, different types of T. congolense, and T. brucei including the gambiense subspecie. Finally, nagana is less profound in sheep and goats compared to cattle, with seasonal and regional variations playing a significant role in the disease dynamics.

中文翻译：

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冈比亚家畜反刍动物锥虫的流行病学和分子鉴定

介绍

非洲动物锥虫病 (AAT) 或动物中的 nagana 是由称为锥虫的血液传播的寄生原生动物引起的，并且可能是致命的。据估计，由于采采带的纳加纳牲畜死亡，非洲每年损失 4-50 亿美元。

目的

尽管冈比亚位于这一带内，但关于冈比亚纳加纳动物流行病学的数据很少。在这里，回顾性分析了冈比亚国际锥虫病中心 (ITC) 2010-2019 年期间报告的 nagana 病例记录。

方法

为了深入了解 AAT 的当前流行情况，对来自中部河流地区 (CRR) 和下游河流地区 (LRR) 的 384 头牛、42 只山羊和 59 只绵羊的血液样本进行了显微镜分析，以进行寄生虫鉴定。此外，使用一组引物通过聚合酶链反应 (PCR) 对锥虫进行表征，这些引物通过靶向核糖体 RNA 的一部分内部转录的间隔区一 (ITS-1) 将锥虫鉴定到物种和亚种的水平。

结果

回顾性研究表明，间日锥虫(66%) 和刚果锥虫(33.4%) 是主要物种。根据 ITC 的档案记录，冈比亚 CRR 中的 Touba、Misera 和 Sambel Kunda 村的 AAT 负担最重。对牛血样的显微镜检查显示患病率为 1.56%，而基于 PCR 的分析得出的患病率更高，为 12.5%。分子分析显示存在间日疟原虫(3.65%)、刚果三日疟原虫(2.6%)、T. b. brucei (1.3%), T. congolense savannah/forest (0.52%), T. b. 冈比亚（0.52%）。有趣的是，4.43% 的混合感染即记录了个体动物中的多种锥虫物种。在 18% 的混合感染病例中，T. godfreyi和T. simiae与T. congolense一起感染牛。包括系统发育分析在内的分子鉴定表明刚果锥虫是冈比亚感染动物的最主要锥虫物种。

结论

冈比亚 nagana 的发病率已记录在案，流行的锥虫被确定为间日锥虫、不同类型的刚果锥虫和包括冈比亚亚种的布氏锥虫。最后，与牛相比，绵羊和山羊的 nagana 影响较小，季节性和区域变化在疾病动态中发挥着重要作用。