Analytical validation of real-time quantitative PCR assays for optimum diagnosis of vivax malaria

Novel isothermal nucleic acid amplification method for detecting malaria parasites

Malaria, a parasitic disease caused by Plasmodium spp. and transmitted by Anopheles mosquitoes, remains a major global health issue, with an estimated 249 million cases and 608,000 deaths in 2022. Rapid and accurate diagnosis and treatment are crucial for malaria control and elimination. However, limited access to sensitive molecular tests means that microscopic examination and rapid diagnostic tests (RDT) are the most used methods in endemic areas, despite their lower diagnostic accuracy. Therefore, there is a need for developing sensitive, simple, accurate, and rapid diagnostic tools suitable for field conditions. Herein, we aimed to explore the potential of the enzymatic recombinase amplification assay (ERA® Technology) as a remote laboratory test by evaluating and validating the GENEYE® ERA Plasmodium detection kit in Brazilian endemic areas. A cross-sectional cohort study was conducted between June and August of 2023 in the Brazilian Amazon. The study enrolled 323 participants residing in three malaria-affected regions: Cruzeiro do Sul and Mâncio Lima (Acre State) and Guajará (Amazonas State). The participants were tested for malaria by microscopy, rapid diagnostic tests (RDT), nested PCR (nPCR), quantitative real-time PCR (qPCR), and ERA. The sensitivity, specificity, and predictive values were assessed using nPCR as a gold standard. Plasmodium prevalence was 21.7%, 18.8%, 19.2%, 21.7%, and 21.7% by nPCR, microscopy, RDT, qPCR, and ERA respectively. Using nPCR as the standard, qPCR, and ERA showed a sensitivity of 100%. In comparison, microscopy and RDT showed a sensitivity of 87.1% and 88.6%, a negative predictive value (NPV) of 96.56 and 96.93, and kappa values of 0.91 and 0.92, respectively. For Plasmodium falciparum, the sensitivity of qPCR and ERA was 100% while the sensitivity of microscopy and RDT was 96.9% and 93.7%, and the NPV was 99.66 and 99.32, respectively. For Plasmodium vivax, only ERA showed the same sensitivity of nPCR. The sensitivity, NPV, and kappa values were 78.85%, 97.27, and 0.87 for qPCR and microscopy, and 84.21%, 97.94, and 0.9 for RDT. The data presented here show that the GENEYE® ERA Plasmodium detection kit offers a promising alternative to traditional malaria diagnostic methods. Its high sensitivity, specificity, fast processing time, and operational simplicity position it as a valuable point-of-care diagnostic tool, particularly in resource-limited and remote malaria-endemic areas. KEY POINTS: • GENEYE® ERA kit detects Plasmodium in under 25 min, no DNA purification needed. • The kit matches or exceeds the compared methods in sensitivity and specificity. • The kit is suitable for accurate testing in low-infrastructure, point-of-care settings.

A highly sensitive and specific real-time quantitative polymerase chain reaction assay for Perkinsus marinus detection in oysters

Oyster aquaculture is one of the fastest-growing food production industries worldwide; however, it faces a significant challenge from the protist Perkinsus marinus, particularly in the USA. Although several quantitative molecular diagnostic methodologies are available for identifying diseases caused by P. marinus, the primer pairs used therein led to non-specific identification of other Perkinsus spp. Hence, a quantitative real-time PCR (Pm-qPCR) assay specific for P. marinus was developed using a TaqMan-based probe with the internal quencher in this study. A primer pair and probe specific to P. marinus were designed from a hypothetical protein of P. marinus collected from the whole-genome shotgun sequence database of the National Center for Biotechnology Information (NCBI). In silico analysis using homologous sequences of P. olseni and P. chesapeaki confirmed the high specificity of primers designed in this study. The Pm-qPCR assay was performed using seven different strains of P. marinus, P. olseni, and P. chesapeaki, revealing high specificity and sensitivity for detecting only P. marinus strains. In conclusion, it was demonstrated that Pm-qPCR can effectively and accurately diagnose P. marinus with high specificity and sensitivity. This assay is promising for monitoring oyster health and disease management in ecosystems and aquaculture.

Relapsing Plasmodium vivax malaria in a 12-year-old Brazilian girl: A case report

Plasmodium vivax causes the vast majority of malaria cases in Brazil. The lifecycle of this parasite includes a latent stage in the liver, the hypnozoite. Reactivation of hypnozoites induces repeated relapses. We report a case of two relapses of vivax malaria in a teenage girl after conventional treatment with chloroquine and primaquine. Chloroquine prophylactic treatment for three months was prescribed with a favourable outcome of the case.

Are pvcrt-o and pvmdr1 Gene Mutations Associated with Plasmodium vivax Chloroquine-Resistant Parasites?

(1) Background: Malaria remains a significant global public health issue. Since parasites quickly became resistant to most of the available antimalarial drugs, treatment effectiveness must be constantly monitored. In Brazil, up to 10% of cases of vivax malaria resistant to chloroquine (CQ) have been registered. Unlike P. falciparum, there are no definitive molecular markers for the chemoresistance of P. vivax to CQ. This work aimed to investigate whether polymorphisms in the pvcrt-o and pvmdr1 genes could be used as markers for assessing its resistance to CQ. (2) Methods: A total of 130 samples from P. vivax malaria cases with no clinical and/or parasitological evidence of CQ resistance were studied through polymerase chain reaction for gene amplification followed by target DNA sequencing. (3) Results: In the pvcrt-o exons, the K10 insert was present in 14% of the isolates. Regarding pvmdr1, T958M and F1076L haplotypes showed frequencies of 95% and 3%, respectively, while the SNP Y976F was not detected. (4) Conclusions: Since K10-pvcrt-o and F1076L/T958M-pvmdr1 polymorphisms were detected in samples from patients who responded well to CQ treatment, it can be concluded that mutations in these genes do not seem to have a potential for association with the phenotype of CQ resistance.

Malarial and intestinal parasitic co-infections in indigenous populations of the Brazilian Amazon rainforest

The Brazilian Amazon rainforest region has a significant prevalence of malarial and intestinal parasitic infections in indigenous populations, accounting for a disproportionate burden. Thus, a cross-sectional study was conducted to assess the prevalence and association between malarial and intestinal protozoan and helminth infections in four remote indigenous villages in the Brazilian Amazon Forest. A total of 430 individuals participated in the study, and Plasmodium infections were diagnosed by examination of thick blood smears and PCR. Stool samples 295 individuals (69%) were examined by direct smear and the Kato-Katz technique. The overall prevalence of malaria, intestinal protozoan infection, and intestinal helminth infection was 14.2%, 100%, and 39.3%, respectively. Polyparasitism was predominant (83.7%), and most infected individuals had at least two or more different species of intestinal protozoan and/or helminth parasites. The prevalence of co-infection was 49.5%, and in individuals with intestinal protozoa and helminth infections (34%), Entamoeba. coli, Entamoeba histolytica, and Ascaris lumbricoides were the most common parasites. In individuals with malaria and protozoa infections (10.2%), P. vivax, E. coli, and E. histolytica predominated, and in individuals with malaria, protozoa, and helminth infections (5.4%). P. vivax, E. coli, E. histolytica, and A. lumbricoides predominated. Intestinal polyparasitism was common in the study population, and the presence of helminths was associated with an increased number of intestinal parasitic species. However, Plasmodium infections were neither a risk nor a protective factor for helminth infections; the same was true for helminth infections in relation to Plasmodium. The high prevalence of intestinal polyparasitism with Plasmodium co-infections highlights the need for combining strategies that may help control both malaria and intestinal parasite and generate a health approach aligned with indigenous perspectives.

Reemergence of human malaria in Atlantic Forest of Rio Grande do Sul, Brazil

Unforeseen Plasmodium infections in the Atlantic Forest of Brazilian Extra-Amazonian region could jeopardise malaria elimination. A human malaria case was registered in Três Forquilhas, in the Atlantic Forest biome of Rio Grande do Sul, after a 45 years' time-lapsed without any malaria autochthonous notification in this southern Brazilian state. This finding represents the expansion of the malaria distribution areas in Brazil and the southernmost human malaria case record in South America in this decade. The coexistence of the bromeliad-breeding vector Anopheles (Kerteszia) cruzii and non-human primates in the Atlantic Forest regularly visited by the patient claimed for the zoonotic origin of this infection. The reemergence of Atlantic Forest human malaria in Rio Grande do Sul was also discussed.