Comparative efficacy of two poeciliid fish in indoor cement tanks against chikungunya vector Aedes aegypti in villages in Karnataka, India

<p>Abstract</p> <p>Background</p> <p>In 2006, severe outbreaks of <it>Aedes aegypti</it>-transmitted chikungunya occurred in villages in Karnataka, South India. We evaluated the effectiveness of combined information, education and communication (IEC) campaigns using two potential poeciliid larvivorous fish guppy (<it>Poecilia reticulata</it>) and mosquitofish (<it>Gambusia affinis</it>), in indoor cement tanks for <it>Aedes </it>larval control.</p> <p>Methods</p> <p>Trials were conducted in two villages (Domatmari and Srinivaspura) in Tumkur District from March to May 2006 for <it>Poecilia </it>and one village (Balmanda) in Kolar District from July to October 2006 for <it>Gambusia</it>. A survey on knowledge, attitude and practice (KAP) on chikungunya was initially conducted and IEC campaigns were performed before and after fish release in Domatmari (IEC alone, followed by IEC + <it>Poecilia</it>) and Balmanda (IEC + <it>Gambusia</it>). In Srinivaspura, IEC was not conducted. Larval surveys were conducted at the baseline followed by one-week and one-month post-intervention periods. The impact of fish on <it>Aedes </it>larvae and disease was assessed based on baseline and post-intervention observations.</p> <p>Results</p> <p>Only 18% of respondents knew of the role of mosquitoes in fever outbreaks, while almost all (<it>n </it>= 50 each) gained new knowledge from the IEC campaigns. In Domatmari, IEC alone was not effective (OR 0.54; <it>p </it>= 0.067). Indoor cement tanks were the most preferred <it>Ae. aegypti </it>breeding habitat (86.9%), and had a significant impact on <it>Aedes </it>breeding (Breteau Index) in all villages in the one-week period (<it>p </it>< 0.001). In the one-month period, the impact was most sustained in Domatmari (OR 1.58, <it>p </it>< 0.001) then Srinivaspura (OR 0.45, <it>p </it>= 0.063) and Balmanda (OR 0.51, <it>p </it>= 0.067). After fish introductions, chikungunya cases were reduced by 99.87% in Domatmari, 65.48% in Srinivaspura and 68.51% in Balmanda.</p> <p>Conclusions</p> <p><it>Poecilia </it>exhibited greater survival rates than <it>Gambusia </it>(86.04 <it>vs</it>.16.03%) in cement tanks. Neither IEC nor <it>Poecilia </it>alone was effective against <it>Aedes </it>(<it>p </it>> 0.05). We conclude that <it>Poecilia </it>+ IEC is an effective intervention strategy. The operational cost was 0.50 (US$0.011, 1 US$= 47) per capita per application. Proper water storage practices, focused IEC with <it>Poecilia </it>introductions and vector sanitation involving the local administration and community, is suggested as the best strategy for <it>Aedes </it>control.</p