Insecticide-treated net ownership, utilization and knowledge of malaria in children residing in Batoke–Limbe, Mount Cameroon area: effect on malariometric and haematological indices

Globally, malaria is still a public health concern as 228 million cases of malaria occurred worldwide in 2018 compared with 251 million cases in 2010 and 231 million cases in 2017, with Cameroon accounting for 3% of the total number [1]. Also, an estimated 445,000 deaths was caused by malaria in 2016 and Cameroon alone accounted for 3% of this number [2], despite the control measures put in place [3‐5]. Insecticide-treated nets (ITNs) are effective tools for malaria prevention and have been shown to significantly reduce malaria episodes, severe disease, and malaria-related deaths especially among children aged less than five years in endemic areas [6]. At high coverage levels, ITNs provide both individual and community protection for both users and non-users by killing the Anopheles vector, thereby considerably reducing their longevity and entomological inoculation rate [7]. Lengeler [8] reported that ITNs had helped to reduce malaria episodes by 48–50% and in addition, Bhatt et al. [9], reported that between 2001 and 2015, malaria parasite prevalence in endemic countries reduced by 50%, with 68% of this decline attributed to the use of ITNs. Conversely, some studies have reported an increase in malaria parasites after increasing the coverage of ITN [10‐12].

In 2018, the World Health Organization (WHO) [1], reported that 50% of the people at risk of malaria in sub-Saharan Africa slept under an ITN, with half of the population being protected by this intervention, an increase from 29% in 2010. In order to achieve the Abuja target of 80% usage and reduce malaria burden in Cameroon, so far, progress has been made in the distribution of long-lasting insecticidal nets (LLINs), particularly through campaigns for more than 8 million to 12 million LLINs were distributed between 2011 and 2016 [13]. Yet, proportions (18.2%) of these nets are used for other purposes, such as fishing, nursing seeds and football nets [6]. In some cases, they are not used at all for varied reasons such as heat, the feeling of being in a coffin, dislike of colour or pregnant woman keeping it to use for the new-born. So, ownership does not necessarily translate to utilization. Therefore, this could undermine the aim of the 2016 net distribution campaign. Studies carried out in the Mount Cameroon area reported a higher proportion of households with at least one ITN (77.6%), with a low bed space coverage of 58.5% [14], indicating that coverage defined by the WHO as one ITN for every two persons remains a challenge. Furthermore, several intervention studies have been carried out on malaria and some enhanced control measures [4, 5, 15] in the Mount Cameroon area, and the findings revealed ITN efficacy in reducing malaria parasite infection, although such drop may not be homogenous across the country. However, there are also concerns on the increasing pyrethroid resistance, which is likely to affect LLIN efficacy in preventing malaria parasite infection. Even though a study in Cameroon [16] as well as various studies in Malawi [17], Benin [18, 19] and several countries in Africa [20] reported that LLINs still offers some protection even in areas of high pyrethroid resistance, there is need for continuous surveillance and evaluation on the effective use of LLINs distributed by the Cameroon government and its partners to reduce malaria mortality and morbidity.

Irrespective of the increased ownership of ITNs/LLINs, a decrease in malaria transmission or morbidity is still to be appreciated especially as Cameroon is reported to harbour the five most efficient and common malaria vectors (Anopheles gambiae, Anopheles arabiensis, Anopheles funestus, Anopheles nili and Anopheles moucheti) [21]. Moreover, the effective control of malaria within a community is affected by their cultural beliefs [22, 23]. In addition, Tyagi et al. [23] reported that community knowledge about malaria causation, symptoms, treatment and prevention has been linked to the inability of malaria programs to achieve sustainable control. It is thus imperative to evaluate the influence of the ownership and utilization of treated mosquito bed nets, malaria knowledge and it influence on the malariometric and haematological indices in children living in a malaria endemic zone, such as Batoke–Limbe, in the Mount Cameroon area.

Insecticide-treated net use is a well-established malaria control intervention recommended in malaria endemic countries around the globe. Considerable progress with the use of interventions such as ITN and use of artemisinin-based combination therapy has been made in the past decade in reducing the burden of malaria in Africa, with Cameroon inclusive [4, 9]. The objective of this study was to determine the impact of ITN ownership and utilization as well as knowledge of malaria on malariometric and haematological indices in children in Batoke, a malaria meso endemic coastal town in the Mount Cameroon area.

The overall malaria parasitaemia of 46.7% in the population confirms earlier findings of the meso-to-hyper endemicity of malaria in the Mount Cameroon area [31, 32]. The observation is similar to the 47.5% reported by Sumbele et al. [31] among children less than 15 years in this lowland area and a 45.3% reported by Eyong et al. [32] in pupils between 4 and 16 years in other areas in the Mount Cameroon area. In addition, a similar prevalence (45.47%) was reported among school children in the Littoral Region, another coastal area of the country [33]. Worthy of note is that, this prevalence is lower than the 60.5% obtained by Ndamukong-Nyanga et al. [34] in a lowland study in the Mount Cameroon area. On the contrary, lower prevalence of 27.7% [35], 29.6% [15] and 32.9% [36] among a similar age group was reported in higher altitude areas, in the Mount Cameroon area and the Northern part of the country, respectively. This reveals that malaria remains a major cause of illness during childhood and the prevalence in this part of the country is not on a speedy decline. In addition, Batoke is at a lower altitude and several studies have reported that malaria prevalence is higher in lower altitude compared to their higher altitude counterparts [24, 25].

Interestingly, higher prevalence of the malaria parasite in children of the 5–9 years’ age group was consistent with the findings of Apinjoh et al. [15] within the same age group in the Mount Cameroon area. Also, higher prevalence among children aged 5–15 years compared to the under-five age group in this area has been reported by Ebai et al. [37]. Additionally, in another part of the Mount Cameroon area, Bate et al. [38] reported higher malaria prevalence among children aged 5–10 years when compared to their contemporaries. The epidemiological shift in malaria burden from the under-five age group to the 5–9 years age can be attributed to the playful and adventurous nature of children of this age group in the fields, which exposes them to the malaria vector. Another possible reason for this epidemiological shift in malaria prevalence from the less than five to the 5–9 years age group could be as a result of intensive malaria control including free LLINs distribution and ACT for less than five age group in all government health centres in Cameroon as decreed by the Head of state. Furthermore, the reduced malaria prevalence in the < 5 age group could be associated to parental guidance, bed sleeping time of the children of this age group and reinforcement on the proper use of these ITNs compared to the 5–9 age groups whose maternal care would have reduced and are more independent and less likely to use the ITNs.

Even though malaria parasite prevalence was lowest in the < 5 years age group, children in this group had the highest GMPD. The findings are in line with those of Achidi et al. [39]; Udoh et al. [40]; Bate et al. [38] carried out in Cameroon and Nigeria. Children under five years are more vulnerable to the disease in areas of high transmission [41] and it is often associated to the poorly developed immune system in this age group [42]. Observations from this study did not report any association between gender and Plasmodium infection, consistent with studies by Kwenti et al. [43] and Mbohou et al. [44] in other parts of the country.

The overall knowledge of malaria (i.e. mode of transmission, signs and symptoms, effects and control measures) in the study area is very low. Similar results were obtained by Birhanu et al. [45] in Ethiopia, whose study revealed that local understanding of malaria was unsatisfactory and very limited. Higher educational level was significantly associated with the knowledge of malaria. The findings are in congruence with those of Yaya et al. [46] who reported the likelihood of having accurate knowledge of malaria increased as the educational level increased. Additionally, Ndibuagu et al. [47] reported respondents with formal education had significantly better knowledge of malaria than those without formal education. Higher levels of education are generally associated with improved knowledge in relation to appropriate prevention and treatment strategies [3]. Consequently, this justifies the findings which revealed a higher prevalence of malaria parasite among children whose parents/caregivers were less educated. Therefore, they will put in less protective measures to reduce exposure thus preventing Plasmodium infection [48].

The prevalence of anaemia (54.6%) in children less than 15 years underscores the high burden of anaemia among the population in this area. However, this prevalence is lower compared to the 72.7% reported by Teh et al. [35] and the 62.0% and 75.3% reported by Sumbele et al. [4, 49] respectively, in the Mount Cameroon area. It is also lower than the national value of 62.5% [50]. It was however higher than the 44.8%, 49.6% and 44.7% reported by Njunda et al. [51], Bate et al. [38] and Tientche et al. [52] respectively in different locations in the Mount Cameroon area. The higher prevalence of anaemia in the population could be attributed to the burden of malaria in the population. A recent study [53] in 16 sub-Saharan African countries including Cameroon showed that anaemia is an important indicator for monitoring malaria burden.

Children of the < 5 years age group had a significantly higher occurrence of anaemia compared to their counterparts. The higher prevalence could be linked to the higher Plasmodium density observed in this age group. Similar findings were also reported by Sumbele et al. [49]. Udoh et al. [40] reported that, anaemia due to malaria is more severe in younger children in areas of intense transmission. Likewise, there was a negative correlation between Hb and malaria parasitaemia, further indicating that high parasite load causes more destruction of RBCs, consequently decreasing haemoglobin levels leading to anaemia.

The proportion of bed net possession was 78.8% among the children. The coverage rate was slightly lower than the WHO recommended 80% for acceptable protection. This ownership frequency is higher than the 63.5% obtained by Fokam et al. [5] in another part of Cameroon. Also, the ownership frequency was higher than that obtained in other countries, such as Angola (52.0%), and may be accounted for by the fact that during the free distribution campaign in Cameroon, all households were included, unlike in Angola where the distribution exercise was targeted [54]. With respect to utilization, 50.9% of the children had at least used a net the previous night, with an effective utilisation rate of 29.9%. These findings are in line with those of Fokam et al. [5] who reported that, there was a negative association between bed net ownership and utilization by households as bed net ownership was high and utilisation of these nets was low. Furthermore, Inungu et al. [55] in a study in the Democratic Republic of Congo reported lower utilization rates although ownership proportions were quite high (81.6%). These findings are not in conformity with those of Ntonifor and Veyufambom [6], where in a study carried out in the high western plateau part of the country observed that, most of the respondents that had nets usually sleep under them.

Observations from the study demonstrated significantly lower prevalence of malaria parasitaemia in children who effectively utilized the ITNs. This finding corroborates those of Ntonifor and Veyufambom, [6]. Insecticide-treated net is a highly effective means of preventing malaria vector transmission through a physical and chemical barrier, thereby reducing associated malaria morbidity and mortality, particularly in endemic areas [8]. Since transmission takes place mainly at night and, therefore, inside the house, the effective use of LLINs offers a degree of protection against the female Anopheles mosquito thus preventing malaria transmission [56].

This study confirms that haematological changes including RBC and its indices, are common complications encountered in Plasmodium parasite infection in children. Although malaria parasitaemia was not significantly associated with WBCs. The mean WBC counts in malaria infected and negative groups were normal and is in line with other studies [57]. Nevertheless, normal WBC counts are not enough to clearly indicate freedom from underlying disease. A differential analysis of the individual WBC counts which was a limitation of this study could have given a more precise blood picture. However, the finding contrasts those of Kimbi et al. [58] who indicated that as malaria parasitaemia rises in blood, the amount of WBC also rises. Moreover, Kotepui et al. [59] and Sumbele et al. [60], reported a lower amount of white blood cell count with increased parasitaemia.

Children who used ITN had significant higher mean Hb levels, RBC count, MCHC, RDW-CV and Plt count compared to those who did not use ITNs. Based on the results of the linear regression model, it was observed that ITN use had a significant influence on WBC, Hb, RBC, Hct, MCHC, RDW-CV and Plt. The significantly higher Hb, RBC, MCHC, RDW-CV and Plt count in ITN users than non-users, may be as a result of the protective efficacy of the ITNs that prevents the ITN users from the bite of the Anopheles vector thereby preventing them from contracting the Plasmodium infection, which has been proven in several studies [58, 61, 62] to reduce the haematological parameters of children. This finding corroborates with results of Maina et al. [61] and Kotepui et al. [59] who reported that; red blood cell counts, haemoglobin and platelets counts were significantly lower in malaria positive children than negative children. The significantly lower RBCs in malaria positive children than negative children could be associated with haemolysis, cytoadherance, rosetting, clumping [63]. Furthermore, significantly lower levels of haemoglobin in malaria positive than negative children can be attributed to the digestion of haemoglobin by erythrocytic stages of the malaria parasite.

The age of the children had a significant influence on MCV, MCH, RDW-CV and Plt counts. Likewise, the gender had a significant influence on the WBC counts, Hb and RDW-CV of the children. The results are in line with those of Onwurah et al. [64] who reported that age and gender have an effect on the haematological parameters. This study suggests that changes in haematological parameters accompanied with age and gender may depend on the population and geographical area studied [65] and, therefore, reference values validated for one country should not be assumed for application in population from other countries [66].

As a limitation, the study did not explore other personal and behavioural factors such as attitude, beliefs and perception regarding the role of ITN and health care-seeking which have been reported to influence behaviours.