Impact of pfhrp2 and pfhrp3 deletions in diagnosis of asymptomatic malaria among school children in Osun State, Nigeria

Abstract

Abstract Background Nigeria has a high prevalence of malaria, being asymptomatic patients one of the possible reservoirs of malaria. In that context, accurate diagnosis is essential for malaria control. Rapid Diagnostic Test (RDT) efficacy is being threatened by false negatives due to pfhrp2 and pfhrp3 deletions. This study aims to describe malaria in asymptomatic school children in Osun State, southwestern Nigeria and to assess the performance of malaria diagnosis, including the characterization of pfhrp2 and pfhrp3 deletions. Methods 350 dried blood spot (DBS) samples from school children were used for malaria diagnosis using microscopy, RDT and PCR. Sensitivity and specificity were calculated for microscopy and RDT using PCR as gold standard. Pfhrp2 and pfhrp3 deletions were analysed for all P. falciparum-positive samples. Results Malaria prevalence among asymptomatic school children in Osun state was 89%. Considering PCR as gold standard, microscopy presented better sensitivity 100% (86% for RDT) but RDT had better specificity 76% (60% for microscopy). Deletion frequency of pfhrp2 exon among all samples was 41.5%, and 52.8% for pfhrp3 exon. But deletion frequency among false negatives by RDT was lower, 3% for pfhrp2, 5% for pfhrp3 and 2% for double pfhrp2 and pfhrp3 deletions. Conclusions Malaria has a high prevalence in asymptomatic school children, being a potential hotspot for malaria. Combination of RDT and microscopy could increase the accuracy of malaria diagnosis. Deletions in pfhrp2 and pfhrp3 are highly common in Osun state, but their impact on RDT results is still limited. More surveillance studies are recommended to assess the contribution of asymptomatic children to malaria transmission and the impact of deletions.