Cattle-induced eutrophication favours disease-vector mosquitoes

Free-range cattle rearing in arid landscapes contributes profoundly to ecosystem degradation. Cattle dung nutrification in aquatic habitats potentially shapes species diversity and abundance due to resource availability. These nutrient-enriched environments may increase oviposition by mosquitoes and influence proliferation of disease vectors. Here, we examined mosquito larval abundance of Culex pipiens pipiens (culicine) and an unidentified Anopheles (anopheline) species across different concentration treatments of nutrient (cattle dung) loadings (T1-T4: L-1 g L-1, 2 g L-1, 4 g L-1 and 8 g L-1, respectively) in a randomised outdoor mesocosm experiment. The experiment was run for two weeks post-dung inoculation (Day 7 to 21), with mosquito larvae collected (Day 14 and 21), identified and quantified. Higher dung nutrient concentrations significantly increased mosquito larval abundance relative to dung-free controls. Culicine larvae were 26-times more abundant than anopheline on average. Higher dung concentrations also tended to promote more rapid development in larval mosquitoes. With no colonisation by mosquito larvae in the control treatments, we conclude that the input of dung in aquatic ecosystems promotes vector development and abundance with the potential to increase risk of mosquito-borne infections. We therefore recommend sustainable management policies that tackle likely ecological disservices attributable to free-ranging livestock communities. (C) 2020 Elsevier B.V. All rights reserved.