Adult blackfly ( <i>Simulium damnosum</i> s.l.) collection methods: overview and research needs

Abstract

BACKGROUND: River blindness, caused by Onchocerca volvulus and transmitted by Simulium damnosum s.l., requires robust and ethical vector surveillance for its elimination. The human landing catch (HLC) remains the gold standard for collecting blackflies but presents ethical and operational challenges. This review evaluates alternative blackfly collection methods in relation to their effectiveness, consistency, operational feasibility and alignment with a target product profile (TPP) framework for field programmatic use. METHODS: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines, PubMed, Web of Science, WHO IRIS, Scopus and Google Scholar were searched through June 2024 using terms related to blackfly traps, vector collection and onchocerciasis. Peer-reviewed and selected grey literature in English and French was included. Data were thematically synthesised and grouped by trap type, assessing performance against defined TPP criteria. RESULTS: Fifteen studies met inclusion criteria. The Esperanza window trap (EWT) and host decoy trap (HDT) achieved high catches in some settings, occasionally matching or surpassing HLC performance, though results varied by ecology. Modified HLC methods reduced exposure while maintaining yields but still required human participation. CONCLUSIONS: No single alternative method consistently matched HLC across settings; however, optimized EWT and HDT designs show promise for ethical, effective onchocerciasis surveillance.