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Frontiers in Cellular and Infection... 2024
Topics: Antigens, Protozoan; Malaria; Humans; Plasmodium; Animals; Malaria Vaccines
PubMed: 38686096
DOI: 10.3389/fcimb.2024.1408366 -
MedRxiv : the Preprint Server For... Apr 2024Zoonotic and symptomatic and asymptomatic infections occur across endemic areas of Southeast Asia. Most infections are low-parasitemia, with an unknown proportion...
BACKGROUND
Zoonotic and symptomatic and asymptomatic infections occur across endemic areas of Southeast Asia. Most infections are low-parasitemia, with an unknown proportion below routine microscopy detection thresholds. Molecular surveillance tools optimizing the limit of detection (LOD) would allow more accurate estimates of zoonotic malaria prevalence.
METHODS
An established ultra-sensitive genus quantitative-PCR (qPCR) assay targeting the 18S rRNA gene underwent LOD evaluation with and without reverse transcription (RT) for , and using total nucleic acid preserved (DNA/RNA Shield) isolates and archived dried blood spots (DBS). LODs for selected specific assays, and reference and -specific assays were determined with RT. Assay specificities were assessed using clinical malaria samples and malaria-negative controls.
RESULTS
The use of reverse transcription improved species detection by up to 10,000-fold ( genus), 2759-fold (), 1000-fold () and 10-fold (). The median LOD with RT for the Kamau et al. genus RT-qPCR assay was ≤0.0002 parasites/μL for and 0.002 parasites/μL for both and . The LODs with RT for -specific PCRs were: Imwong et al. 18S rRNA (0.0007 parasites/μL); Divis et al. real-time 18S rRNA (0.0002 parasites/μL); Lubis et al. hemi-nested (1.1 parasites/μL) and Lee et al. nested 18S rRNA (11 parasites/μL). The LOD for and specific assays with RT were 0.02 and 0.20 parasites/μL respectively. For DBS samples the median LOD for the genus qPCR with RT was 0.08, and without RT was 19.89 parasites/uL (249-fold change); no LOD improvement was demonstrated in DBS archived beyond 6 years. The genus and -assays were 100% specific for species and detection, respectively, from 190 clinical infections and 48 healthy controls. Reference specific primers demonstrated known cross-reactivity with .
CONCLUSION
Our findings support the use of an 18S rRNA genus qPCR and species-specific nested PCR protocol with RT for highly-sensitive surveillance of zoonotic and human species infections.
PubMed: 38633782
DOI: 10.1101/2024.04.04.24305339 -
Journal of Travel Medicine Apr 2024Despite the World Health Organisation certifying China malaria-free in 2021, the risk of local transmission caused by imported malaria cases remains a significant...
BACKGROUND
Despite the World Health Organisation certifying China malaria-free in 2021, the risk of local transmission caused by imported malaria cases remains a significant clinical and public health issue. It is necessary to present the changing trends of malaria in China and discuss the role of travel medicine services in consolidating malaria elimination.
METHODS
This study systematically reviewed articles and reports related to human malaria from 2013 to 2022 published in international and Chinese databases. Data on malaria (i.e. number of cases, Plasmodium spp., diagnostic method, country of acquisition, provinces with high risk of re-introduction and transmission) were collected and synthesised, then summarised using descriptive statistics.
RESULTS
Overall, 24 758 cases of malaria (>99.5% laboratory confirmed, > 99.2% imported, 0.5% fatal) were reported in China from 2013 to 2022, with a downward trend over the years (4128 cases in 2013 compared to 843 cases in 2022; χ2 trend p-value = 0.005). The last locally acquired case was reported in 2017. P. falciparum (65.5%) was the most common species identified, followed by P. vivax (20.9%) and P. ovale (10.0%). Two Pheidole knowlesi cases were also identified in 2014 and 2017 in returned travellers from Malaysia and Indonesia, respectively. The most common countries of malaria acquisition were Ghana, Angola, and Myanmar. P. vivax was mainly detected in returned travellers from Myanmar, while P. falciparum and P. ovale were detected in travellers from Sub-Saharan Africa. Imported cases were mainly reported in Yunnan, Jiangsu, Sichuan, Guangxi, Shandong, Zhejiang, and Henan provinces, where large numbers of Chinese people travel overseas for work.
CONCLUSION
Returned travellers from malaria-endemic countries pose a significant risk of malaria re-introduction to China. Travel medicine should be strengthened to improve the capacity and accessibility of both pre- and post-travel services, including malaria prophylaxis and prompt diagnosis of illness in returned travellers.
PubMed: 38591791
DOI: 10.1093/jtm/taae056 -
Inhibition of malaria and babesiosis parasites by putative red blood cell targeting small molecules.Frontiers in Cellular and Infection... 2024Chemotherapies for malaria and babesiosis frequently succumb to the emergence of pathogen-related drug-resistance. Host-targeted therapies are thought to be less...
BACKGROUND
Chemotherapies for malaria and babesiosis frequently succumb to the emergence of pathogen-related drug-resistance. Host-targeted therapies are thought to be less susceptible to resistance but are seldom considered for treatment of these diseases.
METHODS
Our overall objective was to systematically assess small molecules for host cell-targeting activity to restrict proliferation of intracellular parasites. We carried out a literature survey to identify small molecules annotated for host factors implicated in infection. Alongside , we implemented parasite susceptibility assays also in the zoonotic parasite and the veterinary parasite . We additionally carried out assays to test directly for action on RBCs apart from the parasites. To distinguish specific host-targeting antiparasitic activity from erythrotoxicity, we measured phosphatidylserine exposure and hemolysis stimulated by small molecules in uninfected RBCs.
RESULTS
We identified diverse RBC target-annotated inhibitors with -specific, specific, and broad-spectrum antiparasitic activity. The anticancer MEK-targeting drug trametinib is shown here to act with submicromolar activity to block proliferation of spp. in RBCs. Some inhibitors exhibit antimalarial activity with transient exposure to RBCs prior to infection with parasites, providing evidence for host-targeting activity distinct from direct inhibition of the parasite.
CONCLUSIONS
We report here characterization of small molecules for antiproliferative and host cell-targeting activity for malaria and babesiosis parasites. This resource is relevant for assessment of physiological RBC-parasite interactions and may inform drug development and repurposing efforts.
Topics: Animals; Humans; Parasites; Babesiosis; Malaria; Erythrocytes; Plasmodium; Malaria, Falciparum; Babesia; Antimalarials; Plasmodium falciparum
PubMed: 38572319
DOI: 10.3389/fcimb.2024.1304839 -
Acta Tropica Jun 2024Over the past year, P. falciparum infections have declined in Thailand, yet nonhuman primate malaria infections have correspondingly increased, including Plasmodium...
Over the past year, P. falciparum infections have declined in Thailand, yet nonhuman primate malaria infections have correspondingly increased, including Plasmodium knowlesi and P. cynomolgi. Nevertheless, little is known about simian malaria in its natural macaque hosts, Macaca mulatta and Macaca fascicularis. This study aims to address several research questions, including the prevalence and distribution of simian malaria in these two Thai wild macaque species, variations in infection between different macaque species and between M. fascicularis subspecies, and the genetic composition of these pathogens. Blood samples were collected from 82 M. mulatta and 690 M. fascicularis across 15 locations in Thailand, as well as two locations in Vietnam and Myanmar. We employed quantitative real-time PCR targeting the Plasmodium genus-specific 18S ribosomal RNA (rRNA) gene to detect malaria infection, with a limit of detection set at 1,215.98 parasites per mL. We genotyped eight microsatellite markers, and the P. cynomolgi dihydrofolate reductase gene (DHFR) was sequenced (N = 29). In total, 100 of 772 samples (13 %) tested positive for malaria, including 45 (13 %) for P. cynomolgi, 37 (13 %) for P. inui, 16 (5 %) for P. coatneyi, and 2 (0.25 %) for Hepatocystis sp. in Saraburi, central and Ranong, southern Thailand. Notably, simian malaria infection was observed exclusively in M. fascicularis and not in M. mulatta (P = 0.0002). Particularly, P. cynomolgi was detected in 21.7 % (45/207) of M. f. fascicularis living in Wat Tham Phrapothisat, Saraburi Province. The infection with simian malaria was statistically different between M. fascicularis and M. mulatta (P = 0.0002) but not within M. fascicularis subspecies (P = 0.78). A haplotype network analysis revealed that P. cynomolgi shares a lineage with reference strains obtained from macaques. No mutation in the predicted binding pocket of PcyDHFR to pyrimethamine was observed. This study reveals a significant prevalence of simian malaria infection in M. fascicularis. The clonal genotypes of P. cynomolgi suggest in-reservoir breeding. These findings raise concerns about the potential spread of nonhuman primate malaria to humans and underscore the need for preventive measures.
Topics: Animals; Thailand; Malaria; Macaca fascicularis; Prevalence; RNA, Ribosomal, 18S; Genetic Variation; Macaca mulatta; Genotype; Microsatellite Repeats; Monkey Diseases; Humans; Myanmar; Tetrahydrofolate Dehydrogenase; Plasmodium knowlesi; Plasmodium; Vietnam; DNA, Protozoan; Plasmodium cynomolgi; Real-Time Polymerase Chain Reaction
PubMed: 38518834
DOI: 10.1016/j.actatropica.2024.107187 -
Heliyon Mar 2024Malaria remains a major public health problem worldwide, including in Southeast Asia. Chemotherapeutic agents such as chloroquine (CQ) are effective, but problems with...
Malaria remains a major public health problem worldwide, including in Southeast Asia. Chemotherapeutic agents such as chloroquine (CQ) are effective, but problems with drug resistance and toxicity have necessitated a continuous search for new effective antimalarial agents. Here we report on a virtual screening of ∼300 diarylpentanoids and derivatives, in search of potential lactate dehydrogenase (LDH) inhibitors with acceptable drug-like properties. Several molecules with binding affinities comparable to CQ were chosen for in vitro validation of antimalarial efficacy. Among them, MS33A, MS33C and MS34C are the most promising against CQ-sensitive (3D7) with EC values of 1.6, 2.5 and 3.1 μM, respectively. Meanwhile, MS87 (EC of 1.85 μM) shown the most active against the CQ-resistant Gombak A strain, and MS33A and MS33C the most effective inhibitors (EC of 3.6 and 5.1 μM, respectively). The in vitro cytotoxicity of selected diarylpentanoids (MS33A, MS33C, MS34C and MS87) was tested on Vero mammalian cells to evaluate parasite selectivity (SI), showing moderate to low cytotoxicity (CC > 82 μM). In addition, MS87 exhibited a high SI and the lowest resistance index (RI), suggesting that MS87 may exert effective parasite inhibition with low resistance potential in the CQ-resistant strain. Furthermore, the in vivo toxicity of the molecules on early embryonic development, the cardiovascular system, heart rate, motor activity and apoptosis were assessed in a zebrafish animal model. The overall results indicate the preliminary potential of diarylpentanoids, which need further investigation for their development as new antimalarial agents.
PubMed: 38495201
DOI: 10.1016/j.heliyon.2024.e27462 -
Scientific Reports Mar 2024The parasite Plasmodium knowlesi has been the sole cause of malaria in Malaysia from 2018 to 2022. The persistence of this zoonotic species has hampered Malaysia's...
The parasite Plasmodium knowlesi has been the sole cause of malaria in Malaysia from 2018 to 2022. The persistence of this zoonotic species has hampered Malaysia's progress towards achieving the malaria-free status awarded by the World Health Organisation (WHO). Due to the zoonotic nature of P. knowlesi infections, it is important to study the prevalence of the parasite in the macaque host, the long-tailed macaque (Macaca fascicularis). Apart from P. knowlesi, the long-tailed macaque is also able to harbour Plasmodium cynomolgi, Plasmodium inui, Plasmodium caotneyi and Plasmodium fieldi. Here we report the prevalence of the 5 simian malaria parasites in the wild long-tailed macaque population in 12 out of the 13 states in Peninsular Malaysia using a nested PCR approach targeting the 18s ribosomal RNA (18s rRNA) gene. It was found that all five Plasmodium species were widely distributed throughout Peninsular Malaysia except for states with major cities such as Kuala Lumpur and Putrajaya. Of note, Pahang reported a malaria prevalence of 100% in the long-tailed macaque population, identifying it as a potential hotspot for zoonotic transmission. Overall, this study shows the distribution of the 5 simian malaria parasite species throughout Peninsular Malaysia, the data of which could be used to guide future malaria control interventions to target zoonotic malaria.
Topics: Animals; Macaca fascicularis; Malaysia; Prevalence; Malaria; Plasmodium knowlesi; Parasites
PubMed: 38472278
DOI: 10.1038/s41598-024-54981-2 -
Frontiers in Cellular and Infection... 2024, the most widespread human malaria parasite, and , an emerging that infects humans, are the phylogenetically closest malarial species that infect humans, which may...
, the most widespread human malaria parasite, and , an emerging that infects humans, are the phylogenetically closest malarial species that infect humans, which may induce cross-species reactivity across most co-endemic areas in Southeast Asia. The thrombospondin-related anonymous protein (TRAP) family is indispensable for motility and host cell invasion in the growth and development of parasites. The merozoite-specific TRAP (MTRAP), expressed in blood-stage merozoites, is supposed to be essential for human erythrocyte invasion. We aimed to characterize MTRAPs in blood-stage and parasites and ascertain their cross-species immunoreactivity. Recombinant and MTRAPs of full-length ectodomains were expressed in a mammalian expression system. The MTRAP-specific immunoglobulin G, obtained from immune animals, was used in an immunofluorescence assay for subcellular localization and invasion inhibitory activity in blood-stage parasites was determined. The cross-species humoral immune responses were analyzed in the sera of patients with or infections. The MTRAPs of (PvMTRAP) and (PkMTRAP) were localized on the rhoptry body of merozoites in blood-stage parasites. Both anti-PvMTRAP and anti-PkMTRAP antibodies inhibited erythrocyte invasion of blood-stage parasites. The humoral immune response to PvMTRAP showed high immunogenicity, longevity, and cross-species immunoreactivity with . MTRAPs are promising candidates for development of vaccines and therapeutics against vivax and knowlesi malaria.
Topics: Animals; Humans; Plasmodium vivax; Parasites; Merozoites; Thrombospondins; Plasmodium; Malaria; Malaria, Vivax; Protozoan Proteins; Mammals
PubMed: 38465236
DOI: 10.3389/fcimb.2024.1354880 -
Usefulness of serial testing for the diagnosis of malaria in cases of fever upon return from travel.Journal of Travel Medicine Apr 2024When malaria is suspected in case of fever after travel in endemic areas, the current recommendation is to repeat the malaria test at 24-hour intervals, with up to two...
BACKGROUND
When malaria is suspected in case of fever after travel in endemic areas, the current recommendation is to repeat the malaria test at 24-hour intervals, with up to two additional tests, as long as the test result is negative. A retrospective analysis was conducted to investigate the appropriateness of this recommendation by determining the proportion of tests with negative result at first and subsequently with a positive one at second or third attempt.
METHODS
A retrospective study was conducted at the Centre for Primary Care and Public Health, Lausanne, covering a period of 15 years. All patients tested once for malaria were included. Testing included microscopy thick and thin films as well as malaria rapid diagnostic test used in combination. The main outcome measure was the proportion of patients with a first negative test result, subsequently positive on second or third test over the total patients with suspected malaria assessed. Demographic, travel, clinical, and laboratory variables were collected from patients' records to identify potential predictors of an initially negative and then positive test result.
RESULTS
Four thousand nine hundred seventy-two patients were included. Of those, 4557 (91.7%) had definitive negative test results, and 415 (8.3%) had a positive result on the first test [332/415 (80%) Plasmodium falciparum, 40/415 (9.6%) P. vivax, 21/415 (5.1%) P. ovale, 12/415 (2.9%) P. vivax/ovale, 9/415 (2.2%) P. malariae and 1/415 (0.2%) P. knowlesi], and 3/4972 (0.06%) had a positive result on the second test after a first negative result, 1/4972(0.02%) had a positive test result after 2 negative results, all with P. falciparum. One of the four patients that were positive after their initial negative test was pregnant. The very small number of patients with an initially negative test result and secondarily positive did not allow for risk factor analysis.
CONCLUSIONS
The current recommendation of serial malaria testing is not supported by the present study, a fortiori for those who do not present with a strong clinical or laboratory predictor of malaria.
Topics: Pregnancy; Female; Humans; Retrospective Studies; Malaria; Malaria, Falciparum; Malaria, Vivax; Travel; Fever
PubMed: 38431851
DOI: 10.1093/jtm/taae030 -
The American Journal of Tropical... Apr 2024Loop-mediated isothermal amplification (LAMP) is a nucleic acid amplification technique that can amplify specific nucleic acids at a constant temperature (63-65°C)...
Loop-mediated isothermal amplification (LAMP) is a nucleic acid amplification technique that can amplify specific nucleic acids at a constant temperature (63-65°C) within a short period (<1 hour). In this study, we report the utilization of recombinase-aided LAMP to specifically amplify the 18S sRNA of Plasmodium knowlesi. The method was built on a conventional LAMP assay by inclusion of an extra enzyme, namely recombinase, into the master mixture. With the addition of recombinase into the LAMP assay, the assay speed was executed within a time frame of less than 28 minutes at 65°C. We screened 55 P. knowlesi samples and 47 non-P. knowlesi samples. No cross-reactivity was observed for non-P. knowlesi samples, and the detection limit for recombinase-aided LAMP was one copy for P. knowlesi after LAMP amplification. It has been reported elsewhere that LAMP can be detected through fluorescent readout systems. Although such systems result in considerable limits of detection, the need for sophisticated equipment limits their use. Hence, we used here a colorimetric detection platform for the evaluation of the LAMP assay's performance. This malachite green-based recombinase-aided LAMP assay enabled visualization of results with the naked eye. Negative samples were observed by a change in color from green to colorless, whereas positive samples remained green. Our results demonstrate that the LAMP assay developed here is a convenient, sensitive, and useful diagnostic tool for the rapid detection of knowlesi malaria parasites. This method is suitable for implementation in remote healthcare settings, where centralized laboratory facilities, funds, and clinicians are in short supply.
Topics: Humans; Plasmodium knowlesi; Malaria; Recombinases; Sensitivity and Specificity; Nucleic Acid Amplification Techniques; Molecular Diagnostic Techniques
PubMed: 38412548
DOI: 10.4269/ajtmh.23-0572