Background
Malaria is one of the leading causes of death in the world. According to WHO report, there were 214 million cases and 438,000 deaths that were attributed to malaria in 2015 [
1]. It is a deadly disease, especially in Africa, including Ethiopia [
2], where the disease is prevalent at altitudes below 2000 m above sea level (asl). Its peak transmission occurs from September to December and April to May, coinciding with the major agricultural seasons. This has a negative impact on the Ethiopian subsistence agriculture-based economy [
2]. Areas below 2000 m asl cover three-quarters of the country’s land mass. Malaria epidemics occur every 5–8 years in these parts of the country [
3].
In Ethiopia,
Plasmodium falciparum and
Plasmodium vivax account for 60 and 40% of the total reported cases, respectively. These
Plasmodium species substantially contribute to malaria morbidity in the country [
4]. However, information on the trend of
P. falciparum and
P. vivax malaria in endemic areas is still insufficient.
Several countries have eliminated malaria since a programme for its global eradication was launched in 1955. However, no country has declared malaria elimination in Africa. The Global Technical Strategy for Malaria (GTS) calls for the elimination of malaria in at least 10, 20, and 35 countries by 2020, 2025, and 2035, respectively [
5]. In fact, the fight against malaria has shown a remarkable progress in controlling the disease over the last 20 years in Ethiopia. The burden has declined significantly, over the last decade, due to an improved coverage of high impact interventions, including the distribution of insecticide-treated nets (ITNs) and indoor residual spraying (IRS). Moreover, prompt and effective treatment with artemisinin-based combination therapy (ACT) was introduced to all health facilities free of charge to all age groups as a first line treatment for uncomplicated malaria in 2004. Targeted areas for key malaria control interventions were selected in accordance with criteria such as altitude (< 2000 m), morbidity data, and history of epidemics [
6‐
8]. Accordingly, Adi Arkay was one of the hot spot areas where malaria epidemic control interventions were carried out. Epidemiological data such as trends of malaria positivity rates at health institution is essential to design appropriate interventions. Furthermore, there is no published data regarding the trends of malaria cases at health institution and particularly at Adi Arkay town. Therefore, the present study aims at assessing the malaria positivity rate for the past 17 years at the institution as a proxy measure for the trend of malaria in the area which may contribute to evidence-based decision on malaria control activities.
Discussion
Over the 17 years (1997–2013), a 36.1% annual mean positivity rate of malaria was reported in the study area. This is lower than that of a study conducted at Kola Diba health centre [
6]. However, the result of this study indicates that malaria was a significant health burden in the area. Their differences might be related to variations in malaria diagnosis techniques and the skills of the laboratory personnel to detect and identify malaria parasites. Moreover, the implementation of malaria prevention and control activities might differ from one area to another showing that the interventions in this community might have been stronger. This study also revealed that malaria cases due to
P. falciparum and
P. vivax species accounted for 68.85 and 28.79% of the cases, respectively. The remaining 2.34% of malaria positivity rate was due to mixed infections. This is not in line with the national malaria parasite distribution figure in Ethiopia, which showed that
P. falciparum and
P. vivax accounting for 60 and 40% of the cases, respectively [
6,
11]. The national estimation of malaria parasites indicates the average distribution in the whole country, whereas the present study is limited to only a small part of Ethiopia could have resulted in the variation of the prevalence.
Over the 17 years, there was a dropping trend of total malaria cases from 47.4% in 1997 to 26.6% in 2009 (Table
1). The curve estimation analysis models (linear, quadratic and cubic) which explained practically significant overall malaria trend reduction across the years were used (each models showed; R
2 = 0.85, P < 0.001). This overall reduction of malaria is mainly related to the dramatic drop in the rate of falciparum malaria. This declining trend testifies the commitment of the government and other partners in Ethiopia. Malaria control has been one of the major components of the country’s prioritized health sector agenda since 2004. The Ethiopian Government together with collaborators launched multiple interventions for malaria prevention and control for the entire communities at risk including the study area [
7]. The national strategic malaria elimination plan currently recommends key intervention methods including prompt diagnosis using rapid diagnostic tests (RDT), artemisinin combination therapy (ACT) as first line drug to treat uncomplicated
Plasmodium falciparum malaria, and targeting the vector using indoor residual spraying (IRS) and long lasting insecticide treated nets (LLITNs). Chemoprophylaxis and environmental management are also key intervention measures applied to control malaria [
7,
12,
13]. Moreover, in the past several years, malaria control and prevention activities were intensified by all stockholders in the area. Awareness creation of the community about malaria transmission and control methods, the increment of budget and increased accessibility of ITNs to the community were the major interventions made by health professionals and representative of the government working in the town. All these efforts might have resulted in such significant reduction of malaria positivity rate.
Despite the national malaria intervention initiatives [
7], the prevalence of
P. vivax did not drop, instead showed a slight rise (Fig.
1). Its persistence may be related to the emergence of chloroquine resistance in
P. vivax [
11,
14]. Moreover, its ability to assume a dormant stage in the liver during its life-cycle might be the other reason for the insignificant reduction. A control strategy on the distribution of Co Artem
® in endemic areas targets mostly
P. falciparum and a greater emphasis on
P. vivax is needed [
7]. The month of September, October and November is the season when the highest peak of malaria has been frequently reported from different parts of Ethiopia [
6,
15,
16]. In a similar fashion, over the study period, the highest prevalence of malaria was observed during this season followed by spring (March, April, and May) in the study area during the study period. However, malaria cases were reported in the area in all seasons across the 17 years.
The present study also revealed a slightly higher positivity rate of malaria among males (39.4%) than females (32.4%). This is in agreement with the report from other parts of Ethiopia [
6]. Most people in Adi Akay are farmers, thus, most of the time males are engaged in agricultural activities during which they are more exposed to the bite of Anopheles mosquitoes, vectors of malaria parasites. The 15–45 year age group was the most affected age groups in both sexes (Fig.
4), and similar findings were also reported from Kola Diba, Ethiopia [
6]. This is the most productive age group which actively involves in several agricultural activities which expose them to the infection.
The present study indicates that a 17 years cases of malaria at the health institution as a proxy measure in the trend of malaria, but secondary data was used for analysis and this might have affected the accuracy of positivity rate of malaria. Thus, it has a limitation and should be interpreted with caution.
Authors’ contributions
HT conceived the study and involved in data collection. AJZ performed the data analysis and wrote the first draft of the manuscript. AGB critically reviewed the manuscript. All authors read and approved the final manuscript.