Mesocosm Experiments to Quantify Predation of Mosquito Larvae by Aquatic Predators to Determine Potential of Ecological Control of Malaria Vectors in Ethiopia

• Main Authors: Beekam Kebede Olkeba, Peter L. M. Goethals, Pieter Boets, Luc Duchateau, Teshome Degefa, Kasahun Eba, Delenasaw Yewhalaw, Seid Tiku Mereta
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: malaria; <i>Anopheles</i> larvae; predators; gut analysis; semi-field experiment; Ethiopia
• Online Access: https://www.mdpi.com/1660-4601/18/13/6904

Malaria parasites are transmitted to humans by infectious female <i>Anopheles</i> mosquitoes. Chemical-insecticide-based mosquito control has been successful in reducing the burden of malaria. However, the emergence of insecticide resistance in malaria vectors and concerns about the effect of the chemicals on the environment, human health, and non-target organisms present a need for new or alternative vector control intervention tools. Biocontrol methods using aquatic invertebrate predators have emerged as a potential alternative and additional tool to control mosquito populations. Ecological control specifically makes use of species insights for improving the physical habitat conditions of competitors and predators of vectors. A first step towards this is to gain knowledge on the predation potential of several typically present macroinvertebrates. Hence, this study aimed at (1) examining the influence of the predation of hemipterans on the number of emerging adult mosquitoes and (2) detecting <i>Anopheles</i> mosquito DNA in the gut of those predators. The prey and predators were collected from a range of water bodies located in the Gilgel Gibe watershed, southwest Ethiopia. A semi-field study was carried out using mesocosms which were constructed using plastic containers mimicking the natural aquatic habitat of immature <i>Anopheles</i> mosquitoes. Adult mosquitoes that emerged from the mesocosms were collected using a mechanical aspirator. At the end of the experiment, predators were withdrawn from the mesocosms and identified to genus level. Polymerase Chain Reaction (PCR) was employed to identify sibling species of <i>Anopheles gambiae</i> s.l. and to detect <i>Anopheles</i> mosquito DNA in the gut of the predators. Data were analysed using R software. Giant water bugs (belostomatids) were the most aggressive predators of <i>Anopheles</i> larvae, followed by backswimmers (notonectids) and water boatmen (corixids). All female <i>Anopheles gambiae</i> s.l. emerged from the mesocosms were identified as <i>Anopheles arabiensis</i>. <i>Anopheles arabiensis</i> DNA was detected in the gut content of hemipteran specimens analysed from the three families. The number of the adult mosquitoes emerging from the mesocosms was affected by the presence of predators. The findings of this study provide evidence of the potential use of aquatic macroinvertebrate predators as biocontrol agents against immature <i>Anopheles</i> mosquitoes and their potential to be considered as a component of integrated vector management for insecticide resistance and the combined restoration of aquatic ecosystems via smart ecological engineering.