Abstract:
Background: Ethiopia has recently constructed dams to produce electricity, irrigate farmlands and
control flood to reduce poverty and sustain economic growth, this may result in elevated malaria
transmission. In this paper, we investigate the effects of a mega hydropower dam on Anopheles mosquito
species composition, density, longevity and malaria prevalence.
Method: Longitudinal entomological study was conducted from June –December 2013 in two kebeles (four
villages) in Tiro Afeta district, jimma zone Southwest Ethiopia. The two kebeles are; Koticha Gibe, which
is located near Gilgel Gibe hydroelectric dam and Decha Nadi, located away from the dam. Anopheline
mosquitoes were collected using CDC light trap catches and pyrethrum spray catches. In addition
retrospective parasitological study was conducted from June-December 2013. Data were analyzed using
SPSS version 16.0 statistical package. Descriptive statistics and student t-test were used during analysis
and p-value less than 0.05 was considered statically significant.
Results: Overall, 1521 Adult anopheline mosquitoes belonging to two species were collected. An. gambiae
s.l. was the predominant species accounting for 72.9% followed by An. coustani s,l (27.1%). Over all mean
monthly An. gambiae s.l. density collected by LTCs and PSCs was 5.6 per trap/night and 3.51 per house,
respectively. Of these 8.5 per trap/night and 5.6 per house/day of them was collected from kebele located
near to the dam (Koticha Gibe) by LTCs and PSCs, respectively and the rest 2.71and 1.95 was collected by
the same methods from kebele far from the dam (Decha Nadi). There was significant difference in mean
monthly An. gambiae s.l. density between the two kebeles (P ˂ 0.05).There was significant (P < 0.05)
difference between mean indoor and outdoor An. gambiae s.l. density. However, there was no significant
(P > 0.05) difference between mean indoor and outdoor density of An. coustani s.l between the two kebeles.
duration of indoor resting after blood feeding decreased from 1.61to 1.28 and1.35 to 1.23 in Koticha Gibe
and Decha Nadi kebele, respectively during Post IRS operations and LLITNs distributions .Over all
probability of daily survival of An. gambiae s.l. decreased from 0.70 to 0.56 during Post IRS operations
and LLITNs distributions. The prevalence of malaria in the study setting was 10.71%. There was no
significance difference in malaria prevalence between two kebeles (x2 = 9.386, P = 0.052).
Conclusion: A Clear impact of dam on Anopheline mosquito density has been seen. In other word, the dam
is more favorable than the area far from it.
