Significant reduction in blackfly bites following implementation of Slash and Clear: An option to consider for onchocerciasis elimination in areas of persistent transmission

Domche, A.; Nana Djeunga, H. C.; Nwane, P. B.; Njitchouang, G. R.; Fesuh, B. N.; Njiokou, F.; Jacob, B.; Pion, S. D.; Kamgno, J.

doi:10.1101/2023.03.27.534316

bioRxiv · 10.1101/2023.03.27.534316

Significant reduction in blackfly bites following implementation of Slash and Clear: An option to consider for onchocerciasis elimination in areas of persistent transmission

Domche, A.·Nana Djeunga, H. C.·Nwane, P. B.·Njitchouang, G. R.·Fesuh, B. N.·Njiokou, F.·Jacob, B.·Pion, S. D.·Kamgno, J.

View original source ↗Export metadata ↓

Abstract

BackgroundAlthough "Slash and Clear" has proven effective in reducing blackfly densities in low transmission foci, the impact of this strategy in high transmission settings with large rivers and important vector densities remains to be demonstrated. Methods/Principal findingsA controlled before-and-after community-based intervention comprising two arms (Bayomen as control site and Biatsota as intervention site) was carried out in the Mbam Valley (Centre Region, Cameroon). In each arm, baseline blackfly densities were collected over one year using the human landing method. The intervention consisted of destroying the trailing vegetation where blackflies breed. Blackfly densities were collected post-intervention to assess the impact of the intervention. Before the intervention, a total of 36,273 and 29,041 blackflies were collected in Bayomen and Biatsota, respectively. After the intervention period, the total blackfly density in the intervention site decreased from 29,041 to 20,011 (31.1% reduction), while an increase of 2{middle dot}7% was observed in the control site (from 36,273 to 37,248). The Poisson mixed regression model shows that the reduction was significantly greater in the intervention site than in the control site (p<0.0005). Conclusions/SignificanceThis study showed that "Slash and Clear" approach is feasible and has a significant impact on vector densities in a high transmission setting. Further studies are needed to investigate the long-term impact of this vector control approach, and how this promising strategy can be scaled-up and sustained until elimination of onchocerciasis. Author summaryRiver blindness persists in some foci in Cameroon despite more than two decades of ivermectin-based preventive chemotherapy. Mass drug administration (MDA) appears insufficient to interrupt onchocerciasis transmission in these hotspots, and should be complemented by vector control, the most promising alternative strategy to date. In 2018, the effectiveness of a new community-based vector control approach, known as slash and clear, was demonstrated. This strategy involves the removal of trailing vegetation at breeding sites, a primary attachment points for blackfly larvae. In this study, we show that this environment-friendly intervention is feasible and has a significant impact on blackfly densities in high transmission settings. This promising intervention can be combined with regular annual ivermectin-based preventive chemotherapy to accelerate onchocerciasis elimination.

Explore related subjects

ecology Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Domche, A., Nana Djeunga, H. C., Nwane, P. B., Njitchouang, G. R., Fesuh, B. N., Njiokou, F., Jacob, B., Pion, S. D., Kamgno, J.. 2023-03-27. Significant reduction in blackfly bites following implementation of Slash and Clear: An option to consider for onchocerciasis elimination in areas of persistent transmission. https://doi.org/10.1101/2023.03.27.534316

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

PlanktonLake-CEREEP- A Freshwater Plankton Image Dataset with Semi-Automated Label Cleaning

Plankton plays a fundamental role in aquatic ecosystems, influencing biogeochemical cycles and serving as a key food source for many organisms. Recent high-throughput imaging technologies enable the rapid acquisition of large volumes of microscopic images, creating new opportunities for monitoring planktonic ecosystems. However, the manual processing and annotation of the vast amounts of data generated by these devices remain time-consuming tasks. In this context, machine learning-based classification models offer a promising solution. In this data paper, we introduce a new labeled freshwater plankton dataset comprising approximately 88,000 images distributed across 43 taxa. We also present the labeling assistance method we used to facilitate dataset annotation. Finally, we present a baseline based on a convolutional neural network (CNN), which achieves a classification accuracy of 93% on our dataset.

ecology↗

bioRxiv2026

A training protocol for human classification of Asian elephant images from trail cameras

Trail cameras have become ubiquitous tools for ecological data collection over recent decades. Despite progress in the development of automated algorithms and artificial intelligence for image classification, our ability to process large volumes of data remain limited by the need for trained human observers to make refined judgements. We provide guidance on placement of trail cameras for observing Asian elephants (Elephas maximus) and outline a protocol for training and testing naive human observers in performing image classifications (age/sex class and group composition) that cannot yet be automated. This process can be used to develop a high-throughput workflow capable of extracting useful data from large volumes of images. Our training material consisted of 14,007 images collected from 6 trail cameras around Udawalawe National Park in Sri Lanka from 2017-2019. In the first stage, expert observers (n=3) trained a group of inexperienced participants (n=4), who engaged in an iterative process to develop a protocol document. The document was then tested on a second set of subjects (n=6) each of whom classified 350 test images in four separate sequential batches using quantitative measures of precision and accuracy. The test set was sampled from 54,435 images from an additional 25 cameras. When compared to expert observers, they achieved a fair level of precision (Fleiss' kappa = 0.247) and 82.6% accuracy. Our approach can usefully be extended to other species and contexts.

ecology↗

bioRxiv2026

Forest belowground productivity and carbon allocation predominantly driven by soil properties rather than climate

Forests are threatened by a multitude of stressors, including anthropogenic disturbances and climate change. Assessing how forests will respond to these stressors requires a comprehensive understanding of net primary productivity (Npp), environmental constraints on growth, and adaptive capacity. A parameter of significant uncertainty is belowground Npp (bNpp), which can account for up to 80% of total Npp but is poorly estimated and rarely measured directly. We used a cross-biome dataset of direct, field-based measurements of aboveground and belowground primary productivity and 21 climatic and soil variables to identify potential constraints on bNpp and belowground carbon allocation in boreal and cold temperate forests. Soil variables, rather than climate variables, were the main drivers of bNpp and belowground allocation across biomes. The importance of soil variables suggests that soil nutrient dynamics, especially soil nutrient pool and flux variables, must be explicitly modeled to more accurately predict feedbacks between climate, productivity, and within-tree carbon allocation. Within biomes, environmental drivers of belowground allocation varied between low versus high allocation forests, indicating that environmental drivers are site-specific and the development of within-biome, site-scale classifications for forest ecosystems could be useful. Changes in soil variables, such as increasing soil nitrogen pools, caused abrupt and large decreases in bNpp for boreal, but not cold temperate forests. Threshold-like shifts indicate that boreal forests might have lower adaptive capacity and higher sensitivity to disturbances than cold temperate forests. With 70% of boreal forests characterized by low bNpp, disturbances such as anthropogenic nitrogen deposition could cause large-scale decreases in bNpp that could push these forests beyond their adaptive capacity.

ecology↗