Seasonal pattern of questing ticks and prevalence of pathogenic Rickettsia and Anaplasmataceae in Khao Yai national park, Thailand.

Background: Tick-borne diseases (TBD) are considered neglected diseases in Thailand with disease burden likely underestimated. To assess risk for emerging TBD in Thailand, the seasonality of questing tick and pathogen prevalence were studied in Khao Yai National Park, a top tourist destination.

Methods: During 2019, questing ticks around tourist attractions were systematically collected bimonthly and analyzed for Rickettsia and Anaplasmataceae bacterial species by polymerase chain reaction and DNA sequencing.

The parasite intraerythrocytic cycle and human circadian cycle are coupled during malaria infection.

During infections with the malaria parasites , patients exhibit rhythmic fevers every 48 h. These fever cycles correspond with the time the parasites take to traverse the intraerythrocytic cycle (IEC). In other species that infect either humans or mice, the IEC is likely guided by a parasite-intrinsic clock [Rijo-Ferreira, , 746-753 (2020); Smith .

In vitro activity of rhinacanthin analogues against drug resistant Plasmodium falciparum isolates from Northeast Thailand.

Background: New anti-malarial drugs are needed urgently to address the increasing challenges of drug-resistant falciparum malaria. Two rhinacanthin analogues containing a naphthoquinone moiety resembling atovaquone showed promising in-vitro activity against a P. falciparum laboratory reference strain (K1).

The Bacterial Community in Questing Ticks From Khao Yai National Park in Thailand.

Ticks are known vectors for a variety of pathogens including bacteria, viruses, fungi, and parasites. In this study, bacterial communities were investigated in active life stages of three tick genera (, and ) collected from Khao Yai National Park in Thailand. Four hundred and thirty-three questing ticks were selected for pathogen detection individually using real-time PCR assays, and 58 of these were subjected to further metagenomics analysis.

Tracking tick-borne diseases in Mongolian livestock using next generation sequencing (NGS).

The livestock industry in Mongolia accounts for 24% of national revenue, with one third of the population maintaining a pastoral lifestyle. This close connection between Mongolian population and livestock is a major concern for pathogen transfer, especially given the increase in vector-borne diseases globally. This study examines blood samples from livestock to assess the prevalence of tick-borne bacterial infections across three provinces in Mongolia (Dornogovi, Selenge, Töv).

Plasmodium falciparum phenotypic and genotypic resistance profile during the emergence of Piperaquine resistance in Northeastern Thailand.

Malaria remains a public health problem in Thailand, especially along its borders where highly mobile populations can contribute to persistent transmission. This study aimed to determine resistant genotypes and phenotypes of 112 Plasmodium falciparum isolates from patients along the Thai-Cambodia border during 2013-2015. The majority of parasites harbored a pfmdr1-Y184F mutation.

Amplicon-Based Next Generation Sequencing for Rapid Identification of and Ectoparasite Species from Entomological Surveillance in Thailand.

Background: Next generation sequencing (NGS) technology has been used for a wide range of epidemiological and surveillance studies. Here, we used amplicon-based NGS to species identify and their arthropod hosts from entomological surveillance.

Methods: During 2015-2016, we screened 1825 samples of rodents and ectoparasites collected from rodents and domestic mammals (dog, cat, and cattle) across Thailand for .

Distribution and Temporal Dynamics of Plasmodium falciparum Chloroquine Resistance Transporter Mutations Associated With Piperaquine Resistance in Northern Cambodia.

Background: Newly emerged mutations within the Plasmodium falciparum chloroquine resistance transporter (PfCRT) can confer piperaquine resistance in the absence of amplified plasmepsin II (pfpm2). In this study, we estimated the prevalence of co-circulating piperaquine resistance mutations in P. falciparum isolates collected in northern Cambodia from 2009 to 2017.

Genetic association study of interferon lambda 3, CD27, and human leukocyte antigen-DPB1 with dengue severity in Thailand.

Background: Dengue patients develop different disease severity ranging from mild (dengue fever [DF]) to severe forms (dengue hemorrhagic fever [DHF] and the fatal dengue shock syndrome [DSS]). Host genetics are considered to be one factor responsible for the severity of dengue outcomes. To identify genes associated with dengue severity that have not been studied yet, we performed genetic association analyses of interferon lambda 3 (IFNL3), CD27, and human leukocyte antigen-DPB1 (HLA-DPB1) genes in Thai dengue patients.

Interferon lambda 1 is associated with dengue severity in Thailand.

Objectives: Patients with dengue exhibit a range of symptoms from an acute febrile illness (dengue fever, DF), to dengue hemorrhagic fever (DHF), and to the most severe outcome, dengue shock syndrome (DSS). This study was performed to determine the host genetic factors responsible for dengue severity. Two single nucleotide polymorphisms (SNPs) of the interferon lambda 1 (IFNL1) gene (rs30461 and rs7247086) were analyzed for their association with dengue severity in a Thai population.

Gametocyte Carriage, Antimalarial Use, and Drug Resistance in Cambodia, 2008-2014.

Gametocytes are the malaria parasite stages responsible for transmission from humans to mosquitoes. Gametocytemia often follows drug treatment, especially as therapies start to fail. We examined gametocyte carriage and drug resistance profiles among 824 persons with uncomplicated malaria in Cambodia to determine whether prevalent drug resistance and antimalarial use has led to a concentration of drug-resistant parasites among gametocyte carriers.

Correction: Sequence variation in Plasmodium falciparum merozoite surface protein-2 is associated with virulence causing severe and cerebral malaria.

[This corrects the article DOI: 10.1371/journal.pone.

Sequence variation in Plasmodium falciparum merozoite surface protein-2 is associated with virulence causing severe and cerebral malaria.

Parasite virulence, an important factor contributing to the severity of Plasmodium falciparum infection, varies among P. falciparum strains. Relatively little is known regarding markers of virulence capable of identifying strains responsible for severe malaria.

Measuring ex vivo drug susceptibility in Plasmodium vivax isolates from Cambodia.

Background: While intensive Plasmodium falciparum multidrug resistance surveillance continues in Cambodia, relatively little is known about Plasmodium vivax drug resistance in Cambodia or elsewhere. To investigate P. vivax anti-malarial susceptibility in Cambodia, 76 fresh P.

Association of a Novel Mutation in the Plasmodium falciparum Chloroquine Resistance Transporter With Decreased Piperaquine Sensitivity.

Background: Amplified copy number in the plasmepsin II/III genes within Plasmodium falciparum has been associated with decreased sensitivity to piperaquine. To examine this association and test whether additional loci might also contribute, we performed a genome-wide association study of ex vivo P. falciparum susceptibility to piperaquine.

Partner-Drug Resistance and Population Substructuring of Artemisinin-Resistant Plasmodium falciparum in Cambodia.

Plasmodium falciparum in western Cambodia has developed resistance to artemisinin and its partner drugs, causing frequent treatment failure. Understanding this evolution can inform the deployment of new therapies. We investigated the genetic architecture of 78 falciparum isolates using whole-genome sequencing, correlating results to in vivo and ex vivo drug resistance and exploring the relationship between population structure, demographic history, and partner drug resistance.

Ex vivo piperaquine resistance developed rapidly in Plasmodium falciparum isolates in northern Cambodia compared to Thailand.

Background: The recent dramatic decline in dihydroartemisinin-piperaquine (DHA-PPQ) efficacy in northwestern Cambodia has raised concerns about the rapid spread of piperaquine resistance just as DHA-PPQ is being introduced as first-line therapy in neighbouring countries.

Methods: Ex vivo parasite susceptibilities were tracked to determine the rate of progression of DHA, PPQ and mefloquine (MQ) resistance from sentinel sites on the Thai-Cambodian and Thai-Myanmar borders from 2010 to 2015. Immediate ex vivo (IEV) histidine-rich protein 2 (HRP-2) assays were used on fresh patient Plasmodium falciparum isolates to determine drug susceptibility profiles.

Antibody profiles to plasmodium merozoite surface protein-1 in Cambodian adults during an active surveillance cohort with nested treatment study.

Background: In addition to evidence for a protective role of antibodies to the malaria blood stage antigen merozoite surface protein 1 (MSP1), MSP1 antibodies are also considered as a marker of past malaria exposure in sero-epidemiological studies.

Methods: In order to better assess the potential use of MSP1 serology in malaria chemoprophylaxis trials in endemic areas, an analysis for the prevalence of antibodies to both Plasmodium falciparum and Plasmodium vivax MSP142 in healthy Cambodian adults was conducted at two sites as part of an active, observational cohort evaluating the efficacy of dihydroartemisinin-piperaquine (DP) for uncomplicated malaria (ClinicalTrials.gov identifier NCT01280162).

Atovaquone-Proguanil Remains a Potential Stopgap Therapy for Multidrug-Resistant Plasmodium falciparum in Areas along the Thai-Cambodian Border.

Our recent report of dihydroartemisinin-piperaquine failure to treat Plasmodium falciparum infections in Cambodia adds new urgency to the search for alternative treatments. Despite dihydroartemisinin-piperaquine failure, and higher piperaquine 50% inhibitory concentrations (IC50s) following reanalysis than those previously reported, P. falciparum remained sensitive to atovaquone (ATQ) in vitro.

Attenuation of Plasmodium falciparum in vitro drug resistance phenotype following culture adaptation compared to fresh clinical isolates in Cambodia.

Background: There is currently no standardized approach for assessing in vitro anti-malarial drug susceptibility. Potential alterations in drug susceptibility results between fresh immediate ex vivo (IEV) and cryopreserved culture-adapted (CCA) Plasmodium falciparum isolates, as well as changes in parasite genotype during culture adaptation were investigated.

Methods: The 50 % inhibitory concentration (IC50) of 12 P.

Ex Vivo Drug Susceptibility Testing and Molecular Profiling of Clinical Plasmodium falciparum Isolates from Cambodia from 2008 to 2013 Suggest Emerging Piperaquine Resistance.

Cambodia's first-line artemisinin combination therapy, dihydroartemisinin-piperaquine (DHA-PPQ), is no longer sufficiently curative against multidrug-resistant Plasmodium falciparum malaria at some Thai-Cambodian border regions. We report recent (2008 to 2013) drug resistance trends in 753 isolates from northern, western, and southern Cambodia by surveying for ex vivo drug susceptibility and molecular drug resistance markers to guide the selection of an effective alternative to DHA-PPQ. Over the last 3 study years, PPQ susceptibility declined dramatically (geomean 50% inhibitory concentration [IC50] increased from 12.

Dihydroartemisinin-piperaquine failure associated with a triple mutant including kelch13 C580Y in Cambodia: an observational cohort study.

Background: Dihydroartemisinin-piperaquine has been adopted as first-line artemisinin combination therapy (ACT) for multidrug-resistant Plasmodium falciparum malaria in Cambodia because of few remaining alternatives. We aimed to assess the efficacy of standard 3 day dihydroartemisinin-piperaquine treatment of uncomplicated P falciparum malaria, with and without the addition of primaquine, focusing on the factors involved in drug resistance.

Methods: In this observational cohort study, we assessed 107 adults aged 18-65 years presenting to Anlong Veng District Hospital, Oddar Meanchey Province, Cambodia, with uncomplicated P falciparum or mixed P falciparum/Plasmodium vivax infection of between 1000 and 200,000 parasites per μL of blood, and participating in a randomised clinical trial in which all had received dihydroartemisinin-piperaquine for 3 days, after which they had been randomly allocated to receive either primaquine or no primaquine.

Ex vivo activity of endoperoxide antimalarials, including artemisone and arterolane, against multidrug-resistant Plasmodium falciparum isolates from Cambodia.

Novel synthetic endoperoxides are being evaluated as new components of artemisinin combination therapies (ACTs) to treat artemisinin-resistant Plasmodium falciparum malaria. We conducted blinded ex vivo activity testing of fully synthetic (OZ78 and OZ277) and semisynthetic (artemisone, artemiside, artesunate, and dihydroartemisinin) endoperoxides in the histidine-rich protein 2 enzyme-linked immunosorbent assay against 200 P. falciparum isolates from areas of artemisinin-resistant malaria in western and northern Cambodia in 2009 and 2010.

Efficacy of two versus three-day regimens of dihydroartemisinin-piperaquine for uncomplicated malaria in military personnel in northern Cambodia: an open-label randomized trial.

Introduction: Emerging antimalarial drug resistance in mobile populations remains a significant public health concern. We compared two regimens of dihydroartemisinin-piperaquine in military and civilians on the Thai-Cambodian border to evaluate national treatment policy.

Methods: Efficacy and safety of two and three-day regimens of dihydroartemisinin-piperaquine were compared as a nested open-label evaluation within a malaria cohort study in 222 otherwise healthy volunteers (18% malaria-infected at baseline).

Direct comparison of the histidine-rich protein-2 enzyme-linked immunosorbent assay (HRP-2 ELISA) and malaria SYBR green I fluorescence (MSF) drug sensitivity tests in Plasmodium falciparum reference clones and fresh ex vivo field isolates from Cambodia.

Background: Performance of the histidine-rich protein-2 enzyme-linked immunosorbent assay (HRP-2 ELISA) and malaria SYBR Green I fluorescence (MSF) drug sensitivity tests were directly compared using Plasmodium falciparum reference strains and fresh ex vivo isolates from Cambodia against a panel of standard anti-malarials. The objective was to determine which of these two common assays is more appropriate for studying drug susceptibility of "immediate ex vivo" (IEV) isolates, analysed without culture adaption, in a region of relatively low malaria transmission.

Methods: Using the HRP-2 and MSF methods, the 50% inhibitory concentration (IC50) values against a panel of malaria drugs were determined for P.