Ongoing Transmission of Onchocerca volvulus after 25 Years of Annual Ivermectin Mass Treatments in the Vina du Nord River Valley, in North Cameroon.
Ongoing Transmission of Onchocerca volvulus after 25 Years of Annual Ivermectin Mass Treatments in the Vina du Nord River Valley, in North Cameroon.
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DOI：
10.1371/journal.pntd.0004392
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发表时间：
2016-02
影响因子：
3.8
通讯作者：
Renz A
中科院分区：
文献类型：
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作者：
Eisenbarth A;Achukwi MD;Renz A
最近有报告称，在美洲以前的地方性疫源地，以及最近在西非和东非，造成河盲症的病原体螺旋体丝虫传播中断，这引发了这样一个问题：在对使用伊维菌素的高危人群进行长期治疗后，是否正在消除这种使人衰弱的疾病。中部非洲的局势尚未得到明确评估。来自喀麦隆北部两个以前流行的河流流域的昆虫学数据是在43个月和48个月期间产生的，以跟踪伊维菌素长期控制地区的传播水平。此外，还测定了动物传播的钉螺的流行病学参数。记录了丹参复合体相同的局部黑蝇传播媒介，并评价了它们对稻纵卷叶蝉传播成功率的影响。使用线粒体DNA标记，我们明确地证实了来自苏丹大草原地区(2009-2012年平均传播潜力：98，范围47-221)的媒介中存在感染性螺旋体幼虫，但不是来自阿达马瓦高原地区。泽布牛寄生虫Ochochengi在两个疫源地的传播率都很高。牛的高家畜密度和牛丝虫的高传播率阻止了旋毛虫在阿达马瓦高原的传播，而在以前的高流行区的传播显著减少，但在伊维菌素控制25年后并未完全中断。这项研究可能有助于评估动物丝虫的存在对撒哈拉以南国家不断增长的人和牲畜种群的影响。在过去的几十年里，防治河盲症的斗争相对成功，据报道，一些国家没有寄生虫传播。河盲症是一种由线虫引起的热带疾病。在喀麦隆北部，我们检查了三年多来传播黑蝇种群中螺旋体螺旋体感染阶段的发生情况，并能够确认那里的传播是低的，但尚未中断。然而，在高原上的第二个地点，没有发现人类寄生虫的感染阶段。相反，在这两个地方都出现了一种密切相关的牛寄生虫。鉴于这些地区彼此相距不远，而且黑蝇种群的叮咬频率相似，其中一个地区历史上较早的牛群和较高的密度将解释为什么由于被称为动物预防和交叉反应的预防措施的影响，它现在没有寄生虫。社会经济环境的变化，特别是人和牛数量的增加，对河盲症在非洲的蔓延产生了很大的影响。
Recent reports of transmission interruption of Onchocerca volvulus, the causing agent of river blindness, in former endemic foci in the Americas, and more recently in West and East Africa, raise the question whether elimination of this debilitating disease is underway after long-term treatment of the population at risk with ivermectin. The situation in Central Africa has not yet been clearly assessed. Entomologic data from two former endemic river basins in North Cameroon were generated over a period of 43 and 48 months to follow-up transmission levels in areas under prolonged ivermectin control. Moreover, epidemiologic parameters of animal-borne Onchocerca spp. transmitted by the same local black fly vectors of the Simulium damnosum complex were recorded and their impact on O. volvulus transmission success evaluated. With mitochondrial DNA markers we unambiguously confirmed the presence of infective O. volvulus larvae in vectors from the Sudan savannah region (mean Annual Transmission Potential 2009–2012: 98, range 47–221), but not from the Adamawa highland region. Transmission rates of O. ochengi, a parasite of Zebu cattle, were high in both foci. The high cattle livestock density in conjunction with the high transmission rates of the bovine filaria O. ochengi prevents the transmission of O. volvulus on the Adamawa plateau, whereas transmission in a former hyperendemic focus was markedly reduced, but not completely interrupted after 25 years of ivermectin control. This study may be helpful to gauge the impact of the presence of animal-filariae for O. volvulus transmission in terms of the growing human and livestock populations in sub-Saharan countries. Over the past decades the Fight against river blindness, a tropical disease caused by a nematode worm, has been relatively successful, and a number of countries have been reported to be free of parasite transmission. In North Cameroon, we checked the occurrence of infective stages of Onchocerca volvulus in the transmitting black fly populations for more than three years and were able to confirm that the transmission there is low, but not yet interrupted. In a second location on a highland plateau, however, no infective stages of the human parasite were found. Instead, a closely-related parasite of cattle was present in both places. Given that the areas are not far away from each other and the biting frequencies of the black fly populations are similar, the historically earlier and higher density of cattle herds in one of the regions would explain why it is now free of the parasite due to the effects called zooprophylaxis and cross-reacting premunition. Changes in the socio-economic environment, especially the increase of human and cattle populations have a strong influence on the spread of river blindness in Africa.