The presence of malaria and anemia in pregnancy, regardless of the gestational stage, are potentially harmful to both the fetus and mother as well as to the family and community [2–7, 28, 29]. Our study provides insights into the extent of asymptomatic MiP and its corollary, anemia, at the community level (i.e., pregnant women surveyed in their own family home) throughout different malaria transmission periods of the year.
Our study findings show that the prevalence of asymptomatic MIP and anemia at the household level was high. This prevalence increased significantly during the high transmission season. In addition, our study shows that asymptomatic MiP was strongly associated with maternal anemia, and the risk of MiP was significantly higher among young women, first pregnancy, and during the first trimester of pregnancy.
The prevalence of asymptomatic carriage found in our household-based study was lower compared with the estimated prevalence reported in previous studies, where it was reported to range from 19–51%, among pregnant women attending health facilities as part of their ANC in Burkina Faso [18–21]. However, the overall aggregate prevalence of asymptomatic MiP (11.0%) reported in our study corroborates the results (12.2%) from the COSMIC household-based survey conducted in Burkina Faso between March 2014 and January 2016 [22, 30]. In addition, the prevalence of asymptomatic malaria at the community level during the low transmission season was slightly lower in our study compared to the prevalence of 9.1% reported from a community-based study conducted in Ethiopia during the minor (“low”) malaria transmission season . Therefore, our results underline the need for maintaining effective prevention measures throughout the entire course of pregnancy. These results showed that pregnant women living in Burkina Faso (or other SSA countries) are consistently exposed to malaria risk and its harmful consequences at any time of the year. However, the highest risk of asymptomatic carriage in our study occurred among younger women (primi- or secundigravida), in the second trimester, and during the high malaria transmission season. These risk factors have been documented in other previous studies [8, 18–20, 25, 26, 32–34]. Thus, it is crucial to explore supplementary measures that could increase the chance of accurately detecting and treating MiP by taking into account these risk factors. From this perspective and according to the WHO recommendations , several countries, including Burkina Faso, have set up strategies involving community-based health workers (CHWs) whose tasks include community-based sensitization activities, conducting malaria home diagnoses by RDT, and treatment of uncomplicated malaria within their respective communities [22, 36].
Our study showed a high prevalence of anemia among pregnant Burkinabe women living in their communities, though this prevalence was lower compared with the prevalence among pregnant women attending health facilities as part of their ANC [20, 21]. Although the literature states that nutritional deficiencies, particularly of iron and folic acid, are associated with anemia, the highest proportion of pregnant women with anemia in our study were mainly in the second trimester of pregnancy (Adj. PR: 1.52; 95%CI: 1.31–1.76) and during the high transmission season. The difference in prevalence of anemia observed during the transmission season (especially between 2013/2014 and 2017) could be explained by the food shortage period in Burkina Faso in 2017. In addition, in our context, malaria (sequestration of parasitized red blood cells in the placenta), second trimester of pregnancy, and the high malaria transmission season may not be the only causes of anemia in pregnant women. Indeed, the causes of anemia during pregnancy in developing countries are multifactorial and may be a result of other co-morbidities (worm infestation), complication events (placenta previa, placental abruption, etc.), chronic diseases (HIV, sickle cell disease, and TB), or nutritional deficiency (inadequate intake of iron and folic acid and/or inadequate iron + folic acid supplementation) [37–43]. Appropriate community-based strategies to prevent anemia in pregnancy can help to significantly reduce the occurrence of maternal anemia and, thereby, avoid progression to fatal outcomes. In this respect, the capacity of CHWs should be strengthened to allow them to carry out targeted sensitization of the risk factors leading to anemia, ensure effective adherence to preventive measures among the community, detect clinical signs of anemia (pallor, fatigue, bleeding, etc.), and direct people to a health center for appropriate clinical management (such as administering of a double dose of iron) .
Although our findings provide an overview of the extent of asymptomatic malaria and anemia in pregnant women at the community level, both during the high and the low transmission seasons in Burkina Faso, some potential limitations need to be considered. First, we defined asymptomatic carriage of malaria parasites using a malaria RDT, which could lead to underestimation (due to false negatives) or overestimation (false positives) of the true prevalence. False negatives from the malaria RDT may be due to the detection threshold of the test (around 200 parasites/µL) . Regarding the false negative results, some studies found that more than half of all false negatives were in cases of parasitemia in which the detected antigen was under the detection threshold (i.e., lower density). False positives could be due to prolonged antigen circulation following clearance of malaria parasites. Indeed, it was shown that HRP2 antigens can persist in the bloodstream of pregnant women for up to four weeks after successful treatment . However, in high-transmission areas such as Burkina Faso, HRP2 RDT could be a useful tool for malaria diagnosis, since previous studies found its performance was better than that of microscopy when used in pregnant women . Second, the cross-sectional study design did not allow us to determine cause and effect. Third, the two survey periods (not overlapping) did not allow us to compare outcomes over time, although this was not in the scope of this study.