Irene Molina-De la Fuente

Background: Nigeria has a high prevalence of malaria, with asymptomatic patients being one of the possible reservoirs. In this context, accurate diagnosis is essential for malaria control. The efficacy of rapid diagnostic tests (RDTs) is being threatened by false negatives due to pfhrp2 and pfhrp3 deletions. This study aims to describe malaria in asymptomatic schoolchildren in Osun State, Southwestern Nigeria and to assess the performance of malaria diagnosis, including the characterisation of pfhrp2 and pfhrp3 deletions. Methods: A total of 350 dried blood spot (DBS) samples from schoolchildren were used for malaria diagnosis using microscopy, RDTs, and polymerase chain reaction (PCR). Sensitivity and specificity were calculated for microscopy and RDTs, using PCR as the gold standard. Pfhrp2 and pfhrp3 deletions were analysed for all P. falciparum-positive samples using multiplex qPCR. Results: The P. falciparum infection frequency among asymptomatic schoolchildren in Osun State was 89%. Considering PCR as the gold standard, microscopy presented better sensitivity at 100% (86% for RDTs), but RDTs had better specificity at 76% (60% for microscopy). The deletion frequency of the pfhrp2 gene among positive samples was 16.6%, while it was 1.3% for pfhrp3 and 0.9% for double deletion. However, considering all positive samples, only 3% of samples yielded false negatives by RDT with deletion in pfhrp2. Conclusions: P. falciparum infection has a high frequency in asymptomatic schoolchildren, being a potential hotspot for malaria. The combination of RDTs 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.

Background/Objectives: The impact of COVID-19 in Africa has been controversial. Data from African countries are heterogeneous and generally scarce. Many regions are also highly endemic for other infectious diseases like malaria, and it has been suggested that the low incidence and mortality of COVID-19 in malaria-endemic regions could have been related to cross-immunity between malaria and SARS-CoV-2. The aim of this study was to determine the prevalence of SARS-CoV-2 and circulating variants as well as the frequency of co-infections with malaria in Equatorial Guinea. Methods: We conducted antigen tests for SARS-CoV-2 and microscopy malaria examinations in 1556 volunteer participants at six health centres in Bioko and Bata from June to October 2021 and performed SARS-CoV-2 whole-genome sequencing on positive samples to determine the diversity and origin of circulating variants. Results: We report 3.03% of SARS-CoV-2 and 22.25% of malaria prevalence over the sampling period; SARS-CoV-2 cases were found at a similar frequency in all age groups, whereas malaria was most frequent in children and teenagers. Six cases of malaria and SARS-CoV-2 co-infection were found, representing 0.37% prevalence. Genome sequences of 43 SARS-CoV-2 isolates are reported, most of which belong to the lineage Delta and, according to pandemic-scale phylogenies, were introduced from Europe on multiple occasions. Conclusions: This study is relevant in providing first-time estimates of the real prevalence of SARS-CoV-2 in this malaria-endemic country, with the identification of circulating variants, their origin, and co-occurrence with malaria. These data regarding the impact of the pandemic and co-infection with endemic diseases are relevant in future pandemics preparedness.

Malaria in pregnancy causes adverse consequences and prompt and accurate diagnosis is essential for case management. In malaria endemic countries, diagnosis is mainly based on rapid diagnostic tests (RDT) and microscopy. However, increasing reports of false negatives caused by low parasitemia and pfhrp2/3 deletions raise concerns about HRP2-based RDT usefulness. This study aimed to assess RDT and microscopy performance and to describe pfhrp2/3 deletions in a cohort of 418 pregnant women in Burkina Faso. Malaria was diagnosed using RDT and microscopy and blood samples were collected during antenatal care visits. Diagnostic results were compared to PCR as gold standard. Pfhrp2 and pfhrp3 deletions were characterized for patients with confirmed P. falciparum infection. RDT had better sensitivity (76%) but lower specificity (83%) than microscopy (sensitivity = 57%; specificity = 98%). Low parasitemia (<150 parasites/L), especially in multigravidae, was the principal factor causing false negatives by both methods. Moreover, pfhrp2 deletion frequency among overall false negatives by RDT was 21.43%. Higher frequency of deletions was found among all samples, independently of RDT result, for example around 2% of samples had double deletions meaning that the majority of deletions had no effect on RDT testing. Finally, it was found higher pfhrp2 deletion in women with lower uterine height during the first trimester. Wider and National surveillance study of deletions is recommended among pregnant women and in Burkina Faso.

Background: Pfhrp2 and pfhrp3 deletions are threatening Plasmodium falciparum malaria diagnosis by rapid diagnostic tests (RDT) due to false negatives. This study assesses the changes in the frequencies of pfhrp2 and pfhrp3 deletions (pfhrp2^Del and pfhrp3^Del, respectively) and the genes in their flaking regions, before and after RDT introduction in Equatorial Guinea. Methods: A total of 566 P. falciparum samples were genotyped to assess the presence of pfhrp2 and pfhrp3 deletions and their flanking genes. The specimens were collected 18 years apart from two provinces of Equatorial Guinea, North Bioko (Insular Region) and Litoral Province (Continental Region). Orthologs of pfhrp2 and pfhrp3 genes from other closely related species were used to compare sequencing data to assess pfhrp2 and pfhrp3 evolution. Additionally, population structure was studied using seven neutral microsatellites. Results: This study found that pfhrp2Del and pfhrp3Del were present before the introduction of RDT; however, they increased in frequency after their use, reaching more than 15%. Haplotype networks suggested that pfhrp2Del and pfhrp3Del emerged multiple times. Exon 2 of pfhrp2 and pfhrp3 genes had high variability, but there were no significant changes in amino acid sequences. Conclusions: Baseline sampling before deploying interventions provides a valuable context to interpret changes in genetic markers linked to their efficacy, such as the dynamic of deletions affecting RDT efficacy.

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 topfhrp2andpfhrp3deletions. 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 ofpfhrp2andpfhrp3deletions. 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.Pfhrp2andpfhrp3deletions were analysed for allP. 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 ofpfhrp2exon among all samples was 41.5%, and 52.8% forpfhrp3exon. But deletion frequency among false negatives by RDT was lower, 3% forpfhrp2, 5% forpfhrp3and 2% for doublepfhrp2andpfhrp3deletions. 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 inpfhrp2andpfhrp3are 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.