Participants and procedures
The baseline survey set out to investigate knowledge, attitudes and previous testing and treatment behaviour of fishermen in southern Malawi fishing communities. Within each cluster peer leaders provided a list of fishing boats operating in the cluster as well as a list of fishermen operating in the listed boats. To be eligible for the survey, fishermen needed to: be 18 years old or over; have a fixed residence in a trial cluster; and consent to participate. We excluded fishermen who were not permanent residents of the fishing community or were underage (<18y).Fishermen completed a face-to-face interview on tablets running open data kit (ODK) questionnaires. A total of seven interviewers were involved in the data collection. The interviewers were selected on the basis of being from within the Mangochi district to ensure quality of responses due to familiarity with the local dialect spoken in this part of the district. Interviews were conducted on the lakeshore at a private space chosen by the fishermen. All outcomes were measured via self-reports by the fishermen.