Is elimination of human onchocerciasis possible? Epidemiological, entomological and parasitological studies in a bovine model in Cameroon

消除人类盘尾丝虫病有可能吗？

• 批准号: 234586079
• 负责人: Privatdozent Dr. Norbert Brattig
• 金额: --
• 依托单位: Bernhard-Nocht-Institut für Tropenmedizin (BNITM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/234586079?language=en
• 关键词: elimination; human; onchocerciasis; possible; Epidemiological

Onchocerca volvulus, the causative agent of human onchocerciasis, which we study in Cameroon since 1976, has been brought close to elimination by the mass-distribution of the microfilaricidal drug ivermectin. Whether the few infective larvae that we still find in the man-biting vectors are sufficient to maintain the parasite endemic, shall be studied in three different geographic regions: The Adamawa highland, where transmission seems to be interrupted already due to zooprophylaxix, in the Sudan savanna in the North, where transmission still goes on at a rate close to the threshold level, and in the Metchum valley near Bamenda, from where there are no data yet. Simulium-fly catches on man and cattle shall provide data on the ongoing transmission and the proportion of bovine and animal filariae in the vectors, which are indicators of zooprophylaxis.Whether human onchocerciasis can be finaly eradicated shall basically depend from the population dynamics and reproductive biology of the Onchocerca worms, about which we know very little, because it cannot be studied in the human host. Instead we focus on a bovine homologue, Onchocerca ochengi, which we study in a herd of zebu cattle, exposed to natural transmission:- How do these worms regulate their population density in the vertebrate host?- Which factors govern the establishment of new-coming larvae and the mating and reproduction behaviour of adult worms?- How does the evolution of Onchocerca-species and strains go on, and how quickly resistance may be distributed amongst the worms?The bovine filaria O. ochengi, which is highly prevalent in our study area, provides an excellent research tool. In our herd of Zebu cattle, exposed to natural transmission from birth since almost three years, we can study the worm population dynamics in an ideal system. We expect their parasite population to reach its equilibrium during the period of this project, i.e. the rate of acquisition of new worms should equal the natural death-rate of old parasites. This has never been followed-up by a longitudinal study under well-controlled conditions!At the Max-Planck-Institute in Tübingen, molecular genetic techniques were developed that allow assigning single microfilariae to their mother and father worm. So we can study the reproductive behaviour and population dynamics in great detail. At the same time, we focus on the evolution of Onchocerca strains and species that are present in this hot-spot of Onchocerca speciation in the savanna of Central Africa.This project is based on over 20 years of successful collaboration with the Cameroonian Institute for Research for Rural Development (IRAD), which aims to study and control cattle parasites. Though bovine filariae are not of much veterinary importance, their research forms a bridge to human diseases and the participation of the Ngaoundere and Bamenda universities strengthens the research and teaching capacities of these institutions.

自1976年以来，我们在喀麦隆研究了人类盘尾丝虫病的病原体--螺旋体丝虫，由于杀丝剂伊维菌素的质量分布，它已接近消除。我们仍然在叮咬人的媒介中发现的少数感染幼虫是否足以维持寄生虫的流行，应该在三个不同的地理区域进行研究：阿达马瓦高地，传播似乎已经由于动物预防松弛而中断；在北部的苏丹稀树大草原，传播率仍在接近阈值水平；以及在巴门达附近的梅彻姆山谷，那里还没有数据。在人和牛身上捕捉的模拟蝇应提供正在进行的传播和媒介中牛和动物丝虫的比例的数据，这是动物预防的指标。人类丝虫病能否最终根除基本上取决于丝虫的种群动态和繁殖生物学，我们对此知之甚少，因为它不能在人类宿主中进行研究。相反，我们将重点放在一种牛的同源物上，我们在一群接触自然传播的泽布牛中进行了研究：-这些蠕虫如何调节它们在脊椎动物宿主中的种群密度？-哪些因素控制着新来幼虫的建立以及成虫的交配和繁殖行为？-盘尾丝虫--物种和品系的进化如何进行，以及抗药性在蠕虫中传播的速度有多快？在我们研究地区非常普遍的牛丝虫O.ochengi提供了一个很好的研究工具。在我们的泽布牛群中，从出生起就暴露在自然传播中近三年，我们可以在理想的系统中研究蠕虫种群的动态。我们预计它们的寄生虫种群将在本项目期间达到平衡，即新寄生虫的获得率应等于旧寄生虫的自然死亡率。在控制良好的条件下，从来没有进行过纵向研究！在Tübingen的Max-Planck研究所，分子遗传技术被开发出来，可以将单个微丝虫分配给它们的母亲和父亲。因此，我们可以更详细地研究它们的繁殖行为和种群动态。与此同时，我们专注于中部非洲稀树草原这一钉螺物种形成热点地区的钉螺菌株和物种的进化。该项目基于与喀麦隆农村发展研究所(IRAD)20多年的成功合作，该研究所旨在研究和控制牛寄生虫。虽然牛丝虫在兽医上不是很重要，但它们的研究构成了人类疾病的桥梁，恩冈代雷大学和巴门达大学的参与加强了这些机构的研究和教学能力。