Northern Cambodia Research Articles

Elimination of schistosomiasis mekongi in reach for Lao PDR: The last patient with severe disease?

Schistosomiasis mekongi is endemic in a restricted area in Northern Cambodia and the Southern Lao People's Democratic Republic. Severe hepatobiliary morbidity is associated with chronic untreated S. mekongi infection. Since the 1980s extensive control efforts have been employed in endemic areas, resulting in substantial reduction of infection rates and disease burden. We report on a patient with a fatal course of clinically-assessed chronic schistosomiasis. This report underscores that patients with severe chronic Mekong schistosomiasis may still exist and may need treatment support.

Quantifying the availability of seasonal surface water and identifying the drivers of change within tropical forests in Cambodia.

Surface freshwater is a vital resource that is declining globally, predominantly due to climate and land use changes. Cambodia is no exception and the loss threatens many species, such as the giant ibis a Critically Endangered waterbird. We aimed to quantify the spatial and temporal (2000-2020) change of surface water availability across northern and eastern Cambodia and to assess the impact of this on the giant ibis. We used a Random Forest Classifier to determine the changes and we tested the impact of land use and geographical covariates using spatially explicit regression models. We found an overall reduction of surface water availability of 4.16%. This was predominantly driven by the presence of Economic Land Concessions and roads which increased the probability of extreme drying and flooding events. The presence of protected areas reduced these probabilities. We found changes in precipitation patterns over the wider landscape did not correlate with changes in surface water availability, supporting the overriding influence of land use change. 98% of giant ibis nests recorded during the time period were found within 25m of surface water during the dry season, highlighting their dependency on surface water. The overall surface water decline resulted in a 25% reduction in dry season suitable habitat for the giant ibis. Although absolute changes in surface water over the whole area were relatively small, the impact on the highest quality habitat for ibis is disproportionate and therefore threatens its populations. Defining the threats to such an endangered species is crucial for effective management.

A Prognostic Model for Critically Ill Children in Locations With Emerging Critical Care Capacity.

To develop a clinical prediction model to risk stratify children admitted to PICUs in locations with limited resources, and compare performance of the model to nine existing pediatric severity scores. Retrospective, single-center, cohort study. PICU of a pediatric hospital in Siem Reap, northern Cambodia. Children between 28 days and 16 years old admitted nonelectively to the PICU. None. Clinical and laboratory data recorded at the time of PICU admission were collected. The primary outcome was death during PICU admission. One thousand five hundred fifty consecutive nonelective PICU admissions were included, of which 97 died (6.3%). Most existing severity scores achieved comparable discrimination (area under the receiver operating characteristic curves [AUCs], 0.71-0.76) but only three scores demonstrated moderate diagnostic utility for triaging admissions into high- and low-risk groups (positive likelihood ratios [PLRs], 2.65-2.97 and negative likelihood ratios [NLRs], 0.40-0.46). The newly derived model outperformed all existing severity scores (AUC, 0.84; 95% CI, 0.80-0.88; p < 0.001). Using one particular threshold, the model classified 13.0% of admissions as high risk, among which probability of mortality was almost ten-fold greater than admissions triaged as low-risk (PLR, 5.75; 95% CI, 4.57-7.23 and NLR, 0.47; 95% CI, 0.37-0.59). Decision curve analyses indicated that the model would be superior to all existing severity scores and could provide utility across the range of clinically plausible decision thresholds. Existing pediatric severity scores have limited potential as risk stratification tools in resource-constrained PICUs. If validated, our prediction model would be a readily implementable mechanism to support triage of critically ill children at admission to PICU and could provide value across a variety of contexts where resource prioritization is important.

Projecting the future incidence and burden of dengue in Southeast Asia

The recent global expansion of dengue has been facilitated by changes in urbanisation, mobility, and climate. In this work, we project future changes in dengue incidence and case burden to 2099 under the latest climate change scenarios. We fit a statistical model to province-level monthly dengue case counts from eight countries across Southeast Asia, one of the worst affected regions. We project that dengue incidence will peak this century before declining to lower levels with large variations between and within countries. Our findings reveal that northern Thailand and Cambodia will show the biggest decreases and equatorial areas will show the biggest increases. The impact of climate change will be counterbalanced by income growth, with population growth having the biggest influence on increasing burden. These findings can be used for formulating mitigation and adaptation interventions to reduce the immediate growing impact of dengue virus in the region.

High endemicity of Opisthorchis viverrini infection among people in northern Cambodia confirmed by adult worm expulsion

Opisthorchis viverrini infection is an emerging disease in Cambodia, especially in central and southeastern areas. However, its status in northern areas bordering Lao PDR has been relatively unknown. The present study was performed to investigate the status of O. viverrini infection among people in Preah Vihear and Stung Treng provinces through fecal examination to detect eggs and recovery of adult flukes from some of the egg-positive cases. Fecal examinations were performed on a total of 1101 people from 10 villages in the 2 provinces using the Kato-Katz thick smear technique. For recovery of adult flukes and other helminth parasites 10 volunteers positive for eggs of Opisthorchis viverrini and/or minute intestinal flukes (Ov/MIF), in Kampong Sangkae village, Preah Vihear province, were administered a single oral dose of 40 mg/kg praziquantel plus 5–10 mg/kg of pyrantel pamoate and purged with 40–50 g magnesium salts. Adult trematodes, together with nematodes and cestodes expelled in diarrheic stools were collected under a stereomicroscope or with the naked eye. The proportion of egg-positive cases for overall liver and intestinal helminths was high but not notably different between the 2 provinces, 65.5% in Preah Vihear versus 64.7% in Stung Treng. The average proportion of Ov/MIF egg-positive cases was 59.8%. A total of 315 adult specimens of O. viverrini were recovered from the 10 volunteers (4–98 specimens per individual; mean, 32). A smaller number of Haplorchis taichui adults, an intestinal fluke, were found mixed-infected in 7 (103 specimens in total; 1–31 per individual; mean, 15) of the 10 volunteers. Adult specimens of hookworms, Enterobius vermicularis, Trichostrongylus sp., and a Taenia tapeworm strobila were recovered in some cases. Based on the results, it has been confirmed that the surveyed areas in Preah Vihear and Stung Treng provinces, Cambodia, are highly endemic areas of O. viverrini infection with a low-grade mixed infection with H. taichui.

Evaluation of Crude and Recombinant Antigens of Schistosoma japonicum for the Detection of Schistosoma mekongi Human Infection.

Asian schistosomiasis caused by the blood fluke Schistosoma mekongi is endemic in northern Cambodia and Southern Lao People's Democratic Republic. The disease is mainly diagnosed by stool microscopy. However, serodiagnosis such as enzyme-linked immunosorbent assay (ELISA) with soluble egg antigen (SEA), has been shown to have better sensitivity compared to the stool examination, especially in the settings with a low intensity of infection. To date, no recombinant antigen has been assessed using ELISA for the detection of S. mekongi infection, due to the lack of genome information for this schistosome species. Thus, the objective of this study is to evaluate several recombinant S. japonicum antigens that have been developed in our laboratory for the detection of S. mekongi infection. The crude antigen SjSEA and recombinant antigens Sj7TR, SjPCS, SjPRx-4, and SjChi-3 were evaluated in ELISA using serum samples positive for S. mekongi infection. The cross-reaction was checked using sera positive for Ophistorchis viverrini. ELISA results showed that S. japonicum SEA at low concentrations showed better diagnostic performance than the recombinant antigens tested using the archived serum samples from Cambodia. However, further optimization of the recombinant antigens should be conducted in future studies to improve their diagnostic performance for S. mekongi detection.

Spatial modeling of Sarus Crane nest site suitability in Cambodia to help target conservation of breeding areas

To understand the breeding habitat requirements of the small, highly threatened migratory population of Eastern Sarus Crane (Grus antigone sharpii) in Cambodia and Vietnam, we assessed nest site selection at two different spatial scales: at the scale of individually occupied wetlands within the deciduous dipterocarp forests of Kulen Promtep and Chep Wildlife Sanctuaries, and at a landscape scale covering all such forested areas in northern Cambodia. To model the likelihood of nest occupancy within the landscape, results of aerial surveys for Sarus Crane nests, conducted in 2001, were combined with topographical and environmental spatial data. A second model incorporated deforestation and road development in the landscape between 2001 and 2016.We found that Sarus Cranes in Cambodia typically nested in remote rain-fed wetlands that formed on flat terrain in the upper reaches of drainage basins. Within these small, forested wetland units, nests were often placed in deeper, well-defined ponds, although three-quarters of all nests were placed randomly in relation to water level. Nest locations were further from roads and agricultural areas than random points.Most of the best nesting habitat, including Kulen Promtep and Chep Wildlife Sanctuaries, was located on Cambodia’s Northern Plains (247 km2 of habitat with a predicted occupancy likelihood of >75 % inside protected areas and 77 km2 outside), with smaller patches of highly suitable areas scattered across the Eastern Plains (15 km2 inside protected areas and 11 km2 outside).Between 2001 and 2016, 14,215 km2 (15 %) of the original deciduous dipterocarp forest cover was cleared for agriculture, 1,605 km of road was constructed and the area of habitat with a predicted occupancy likelihood of >75 % shrank by 69 % in the Northern Plains (66 % inside protected areas and 79 % outside) and 73 % in the Eastern Plains (80 % inside and 64 % outside). In Kulen Promtep and Chep, cranes continued to nest but in areas modeled as having lower suitability. We recommend (i) strengthening protection of Kulen Promtep and Chep Wildlife Sanctuaries in the Northern Plains and of remaining nesting habitat in other protected areas; (ii) surveying for active nesting in areas having the highest suitability classes based on the 2001 model but not currently protected, particularly south of Kulen Promtep; (iii) in the meantime, take immediate steps towards protecting as much remaining habitat as possible, that was modeled as highly suitable, to allow for population recovery or in case subsequent surveys find it occupied.

Discovery of Schistosoma mekongi circulating proteins and antigens in infected mouse sera.

Schistosomiasis is a neglected tropical disease caused by an infection of the parasitic flatworms schistosomes. Schistosoma mekongi is a restricted Schistosoma species found near the Mekong River, mainly in southern Laos and northern Cambodia. Because there is no vaccine or effective early diagnosis available for S. mekongi, additional biomarkers are required. In this study, serum biomarkers associated with S. mekongi-infected mice were identified at 14-, 28-, 42-, and 56-days post-infection. Circulating proteins and antigens of S. mekongi in mouse sera were analyzed using mass spectrometry-based proteomics. Serine protease inhibitors and macrophage erythroblast attacher were down-regulated in mouse sera at all infection timepoints. In addition, 54 circulating proteins and 55 antigens of S. mekongi were identified. Notable circulating proteins included kyphoscoliosis peptidase and putative tuberin, and antigens were detected at all four infection timepoints, particularly in the early stages (12 days). The putative tuberin sequence of S. mekongi was highly similar to homologs found in other members of the genus Schistosoma and less similar to human and murine sequences. Our study provided the identity of promising diagnostic biomarkers that could be applicable in early schistosomiasis diagnosis and vaccine development.

Decadal changes in premature mortality associated with exposure to outdoor PM2.5 in mainland Southeast Asia and the impacts of biomass burning and anthropogenic emissions

In mainland Southeast Asia (SEA), a rapid increase of fossil fuel consumption and massive particulate matter emissions from biomass burning (BB) are severely threatening the health of local inhabitants. In this study, surface PM2.5 data, satellite fire observations and emission inventories were integrated with the Global Exposure Mortality Model (GEMM) to estimate premature mortality attributable to PM2.5 exposure from 1990 through 2019 and to explore and quantify the health burden associated with BB and anthropogenic emissions in mainland SEA. BB in mainland SEA has remained intense over the past decades. Owing to a lack of effective control measures, emission inventory and satellite-observed data both showed that BB has markedly intensified in several regions, including northern Cambodia and northern Laos. The multiannual average (1997–2015) BB PM2.5 emission was 1.6 × 106 t/yr, which is much higher than that of anthropogenic (fossil fuel combustion) PM2.5 emission. GEMM results indicated that PM2.5-related premature mortality in mainland SEA more than doubled from 100 (95 % confidence interval [CI], 88–112) thousand in 1990 to 257 (95 % CI, 228–286) thousand in 2019. Decomposition analysis revealed that variations in population size and age structure also promoted this increase of PM2.5-related deaths. Given that mainland SEA is a rapidly developing region, it is expected that local public health will face increasing challenges due to population growth, population ageing, and increased anthropogenic emissions. Therefore, it is imperative for policymakers to consider these influential factors, set practical mitigation targets, and explore how to effectively and systematically combine BB with anthropogenic emission controls to maximize the health benefits.

Efficacy of three anti-malarial regimens for uncomplicated Plasmodium falciparum malaria in Cambodia, 2009–2011: a randomized controlled trial and brief review

BackgroundAnti-malarial resistance remains an important public health challenge in Cambodia. The effectiveness of three therapies for uncomplicated falciparum malaria was evaluated in Oddar Meanchey province in Northern Cambodia from 2009 to 2011.MethodsIn this randomized, open-label, parallel group-controlled trial, 211 subjects at least 5 years old with uncomplicated falciparum malaria were treated with 3 days of directly observed therapy: 63 received artesunate–mefloquine (AS/MQ), 77 received dihydroartemisinin–piperaquine (DHA/PPQ), and 71 received atovaquone–proguanil (ATQ/PG). The subjects were followed for 42 days or until recurrent parasitaemia. Genotyping of msp1, msp2, and glurp among individual parasite isolates distinguished recrudescence from reinfection. Pfmdr1 copy number was measured by real-time PCR and half-maximal parasite inhibitory concentrations (IC50) were measured in vitro by 48-h isotopic hypoxanthine incorporation assay.ResultsThe per-protocol PCR-adjusted efficacy (95% confidence interval) at 42 days was 80.6% (70.8–90.5%) for AS/MQ, 97.2% (93.3–100%) for DHA/PPQ, and 92.9% (86.1–99.6%) for ATQ/PG. On day 3, 57.9% remained parasitaemic in the AS/MQ and DHA/PPQ arms. At baseline, 46.9% had microscopic Plasmodium falciparum gametocytaemia. Both recurrences in the DHA/PPQ arm lost Pfmdr1 copy number amplification at recrudescence. All four recurrences in the ATQ/PG arm were wild-type for cytochrome bc1. One subject withdrew from the ATQ/PG arm due to drug allergy.ConclusionsThis study was conducted at the epicentre of substantial multi-drug resistance that emerged soon thereafter. Occurring early in the national transition from AS/MQ to DHA/PPQ, both DHA/PPQ and ATQ/PG had acceptable efficacy against uncomplicated falciparum malaria. However, efficacy of AS/MQ was only 80% with apparent mefloquine resistance based on elevated Pfmdr1 copy number and IC50. By 2009, there was already significant evidence of artemisinin resistance not previously reported at the Northern Cambodia–Thai border. This study suggests the basis for early development of significant DHA/PPQ failures within 3 years of introduction. Artemisinin resistance likely occurred on the Northern border concurrently with that reported along the Western border in Pailin.Trial registration This legacy trial was conducted prior to International Committee of Medical Journal Editors’ requirements for preregistration on ClinicalTrials.gov. The full protocol has been provided.

Assessing the status of the Green Peafowl’s “expected stronghold” in dry forests along the Salawin River, north-west Thailand

Summary The suitable habitats of the Endangered Green Peafowl Pavo muticus have declined by 80% over the past century due to extensive anthropogenic degradation. Currently, only six strongholds remain in mainland South-east Asia. While there are estimates of the species’ presence and status in five of these, the sixth one, defined as an “expected stronghold” located in the suitable dry forest along the Salawin River between Thailand and Myanmar, is not well documented. This study assessed the status of the area as a stronghold for the Green Peafowl’s long-term survival by estimating 1) the population density, 2) the current extension of suitable habitats, and 3) the threats to its survival. The area had an estimated density of 0.27 calling males/km2 (CI = 0.07–1.01) inhabiting 9,154 km2 of a mosaic of forest types, including mixed dry pine, mixed deciduous, and dry dipterocarp forests. Higher estimates were reported in other strongholds, including 0.8 birds/km2 in Bago Yoma (Myanmar), 15.8 birds/km2 in north-east Thailand, 1.13–11.34 birds/km2 in HuaiKhaKhaeng Wildlife Sanctuary (Thailand), 0.15–1.7 birds/km2 in northern Cambodia, and 0.15–4.69 birds/km2 in eastern Cambodia / south-central Vietnam. Hunting, habitat disturbance, and the presence of humans posed the greatest danger to the species across the surveyed area. Our results confirm the potential of the area for the species’ long-term survival. However, this “expected stronghold,” which could sustain a population of over 10 calling males/km2 like other high-quality strongholds, is in dire need of a comprehensive management plan to help reduce anthropogenic pressure. Ultimately, transboundary management between Thailand and Myanmar is crucial for the long-term repopulation of this stronghold.

Miliusa microphylla (Annonaceae), a new species from Thailand as evidenced by morphology and plastid phylogeny, with M. glandulifera, a new record for Thailand

On the basis of expansive molecular phylogenetic analyses of the genus Miliusa (Annonaceae) utilising up to seven plastid DNA regions, four major clades are identified: clades A, B, C and D. Members of clade C possess axillary inflorescences and crescent-shaped to semicircular glandular structures at the base or (slightly) higher inside the inner petals. In this clade, accessions of M. mollis are recovered as a monophyletic group, divided into two major clades. One of them is recognised as a new species, M. microphylla, which differs from the other (M. mollis) in the following characters: pedicel length, as well as glandular structures and indumentum on the inner petals. The new species is endemic to southeastern Thailand, whereas M. mollis has a much wider distribution (central, eastern, northeastern, northern and peninsular Thailand plus Cambodia and Vietnam). In addition, M. glandulifera, a new record for Thailand, is retrieved as the sister group of a clade composed of M. microphylla and M. mollis. The name M. glandulifera is lectotypified and the description of M. glandulifera is emended, with the information on mature monocarps added. The conservation status of M. microphylla and M. glandulifera is provisionally assessed. A revised key to the species in clade C in Thailand is provided. The phylogenetic position of M. nakhonsiana and M. sessilis in clade C, as well as of M. chantaburiana and M. eupoda in clade B is confirmed for the first time.

Acceptability and feasibility of malaria prophylaxis for forest goers: findings from a qualitative study in Cambodia

BackgroundIn the Greater Mekong Subregion, adults are at highest risk for malaria, particularly those who visit forests. The absence of effective vector control strategies and limited periods of exposure during forest visits suggest that chemoprophylaxis could be an appropriate strategy to protect forest goers against malaria.MethodsAlongside a clinical trial of anti-malarial chemoprophylaxis in northern Cambodia, qualitative research was conducted, including in-depth interviews and observation, to explore the acceptability of malaria prophylaxis for forest goers, the implementation opportunities, and challenges of this strategy.ResultsProphylaxis with artemether–lumefantrine for forest goers was found to be acceptable under trial conditions. Three factors played a major role: the community’s awareness and perception of the effectiveness of prophylaxis, their trust in the provider, and malaria as a local health concern. The findings highlight how uptake and adherence to prophylaxis are influenced by the perceived balance between benefits and burden of anti-malarials which are modulated by the seasonality of forest visits and its influence on malaria risk.ConclusionsThe implementation of anti-malarial prophylaxis needs to consider how the preventive medication can be incorporated into existing vector-control measures, malaria testing and treatment services. The next step in the roll out of anti-malarial prophylaxis for forest visitors will require support from local health workers.

Quality and benefits of good agricultural practice method on choy sum cultivation in northern Cambodia

Choy sum (Brassica chinensis var. parachinensis) is one of the important green leafy vegetable crops widely produced and consumed in Cambodia. Most of the farmers practically use chemical inputs to increase their choy sum’s yield, yet negatively affecting consumers’ health. Accordingly, assuring food safety and higher yield of choy sum are essential for sustainable economic growth and development in Cambodia. In this study, we aimed to investigate the quality and benefits of choy sum cultivation using good agricultural practice (GAP) over the organic farming systems in northern Cambodia; where growth rate, yield and economic efficiency of choy sum crop were assessed. Completely randomized design was employed on three treatments (non-treated control, organic method, and GAP), while classical statistical tests were used to examine the difference of quality and benefits between the treatments. As a result, cultivation technique-GAP method provided a better growth rate, yield, and economic profitability than other treatments. Thus, GAP method’s application is recommended for choy sum crop production and other potential green leafy crops. These findings provided more concrete evidence on financial benefits and quality of production of the GAP method on leafy plant growth (choy sum). Therefore, agricultural extension using GAP method would be a good technique to promote agricultural value chain, while improving food safety and livelihoods of Cambodian farmers.

What exactly do REDD+ projects produce? A materialist analysis of carbon offset production from a REDD+ project in Cambodia

This article attempts to re-ground analyses of carbon markets by examining the material relations of production of a REDD + project in Cambodia. It focuses on how surplus value is extracted from labour at various points in the production chain of Verified Carbon Units (VCUs). Using extensive field work conducted over three years on a REDD + project in northern Cambodia I argue that VCUs are neither actual avoided units of deforestation and emissions, nor mere imagined or socially constructed commodities. Rather VCUs are packages of technical and affective claims attached to particular REDD + projects which are created through material labour processes. Only by examining the use-values that are created through these labour processes can demand for VCUs be properly understood. This article will start by giving a background to the Oddar Meanchey REDD + project (OMREDD + project). It will then examine the writing of the project document and examine the verification process and consider how these formed critical parts of the commodity production process. After that it will examine how the project collapsed on the ground and yet VCUs were still sold in the market. Finally the article will consider how the claims of the OMREDD + project were challenged by critical work and how future interventions against REDD + projects can successfully undermine the claims of REDD + projects and the extraction of surplus value.

Improving Treatment and Outcomes for Melioidosis in Children, Northern Cambodia, 2009-2018.

We report trends in manifestations, treatment, and outcomes of 355 children with culture-confirmed melioidosis over 10 years at a pediatric hospital in northern Cambodia. Bacteremia and presentation with pneumonia were risk factors for death. A total of 39 children recovered after being given only oral antimicrobial drug treatment.

Anopheles ecology, genetics and malaria transmission in northern Cambodia

In the Greater Mekong Subregion, malaria cases have significantly decreased but little is known about the vectors or mechanisms responsible for residual malaria transmission. We analysed a total of 3920 Anopheles mosquitoes collected during the rainy and dry seasons from four ecological settings in Cambodia (villages, forested areas near villages, rubber tree plantations and forest sites). Using odor-baited traps, 81% of the total samples across all sites were collected in cow baited traps, although 67% of the samples attracted by human baited traps were collected in forest sites. Overall, 20% of collected Anopheles were active during the day, with increased day biting during the dry season. 3131 samples were identified morphologically as 14 different species, and a subset was also identified by DNA amplicon sequencing allowing determination of 29 Anopheles species. The investigation of well characterized insecticide mutations (ace-1, kdr, and rdl genes) indicated that individuals carried mutations associated with response to all the different classes of insecticides. There also appeared to be a non-random association between mosquito species and insecticide resistance with Anopheles peditaeniatus exhibiting nearly fixed mutations. Molecular screening for Plasmodium sp. presence indicated that 3.6% of collected Anopheles were positive, most for P. vivax followed by P. falciparum. These results highlight some of the key mechanisms driving residual human malaria transmission in Cambodia, and illustrate the importance of diverse collection methods, sites and seasons to avoid bias and better characterize Anopheles mosquito ecology in Southeast Asia.

Political violence, migration, lack of citizenship, and agrobiodiversity loss in the borderlands of Thailand and Laos

In the 1970s and 1980s, the borderlands between southern Laos, northeastern Thailand and northern Cambodia were a hotbed of militarized conflict and insurgent activity. Various armed groups, on the political left and right, operated in what was later referred to as the Emerald Triangle. This article considers how ethnic Kuy (Souay) Indigenous peoples from the Lao side of the border in Mounlapoumok District, Champasak Province, southern Laos, fled to neighboring parts of Ubon Ratchathani Province, northeastern Thailand as political refugees after Pathet Lao communists took over Laos in 1975. Many later became stateless insurgents fighting for Lao anti-communist groups opposed to the Lao People’s Democratic Republic. In particular, the article considers the influence of political armed conflict on migration and citizenship status, and subsequently on agrobiodiversity loss, particularly of native varieties of upland rice cultivated in swidden fields. This includes considering the structural violence associated with Thai government policies and practices related to forest conservation and preventing swidden cultivation. Agrobiodiversity loss was not centrally influenced by political violence, but it significantly influenced the conditions that affected agrobiodiversity, emphasizing the potential usefulness of studying political violence and agrobiodiversity loss through considering indirect influences.

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

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. The sequence of pfcrt was determined for 410 P. falciparum isolates using PacBio amplicon sequencing or whole genome sequencing. Quantitative polymerase chain reaction was used to estimate pfpm2 and pfmdr1 copy number. Newly emerged PfCRT mutations increased in prevalence after the change to dihydroartemisinin-piperaquine in 2010, with >98% of parasites harboring these mutations by 2017. After 2014, the prevalence of PfCRT F145I declined, being outcompeted by parasites with less resistant, but more fit PfCRT alleles. After the change to artesunate-mefloquine, the prevalence of parasites with amplified pfpm2 decreased, with nearly half of piperaquine-resistant PfCRT mutants having single-copy pfpm2. The large proportion of PfCRT mutants that lack pfpm2 amplification emphasizes the importance of including PfCRT mutations as part of molecular surveillance for piperaquine resistance in this region. Likewise, it is critical to monitor for amplified pfmdr1 in these PfCRT mutants, as increased mefloquine pressure could lead to mutants resistant to both drugs.

Detection of antibodies to Toxoplasma gondii among owned dogs in Cambodia

Toxoplasma gondii is a protozoan parasite belonging to the phylum Apicomplexa, which has a two-host life cycle and an extensive global distribution. The presence of antibodies to T. gondii was examined in owned dogs in Cambodia. In total, 103 dog serum samples from 37 households in northern Cambodia were collected and examined for evidence of T. gondii infection using an indirect immunofluorescent antibody test. In total, 52 of 103 (50.5%) samples were serologically positive for T. gondii in this study. No significant risk factor associated with T. gondii infection was found. To the best of our knowledge, this is the first report of the seroprevalence of T. gondii in dogs from Cambodia, which revealed a considerable risk of infection for humans. Therefore, consuming undercooked dog meat or contacting feces with contaminated cat feces should be restricted to avoid the possibility of zoonosis. Further studies are needed to determine the epidemiology of T. gondii in populations of larger dogs and other animals to improve our understanding of the situation of the pathogen in this country.