Introduction

Malaria is one of the leading public health challenges that causes morbidity and mortality among infectious diseases in the world. It is caused by a protozoan parasite of the genus Plasmodium and transmitted through the bite of the female Anopheles mosquito1,2. Nearly 3.3 billion individuals are at risk of malaria, with the highest risk of acquiring the disease in Sub-Saharan Africa (SSA)3. The World Health Organization's (WHO) report of 2023 indicated that half of the world’s population has been at risk of malaria, with an estimated 233 million of malaria cases were in 29 countries and an estimated 580,000 deaths, with children under five years of age and pregnant women most severely affected3,4.

Long-lasting insecticidal nets(LLINs) are a the use of long-lasting insecticidal nets (LLITNs) as a vector control measure helps to reduce the incidence of malaria globally. LLITNs can help prevent malaria infection by reducing mosquito contact and bites when used appropriately and regularly 5,6. Evidence suggests that utilizing LLITN can reduce clinical malaria and related deaths by about 20% of all causes of mortality in areas in which malaria remains endemic2,5,7. As a component of the World Health Organization's (WHO's) Global Malaria Technical Strategy (GTS) 2016–2030, which aims to reduce the prevalence of malaria worldwide by 90% by 2030, sleeping under LLINs is one of the most effective strategies to restrict mosquito-human interaction. Together with a physical barrier8, it provides an insecticidal effect and substantial subsidies9. Africa makes up 95% of the estimated global disease burden, and six nations account for slightly more than half of all malaria cases: Nigeria (27%), Burkina Faso (3.4%), Mozambique (4%), Uganda (5%), the Democratic Republic of the Congo (12%), and Mozambique (12%). Malaria contributed to increased poverty in sub-Saharan African nations, resulting in global losses of up to 12 billion dollars5. Sleeping under a long-lasting insecticidal net (LLIN) is one of the best ways to prevent malaria because it creates a chemical and physical barrier against mosquitoes10,11. The use of LLINs is crucial for nations hoping to eradicate malaria12. When mosquitoes try to bite someone sleeping under a LLIN, they are not only blocked by the netting but also killed by the insecticide coating9,13,14. Studies show that the use of LLINs reduced malaria incidence by 50 percent in sub-Saharan Africa, a region that accounts for more than 90 percent of global cases15,16,17.

Following the WHO recommendation of one net per 1.8 people, LLIN planning and distribution in Ethiopia is carried out through a rolling mass campaign that occurs every 3 years to distribute the nets to households2,11. National coverage of bed net ownership and utilization conditional to ownership in Ethiopia was 40% and 61%, respectively2,18. The LLINs are treated net fibers that have been applied with specific insecticides, such as permethrin, in a factory setting to maintain, as recommended, their biological efficacy against malaria vectors for a minimum of three years. Permethrin deltamethrin or alphacypermethrin-treated LLINs provide physical barriers against mosquitoes (malaria vectors) to prevent malaria disease transmission5,14,19.

Previous studies carried out in Ethiopia revealed that factors influencing the use of LLIN included knowledge about the mode of transmission of malaria, information from Health Extension Workers (HEWs), hearing about media campaigns, education at a health facility, attitude and physical discomfort while sleeping under LLIN, inability to hang available LLIN, incompetence in hanging the nets, insufficient educational campaigns, scarcity of nets, risks of malaria, and ignorance of the benefits of nets17,20,21. It was also discovered that other attributes, including family size, age, degree of damage, size, shape, color, and number of sleeping places, were connected to the use of LLINs5,17,18,22. However, some studies reported no significant association between household wealth and LLIN utilization3,23.

Large enough LLINs to fit inside a sleeping space were found to be more frequently used, and numerous studies conducted in malaria-endemic nations have confirmed their value in reducing man-vector contact from malaria as well as other vector-borne diseases7,19,23. In endemic areas, it has been demonstrated that the distribution of LLINs lowers malaria episodes, severe illness, and malaria-related mortality2,5,7,22. Nets treated with insecticides have contributed to a 48–50% decrease in malaria cases. If widely adopted, these nets could avert an estimated 7% of under-five mortality worldwide24 and have been linked to statistically significant decreases in the risk of low birth weight and fetal loss25.

The extent to which people are aware of LLINs utilization and acquire bed nets to utilize is not understood clearly. Observations and rumors of not hanging nets at all, hanging nets in the wrong manner and place, and not giving priority to children and pregnant mothers deserve close examination. The perception of the population on the role of LLINs in the prevention of malaria is still another issue23. The districts in the lowlands of the West Arsi Zone have a high malaria case burden, and there is little data on the use of long-lasting insecticide-treated nets in homes and communities. Therefore, the study aimed to assess the prevalence of LLINs utilization and associated factors among households of West Arsi zone, Oromia, South West Ethiopia.

Methods and materials

Study design, period, and areas

A community-based cross-sectional study was conducted in the West Arsi zone from May 1 to 30, 2023. The West Arsi zone is situated 250 km from Addis Ababa in the region of Oromia, southern Ethiopia. There are 2,926,749 people living in the zone; 1,434,107 of them are men, and 1,492,642 are women. In the West Arsi Zone, approximately 963,102 populations in six districts and one town are living in an environment where there is a high risk of malaria; however, nine districts are malaria-free. There are 352 kebeles in the West Arsi zone, 136 of which are malarious kebeles. Of the 356 health posts, 143 of which are malarious, there are 85 health centers, 32 of which are located in malarious areas. Three hospitals out of a total of five are treating patients with malaria. In the zone, there are rivers and irrigation sites that are suitable for mosquito breeding. In the zone, 312,224 LLINs were distributed for emergency response in 2021 and for a second round of 2022, 150,949 LLINs were distributed26.

Source population

All households in the West Arsi zone and who had been living in the districts of the zone during the study period were considered as source population.

Study population

All randomly selected households in the eligible districts of West Arsi zone and who had been living in the kebeles with high risk of malaria during the study period were considered as study population.

Eligibility criteria

Inclusion criteria

All households found in the selected kebeles of the West Arsi Zone and who had been living in the study area for more than six months were included.

Exclusion criteria

Those households who did not received LLINs during distribution period, and those unable to respond due to hearing and speaking problems were excluded from the study.

Sample size determination and sampling procedure

The required sample size for study participants was determined by using the single population proportion formula based on the assumptions that α (level of significance, 5% = 1.96); P(the proportion of insecticide-treated nets utilization = 72.2%,)19, d(margin of error) = 5% (0.05) and design effect of 2.

$$d = K \times SE = K \times \surd qp/n = 1.96 \times \surd 0.722 \times 0.278/532 = 1.96 \times \surd 0.20/532 = 1.96 \times \surd 0.0004 = 1.96 \times 0.002 = 0.0392 = 4\% .$$

Then, the sample size based on the above assumptions is:

$$n = \, DE{\left( {Z \, \alpha \, /2} \right)^2} \, P \, \left( {1 - P} \right) \, / {d^2}$$
$$n = 2({\left( {1.96} \right)^2} \times \, \frac{(0.0.722 \times 0.278)}{{{{\left( {0.04} \right)}^2}}}) = 2\left( {3.84} \right) \times \left( {0.2} \right)/0.0016 = 2(0.768/0.0016 = 960 \,$$

where n is the required sample size, the standard score corresponding to a 95% confidence interval, and by adding a response rate of 10%, the sample size from the first objective was 48 + 480 = 1056.

The sample size determination for the second objective for factors associated with LLINs utilization was calculated based on the double population proportion formula using Epi info version 7 stat calc software. Using assumption of 95% CI, 80% of power, Percent of outcome in unexposed group 61.1% which was taken from study done in Central India13 using uneducated household head as a factor variable and OR 1.25. Using the above assumption, and after comparing the variables with large number, the variable uneducated household head were considered for the final sample size determination since it provide the large sample size of 2808.

Sampling procedures

A multi-stage sampling method was employed to choose representative participants. Initially, based on the distribution status of LLINs in high-risk areas, six districts, and one administration town were purposefully chosen. After that, 28 kebeles were chosen using a simple random sampling method from six districts and one town in the West Arsi Zone. The lists of kebeles from the districts that were chosen revealed that there are 32 kebeles in the Siraro district, 8 kebeles in the Heban Arsi district, 15 kebeles in Negelle Arsi Rural, and 5 kebeles in Negelle Arsi Town. There are 37 kebeles in the Shala district, 7 kebeles in the Wondo district, 14 kebeles in the Shashemene district, and 32 kebeles in the Siraro district. Using a lottery method, the following kebeles were chosen from the lists: 11 kebeles from Shala district, 2 kebeles from Wondo district, 4 kebeles from Shashemene district, 10 kebeles from Siraro district, 2 kebeles from Heban Arsi district, 5 kebeles from Negelle Arsi Rural, and 1 kebele from Negelle Arsi Town.

Following proportional allocation to the sample size based on the number of households in each kebele, 2808 households were chosen from eligible kebeles using simple random sampling techniques. The total number of households in each kebele was obtained from the community health information system (CHIS) of the kebele. The first household was selected by using the lottery method. If the study participant's home was closed while the data was being collected, a revisit was conducted up to twice, and it was considered as no response.

Study variables

Dependent variable

LLINs utilization.

Independent variables

Socio-demographic characteristics (age, marital status, religion, education, occupation, family size, place of residence, ethnicity, and monthly income), Knowledge status, and LLINs utilization-related variables were some of the independent variables.

Measurement and operational definition

Knowledge about LLINs

Households were asked thirteen knowledge questions about LLINs utilization and the correct answer scored 1 and the incorrect answer scored 0. After computing the sum of the score for each participant, the mean score was calculated and those participants who scored above were considered as having “good knowledge” and those who scored below the mean were considered as having “poor knowledge” about about LLINs utilization.

Data collection tools and procedures

Data were collected using face-to-face interviewer-administered structured questionnaires that were adapted from different literatures2,3,7,19. It consists of socio-demographic characteristics, environmental characteristics, and knowledge of the participants on LLINs utilization. Data were collected by 28 malaria focal persons from outside their catchment area and supervised daily by 7 Health office malaria experts.

Data quality assurance

The questionnaires were prepared in English language version and translated into the local language (Afaan Oromo) and retranslated to English to check their consistency. The questionnaire was pre-tested on 5% of sample size (135) outside of the study health facilities. After conducting the pre-test the possible modification concerning clarification of content and simplification of wording was done after pretesting of the questionnaires. Data clearance, completeness, range, and logic checks were carried out regularly to ensure the quality of data before data entry. Any data that is incomplete and inconsistent was excluded from the data after checking with the supervisors. Data collectors and supervisors were trained for one day on how and what information could be collected. The investigators monitored the data collectors and supervisors to ensure the quality of data during the data collection period.

Data processing and analysis

Data were checked for accuracy and consistency and then, coded and entered into Epi-info version 7, cleaned and analyzed by SPSS version 25. Descriptive statistics such as frequencies, proportions, and graphs were used to present study results. Bivariable binary logistic regression analysis was computed, in the bivariate model, covariates with p-values less than 0.25 were selected to be included in the multivariate model. The final model was interpreted using an adjusted odd ratio with a 95% confidence interval and p-value < 0.05 to determine the association between the outcome and independent variables. Multicollinearity was checked by using standard error (SE) and the standard error of this study was found to be less than 2. Model fitness was checked with the Hosmer and Lemeshow model goodness of fit test and the p-value of the Hosmer and Lemeshow test for this study was 0.746.

Ethical approval and consent to participate

Ethical approval was obtained from the Ethical Review Committee of West Arsi Zone Health office before conducting the study based on the Declaration of Helsinki. The official permission letter was obtained from selected Districts and Town Health Offices after explaining the purpose of the study. The objective of the study, privacy, and confidentiality were informed to study participants. Verbal informed consent was obtained from study participants before starting the actual data collection process. Respondents’ name was not taken rather only a code was given to each respondent to keep confidentiality.

Results

Socio-demographic related characteristics

A total of 2772 respondents participated in the study with a response rate of 98.7%. The mean age of the study participants was 35 years with SD of ± 34.98. More than half of the study participants, 1463 (52.8%) were male as household head. Among 2772 respondents’ the majority of them, 907 (32.7) and 894 (32.35) were in the age group of > 64 and 45–64 years respectively.

Of the study participants about 2574 (92.9%) were Oromo by ethnic group and 1912 (69.0%) were Muslim by their religion. Regarding the educational status of the study participants, the majority of them 1602 (57.8%) had not attended formal education. Concerning occupational status, more than half of the participants 1663 (60%) were farmers. Of the total study respondents about 2595 (93.6%) of participants were married.

Of the respondents, about 2337 (84.3%) of the households did not have television. The average monthly income of the study participants was 1504.08 (SD of ± 1399.784). The mean family size of the study participants was 5.67 with SD of ± 2.747. Nearly three-fourths of the participants 2052 (74.0%) had at least one separate room in the house. The mean score of the separate rooms in the house of study participants was 1.96 with SD of ± 0.938. Of the study participants, 2418 (87.2%) had at least one separate sleeping beds/spaces for sleeping in the house with a mean score of 1.70 with SD of ± 0.747. The mean number of rooms in the household used for sleeping of the study participants was 1.65 with SD of ± 0.789) (Table 1).

Table 1 Socio-demographic characteristics of participants on Long Lasting Insecticide Nets Utilization among Households of West Arsi Zone, Oromia, Southern Ethiopia, 2023.
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Knowledge about LLINs

Of the respondents, the majority of them 2738 (98.8%) were heard about LLINs utilization. Concerning the sources of information on LLINs utilization, most of the respondents 2202 (71.1%) got information from Health care providers. Almost all 2735 (99.9%) of the respondents were aware that torn LLINs can repaired. Nearly all of the participants, 2614 (95.5%) have an awareness on LLINs as it can prevent malaria. Majorities of households 2529 (91.5%) had good knowledge about LLINs. The mean knowledge score of the households on LLINs utilization was 7.77 with SD ± 0.91 (Table 2).

Table 2 Knowledge about long lasting insecticide nets utilization and associated factors among Households of West Arsi Zone, Oromia, Southern Ethiopia, 2023.
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Households' level of LLINs utilization status

Of the participants, 2389 (86.2%) households have mosquito nets (LLINs) that can be used while sleeping. The majority of the households, 1870 (67.5%) had at least one LLINs of mosquito nets that can prevent malaria. About 2032 (85.3%) of all received LLINs were physically observed. From the total of study participants, 1605 (78.7%) of the families have hanged the received LLINs in the sleeping room. From hanged LLINs, about 1397 (87.4%) of the LLINs were hanged properly. Most of the LLINs haven’t hanged 430 (55.2%) were found packed as it is without using it for malaria prevention. The overall household level of LLINs utilization status was 1666 (69.9%) with 95% (CI 68.1–71.8). Regarding the frequency of utilization, the majority of them 1147 (68.6%) had utilized every night. The reason for LLINs utilization1430 (86.4%) was to prevent malaria. Most of the respondents raised the reason for not sleeping under LLINs 218 (30.2%) was not like the smell of the nets (Table 3).

Table 3 Long lasting insecticide nets utilization and associated factors among Households of West Arsi Zone, Oromia, Southern Ethiopia,2023.
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Households status of LLINS utilization by districts

The districts with the highest households LLINs utilization were Shashamane 304 (95.3%), Negelle Arsi Rural 223 (93.3%), and Heban Arsi 133 (75.6%) (Fig. 1). The result of this study revealed that the districts with the lowest utilization of LLINs were Siraro District 553 (58.1%) and Nagelle Arsi Town 76 (64.4%) ( Table 4).

Figure 1
figure 1

Households utilization of long lasting insecticide nets by district among Households of West Arsi Zone, Oromia, Southern Ethiopia, 2023.

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Table 4 Households level LLINS utilization status by districts among Households of West Arsi Zone, Oromia, Southern Ethiopia, 2023.
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Factors associated with LLINs utilization

In a bi-variable analysis for factors associated with LLINs utilization, the variables such as sex of respondents, place of residence, family size, educational status, marital status, occupation of respondents, number of separate rooms in house, knowledge about LLINs, place where to get LLINs, duration of LLINs being used to be replaced and number of mosquito nets household owned were associated with LLINs utilization. All variables with a p-value < 0.25 in the bivariable analysis were recruited for multivariable logistic regression analysis after adjusting for confounders.

In multivariable analysis, the variables with p-value < 0.05 were considered as significantly associated variables with LLINs utilization. Being female sex was 1.69 times more likely to utilize LLINs as compared to male (AOR 1.69, 95% CI 1.33–4.15). The result of the study revealed that the number of separate rooms in the house of the participants were significantly associated with LLINs utilization. Those households who had two separate rooms in the house were 1.80 times more utilized than their counterparts (AOR 1.80, 95% CI 1.23–2.29). Three years duration of LLINs being used to be replaced was 2.81 times more likely to utilize LLINs as compared to less than 3 years duration of being replaced (AOR 2.81, 95% CI 2.18–5.35). Another result of this study showed that those households who had good knowledge about LLINs were 3.68 times more likely to utilize LLINs as compared to those who had poor knowledge (AOR 3.68; 95% CI 2.48–6.97) (Table 5).

Table 5 Bivariable and multivariable analysis for factors associated with LLINs utilization and associated factors among Households of West Arsi Zone, Oromia, Southern Ethiopia, 2023.
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Discussion

The study aimed to assess the utilization of long-lasting insecticide nets and associated factors among households in West Arsi Zone, Ethiopia. The study identified the factors that showed association with long-lasting insecticide nets utilization such as being female sex of the respondents, number of separate rooms in the living house, duration of long-lasting insecticide nets used to be replaced, knowledge status of the respondents were significantly associated with long-lasting insecticide nets utilization.

The overall utilization of long-lasting insecticide nets among households of West Arsi Zone was 69.9% with 95% CI of (68.1–71.8). The result of the present study was in line with the study conducted in Ilu Galan District 72.2%5, Limu Seka 68.3%14, and Asgede Tsimbla District 63%3. However, this result was higher than the study done in East Belessa District 56.5%7, Eastern Ethiopia 59.4%27, Dara Mallo and Debretsehay districts of Amhara Region 19.3%2, Tiko District, Southwest region 24.9%28, South-Central Ethiopia 24.3%17 and South West Nigeria 39.3%29. But the current study is lower than the study conducted in Adama town 76%21, Bahir Dar City, Northwest Ethiopia 76.8%)20, Mogadishu districts (84.0%)30, Kenyan Coast (72%)31 and Kachin Special Region II, northeastern Myanmar (97.3%)32.

This difference might be attributed to the differences in sample size used, study population, difference in the setting of the study area, and socioeconomic status. Currently, in Ethiopia, there are several interventions made to reduce the burden of malaria by the Ministry of Health through the implementation of malaria prevention activities at primary health care programs that might contribute its share for reducing malaria-related morbidity and mortality.

The result of this study revealed that being female as household head was more likely to utilize LLINs as compared to male. This finding is consistent with the study done in the Ilu Galan District5, Raya Alamata regions of Ethiopia33, and Arbaminch town of Ethiopia34, which revealed that women were more likely to use LLINs than men. This may also be a result of Ethiopia's sociocultural heritage, which prioritizes women over men and when women’s become the head of househlds the pressure of male become minimized, and decided to utilize the LLINs independently. Additionally, this study was carried out in rural areas where better respect and priority can be given to pregnant women in consideration of cultural habits and practices in the communities to utilize the LLINs as not be affected by malaria.

Another result of the study showed that the number of separate rooms in the house of the participants were significantly associated with LLINs utilization. This finding is supported by the study done in East Belessa District7, Galan District5, Adama District21, and Bahir Dar City20. This might be attributed to the households that have few separate rooms in the house that may use LLINs than those households that have many separate rooms with large family members in the house which can lead to scarcity of bed nets for all separated rooms.

The duration of LLINs being utilized to be replaced was significantly associated with LLINs utilization among households. Three years duration of LLINs being used to be replaced was more likely to utilize LLINs as compared to less than 3 years duration of being replaced. The result of the finding is in line with the study done in Arbaminch town of Ethiopia34 and Northwest Ethiopia20. This might be due to those households who had a chance of getting new bed nets to replace the old bed nets may utilize long-lasting insecticide nets within family members and they may satisfied and more motivated to use new bed nets for the prevention of malaria disease.

Another result of this study showed that those households who had good knowledge about LLINs were four times more likely to utilize LLINs as compared to those who had poor knowledge. This finding is also consistent with the study conducted in Hawasa City and Southwest Ethiopia18,22. This could be explained by the fact that the likelihood of engaging in preventative measures would rise as households' knowledge and awareness of the disease's prevention mechanism of transmission, risk factors, severity, and individual prevention mechanisms grow. Furthermore, possessing strong knowledge and a positive comprehension of malaria prevention techniques sets off practices to utilize the LLINs. For this reason, behavioral change interventions aimed at promoting the members of households to adhere to malaria preventive programs through prioritizing sociocultural factors and universal education.

Limitations of the study

This study used cross-sectional study designs which does not show cause and effect relationship. Recall bias might have been introduced. Observation of the nets validated reporting on other study outcomes such as net use in the past night, washing frequency, and average income, among others, relied on self-reporting which is subject to response bias.

Conclusion and recommendation

The overall household level of LLINs utilization was found to be low as compared to the National standard of Ethiopia which is to be ≥ 85. The study identified that being female as households head, the number of separate rooms in the living house, the duration of long-lasting insecticide nets used to be replaced, knowledge status of the respondents were significantly associated with long-lasting insecticide nets utilization.Therefore, the West Arsi Zone Health Office and concerned stakeholders should work on strengthening the long-lasting insecticide nets utilization at the household level through the dissemination of information and appropriate education with sustainable behavioral change communication would be needed to improve LLINs utilization. Enhance training for volunteers, community structures, and religious leaders toward proper utilization of LLINs at the household level.