Significant reduction of blackfly densities in persistent onchocerciasis area following pilot implementation of an environment friendly approach (Slash and Clear)

Abstract

The effectiveness of the “Slash and Clear” method in reducing blackfly populations in low transmission areas is established, but its impact in high transmission settings with large rivers and dense vectors is yet to be proven. A community-based intervention study was conducted in the Mbam Valley, Centre Cameroon, involving two sites: Bayomen (control) and Biatsota (intervention). 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. Post-intervention data showed a 50.8% reduction in blackfly density in Biatsota (mean number of collected blackflies from 1936 to 953), while a reduction of 26.7% was observed in Bayomen (mean number of collected blackflies from 2418 to 1774). The reduction rate attributable to the intervention was 32.9%. Statistical analysis confirmed that the reduction in blackfly density was significantly greater in the intervention site. This study demonstrates the feasibility and significant impact of the “Slash and Clear” method in high transmission areas. However, further research is required to assess its long-term effects and determine how this strategy can be scaled up and sustained until onchocerciasis elimination is achieved.

Community Perceptions of Blackfly Nuisance and Acceptability of the “Slash and Clear” Vector Control Approach in the Ntui Health District of Cameroon: A Qualitative Study

“…The participants were enthusiastic regarding the implementation of a vector control intervention to reduce blackflies in their community. Despite highlighting some major difficulties and challenges with the "Slash and Clear" approach, it was well received and offers promising perspectives to accelerate onchocerciasis elimination even in places of high endemicity such as Cameroon [22,26] and South Sudan [39]. The community volunteers who actively participated in "Slash and Clear" implementation were willing to perpetuate this strategy with little or no supervision, as long as the right equipment was provided.…”

“…The community volunteers who actively participated in "Slash and Clear" implementation were willing to perpetuate this strategy with little or no supervision, as long as the right equipment was provided. Acceptability of the "Slash and Clear" strategy is all the more relevant because this technique is environmentally friendly [22] as opposed to the use of chemical larvicides in the river to destroy blackfly larvae. Furthermore, "Slash and Clear" is less demanding technically and can be carried out even by illiterate village volunteers.…”

“…In addition, "Slash and Clear" has been shown to be a cost-effective intervention that could accelerate onchocerciasis elimination even in resourcelimited settings [21]. "Slash and Clear" activities were recently conducted along the Mbam River in Cameroon by Domche et al, who also observed significant reductions in biting rates [22]; however, they did not document the population's perception or acceptability of this new technique.…”