Prevalence and associated risk factors of malaria among adults in East Shewa Zone of Oromia Regional State, Ethiopia: a cross-sectional study

Ethiopia is one of the malaria-epidemic prone countries in Africa. Malaria is prevalent in over 75% of the country’s area, with 68% of the total population being at risk [1‐3]. The disease was responsible for about 12% of outpatient consultations and 10% of health facility admissions, and represents the largest single cause of morbidity [4, 5]. In 2010, there were more than four million clinical and confirmed malaria cases [6]. Ethiopia is at a high risk of epidemics of malaria due to climate and topography. Broad range of epidemics happen every 5–8 years in some areas due to climatic fluctuations and drought-related nutritional emergencies [7‐9]. P. falciparum and P. vivax are the two predominant malaria parasites in the country, accounting for 60–70% and 30–40% of infections, respectively [10], transmitted by inoculation by mosquitos (Anopheles species including Anopheles arabiensis) [9].

As per the National Strategic Plan, the four major intervention strategies that are being applied in the country to combat malaria include early diagnosis and prompt treatment, selective vector control that involves the use of indoor residual spraying (IRS) and insecticide treated nets (ITNs) and environmental management [11]. Since 2007, malaria control interventions have been scaled-up and significantly reduced the prevalence of malaria [3]. Nevertheless, malaria is still among the leading causes of outpatient visits and hospital admissions in the country [4]. There is a scarcity of information on the prevalence of malaria among suspected malaria patients attending health facilities and the associated individual and household factors. Such information provides both a measure of the pre-test probability of a positive result as well as geographical and personal risk factors for having a positive diagnosis of infection for patients who present with symptoms of malaria. The World Health Organization (WHO) considers that when the slide positivity rate of all febrile patients with suspected malaria is less than 5%, then this region may be considered as transitioning into a state of pre-elimination of malaria infection [11].

A significant number of P. falciparum cases occur in Ethiopia during the peak malaria transmission mainly in October. The national figure of 30%–40% of malaria cases in Ethiopia is due to P. vivax [10]. In contrast, in this study the prevalence of P. vivax is higher than P. falciparum. Likewise, P. vivax was the main causative agent of malaria in Oromia Regional State of Ethiopia, which accounted for 60% of slide-positive cases [3]. A study conducted in East Shewa indicated a proportion of 53% for P. falciparum and 47% for P. vivax [17]. The higher proportion of P. vivax in our study is consistent with studies conducted in other parts of Ethiopia [16, 18‐20], which indicates trend shift of species composition. Conversely, the dominance of P. falciparum was indicated by other studies conducted in different parts of Ethiopia [21‐23]. This could be explained by the fact that the prevention and control activities of malaria in Ethiopia [20] mainly focus on P. falciparum as it is deadlier than P. vivax [24]. Other possible reasons might be climate variability or that P. vivax might have developed resistance for Chloroquine.

Appropriate utilization of ITNs is one of the key interventions for the prevention of malaria [3]. In the present study, 50% of households had at least one ITN. Similarly, according to a malaria indicator survey conducted in 2011, 55% of households residing in malaria-prone areas of Ethiopia owned at least one mosquito net (of any type), and Oromia was found to have the lowest net ownership (44%) [3]. It is estimated that 42% of households in Africa owned at least one ITN in mid-2010 [25]. Moreover a study conducted in Eastern Ethiopia indicated an ITN ownership of 62% [26]. To the contrary, a study conducted in malaria epidemic prone areas of Ethiopia indicated that the overall ITN distribution was 98% [27]. The difference for this high value compared to our data could be explained by the reason that the present study is not a household survey which might have underestimated it. On the other hand, 41% of households without a single ITN represent a public health concern which needs to be addressed. The mean possession of bed net of 1.82 per household reported in our study is consistent with the report (1.73 /household) from study conducted in Ghana [28]. However, it is by far higher than the findings of malaria indicator survey conducted in 2011 (mean 0.7 /household) [3]. The ITN utilization of our study is high as compared to the study conducted in Eastern Ethiopia (21.5%) [26].

The use of representative samples with a high response rate of 97% is the strength of the present study, however it has some limitations. This study is a facility based survey. Therefore, it does not represent the situation in the whole population but it already provides reliable important data. Data collection relied on information given by the interviewees. Practices such as presence, type and use of ITN could not be verified by direct observation. Moreover, the diagnosis of malaria did not include PCR (Polymerase Chain Reaction). As this was a pragmatic study in a real-life rural environment, blood film was available to diagnose malaria infection, rather than rapid diagnostic testing which has a higher sensitivity [29]. On top of that, microscopic tests of malaria were done by the laboratory technicians in the different settings who didn’t get training about the determination of test positivity which could have led to bias due to interpersonal variation. However, these details reflect the ‘real-world’ nature of our data, that were based on usual clinical practice, and do not necessarily invalidate our findings.

In conclusion, findings of this study indicate that malaria is an important public health problem among adults in East Shewa with the predominance of P. vivax and P. falciparum; and being in the productive age group, living in Meki or Shashemene, and living in rural areas, were risk factors for malaria infection. According to WHO when the slide positivity rate of all febrile patients with suspected malaria is less than 5%, the country could consider transitioning into “pre-elimination” [11]. Therefore, a test positivity rate of 25% at health facility level indicates that malaria is a major burden in the zone, which is not in line with the national strategic plan for malaria prevention control and elimination in Ethiopia. Moreover, there is a gap regarding the mosquito nets/ITNs ownership and utilization. Hence, more focus should be given to environmental sanitation as well as the consistent utilization of ITNs should be promoted by health workers and health extension workers in particular. In addition, the number of mosquito nets/ITNs supplied to households should be increased in order to assure adequate mosquito nets/ITNs ownership in each household. Further study using direct observation at sleeping time rather than reported use is important to assess ownership proper utilization of ITNs. Special attention should be given to those living in the rural area of the zone. Furthermore, there was an increased risk of malaria infection among the younger age group as well as among those living in Meki and Shashemene areas which needs a further investigation.