In Ethiopia, zero malaria death in malaria-endemic localities and complete malaria elimination from hypo-endemic areas could not be achieved despite the WHO-recommended interventions targeted at mosquito vector control, rapid case detection, and treatment of symptomatic cases. According to this retrospective analysis, 15,978 blood films were requested over a ten-year period (2012–2021) to confirm Plasmodium parasites, and 25.2% (N = 4019) (95% CI: 23.83–26.59) of the examined individuals were infected with malaria parasites. This is lower than a study conducted in Adi-Arkay Health Center [21] and Ziquala district [22], and higher than a study conducted in Bichena primary hospital [23], University of Gondar [24], and Mojo Town [25]. This variation might be due to differences in community awareness about malaria transmission and prevention, study time frame, malaria endemicity of the study areas, and skill among laboratory professionals in detecting and identifying Plasmodium species correctly.
The present study also demonstrated that P. falciparum and P. vivax were the species responsible for malaria in Maraki Sub-city and the surrounding population diagnosed at Maraki Health Center; the former accounted for most infections. The prevalence of P. falciparum, P. vivax, and mixed infections was 13.4%, 10.6%, and 1.2%, respectively. Plasmodium falciparum was the predominant species, comprising 53.37% of the total reported malaria cases, although there was a species fluctuation from year-to-year and month-to-month. Plasmodium vivax and mixed infections consisted of 42.0% and 4.63%, respectively. A retrospective study conducted in Bichena primary hospital reported a species composition of 51.18%, 41.78%, and 7.04% for P. falciparum, P. vivax, and mixed infections, respectively [23]. A study conducted in Ziquala district reported 59.7%, 37.0%, and 3.3%% for P.falciparum, P.vivax, and mixed infections respectively [22]. In contrast, studies conducted in Shewarobit [26], Mojo town [25], and at the University of Gondar [24] showed the dominance of P. vivax over P. falciparum despite year-to-year species fluctuation. The present finding is not also consistent with the national Plasmodium species distribution (P. falciparum, 60%, and P. vivax, 40%), even if it indicates the mean distribution in all parts of Ethiopia [11]. Failure to correctly identify Plasmodium species and the possibility of relapse might explain the reason for the dominance of vivax malaria over falciparum malaria in the above-mentioned areas.
In the current study, malaria cases were observed all over the years, with a significant year-to-year fluctuation (P < 0:001). Both P. falciparum and P. vivax contributed to the overall year-to-year fluctuating trend of malaria cases. The highest peaks of total malaria cases were observed in 2012, and the lowest peaks were observed in 2016. There was a decreasing trend of malaria prevalence from 66.4% in 2012 to 11.2% in 2016, although a significant rise was observed in 2017, which continued up to 2020 and then dropped in 2021. Malaria cases dropped from 2012 to 2016 by 15.97% (952 cases in 2012 to 152 cases in 2016). The highest and lowest peaks of P. falciparum cases followed the same pattern. The highest and lowest peaks of P. vivax were observed in 2012 and 2018 respectively. This declined trend might be the outcome of the continuous national struggle made by stakeholders and their strong commitment to decrease malaria-related death and illness to a level that has no public health effect. The highest malaria case in 2020 might be the effect of the COVID-19 pandemic on malaria prevention measures. Less attention was given to malaria and HIV prevention during the COVID-19 pandemic. Similarly, a fluctuating trend of malaria cases was reported from studies conducted at University of Gondar [24], Ziquala district [22], and Bichena Primary Hospital [23], and fluctuation is a result of both P. vivax and P. falciparum. A five year (2016–2020) declining trend in malaria prevalence was reported from a study conducted in Mojo town, Central Ethiopia [25].
Malaria cases were observed in all months, regardless of variation. The prevalence varied among different months, ranging from 13.24–39.15%, and there was a statistically significant monthly variation (P < 0:001). Relatively highest peaks of total malaria cases were observed during September to October, and the least peaks were observed during February to April. Similarly, P. falciparum cases followed the same pattern as the total malaria cases. The highest peak for P. vivax cases was observed during the months of October, November, and December. Whereas, the highest and least mixed cases were observed in September and March, respectively. This is consistent with studies conducted in Ziquala district [22], Guba district [14], and Bichena Primary Hospital [23]. A fluctuating monthly trend of malaria cases was also reported from studies conducted in Mojo town [25] and University of Gondar Specialized Referral Hospital [24], with maximum malaria cases reported from September to November and minimum cases reported from December to February. The possible reason for this type of malaria transmission pattern is that mosquito breeding and feeding cycles merely depend on rainfall and temperature. These factors contributed to the formation of favorable mosquito breeding sites and an increased rate of larval development.
The present study also confirmed that malaria cases were reported in both sexes and all age groups. There was a higher positivity rate of malaria among males (18.05%) than females (7.15%). Individuals in the age group 15–45 years old accounted for the highest malaria cases across all years, followed by those in the age group 5–14 years old. Participants with the age of above 65 acconted the least malaria cases. Males were more affected than females in all age groups. There was a statistically significant difference in malaria cases among sex and age groups (P < 0.001). The possible explanation for the dominance of male malaria cases over females and the age group 15–45 years old over other age groups is due to the fact that males in the age group 15–45 are usually involved in different outdoor activities and are traveling to malaria hotspot areas for work opportunities, which in turn increases their susceptibility to mosquito bites. Whereas females are less likely to perform such activities and are usually cookers at home, this might decrease the risk of infection with malaria parasites. Under-five children and people above the age of 65 showed relatively lower malaria cases because they are less likely to be exposed to mosquito bites as they usually sleep under bed nets. This finding agreed with a study reported in Adi-Arkay [21], Ziquala district [22], Bichena Primary Hospital [23], and Mojo Town [25], where males are more affected than females and the age group 15–45 years old consisted of the dominant malaria cases, followed by 5–14 and < 5 years old.
Strengths and Limitations of the Study
This retrospective study was the first survey conducted at Maraki Health Center since its establishment to assess the ten-year trend of malaria. The study manipulated a large amount of data from Maraki Health Centre Laboratory and allowed us to evaluate the ten-year trend of malaria prevalence. These findings might provide input for stakeholders to understand the obstacles to malaria elimination, future directions, and the need for further research. However, due to the nature of the study, we were unable to illustrate the possible risk factors that could have been predisposing to malaria in the area.