An active and targeted survey reveals asymptomatic malaria infections among high-risk populations in Mondulkiri, Cambodia

Asymptomatic Malaria Reservoirs in Honduras: A Challenge for Elimination

BACKGROUND

Efforts on a global scale for combating malaria have achieved substantial progress over the past twenty years. Two Central American nations have accomplished their goal of eliminating malaria: El Salvador and Belize. Honduras has decreased the incidence of malaria and now reports fewer than 4000 malaria cases annually, aspiring to reach elimination by 2030. To accomplish this goal, it is essential to assess the existing strategies employed for malaria control and to address the task of incorporating novel intervention strategies to identify asymptomatic reservoirs.

METHODS

A survey for detecting asymptomatic cases was carried out in the community of Kaukira, in Gracias a Dios, Honduras, focusing on malaria transmission during 2023. Asymptomatic community members were recruited as participants, malaria screening was performed through a rapid diagnostic test in situ, and a blood sample was collected on filter paper. Highly sensitive molecular assays based on photo-induced electron transfer PCR (PET-PCR) were performed to detect the two species of Plasmodium circulating in Honduras: Plasmodium vivax and Plasmodium falciparum. In addition, the identification of the parasite species was verified by amplifying three genetic markers (Pvmsp3α, Pvmsp3ß, and Pfmsp1).

RESULTS

A total of 138 participants were recruited, mostly adult women. All individuals tested negative on the rapid diagnostic test. Positive results for malaria were detected by PET-PCR in 17 samples (12.3%). Most samples (12 out of 17) were amplified with a Ct value between 37 and 42, indicating very low parasitemias. Out of the 17 samples, 16 of them also showed amplification in the species assays. There were nine cases of P. falciparum infections and seven cases of P. vivax infections that were further confirmed by nested PCR (nPCR) of Pvmsp3 and Pfmsp1. Parasitemias ranged from 100 p/μL to less than 0.25 p/μL. One sample showed mixed infection.

CONCLUSIONS

The existence of asymptomatic malaria reservoirs in Honduras can contribute to disease transmission and pose a challenge that may hinder elimination efforts, requiring public health authorities to modify surveillance strategies to identify the disease and treat this population accordingly.

A systematic review of the factors associated with malaria infection among forest rangers

INTRODUCTION

Malaria is a vector-borne disease that initially manifests as fever, headache, and chills. The illness could progress to more severe conditions, including lethargy, impaired consciousness, convulsions, shortness of breath, blood in urine, jaundice, and haemorrhage if left untreated. The risk of contracting malaria is considerably heightened in specific occupational settings, particularly among forest rangers, following frequent exposure to natural habitats. Consequently, advancing the understanding of malaria and emphasising how specific occupational environments (including those of forest rangers) contribute to disease risk and management is imperative.

OBJECTIVE

The present study aims to determine the factors associated with malaria infection among forest rangers by systematically reviewing electronic articles from three databases (EBSCOhost, ScienceDirect, and ResearchGate).

METHODS

The current review was prepared based on the updated preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. First, three independent reviewers screened the titles and abstracts of the data collected. The information was then stored in Endnote20 based on the inclusion and exclusion criteria. The articles were critically appraised with the mixed methods appraisal tool (MMAT) to assess their quality.

RESULT

A total of 103, 31, and 51 articles from EBSCOhost, ScienceDirect, and ResearchGate, respectively, were selected, resulting in 185 unique hits. Nevertheless, only 63 full-text publications were assessed following a rigorous selection screening, from which only five were included in the final review. The studies revealed that several factors contribute to malaria infection among forest rangers. The parameters were classified into sociodemographic, individual, and living condition-related.

CONCLUSION

A better understanding of malaria progresses and identifying its potential risk factors is essential to impact worker well-being. The findings might be utilised to improve malaria infection prevention programme implementations, hence maximising their success. Pre-employment and regular health screenings could also aid in evaluating and identifying potential risks for malaria infection among forest rangers.

Genetic polymorphism and clustering of the Plasmodium cynomolgi Duffy binding protein 1 region II of recent macaque isolates from Peninsular Malaysia

Plasmodium cynomolgi is a simian malaria parasite that has been increasingly infecting humans. It is naturally present in the long-tailed and pig-tailed macaques in Southeast Asia. The P. cynomolgi Duffy binding protein 1 region II [PcDBP1(II)] plays an essential role in the invasion of the parasite into host erythrocytes. This study investigated the genetic polymorphism, natural selection and haplotype clustering of PcDBP1(II) from wild macaque isolates in Peninsular Malaysia. The genomic DNA of 50 P. cynomolgi isolates was extracted from the macaque blood samples. Their PcDBP1(II) gene was amplified using a semi-nested PCR, cloned into a plasmid vector and subsequently sequenced. The polymorphism, natural selection and haplotypes of PcDBP1(II) were analysed using MEGA X and DnaSP ver.6.12.03 programmes. The analyses revealed high genetic polymorphism of PcDBP1(II) (π = 0.026 ± 0.004; Hd = 0.996 ± 0.001), and it was under purifying (negative) selection. A total of 106 haplotypes of PcDBP1(II) were identified. Phylogenetic and haplotype analyses revealed two groups of PcDBP1(II). Amino acid length polymorphism was observed between the groups, which may lead to possible phenotypic difference between them.