An International Water Management Institute (IWMI) study has found that communities living within 1km of the Koka Dam in Central Ethiopia are 3x more likely to get malaria than those living 1-2km away and 20x more likely than those living over 5km away. The increased risk is due to the reservoir being a standing body of water which is a better breeding ground than the free flowing river.
However, these risks may be mitigated by better management of water releases from the reservoir. The study found that changes in reservoir water levels influenced mosquito larvae prevalence in shoreline puddles.
The study authors concluding remarks are:
"By creating numerous mosquito vector breeding sites close to the reservoir shore, the Koka Dam in Ethiopia has substantially increased the frequency of diagnosed cases of malaria. As a result, communities closest to the reservoir are at increased malaria risk.
Although not conclusive, evidence from this study suggests that increased rates of drawdown could play a role in reducing larval habitat with a consequent impact on malaria transmission in the area.
In light of the likely increase in dam building in sub-Saharan Africa in the near future, methods to control malaria need to be prioritized. In conjunction with historic experiences from elsewhere in the world, results from the current study indicate that manipulation of water levels to control Anopheles larvae has the potential to suppress malaria and could be a useful supplement to control measures targeting adult mosquitoes. More research is required to gain insight into the processes and mechanisms operating and to be able to predict under exactly what conditions such control measures are likely to be both successful and cost-effective."
Source: Circle of Blue Waternews
Download Report: IWMI Research Report 132 Malaria transmission in the vicinity of impounded water: evidence from the Koka Reservoir, Ethiopia