The effect of dams and seasons on malaria incidence and anopheles abundance in Ethiopia

Abstract

BackgroundReservoirs created by damming rivers are often believed to increase malaria incidence risk and/or stretch the period of malaria transmission. In this paper, we report the effects of a mega hydropower dam on P. falciparum malaria incidence in Ethiopia.MethodsA longitudinal cohort study was conducted over a period of 2 years to determine Plasmodium falciparum malaria incidence among children less than 10 years of age living near a mega hydropower dam in Ethiopia. A total of 2080 children from 16 villages located at different distances from a hydropower dam were followed up from 2008 to 2010 using active detection of cases based on weekly house to house visits. Of this cohort of children, 951 (48.09%) were females and 1059 (51.91%) were males, with a median age of 5 years. Malaria vectors were simultaneously surveyed in all the 16 study villages. Frailty models were used to explore associations between time-to-malaria and potential risk factors, whereas, mixed-effects Poisson regression models were used to assess the effect of different covariates on anopheline abundance.ResultsOverall, 548 (26.86%) children experienced at least one clinical malaria episode during the follow up period with mean incidence rate of 14.26 cases/1000 child-months at risk (95% CI: 12.16 - 16.36). P. falciparum malaria incidence showed no statistically significant association with distance from the dam reservoir (p = 0.32). However, P. falciparum incidence varied significantly between seasons (p < 0.01). The malaria vector, Anopheles arabiensis, was however more abundant in villages nearer to the dam reservoir.ConclusionsP. falciparum malaria incidence dynamics were more influenced by seasonal drivers than by the dam reservoir itself. The findings could have implications in timing optimal malaria control interventions and in developing an early warning system in Ethiopia.

Joint Bayesian modeling of time to malaria and mosquito abundance in Ethiopia

“…There is a substantial body of literature documenting the increases in malaria incidence as a consequence of such projects [3]. Ethiopia has recently constructed a large number of dams to produce electricity and for irrigation [10, 11]. Even though dams give economic benefits, they can increase the survival, density and distribution of disease vectors transmitting parasites such as malaria, by providing appropriate habitats.…”

“…They found that distance of households to the dam was not significantly associated to malaria incidence, while seasonal effects were significantly associated with malaria incidence. In the paper [11] the authors investigated further the effect of distance of households from the dam on Anopheles mosquito abundance. They found that the abundance was varying significantly between seasons and was higher in villages near the dam.…”

“…The Gilgel Gibe hydro-electric dam area, together with the location of the study households in sixteen villages around the dam are shown in Fig. 1, taken from [11]. The sixteen villages were selected at various distances from the closest dam shore, ranging from 0.265 to 9.056 km.…”

Dynamics of Plasmodium falciparium and Plasmodium vivaxin a micro-ecological setting, Southwest Ethiopia: effects of altitude and proximity to a dam

“…However, a follow up study on children two to nine years reported that risk of malaria infection due to proximity to hydro-power dam was insignificant [20]. Still, a few other longitudinal studies [21],[22] reported presence of malaria hot spots and heterogeneity of the disease at some relatively wider intervals.…”

Water resource developments in Ethiopia: potential benefits and negative impacts on the environment, vector-borne diseases, and food security

“…The construction of large dams in Ethiopia has been documented to result in increases in vector populations by creating insect and snail habitats (Yewhalaw et al 2013;Kibret et al 2009;Lautze et al 2007;Kloos and Legesse 2010b;Meskal and Kloos 1989). A study by Yewhalaw et al (2009) showed a higher Plasmodium vivax prevalence in children living in communities near the reservoir created by the Gilgel-Gibe hydroelectric dam in south-western Ethiopia than in children in communities located farther away.…”