A systematic review comparing the performance of alternative blackfly (Simulium) trapping methods against the standard human landing catch (HLC) for onchocerciasis surveillance

Despite decades of control efforts, onchocerciasis remains a major public health concern in Africa, the Americas, and Yemen. Human Landing Catch (HLC) is the primary method for collecting blackflies and is central to surveillance. However, HLC raises ethical concerns due to collectors’ exposure to painful and potentially infectious bites and faces operational challenges in areas of very low or high transmission. Consequently, several alternative blackfly trapping methods have been investigated, but no comprehensive synthesis comparing their effectiveness against standard HLC across studies has been conducted. Therefore, we performed a systematic review comparing the performance of alternative blackfly traps with standard HLC. A systematic review (PROSPERO registration number: CRD420261294895) of literature published in Scopus, PubMed, and Web of Science up to December 2025 was supplemented by an expert-provided reference list. From 166 records, 62 were screened, and 13 studies (comprising 79 comparisons with standard HLC) met inclusion criteria. Alternative traps included light traps, Bellec traps, tent traps baited with humans or cows, Esperanza Window Traps, Host Decoy Traps, electric nets, and modified HLC. Most comparisons (75.9%) found alternative traps to be less effective than standard HLC, with statistical analyses often supporting these differences, although nearly half lacked formal significance testing. Variation in study design—including trap placement, rotation, and trapping duration—and inconsistent reporting of key variables such as season, habitat, and species limited direct comparisons. Some studies indicated that increasing trap density or deployment duration of Esperanza Window Traps could improve effectiveness. While HLC remains the most effective method, its ethical and operational limitations highlight the need for reliable alternatives. Most existing traps underperform relative to HLC, but modifications based on deeper understanding of blackfly behaviour and ecology could improve performance. Future research should focus on standardizing trap evaluation methods, exploring species-specific behaviours, and assessing scalability to develop ethical, scalable tools for onchocerciasis surveillance.Author summary: After decades of interventions against onchocerciasis, also called ‘river blindness’, many countries hope to demonstrate they have interrupted disease transmission, allowing them to stop delivering interventions and divert healthcare resources elsewhere. To verify if this has been achieved, the World Health Organization requires evidence that the causative parasite, Onchocerca volvulus, is no longer being transmitted by the insect vector, blackflies of the genus Simulium. This necessitates collecting large numbers of blackflies, which is usually achieved using a manual method called the Human Landing Catch (HLC), using a human as both bait and collector. Several alternative blackfly trapping methods have been developed to avoid the ethical and operational issues associated with exposing a person to potentially infective bites. We systematically reviewed the literature to compare the effectiveness of these alternative traps relative to the standard HLC. We found there to be considerable variability in the design of studies to test these, which made study-to-study comparisons difficult, and suggest standardized study designs would allow future comparisons and meta-analysis. Although the majority of published data suggests that the HLC is the most effective method, there is some evidence that using multiple traps could match HLC results, and trap design could be improved by including additional features to which blackflies are attracted.