Patterns of malaria indices across three consecutive seasons in children in a highly endemic area of West Africa: a three times-repeated cross-sectional study

Abstract

ObjectivesTo study the manifestations of Plasmodium infection, and its relations with the malaria disease, especially when comparing dry and rainy seasons in a hyperendemic area of West Africa.MethodsThe study was carried out in an area where malaria transmission is high, showing important seasonal variations. One thousand children, representing the total child population (1–12 year old), were observed transversally at the end of three consecutive seasons (dry/rainy/dry). The usual indicators, such as parasite density, splenomegaly, anaemia, or febrile disease were recorded and analysed.ResultsThe prevalence of Plasmodium falciparum was high in all age groups and seasons, constantly around 60%. The high transmission season (rainy) showed higher rates of anaemia and spleen enlargement and, in the youngest children only, higher parasite densities. There were also differences between the two dry seasons: in the first one, there was a higher rate of fever than in the second one (p < 0.001). Low parasite density (<2,000 p/μl) was never associated with fever during any season, raising some concern with regard to the usefulness of parasite detection. The possible origins of fever are discussed, together with the potential usefulness of analyzing these indices on a population sample, at a time when fever incidence rises and malaria is one potential cause among others. The distinction to be made between the Plasmodium infection and the malaria disease is highlighted.ConclusionsThese data confirm previous hypotheses of a strong difference in malaria infection and disease between dry and rainy seasons. The most relevant seasonal indicator was not mainly parasite rate and density but anaemia, spleen enlargement, prevalence and possible origin of fever.RecommendationsIn any situation (i.e. fever or not) and especially during the dry season, one must consider that detection of parasites in the blood is only evidence of a Plasmodium infection and not necessarily of a malaria disease. In such a situation, it seems suitable to obtain, through national malaria teams, a well-defined situation of transmission and prevalence of Plasmodium infection following zones and seasons, in order to adapt control strategies. For researchers, a systematic management of data separately for dry and rainy season appears mandatory.

Seasonal Depiction of Malariometric Indices in Children under Five Years in a Sudanese Semi-urban Area of Burkina Faso

“…However, the parasite prevalence in dry season (about 20 -26%) falls in the range of meso-endemic area and confirms the seasonality of the disease. These results corroborate those of some malariometric studies conducted in similar geographical areas [14,26,27,28].…”

Comparing hemoglobin distributions between population-based surveys matched by country and time

“…Given that some paired surveys were conducted in different seasons, it is possible that malarial seasonality may have played a role in these differences. Specifically, lower levels of anemia are typically found in the dry season and higher levels in the rainy season in places with high burden of malaria [8][9][10]. However, the paired surveys with the largest difference in anemia estimates (61% versus 30% in Malawi) were conducted within weeks of each other.…”

Single low-dose primaquine for blocking transmission of Plasmodium falciparum malaria – a proposed model-derived age-based regimen for sub-Saharan Africa

“…40–60%) across all malaria transmission intensities [ 68 – 73 ], but tend to be lower in low-transmission settings [ 69 , 72 ]. Anaemia is inversely related to age in healthy individuals, asymptomatic falciparum carriers and malaria patients independent of malaria transmission intensity [ 68 , 74 , 75 ]. Table 3 shows Hb data in children aged <5 years from a community survey in the Kenyan highlands (low transmission) [ 68 ], and Table 4 shows Hb data in P. falciparum -infected patients of all ages from several African countries (database used in this analysis).…”