Insecticide treated nets use and its determinants among settlers of Southwest Ethiopia

Background Ethiopia is rapidly increasing insecticide-treated nets (ITNs) coverage to combat malaria, but adequate follow-up and factors affecting use of ITNs is lacking. The aim of this study was to assess determinants of the use of ITNs in a southwest area of Ethiopia. Methods This cross-sectional survey was conducted in the Chewaka district settlement area of southwest Oromia from March to May, 2013. Kebeles were stratified by degree of urbanization (rural, peri-urban, or urban). Randomly selected households, which had been freely supplied with at least one ITN, were surveyed using a pre-tested, structured questionnaire administered through household interviews. Logistic regression analysis was used to examine the association between use of ITNs and determinant factors. Results Of 574 households surveyed, 72.6 % possessed ITNs and 80 % of these had been used the night before the survey. The most common reasons for the absence ITNs in the household identified in this study were ITNs were old and therefore discarded and that households use ITNs for purposes other than their intended use. The multivariate analysis found that knowledge of malaria transmission by mosquito bites (Adjusted OR = 3.44, 95 % CI: 1.80–6.59), and washing of ITNs at least once by households (Adjusted OR = 2.66, 95 % CI: 1.35–5.26) were significantly associated with an ITN being used by households. The mean possession was 1.59 ITN per household (3.57 persons per an ITN). One hundred fifty four (36.9 %) of ITNs had at least one hole/tear. Among these, 108 (70.1 %) ITNs had at least one hole/tear with greater than 2 cm and 29 (18.8 %) had greater than seven holes/tears. Conclusions This study in Southwest Ethiopia showed a high proportion of net ownership compared to a household survey from Ethiopia which included in the World Malaria Report. Despite somewhat high percentages ITN ownership, the study demonstrated there was still a gap between ownership and use of ITNs. Use of ITNs was affected by knowledge of malaria transmission by mosquito bite and washing of ITNs at least once by households. Intensive health education and community mobilization efforts should be employed to attempt to influence these factors that significantly affect ITN use.


Background
Malaria remains a major public health problem particularly in sub-Saharan Africa. In 2012, malaria was responsible for over 1.1 million deaths globally [1] and was endemic in 104 countries with substantial geographic disparities. Around 81 % of the malaria incidence and 91 % of the malaria deaths in 2010 occurred in Africa [2]. Approximately 52 million people in Ethiopia (approximately 68 % of the national population) live in malaria risk areas, primarily at altitudes below 2000 m [3]. In Oromia 75 % of the land is considered malarious, accounting for over 17 million people at risk of infection [4].
Insecticide-treated bed nets (ITNs) are a means of malaria control and prevention [5]. The impact of ITNs on reducing malaria episodes is well documented [6,7]. Use of ITNs is one of the major vector control measures in Ethiopia. More than 20 million ITNs were distributed between 2005 and 2007, enabling 68 % of the households living in malaria-endemic areas to own at least one ITN. Indeed, 15 million ITNs were distributed in 2010 and 2011 to replace long-lasting insecticidal nets (LLINs) distributed previously [3,8]. Beyond household possession of ITNs, it is crucial to understand household use of ITNs. The ITNs that are available at a household level may be left unused; or alternatively, even if ITNs are used, usage may be intermittent and/or vulnerable members of the household may not be given priority. The maximum malaria reduction impact of ITNs will only be achieved if people acquire nets, treat/re-treat them, make sure that the most vulnerable household members sleep under them, and use nets through the year [9].
Studies in various African countries, including Ethiopia, have revealed discrepancies between ITN possession and use [8,[10][11][12]. Yet, there is no properly documented evidence regarding the coverage and use of ITNs among settlers in malaria-prone areas. This study was designed to investigate the possession, use, and factors affecting use of ITNs in the Chewaka district settlement area. This study also helped to evaluate the local ITN programs with reference to the Abuja targets.

Study setting and design
This cross sectional survey was conducted in Chewaka district settlement, located approximately 566 km from Addis Ababa in the Southwest Oromia Region of Ethiopia. It has a total population of 65,850, with people residing in 28 kebeles. The climatic condition of the area is a tropical zone referred to as 'cola'. It accounts 54.22 km 2 of land area which is all the land masses are suitable for settlement. The annual temperature and rainfall varies from 37 to 40°c and 1000 to 1200 mm respectively, and the altitude ranges from 900 to 1400 m above sea level. There is known the successful settlement in Oromia and by sesame seed production.
The main rivers in the area include the Didesa and Dabana, which are tributaries of the Abay River. In the district there are three health centers, twenty seven health posts, eighteen clinics and one drug vendor (Chewaka district annual health office report, unpublished).

Sample size and sampling technique
The sample size for the survey was calculated by using the formula for a single population proportion, including a 95 % CI, 5 % margin of error, and estimate of 73 % of household using ITNs based on a previous study in Ethiopia [13]. With a 5 % adjustment for non-response rate and a design effect of 2, the resulting calculation for a total sample size was 636 households. The study employed a multi-stage sampling technique, taking into consideration that socio-demographic factors affecting ITN use might differ based on the household's distance from the district town. The 28 malarious kebeles of the district were first stratified into three groups (urban, semi-urban, and rural kebeles), and then six kebeles were randomly selected by lottery method by proportional allocation to size (1 from the first, 2 from the second and 3 from the third stratum). Health extension workers (HEWs) distributed ITNs to the community at their vicinity/households during free massdistribution campaigns. Households were randomly selected from a list provided by the district administration

Data collection method and analysis
Data were collected by diploma health professionals after training using a pretested, structured questionnaire prepared in English and then translated into the local language of Afan Oromo. The questionnaire was adopted from instruments developed by the Roll Back Malaria (RBM) partnership Monitoring and Evaluation Reference Group by the WHO and UNICEF [14]. Data collection was conducted during the peak malaria transmission period, from March to May, 2013. Data collectors administered the questionnaire through household visits. Information was primarily collected from the head of households (father or mother), or if this was not possible, from another adult household member. The condition of household nets was inspected by use of a checklist. Data was entered using Epidata version 3.1 and Stata version 11.0 was used for analysis. Descriptive statistics provided means and percentages related to socio-demographic characteristics; knowledge of malaria transmission and prevention; and possession, use, and condition of ITNs. Through logistic regression, adjusted odds ratios were calculated to identify predictors of ITN use.

Ethical consideration
Ethical clearance was obtained from the Mettu University Faculty of Public Health and Medical Sciences Institutional Research Ethics Review Committee, as well as from the zonal and woreda-level health offices. Before each interview, researchers sought consent from each respondent.

Socio demographic characteristics
A total of 574 households participated in this study with a response rate of 90.3 %, of which 377 (65.7 %) were heads of households. The majority of the respondents 352 (61.3 %) were female. The mean (SD) age of the respondents was 30.6 (8.9) years and the mean (SD) family size was 5.7 (2.2). Of the total households, 470 (81.9 %) had at least one child under 5 years of age (in total 703) and 86 (15 %) had pregnant women (one in each household). A majority of respondents (379 or 66 %) were illiterate (unable to read and write) and 414 (72.1 %) were farmers ( Table 1).

ITN possession and use
All households (n = 574) that participated in this study were freely provided with at least one ITN by the district health office. Two hundred ninety seven (51.7 %) households were supplied with one, 215 (37.5 %) with two, 61 (10.6 %) with three ITNs and 1 (0.2) with four ITNs. In total, 914 ITNs were supplied to the households included in this study. Of these, 731 (80 %) were reported as being used by households. Use varied among strata at 75 %, 84.9 % and 82.7 % for rural, semi urban and urban strata respectively. Among ITNs that were used, about 37.4 % had at least one hole. Mean possession was 1.59 ITNs per household (3.57 people per an ITN).

Discussion
The study showed that ownership and use of ITNs in the study area were 72.6 % and 80.1 % respectively. The percentage of children under 5 years of age and pregnant women not using ITNs exceeded that of other adults. The two factors strongly associated with use of ITNs the night before the survey were knowledge of malaria transmission by mosquito bites and ITNs being washed at least once by households. The proportion of households possessing ITNs was higher in this study compared to the average figure indicated in World Malaria Report of 2011 (median = 56 %) from household survey results [15]. This implies that the net distribution program is going well when compared to the Roll Back Malaria [16] and World Health Assembly targets [17]. In this study, use of ITNs was in line with WHO recommendation of 80 % utilization [15]. High rates of use achieved within a short period of time demonstrates acceptance of nets by users as a major malaria control tool and reflects the concerted efforts of the Ministry of Health. However, more than half of households had just a single net, and on average four individuals shared a single net. This issue requires great attention, because the national policy aims to provide one ITN for every sleeping space (approximately one net per 1.8 persons in malaria-endemic areas <2000 m) [15]. Hence, to attain sustainable control of the disease, households in the study area require extra nets to reduce the occupant per net gap. The mode of malaria transmission identified by 59.6 % of respondents in this study was mosquito bites. This result is higher than the findings from a study in Wonago Woreda, Southern Ethiopia, where 42.3 % of respondents also listed mosquito bites [18]. But, less compared to a study done in Oromia and Amhara regional state, Ethiopia (67.9 %) [19]. Respondents' perception of net use as a main preventive measure for malaria was also lower compared to a survey done in Southern Ethiopia [18]. The reason for this may be that the majority of respondents included in our study were from rural areas and had less access to health information. Nonetheless, about three quarters of our respondents had ever heard educational messages about mosquito nets, which is high   [20]. This may be because our study included only households who were freely supplied with ITNs, which would contribute to increased exposure to educational messages. The difference might also be due to the presence of extensive promotion of ITNs currently underway in the country.
Presence of holes/tears on nets was also associated with malaria infection. Around 79 % of ITNs had holes/ tears ≥ 2 cm, which is higher than a study done in Tanzania in which 45 % of ITNs had holes/tears ≥ 2 cm [21]. It is also higher than a survey conducted in Malawi, where 12.8 % of owners reported that nets had holes >2 cm [22]. The reasons for this may include structural issues in the house that pose challenges to hang nets, such that the nets are too short to fully cover sleeping areas, long duration in use of ITNs, and frequent washing on rough surfaces.
Our finding revealed that there was strong association between using ITNs and knowledge of malaria transmission by bite of mosquito, which is in line with a study done Ghana [23,24]. Households with ITNs ever been washed shows significant increase of utilization compared to households with unwashed ITNs. This might be due to households having been encouraged to use clean ITNs as opposed to dirty ITNs.
About 20 % of ITNs were not used by households and 29 % of ITNs were used for other purposes such as storage of sorghum, to make fences, protect bulls from insect bites. This implies that distribution of nets to communities without health education on the importance of ITNs in prevention of malaria, as well as how to use nets, may not bring about the desired result. In this study education levels of respondents, and ever heard education messages about ITN were not associated with the use of ITNs. Age and sex of respondents were not significantly associated with ITN utilization in this study. Some studies reported similar findings [25,26], while the others showed significant associations between these factors and ITN use [8,27]. In addition, education levels and income did not significantly affect ITN use in our study which is in line with previous study done Ethiopia [8], Uganda [28] and Nigeria [29]. Given the cross-sectional nature of the results, interpretation of study results is limited. One of the major limitations of this study was that it relied on reported use of ITNs by households prior nights, without any means observation. Thus, the percentage of ITN use in this study might be overestimated due to self-reporting bias. In the future, research using a prospective cohort study design would be valuable.

Conclusions
This study in Southwest Ethiopia showed a high proportion of net ownership compared to a household survey from Ethiopia which included in the World Malaria Report. Despite somewhat high percentages ITN ownership, the study demonstrated there was still a gap between ownership and use of ITNs. On average, four individuals shared a single ITN and over one third of ITNs had at least one hole/tear. The two factors strongly associated with ITN use in surveyed households included knowledge of mosquito bites as a main mode of malaria transmission, and washing of ITNs at least once. To achieve sustained control of malaria, household coverage of nets alone is not sufficient. Public health interventions should also address problems related to utilization and care of ITNs. Intensive health education and community mobilization efforts should be employed to influence the specific factors identified as affecting ITN use.