A study investigating malaria diagnostics along the Brazil-Venezuela-Guyana tri-border region has revealed very low prevalence rates of the pfhrp2 gene deletion, which may significantly impact the efficacy of rapid diagnostic tests (RDTs) used to detect Plasmodium falciparum infections. This research highlights the importance of effective monitoring and surveillance mechanisms as malaria cases continue to rise across the Americas.
Conducted by researchers from the Institute René Rachou/Fiocruz, the study encompassed 365 malaria samples collected between 2016 and 2018. Results show only 1% of the samples contained parasites lacking the histidine-rich protein 2 (HRP2), which is the primary target for many commercial malaria RDTs. The low rates of pfhrp2 deletions are significant because areas with high prevalence of such deletions have reported increased rates of false-negative RDT results.
Over the last decade, the number of malaria cases has surged, with most infections attributed to P. vivax and about 14% due to P. falciparum. Notably, since 2022, Brazil has observed over 130,000 malaria cases, paralleling rising infection rates among indigenous and mining communities. These socio-environmental factors necessitate precise diagnostics to guide effective treatment, emphasizing the relevance of the recent study.
The researchers utilized advanced molecular techniques including nested PCR and quantitative PCR, alongside epidemiological assessments through ELISA to characterize the genetic profile of P. falciparum isolates. Of the 365 samples confirmed through microscopy, 342 tested positive for HRP2 based RDTs, underscoring the reliability of current diagnostic protocols.
While this study showcases successful detection methodologies, it also addressed the issue of false-negative RDT results, which stood at 6%. According to the authors, most of these instances were due to low parasite densities rather than HRP2 deletions, indicating the need for testing enhancements capable of identifying low-level infections.
This research aligns with the World Health Organization's recommendations for continuous surveillance, especially considering the dynamic cross-border migration impacts on malaria transmission. The study’s findings suggest maintaining current HRP2-based RDTs is appropriate since the observed deletion rates remain below the WHO's threshold of 5% for recommending alternative diagnostic strategies.
Further insights from genetic analysis revealed minimal intra-host diversity among the samples, contributing to the overall findings of low genetic variability within the studied population. Yet, some variations were observed, prompting questions about how these genetic dynamics might affect diagnostic approaches.
Given the contrasts with higher deletion rates noted near the Peru border, this study underlines the distinct epidemiological landscapes throughout the region. The results indicate the necessity for additional research efforts to monitor potential shifts toward higher pfhrp2 deletion rates as surrounding habitats remain prone to substantial migratory influences due to socio-economic crises.
Conclusively, the research advocates for sustained vigilance and comprehensive assessments across the tri-border region to maintain regional malaria control efforts effectively. This includes potential revisions to diagnostic protocols to address concerns over changing patterns of parasite expression and genetic deletions as populations continue to migrate and intermingle.