Malaria affects the lives of almost all people living in the area of Sub Saharan African countries where people at risk of the disease live in areas of relatively stable and seasonal malaria transmission[1]. In Ethiopia, malaria continuous as major public health problem despite relatively low prevalence compared to some African countries where malaria is endemic. Unstable malaria transmission patterns make the country prone to epidemics [7, 16]. However, the country has planned to eliminate malaria from the whole country which needs sub-national elimination before nationwide elimination can be achieved. This is because the decrease in malaria burden is not uniform in the country [17] which is imperative to understand the contextual diversity of malaria prevalence within each site. Thus, this study determined epidemiological trends of malaria cases in specific health facility.
The current study found that the total number of microscopically confirmed malaria cases were 793 with a proportion rate of 4.2%. It was markedly lower than previous studies conducted out of Ethiopia elsewhere (25.9%-30.3%) [18, 19], and in several parts of the country such as in Dembia (21.8%) [10], Dembecha (16.34%) [20], Guba (51.04%) [15], Sibu Sire (20.07%) [21], Arjo-Didessa sugar development site (33.4%) [22], Harari (46.9%) [23], Chalia district (7.55%) [24], Abeshge (33.8%) [25], and Bale Zone (66.7%) [26]. The overall prevalence of the current study was also relatively lower than the findings from other parts of Ethiopia like Northwest Tigray (6.96%) [8], Wereta (5.4%) [27], Kombolcha (7.52%) [13], Ataye (8.4%) [28], Halaba (9.5%) [9], Wolkite (8.56%) [29] and Arsi Negelle (11.45%) [30]. However, this study found higher prevalence of malaria relative to studies carried out abroad such as Panama (1.22%) [31] and India (1.3–3.07%) [32, 33].
These differences might be due to the fact that the quality of microscopic diagnosis is highly influenced by slide preparation and staining methodology, microscopist skill and quality of microscope [34]. The difference in time variations of the studies might also brought the difference on the overall prevalence of malaria since malaria is being declined from time to time as supported by the global[1], and national report of decreasing malaria prevalence since 2000 [17]. Moreover, the variations in malaria prevalence might also be due to geographical locations because of the fact that population awareness about malaria and application of intervention activities vary from area to area. Variation in sociodemographic status and utilization of intervention in the same locality also influence the prevalence as documented by previous studies conducted elsewhere [35–39].
In addition, the low prevalence of malaria in the current study could be due to the variation in species showing that P. vivax was the more predominant species in this study than P. falciparum in another studies listed above. This is due to the fact that the parasite density in P. vivax is typically lower than P. falciparum increasing the risk of false negative microscopy diagnosis with acute P.vivax malaria [34, 40, 41]. The thought was also supported by the review stated that microscopists correctly identified only 63%-86% of confirmed P.vivax positive blood films [40]. Another review also summarized that an average of 67% of P. vivax infections were reported as not detected by microscopic examination [42] masking the actual burden of P.vivax related malaria. This might be approved by the reporting of lower prevalence of P.vivax related malaria from studies done in Panama (1.22%) [31], and India (3.07%) [33] where P. vivax was the predominant species.
The results of the present study revealed that a sharply declined fashion of malaria cases was observed during the last five years. This finding was consistent with the worldwide decreasing malaria burden in which 1.5 billion malaria cases have been averted from 2000 to 2019 where most of the averted cases (82%) were in the WHO African regions including Ethiopia [1].A significant decline of malaria has been also reported in Ethiopia since 2000 [17]. The consistent reduction of malaria case in the current study was also concurred with the result of previous studies conducted in Vietnam [43], and other parts of the country such as Wolkite [29] and Jimma [44].
This might be due to the increased scaled-up of malaria control interventions by national malaria control programme of Ethiopia such as prompt diagnosis, community awareness creation, increased accessibility of long-lasting insecticide-treated nets (LLITNs) and high coverage of indoor residual spraying (IRS) [16]. This conclusion is further supported by the study indicating the reduction of malaria cases and deaths after implementing intervention [45]. This is also confirmed by the national malaria elimination roadmap proving that sustained high coverage of such interventions had reduced malaria morbidity by more than 50% between 2001 and 2011 [17]. The current progressive decline in annual malaria cases is suggestive of good national progress towards achieving of 2030 goals to reduce malaria incidence and mortality by at least 90% [17].
In contrary to the national profile of Plasmodium species in which P. falciparum is a dominant species [10, 17, 23, 26, 46], P. vivax accounted for 76.2% and was predominately reported in the current study. However, in line with the current study, P.vivax was reported as predominant species in studies done in Arsi Negelle [30] and Wolkite [29]. It could be due to the fact that malaria control programmes in the past had prioritized to focus on P. falciparum malaria because of its consideration as more pathogenicity, and easier to detect and treat [3, 6]. In addition, it could be due to the emergence of drug resistant [40], the parasite’s ability to transmit early in the course of the disease [47], production of gametocytes transmitted more efficiently [48, 49], and a relapse from dormant liver stages [6, 50, 51]. This increment of the prevalence of P.vivax causing malaria with the decline of P. falciparum related malaria might also be supported by the fact of reporting Duffy independent invasion and genetic diversity of P.vivax leading to generation of new parasite strains that can translate into parasite’s greater adaptability to new challenges for treatments and control measures [47]. Previous meta-analysis found high risk of P.vivax malaria after treatment of P.falciparum malaria [52].
In the present study, distribution of malaria cases was observed in both gender and all age groups of the population throughout the study period. Nevertheless, males were more affected than females which is consistent with studies conducted in other parts of Ethiopia[8–10, 15, 20, 22, 26] and out of Ethiopia in France [53] and Kuwait [19]. This gender difference in malaria prevalence could be due to the fact that males frequently bitten by mosquitoes due to the behavioral differences of males’ working outdoors, little chance of sleeping under nets, travel to endemic sites for work, and dressing norms are more likely than females to expose their bodies increasing their chance of mosquitoes’ bite [54]. Moreover, hormonal differences might play the role in such a way that testosterone was associated with decreased adaptive immunity against malaria [55]. Briggs and the colleagues have also thought that females cleared their infections at a faster rate than males [56] which might support the lower prevalence of malaria among females in the current study.
The present study had observed higher prevalence of malaria among age group of 15–24 years old than younger children and older adults which is in line with studies done in other parts of Ethiopia[10, 15, 28]. This might be due to the fact that productive age groups frequently engaged in outdoor activities. Surprisingly, lower prevalence of malaria was observed in children under 5 years of age which might be because of their less likely exposure to mosquito bite, and sleeping under mosquito nets.
The current study observed malaria cases in all months and seasons throughout the study period. It might indicate that malaria transmission is determined by socio-economic and biological factors such as mosquito control measures, population immunity, governmental policy and drug resistance have also contribution on malaria transmission and prevalence. In spite of that, the peak in malaria cases occurred in July followed by November which is harvesting season during and after the main rainfall. The highest cases of malaria were detected during autumn (September-November) which was in consistent with the findings of the studies carried out in Dembia [10], Dembecha [20], Northwest Tigray [8], Ataye [28], Guba [15], Jimma [44], and Harari [23]. It might be due to the heavy rains creating suitable environment for the breading of Anopheles mosquitoes. In addition, it could be related to the formation of stagnant water after the heavy rain season, favorable temperature, and high vegetation density for mosquito breeding. The coinciding high prevalence of malaria with these cultivation months has a deleterious socioeconomic effect on productivity and development in the country.