Evaluating synthetic odours and trap designs for monitoring Anopheles farauti in Queensland, Australia

BACKGROUND: Monitoring of malaria vectors is important for designing and maintaining effective control interventions as changes in vector-feeding habits can threaten the efficacy of interventions. At present, human landing catches remain the most common method for monitoring malaria vectors of the Anopheles punctulatus complex, including the Anopheles farauti group. The aims of this study were to evaluate the efficacy of different lures and fan-powered traps, including an odour blend that has been demonstrated to be attractive to African anophelines, in Queensland, Australia. METHODS: To evaluate the performance of different lures in trapping An. farauti in the field, four Suna traps were baited with either: CO(2)-alone, a synthetic lure (MB5 or BG-Lure) plus CO(2), or a human odour plus CO(2) and set in the field in Cairns, eastern Australia. A second study evaluated the performance of four traps: a Passive Box trap, BG-Suna trap, BG-Sentinel 2 trap, and BG-Bowl trap, for their ability to trap An. farauti using the best lure from the first experiment. In both experiments, treatments were rotated according to a Latin square design over 16 nights. Trapped mosquitoes were identified on the basis of their morphological features. RESULTS: BG-Suna traps baited with CO(2) alone, a BG-Lure plus CO(2) or a natural human odour plus CO(2) captured comparable numbers of An. farauti. However, the number of An. farauti sensu lato captured when the MB5 lure was used with CO(2) was three times lower than when the other odour lures were used. The BG-Sentinel 2 trap, BG-Suna trap and BG-Bowl trap all captured high numbers of An. farauti, when baited with CO(2) and a BG-Lure. The morphological condition of captured mosquitoes was affected by mechanical damage caused by all fan-powered traps but it was still possible to identify the specimens. CONCLUSIONS: The BG-Sentinel 2 trap, BG-Suna trap and the BG-Bowl trap captured high numbers of An. farauti in the field, when equipped with CO(2) and an odour lure (either the BG-Lure or a natural odour). The most important attractant was CO(2). This study shows that fan-powered traps, baited with CO(2) plus an appropriate odour lure, can be a promising addition to current vector monitoring methods in the Southwest Pacific.