Effectiveness of a serological tool to predict malaria transmission intensity in an elimination setting

Abstract

BackgroundSri Lanka achieved the WHO certificate as a malaria free country in September 2016, thus monitoring of malaria transmission using sensitive and effective tools is an important need. Use of age-specific antibody prevalence as a serological tool to predict transmission intensity is proven to be a cost effective and reliable method under elimination settings. This paper discusses the correlation of four anti-malarial antibodies against vivax and falciparum malaria with the declining transmission intensities in two previously high malaria endemic districts i.e. Kurunegala and Moneragala of Sri Lanka.MethodsSera was collected from 1,186 individuals from the two districts and were subjected to standard ELISA together with control sera from non-immune individuals to obtain Optical Density (OD) values for four anti-malarial antibodies i.e. anti-MSP1 and anti-AMA1 for both Plasmodium vivax and Plasmodium falciparum. The sero-positive samples were determined as mean OD + 3SD of the negative controls. The sero-prevalence was analyzed against the demographic characteristics of the population. A simple reversible catalytic model was fitted into sero-prevalence data to predict the sero-conversion and sero-reversion rates.ResultsOver 60% of the population was sero-positive for one or more antibodies except young children (<10 years). The sero-prevalence was zero in young children and very low in young adults when compared to the older age groups. The model developed for falciparum malaria that assumed the presence of a change in transmission was not significant in the Kurunegala district although significant reduction in transmission was observed when the model was used for P. vivax antibody data in that district. In Moneragala district however, all the serological markers indicated a change in transmission that has occurred approximately 15 years ago.ConclusionsAssessment of MSP1 and AMA1 anti-malarial antibodies of P. vivax and P. falciparum proved to be useful indicators in predicting transmission under elimination settings as prevailed in Sri Lanka. The sero-conversion rates for the two districts studied are shown to be very low or zero indicating the absence of active and/or hidden transmission confirming a “true” state of elimination at least, in the two study districts in Sri Lanka.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-2164-0) contains supplementary material, which is available to authorized users.

Chronic Exposure to Malaria Is Associated with Inhibitory and Activation Markers on Atypical Memory B Cells and Marginal Zone-Like B Cells

“…We analyzed the expression of CD71 as a marker of B cell endocytosis ( 18 ) and observed that CD71 + aaMBCs were more frequent in exposed individuals, suggesting that aaMBCs recognize and internalize fewer antigens than other switched B cell subsets ( 18 ). The correlation between the number of cell surface CD71 molecules and the rate of cell proliferation is well known ( 47 ), as seen in numerous oncogenic cells ( 31 , 39 , 47 – 50 ). The increased frequencies of aaMBCs expressing CD71 in malaria-exposed pregnant women suggests that aaMBCs may proliferate at a higher rate in malaria-exposed individuals and is consistent with the overall higher frequencies of aaMBC in these individuals.…”

Integrated Cross-Sectional Multiplex Serosurveillance of IgG Antibody Responses to Parasitic Diseases and Vaccines in Coastal Kenya

“…Although malaria parasite prevalence and/or EIR have traditionally been used for reporting malaria transmission intensity, 53 serological markers have increasingly been recognized as useful indicators for estimating malaria transmission intensity, which is key for assessing the impact of control interventions. [54][55][56][57] Because of the longevity of the specific antibody response, seroprevalence reflects cumulative exposure and, thus, is less affected by seasonality or unstable transmission. 58 In Kenya, Schistosoma haematobium is highly endemic along the coast where human exposure occurs primarily at pond and stream snail habitats.…”

Mosquito Bite-Induced Controlled Human Malaria Infection with Plasmodium vivax or P. falciparum Generates Immune Responses to Homologous and Heterologous Preerythrocytic and Erythrocytic Antigens

“…Due to the ease of their detection, the presence of antigen-specific antibodies is used as a biomarker for exposure to specific pathogens. Seroepidemiological analysis is widely used as an indicator of clinical immunity (1-4) as well as endemicity and transmission intensity (1,5,6) of malaria caused by both Plasmodium falciparum and P. vivax. Naturally acquired immunity (NAI) studies are usually performed with the goal of understanding clinical (i.e., antidisease) immunity.…”