Department of Zoology, Osun State University, Osogbo, Nigeria.
Department of Animal and Environmental Biology, University of Uyo, Uyo, Nigeria.
Parasit Vectors. 2024 Nov 18;17(1):471. doi: 10.1186/s13071-024-06554-5.
Entomological data for onchocerciasis surveillance relies on sampling black flies through human landing collectors in the field and laboratory testing of the flies for infection using pooled screening O-150 PCR-ELISA assay. Both techniques require improvements. This study aimed to optimize the Esperanza Window Trap (EWT) for black fly collection. We tested alternative carbon dioxide (CO) mimics to attract black flies to the traps. Additionally, we evaluated new quantitative PCR (qPCR) methods that target mitochondrial DNA markers and have been proposed to enhance the sensitivity and specificity for detecting Onchocerca volvulus infections in blackflies.
Traps baited with low, medium and high release rates of either 2-butanone or cyclopentanone as CO mimics were field tested against traps baited with organically generated CO in four ecological zones in Nigeria: Guinea savannah, derived savannah, rainforest and montane forest. The performance of EWTs baited with CO or in combination with 2-butanone (low release) were subsequently evaluated against the human landing collection (HLC). Trap scaling was also pilot tested by comparing two EWTs to a single HLC team. Collected black flies were used to test detection of O. volvulus in black flies using Ov ND5 real-time PCR (qPCR) compared to the conventional pool screening O-150 PCR.
EWTs baited with 2-butanone caught similar numbers of black flies (Simulium damnosum s.l.) to those baited with CO, while cyclopentanone collected significantly fewer flies in all locations. The low release of 2-butanone was the most effective overall, although HLCs collected higher numbers of black flies than EWT baited with CO either singly or in combination with low-release 2-butanone. The combination of two EWTs baited with CO and deployed 100 m apart from each other collected similar numbers of flies as one HLC. More black fly pools were positive for O. volvulus by Ov ND5 qPCR compared with O-150 PCR in derived savannah (31.15 vs. 15.57%), montane forest (11.54 vs. 0%) and rainforest (23.08 vs. 2.56%), with only one positive pool in Guinea savannah detected by both methods.
The 2-butanone has potential to be used in xenomonitoring as a standardized replacement for organically generated CO. Ov ND5 qPCR detected more positive pools than O-150 PCR. The positive pools found in foci hitherto considered to have interrupted/eliminated onchocerciasis highlight the need for more sensitive and specific methods that support programmatic assessments to identify and combat recrudescence.
针对盘尾丝虫病监测的昆虫学数据依赖于在野外和实验室中使用人类着陆采集器采集黑蝇，并使用 pooled screening O-150 PCR-ELISA 检测对其进行感染检测。这两种技术都需要改进。本研究旨在优化 Esperanza Window Trap (EWT) 以用于黑蝇采集。我们测试了替代的二氧化碳 (CO) 类似物，以吸引黑蝇进入陷阱。此外，我们还评估了新的定量 PCR (qPCR) 方法，这些方法针对线粒体 DNA 标记物，已被提议用于提高在黑蝇中检测旋盘尾丝虫感染的敏感性和特异性。
在尼日利亚的四个生态区（几内亚大草原、衍生大草原、雨林和山地森林）中，使用释放率低、中、高的 2-丁酮或环戊酮作为 CO 类似物对陷阱进行了野外测试，与用有机生成的 CO 对陷阱进行了对比。随后，对 CO 或与 2-丁酮（低释放）结合的 EWT 的性能进行了与人类着陆收集（HLC）的比较。还通过比较两个 EWT 与一个单独的 HLC 小组，对陷阱的规模进行了试点测试。收集到的黑蝇被用于使用 Ov ND5 实时 PCR（qPCR）检测黑蝇中的 O. volvulus，与传统的 O-150 PCR 相比。
用 2-丁酮诱捕的 EWT 捕获的黑蝇（Simulium damnosum s.l.）数量与用 CO 诱捕的黑蝇相似，而在所有地点环戊酮的诱捕数量均明显较少。低释放的 2-丁酮总体上最有效，尽管 HLC 收集的黑蝇数量高于单独用 CO 或与低释放的 2-丁酮结合使用的 EWT。相距 100 米放置的两个 EWT 同时用 CO 诱捕收集的黑蝇数量与一个 HLC 相似。与 O-150 PCR 相比，衍生大草原（31.15%比 15.57%）、山地森林（11.54%比 0%）和雨林（23.08%比 2.56%）中的 Ov ND5 qPCR 检测到更多的 O. volvulus 阳性蝇池，而在几内亚大草原，只有一种方法检测到一个阳性蝇池。
2-丁酮有可能成为 Xenomonitoring 中的标准化替代品，替代有机生成的 CO。Ov ND5 qPCR 检测到的阳性蝇池比 O-150 PCR 多。在先前被认为中断/消除盘尾丝虫病的焦点中发现的阳性蝇池突显了需要更敏感和特异的方法来支持方案评估，以识别和打击复发。
