In endemic countries, malaria is a major public health problem, particularly in low-income countries [15]. Despite the complexity of the interaction between malaria, anemia, and nutritional status [1], understanding their relationship is vital for the development of strategies that will reduce child morbidity and mortality. Using repeated cross-sectional surveys and passive case detection at a community health center for five successive years, our study examined the relationship between anemia, underweight, and multiple malaria episodes among children under the age of five in Dangassa.
Based on our baseline descriptive data we found that symptomatic malaria cases varied between SSCs. The number of cases was higher at the end of the rainy season than at the beginning. In malaria-endemic areas, the parasite density is usually higher at the end than the start of the rainy season [16]. During this period, the entomological inoculation rate is particularly high [17]. Toure et al. (2016) in Sélingué, Mali [18] showed that malaria is seasonal in Mali, with a peak at the end of the rainy season. However, in 2013 a single SSCs was carried out in February after the enrolment of the study participants in 2012. Despite the survey being conducted during the dry season, the prevalence of symptomatic malaria was 15.6%, which is quite high compared with the prevalence at the start of the transmission season, i.e., 6.9–15%. Since Dangassa is a riverside village where transmission is particularly prolonged (5 to 6 months), high spatial and temporal clustering of P. falciparum infection during the dry season has been demonstrated [19].
As a baseline, asymptomatic children were selected at each SSCs as a baseline, and this allowed the number of malaria episodes were counted and categorized as 0, 1 episode and 2 + episodes for each child. The percentage of zero malaria episodes in the follow-up period from June to November 2015 indicated a significant difference according to anemia status. Anemia is a major cause of malaria in tropical areas and is also an additional indicator for monitoring the burden of malaria in the community [20], this finding despite the high malaria transmission period could be attributed to the introduction of seasonal malaria chemoprevention in Dangassa in 2015 [21]. Indeed, studies have shown a positive impact of seasonal malaria chemoprevention (SMC) on reducing malaria transmission and malaria indicators such as anemia in children in West Sahelian Africa [22, 23].
The incidence peak in our study was observed in 2013 during the period of high transmission (June to October), with respectively 65 children ((IR = 95.73 in 1000 person-months) for multiple episodes and 24 cases (IR = 35.35 in 1000 person-months) for those with 1 episode. Most malaria cases detected by PCD in Dangassa are symptomatic and occur during the five- to six-month transmission season (June to November) [24]. Also, Ateba F et al in 2020, reported a higher number of cases during the period when SMC was not distributed compared with the period when SMC was implemented in the same area [25].
However, the frequency of malaria episodes decreased significantly between 2013 and 2017 in our cohort. As a result, i) the intensification of malaria control strategies in Dangassa, including the distribution of LLINs and the introduction of SMC, have significantly reduced the burden of malaria in Dangassa [26]; ii) Community sensitization and participation in the study; iii) Qualified staff deployed within the framework of the International Centre of Excellence for Malaria Research in West Africa (ICEMR-1) project, the basis of this study, for the passive case detection of malaria at the health center; iiii) Health center use by residents.
According to our results, underweight is associated with a higher number of episodes compared to normal children 10% error (OR = 1.46, 95% CI [0.95–2.23], p = 0.084). Almeida M. et al in 2015 [27], in a rural community in the Amazon region, demonstrated that malaria-induced anorexia and vomiting during the acute phase of the disease, associated with insufficient micronutrients, in children under five years of age in a specific endemic context, could lead to a delay in the child's physical development after several episodes of malaria.
The adjusted model showed a significant association between multiple episodes in anemic and normal children (OR = 1.6, 95%CI [1.12–2.30], p = 0.011). Thus, in high transmission areas such as Dangassa, where the disease is prevalent, many young children are anemic, and people infected with the disease may receive a single bite each day, exposing them to repeated episodes of the disease. Consequently, in these contexts, severe malarial anemia (hemoglobin < 7g/dl) [28], in young children, a blood transfusion is required, which characterizes a compromised rapid recovery of the anemia, since malaria infection causes hemolysis of parasitized and non-parasitized erythrocytes, and dyserythropoiesis of the bone marrow [29].
The occurrence of multiple episodes was significantly associated with anemic and underweight children during the low transmission period. Anemia has a complex etiology, including single- and multifactorial causality [30]. Thus, the high occurrence of malaria in Dangassa during the low transmission period in anemic and underweight children is associated probably through protein-energy and vitamin deficiencies. from the Democratic Republic of Congo, Aimée M and al in 2018, reported that iron deficiency can negatively affect children's weight growth [31]. Mariken and al in 2021, measuring the association between nutritional status and malaria incidence in young children before the malaria transmission season, found that, underweight was associated with a higher incidence of clinical malaria in Burkina Faso [32].
We found that the risk of having multiple malaria episodes during the high transmission period was 3.23 times higher than during the period of low transmission (CI [2.45–4.26]; p = 0.000). Although the number of multiple malaria episodes increase following exposure to malaria transmission, the rainfall, which is low during periods of low transmission and high during periods of high transmission, is an important factor in the dynamics of malaria transmission. Toure M et al (2016) reported the same results and showed a clear seasonal pattern, with a reduced below 50% malaria incidence during the dry season.
The study has the limitation that, because the data were analyzed secondary, some anthropometric parameters needed to determine children's nutritional status were not collected. Consequently, some variables related to these indices were not able to be incorporated into our data analysis.