Parasites and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, P.O. Box 63, Buea, Cameroon.
Research Foundation in Tropical Diseases and Environment (REFOTDE), P.O. Box 474, Buea, Cameroon.
Parasit Vectors. 2021 Jan 6;14(1):19. doi: 10.1186/s13071-020-04506-3.
The mass drug administration of ivermectin for onchocerciasis control has contributed to a significant drop in Loa loa microfilaria loads in humans that has, in turn, led to reduction of infection levels in Chrysops vectors. Accurate parasite detection is essential for assessing loiasis transmission as it provides a potential alternative or indirect strategy for addressing the problem of co-endemic loiasis and lymphatic filariasis through the Onchocerciasis Elimination Programme and it further reflects the true magnitude of the loiasis problem as excess human mortality has been reported to be associated with the disease. Although microscopy is the gold standard for detecting the infection, the sensitivity of this method is compromised when the intensity of infection is low. The loop-mediated isothermal amplification (LAMP) assay of parasite DNA is an alternative method for detecting infection which offers operational simplicity, rapidity and versatility of visual readout options. The aim of this study was to validate the Loa loa LAMP assay for the detection of infected Chrysops spp. under experimental and natural field conditions.
Two sets of 18 flies were fed on volunteers with either a low (< 10 mf/ml) or high (> 30,000mf/ml) microfilarial load. The fed flies were maintained under laboratory conditions for 14 days and then analysed using LAMP for the detection of L. loa infection. In addition, a total of 9270 flies were collected from the north-west, east, and south-west regions (SW 1 and 2) of Cameroon using sweep nets and subjected to microscopy (7841 flies) and LAMP (1291 flies plus 138 nulliparous flies) analyses.
The LAMP assay successfully detected parasites in Chrysops fed on volunteers with both low and high microfilariaemic loads. Field validation and surveillance studies revealed LAMP-based infection rates ranging from 0.5 to 31.6%, with the lowest levels in SW 2 and the highest infection rates in SW 1. The LAMP assay detected significantly higher infection rates than microscopy in four of the five study sites.
This study demonstrated the potential of LAMP as a simple surveillance tool. It was found to be more sensitive than microscopy for the detection of experimental and natural L. loa infections in Chrysops vectors.
伊维菌素的大规模药物治疗已显著降低了人体中盘尾丝虫的微丝蚴载量，从而降低了 Chrysops 媒介物中的感染水平。准确的寄生虫检测对于评估旋毛虫病的传播至关重要，因为它为解决共同流行的旋毛虫病和淋巴丝虫病问题提供了一种潜在的替代或间接策略，并且通过消灭盘尾丝虫病方案进一步反映了旋毛虫病问题的真实规模，因为据报道，过度的人类死亡率与该疾病有关。尽管显微镜检查是检测感染的金标准，但当感染强度较低时，该方法的敏感性会受到影响。寄生虫 DNA 的环介导等温扩增 (LAMP) 检测是一种替代方法，具有操作简单、快速和视觉读取选项多样的特点。本研究旨在验证 Loa loa LAMP 检测在实验和自然田间条件下感染 Chrysops spp. 的效果。
两组 18 只苍蝇分别喂食低微丝蚴负荷（< 10 mf/ml）或高微丝蚴负荷（> 30,000 mf/ml）的志愿者。饲养后的苍蝇在实验室条件下饲养 14 天，然后用 LAMP 检测 Loa loa 感染情况。此外，使用捕蝇网从喀麦隆西北部、东部和西南部（SW1 和 SW2）共收集了 9270 只苍蝇，进行了显微镜（7841 只苍蝇）和 LAMP（1291 只苍蝇加 138 只未产卵苍蝇）分析。
LAMP 检测成功地检测到了喂食低微丝蚴负荷和高微丝蚴负荷的志愿者的寄生虫。现场验证和监测研究显示，LAMP 检测的感染率范围为 0.5%至 31.6%，SW2 地区的感染率最低，SW1 地区的感染率最高。在五个研究地点中的四个地点，LAMP 检测的感染率明显高于显微镜检测。
本研究证明了 LAMP 作为一种简单监测工具的潜力。它被发现比显微镜更敏感，能够检测 Chrysops 媒介物中实验和自然感染的 Loa loa。
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