The present study revealed that microscopy- confirmed malaria in 5 year at Felegehiwot referral Hospital was 740 (5%). This finding was smaller than a retrospective study done in Northwest Ethiopia [6] and Southwest Ethiopia [7,8,9]. This difference might be due to study period and geographical difference. It was also smaller than the National Ministry of Health report [1]. This might be due to data on Ministry of Health is reports from via out the country while our report is from the study area. Moreover, there might be inter-personal variation on malaria microscopists and this might affect the result.
In this study, the overall prevalence of malaria in males 406 (2.8%) was higher than females 334 (2.3%). This result was in line with the study done in Southwest Ethiopia [8]. This might be due to the fact that agriculture is the main job and sleeping and staying outdoor is common during the night time. And hence, males are more exposed to Anopheles mosquito bites.
The prevalence of P. falciparum 397 (2.7%) and P. vivax 331 (2.2%) in the present study was lower than studies reported from other parts of the country [8, 10]. This difference might be due to climatological differences and altitude variation.
In our study, the age groups, >20 years 411 (55.5%) were highly affected followed by 16–20 years old 135 (18.2%) but from 10 to 15 years old 39 (5.2%) were the least affected. This study coincides with a study done in Northwest [7], but different from a report in Southwest Ethiopia [9]. The possible reason might be due to responsibility of these age groups for caring of the family and hence, the probabilities of staying outdoor for a longer period.
Months and seasonality have a direct role in the transmission of malaria. In our study, the prevalence of P. falciparum throughout the year revealed that it seems stable transmission. The reason might be since Felegehiwot Hospital is a referral Hospital; new cases could be referred from malaria stable transmission areas. The highest prevalence was observed from September to December followed by May to June. This result was in agreement with the monthly trends of malaria transmission stated in ministry of health [11]. This monthly occurrence indicates the real malaria transmission.
According to this study, there were irregular occurrences of cases each year for the last 5 years. From 2011 to 2012, more P. vivax infection was observed compared to P. falciparum with the peak at 2012 which seems epidemic. This was in line with a report in Southwest Ethiopia [9]. This might be due to an overlooked feature of P. vivax [11, 12]. The limitation of this study was that we used microscopy having lower sensitivity rather than polymerase chain reaction (PCR) to identify Plasmodium species in the study area.