Effects of long-lasting insecticide net (LLINs) ownership/ utilisation indicators on annual household malaria episodes (AHMEs) in Bamenda, Santa and Tiko Health Districts in Cameroon

Introduction : Household residents in malaria endemic areas are at high risk of multiple malaria episodes per year. This study investigated the annual household malaria episodes (AHMEs) in three health districts in Cameroon. Methods : A community-based cross-sectional household survey using a multi-stage cluster design was conducted 2 – 3 years post campaign to assess long-lasting insecticide net (LLINs) ownership, utilisation and maintenance as well as demographic characteristics. Multinomial regression analysis was used to identify factors associated with household LLIN ownership, utilization and AHME. Results : Household LLINs ownership, de facto population with universal utilisation and AHME were respectively, 92.5%, 16.0% and 83.4%; thus, 4 out of 25 household residents effectively used LLINs the previous night. AHME was significantly ( p < 0.05) associated with age and gender (OR; 1.6, 95% C.I; 1.1 – 2.3) of household head, health district (OR; 2.8, 95% C.I; 1.1 – 7.2) and tiredness (OR; 2.6, 95% C.I; 1.0 – 6.3). LLINs ownership and insufficiency also significantly contributed AHME. The overall average cost for the treatment of malaria was 6,399.4±4,892.8Fcfa (11.1±8.5US$). Conclusions : The proportion of households with at least one LLIN and those with at least one AHME were high. Findings are of concern given that average cost for the treatment of malaria represents a potentially high economic burden. The results outlined in this paper provide an important tool for the examination of the deficiencies in LLINs regular and universal utilisation.


INTRODUCTION
Studies have identified the factors influencing the ownership and utilisation of longlasting insecticide nets (LLINs) [1][2][3][4][5][6][7][8][9] in and out of Cameroon.The utilisation rate of LLINs, especially amongst children less than five years old and pregnant women are widely low [2,3,10].In malaria-endemic countries, malaria rates are still high, especially amongst the vulnerable population [11].Malaria is a preventable and curable disease transmitted by the bites of female Anopheles mosquitoes [11,12] and a serious global public health problem with an estimated 216 million cases in 91 countries in 2016 [12][13][14][15].90% of all worldwide estimated malaria cases and 91% of deaths in 2016 occurred in 15 African countries alone contributing 80% of all cases [11,13].The prevalence of malaria is 29% [16] and 15.0% in the North West and 46.1% in the South West Region amongst children under five in Cameroon [17].
The determinants of LLINs ownership, coverage, accessibility and utilisation are multiple and their contributions vary according to geographical location, sample size and season of study [1,8,[18][19][20].Indicators of LLINs ownership and utilisation involve differences between health districts/ localities, socio-demographic and economic statutes [10,21,22].
The effective utilisation of LLINs has been reported to be invariably associated with ownership [4,23], although annual household malaria episodes (AHME) is not primarily related to LLINs ownership.It is thought that poor LLINs utilisation by mostly the vulnerable is mostly due to behavioural attitudes of the population [6,7,24], while the persistence of malaria is due in part to, underutilisation of LLINs, other preventive methods and negligence as well as vector resistance.
Studies in Cameroon and beyond have shown consistently that malaria is, and remains a public health problem [10,15,17].Thus in this study, the question is, "In health districts with high malaria endemicity and high LLINs ownership, what is the proportion and determinants of AHME, 2 -3 years after the mass distribution campaign (MDC)?".

Study area
The study was carried out in BHD, SHD and THD which constitute part of the most impoverished populations in Cameroon.These health districts are located in the North West and South West Regions of Cameroon.The characteristics of the study area have been described elsewhere [25].

Sampling design
This study is part of a prospective cross-sectional survey carried out in the THD in July and June 2017 and in Bamenda and Santa Health Districts in March to May 2018 [25].

Sample size determination
A minimum sample size of 385 for each health district was calculated with the assumption that 50% of households suffered at least one AHME in the past one year and with 95% confidence interval, with an acceptable margin of error for proportion being estimated to be 0.05 [26].

Recruitment procedures and measures
At enrolment, a structured questionnaire was used to record ownership of LLINs, utilisation of LLINs and socio-demographic characteristics as well as housing and AHMEs.

Outcome variables
The main LLIN outcome variables were;

LLINs ownership indicators:
LLINs ownership: proportion of households with at least one LLIN, where the numerator comprises the number of households surveyed with at least one LLIN and the denominator, the total number of households surveyed [9].Coverage: proportion of households with at least a LLIN for every two people, where the numerator comprises all households where the ratio between number of LLINs owned and the number of de jure members of that household, that is, usual members excluding visitors, is 0.5 or higher and the denominator is the total number of sampled households.Access to LLINs within the household: proportion of population with access to LLINs (population that could sleep under a LLIN if each LLIN in the household were used by up to two people) and proportion of the de facto household population that slept under a LLIN last night.De facto household members are all people present in the household on night of the survey including visitors [27][28][29].

LLIN utilisation indicators:
Household universal utilisation: proportion of population that slept under a LLIN the previous night [27][28][29].By the vulnerable population in the household: proportion of children under five (or pregnant women) that slept under a LLIN the previous night [27].Regularly sleeping under bed nets: household heads who reported habitually using nets on a daily basis [30].Household head slept under a LLIN last night: proportion of households in which the household head slept under a LLIN last night, where the numerator comprises the number of households surveyed wherein the household head slept under a LLIN last night and the denominator, the total number of households surveyed.

Annual household malaria episodes (AHME):
proportion of households which experienced at least one malaria episode in the last one year, where the numerator comprises the number of households surveyed wherein at least one household member suffered a malaria attack and the denominator, the total number of households surveyed.

Independent variables considered for association with LLIN ownership, use and AHME
were age, gender, marital status, education, occupation, health district, house type and household composition.

Statistical analysis
Data were analysed with IBM-SPSS Statistics 21.0 for windows (IBM-SPSS Corp., Chicago USA).The Chi square (χ 2 ) test was used to compare socio-demographic characteristics with the AHME and multivariate logistic regression to identify significant correlates of the main outcomes.The level of statistical significance was set at p < 0.05.

Ethics statement
The study, obtained approval from the Institutional Review Board of the Faculty of Health Sciences, University of Buea (N o : 624-05).Administrative authorisation was obtained from the South West Regional Delegation of Public Health.Written informed consent was obtained from all participants and confidentiality was maintained at all steps of data collection.

Characteristics of study participants
A total of 1,251 household heads were surveyed, in the three health districts.The mean (±SD) age of study participants was 36.1 ±10.8, while the overall mean (±SD) household size was 4.7 ±2.1 members: 4.6 ±2.2 in BHD, 4.5 ±1.7 in SHD and 5.0 ±2.5 in THD.The overall mean AMHE was 2.2 ±1.7: 3.1 ±1.8 in BHD, 1.4 ±1.1 in SHD and 2.0 ±1.5 in THD.There was a significant association between AHME and house type as well as health district.Most (68.0%) households were headed by females, while majority (54.8 %) of the respondents were married.About 37.6% of the study participants had attained at least secondary education and only 9.3% had no formal education (NFE).The greater percentage (35.3%) of the respondents was realised to be doing unskilled labour.AHME was frequent (89.2%) in households with surrounding bushes/ farms or water pools (Table 1).Pregnant women were recorded in 93 (7.43%) of the households and children under the age of five in 766 (61.23%) of the households.Of the 5,870 individuals (de facto population) covered in the study, 4,908 (82.2%) spent the night in the 1,043 households which had suffered at least an AHME.

Ownership and utilisation of LLINs
A total of 2,958 LLINs were enumerated in the three health districts, overall LLINs density of 2.4 ±1.4.LLINs ownership, coverage and accessibility were 92.5%, 66.7% and 69.1% respectively.The utilisation rates were 14.6% for children less than five years old, 4.7% for expectant mothers and 16.0 % for entire households.

Determinants of household ownership and utilisation of LLINs
To investigate the determinants of LLINs ownership, coverage as well as utilisation in the three health districts, multinomial logistic regression was performed allowing adjustments for possible confounders.Households in the SHD (OR; 3.7, 95% C.I; 1.9 -7.5, p <0.001) were significantly associated with LLINs ownership (Table 3).A majority of households with at least one LLIN (36.1%; 418/1,157) were found in the BHD, while (32.2%; 372/1,157) were in the THD.The difference was statistically insignificant (p =0.243).Secondary educational status, occupational status and family size of 1 -4 members were significantly (p >0.05) not associated with the ownership of at least one LLIN per household.
Being a household head in all the age groups except 31 -40, female, primary and secondary education, BHD and SHD and with no environmental factor were significant determinants associated with the use of LLINs by all children 0 -5 years old in the household (Table 3).It is worth noting that the majority of the households with heads in the age group 21 -30 (35.4%; 184/520), females (68.7%; 357/520), secondary education (37.3%; 194/520) and BHD (48.1%; 250/520), had all children 0 -5 years using LLINs compared with the other groups.Similarly, there was a significant association between household heads in the 21 -30 years age group, BHD, families with sizes 1 -4 and 5 -7 members in the household and the use of LLINs by the entire household.

Determinants of annual household malaria episodes
AHME was associated to age of household head whereby households whose heads were 20 years old had the fewest AHMEs (p = 0.003) (Table 5).Multinomial analysis showed that the 6US$ in Cameroon [35], 4.9 -5.1US$ in Ghana and Ethiopia [44,45].The differences in the cost of the treatment of malaria might be due to, study designs, sample size and time of the study.

RECOMMENDATIONS
The Ministry of Health together with stakeholders should intensify education on the effective use of LLINs by all in the household, especially the vulnerable populations.

Strengths
The data used in this study was collected by trained surveyors, who had mastery of all the health areas in the study area.All the health district offices were consulted for the mapping of the health areas, quarters and census list of households used in the last MDC and Expanded Programme on Immunisation (EPI) campaigns.The quality of data collected was assured through the multistage sampling strategy to minimize bias and pretesting of questionnaires.

Limitations
This was a cross sectional community based study, carried out only in three health districts.Data was collected through self-reporting, with neither question on expenditure on malaria, nor one on diagnosis and type of malaria, rather, there was a question on the AHMEs.
In the calculation of the average expenditure on malaria, we did not distinguish simple from severe malaria.

CONCLUSIONS
In conclusion, the proportion of households with at least one LLIN and those with at least one AHME were high.The average cost for the treatment of malaria in the North and South West of Cameroon represent a potentially high economic burden, mainly to the Internally Displaced Persons and to the national economy as a whole.An implication is that increasing the universal