Control of mosquito larvae in the port city of Assab by an indigenous larvivorous fish, Aphanius dispar.

A randomized controlled trial was carried out in Assab under the auspices of the National Organization for the Control of Malaria and other Vectorborne Diseases of Ethiopia to assess the effectiveness of an indigenous cyprinodontid fish, Aphanius dispar, in controlling mosquito larvae, including the local malaria vector, Anopheles culicifacies adanensis. Cisterns, wells and barrels were found to be important breeding sites for the malaria vector and for culicine mosquitoes. Fish were equally effective in controlling mosquito larvae in all the types of breeding site investigated. The overall proportion of sites with fish that harboured mosquito larvae was 1.6%, ranging from 1.5 to 1.7% according to type of site, as compared to 34% in sites left unstocked, ranging from 17.9 to 60.0%. Monthly restocking of fish where necessary was found to be sufficient to maintain an adequate level of control. Stocking of larvivorous fish in wells and household water storage containers was well-accepted by the participants, who were aware of the role of the fish in malaria prevention and found the fish useful in keeping their water free of other aquatic organisms. Based on the results of this study, larvivorous fish were introduced on an operational scale for the control of malaria transmission in Assab, with the voluntary participation of the population and the collaboration of the Municipality and health authorities of Assab.