Abstract
Co-infection with malaria and intestinal parasites is common in children in Africa and may affect their immune response to a malaria parasite infection. Prior studies suggest that co-infections may lead to increased susceptibility to malaria infection and disease severity; however, other studies have shown the reverse. Knowledge on how co-morbidities specifically affect the immune response to malaria antigens is limited. Therefore, this study sought to determine the prevalence of co-infection of malaria and intestinal parasites and its association with antibody levels to malaria merozoite antigens. A cross sectional study was carried out in two villages with high transmission of malaria in Cameroon (Ngali II and Mfou) where mass drug administration (MDA) had been administered at ~6-month intervals (generally with albendazole or mebendazole). Children aged 1-15 years were enrolled after obtaining parental consent. A malaria rapid diagnostic test was used on site. Four (4) ml of peripheral blood was collected from each participant to determine Plasmodium falciparum infections by microscopy, haemoglobin levels and serology. Fresh stool samples were collected and examined by wet mount, Kato-Katz method and modified Ritchie concentration techniques. A Multiplex Analyte Platform assay was used to measure antibody levels. A total of 320 children were enrolled. The prevalence of malaria by blood smear was 76.3% (244/320) and prevalence of malaria and intestinal parasites was 16.9% (54/320). Malaria prevalence was highest in young children; whereas, intestinal parasites (IP+) were not present until after 3 years of age. All children positive for malaria had antibodies to MSP142, MSP2, MSP3 and EBA175. No difference in antibody levels in children with malaria-co infections compared to malaria alone were found, except for antibody levels to EBA-175 were higher in children co-infected with intestinal protozoa (p = 0.018), especially those with Entamoeba histolytica infections (p = 0.0026). Antibody levels to EBA175 were significantly higher in children co-infected with malaria and E. histolytica compared to children infected with malaria alone. It is important to further investigate why and how the presence of these protozoans might modulate the immune response to malaria antigens.
Highlights
In sub-Saharan Africa, malaria caused by Plasmodium falciparum (Pf) remains an important public health threat, killing over 271,000 children under the age of five each year [1]
Antibody levels to EBA175 were significantly higher in children co-infected with malaria and E. histolytica compared to children infected with malaria alone
Studies on concomitant infections in humans suggest that A. lumbricoides infection may protect against cerebral malaria [10,11], while other studies suggest that children infected by Schistosoma mansoni may be more susceptible to P. falciparum infections and develop acute malaria episodes [12,13]
Summary
In sub-Saharan Africa, malaria caused by Plasmodium falciparum (Pf) remains an important public health threat, killing over 271,000 children under the age of five each year [1]. Co-infections with malaria and intestinal parasites (IP) are common in malaria endemic areas in sub-Saharan Africa [7,8] and infections with IP and Pf are both ranked among the major cause of mortality and morbidity in sub-Saharan Africa. It has been shown that the levels of TNF-α, IL-2, IL-10, IL-6 in Plasmodium-helminth co-infected individuals were significantly higher than the malaria-positive (MP) group [14] dampening the immune response to malaria. To our knowledge, no studies have been conducted regarding host immune responses to malaria in children co-infected with protozoan pathogens. Co-infection with malaria and intestinal parasites is common in children in Africa and may affect their immune response to a malaria parasite infection. This study sought to determine the prevalence of co-infection of malaria and intestinal parasites and its association with antibody levels to malaria merozoite antigens
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