Briefly, antibody responses were considered positive if the optical density ratio (OD ratio?=?mean OD value of sample divided by mean OD value of na?ve sera) was above two. Statistical analysis Antibody levels comparisonComparisons of OD ratio of antibody responses were assessed using KruskalCWallis rank test and this has been presented in a previous study [39]. declining malaria transmission. In addition, the validity of this model was evaluated by comparison with the alternative model. Methods Five cross-sectional surveys were carried out at the end of the wet season in Dielmo, a malaria-endemic Senegalese rural area in 2000, 2002, 2008, 2010 and 2012. Antibodies against schizonts crude extract of a local strain adapted to culture (schizonts crude extract were estimated for each cross-sectional survey and were found strongly correlated with EIR. High variability between SCRs from cross-sectional and longitudinal surveys was observed. In longitudinal studies, the alternative catalytic reversible model adjusted better with serological data than the catalytic model. Clinical malaria attacks and malaria control interventions MT-4 were found to have significant effect on seroconversion. Discussion The results of the study suggested that crude extract was a good serological tool that could be MT-4 used to assess the level of malaria exposure in areas where malaria transmission is declining. However, additional parameters such as clinical malaria and malaria control interventions must be taken into account for determining serological measurements for more accuracy in transmission assessment. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-2052-0) contains supplementary material, which is available to authorized users. Background Falciparum malaria remains a public health priority and a major cause of morbidity and mortality in tropical areas [1]. The observed pathophysiology of malaria contamination is usually strongly dependent upon endemicity, age and level of immunity [2]. In malaria endemic areas, where transmission is SIGLEC7 usually perennial and stable, parasitic tolerance has been described and explained by a partial immunity acquired over years [3, 4]. Age is usually, MT-4 therefore, a major indicator of the duration of exposure to malaria parasite. However, acquired immunity is not completely protective but can be effective against clinical symptoms and severe form of the disease [5]. Several interventions have been implemented during the two last decades in the fight against malaria. These interventions include treatment by artemisinin-based combination therapy (ACT), use of long-lasting insecticide-impregnated bed nets for uncovered populations and use of rapid MT-4 diagnostic assessments for malaria diagnosis. These interventions led to considerable reduction in the number of clinical episodes and deaths due to malaria [1]. Despite the significant progress achieved, the disease remains a major problem. The World Health Business (WHO) reported 212 million clinical malaria cases and 429,000 deaths in 2015. Children under 5?years old are particularly susceptible to malaria illness, infection and death. In 2015, malaria killed an estimated 303,000 under-fives globally, including 292,000 in the African Region [1]. Monitoring malaria transmission intensity and strengthening malaria control steps are necessary since incidence of severe disease and mortality increase with transmission intensity [6C8]. The ongoing changes in malaria endemicity become a key determinant of the progress achieved. Moreover these changes determine the time required to reach the step where elimination could be foreseen [9]. Standard measurements of malaria transmission based on entomological inoculation rate (EIR) and parasite prevalence are expensive, time-consuming and lack of precision because of micro-heterogeneity of malaria transmission [10C12]. In addition, both EIR and parasite prevalence are affected by seasonality [13, 14]. Furthermore, assessing malaria transmission intensity and evaluating the impact of interventions are complicated in areas where transmission has been substantially reduced. Therefore, option approaches are required to assess malaria transmission and evaluate intervention programmes. The use of mathematical models and prevalence of anti-malarial antibodies constitute alternative approaches to evaluate malaria endemicity [15, 16]. Mathematical models allow the determination of seroconversion rate (SCR) and seroreversion rate (SRR) MT-4 which are, for a given time interval, the rates with which a seronegative subject becomes seropositive and a seropositive subject turns back to seronegative, respectively. Predictive seroprevalence (prevalence of antibody responses) can be calculated by using maximum likelihood methods. Seroprevalence reflects cumulative exposure and thus is usually less affected by seasonality because antibody responses can persist for years after infection. Serological markers have been previously used to assess malaria transmission intensity [15C17], to detect recent changes in malaria endemicity [17,.