Anopheles diversity, biting behaviour and transmission potential in forest and farm environments of Gia Lai province, Vietnam.

BACKGROUND: Despite recent reductions in Vietnam, malaria transmission persists in some areas in forests and farmlands where a high density of Anopheles mosquitoes relative to other environments occurs. To inform effective malaria control measures, it is important to understand vector bionomics and the malaria transmission role of Anopheles spp. in the highland regions of Vietnam. This study was conducted to quantify the abundance, composition and biting behaviour of the Anopheles mosquito population, and the proportion of Plasmodium spp. infected mosquitoes collected from forest and agricultural farm sites in Gia Lai province, Vietnam. METHODS: Forest and agricultural farm sites in Gia Lai province were selected for mosquito collections (total eight sites). Mosquito collection was performed by Human-baited Double Net Trap (HDNT), animal-baited traps (ABT) using cattle, and CDC light traps. Captured mosquitoes were identified morphologically, and salivary glands of Anopheles mosquitoes were examined for sporozoites using microscopy. Plasmodium infection was determined by Polymerase Chain Reaction (PCR), and identification of blood meal type was determined by PCR and diffuse serum agglutination assay. RESULTS: A total of 1815 Anopheles mosquitoes belonging to 19 species were collected by ABT (n = 1169), HDNT (n = 471) and CDC light trap (n = 175). Anopheles abundance and diversity varied by district and environment. Capture by HDNT of Anopheles of vectorial concern was observed between early evening and early morning. Plasmodium vivax infection was determined by PCR in two Anopheles dirus specimens captured by HDNT in forest sites. Blood from a range of hosts could, including human blood, could be detected in species considered primary and secondary vectors An. dirus, and Anopheles aconitus, and Anopheles maculatus, respectively. CONCLUSIONS: A low number of Anopheles spp. considered primary vectors of concern and very low numbers of Plasmodium spp. infected Anopheles mosquitoes were captured at the end of the rainy season in the Central Highlands of Vietnam. However, capture species of vectorial concern by HDNT throughout the early to late evening demonstrates that use of additional personal protective measures could supplement current preventative measures, such as bed nets to prevent exposure to vectors of concern in this region.

Radiation exposure in a region with natural high background radiation originated from rare earth element deposits at Bat Xat district, Vietnam.

Surface deposits of rare earth element (REE) were identified in the Bat Xat district, Northern Vietnam. As the area is inhabited, an in-depth investigation was carried out to assess the radioactivity levels and to evaluate the radiation exposure and radiological risks for the population. Samples of REE ore, soils, water and several foods locally produced were collected and analyzed by gamma spectrometry for determination of 232Th, 226Ra, and 40 K. Radon (222Rn and 220Rn) measurements were carried out in dwellings at the villages located near by the REE deposit area, and in Hanoi for comparison. Based on the measured radionuclide concentrations, several radiological parameters were calculated to evaluate the radiological risks for the population and to compare with worldwide values. Results indicate that the representative person of the most exposed group living near the REE deposits may receive a total annual effective dose as high as 37.9 ± 10.6 mSv, i.e., approximately 16 times the world average dose of 2.4 mSv y-1. Consequently, this area should be considered a high background radiation area. Exposure to external radiation and internal radiation from ingestion and inhalation of radionuclides were assessed separately. Radon inhalation contributed to approximately 70% of the total annual effective dose, with both radon isotopes contributing significantly, while the ingestion of local foods and water gave minor contributions to the total effective dose. Several measures were considered to improve the radiation safety and recommendations are given to relocate the most exposed members of the population.

Community perceptions of targeted anti-malarial mass drug administrations in two provinces in Vietnam: a quantitative survey.

BACKGROUND: As part of a targeted malaria elimination project, mass drug administrations (MDAs) were conducted in Vietnam. The impact of MDAs on malaria transmission depends largely on the efficacy of the anti-malarial drug regimen, the malaria epidemiology in the site and the population coverage. To explore why some people participate in MDAs and others do not, a quantitative survey of the villagers' perceptions was undertaken in Vietnam. METHODS: In 2013/2014 MDAs were conducted in a village in Binh Phuoc province and a village in Ninh Thuan province. Within three months of the drug administration, 59 respondents in a village in Binh Phuoc and 79 respondents in a village in Ninh Thuan were randomly selected and interviewed. RESULTS: Comprehension of the purpose of the intervention was of paramount importance for participation in the intervention. Respondents aware that the intervention aims to protect against malaria were significantly more likely to participate than respondents who were unaware of the MDA's purpose. Secondly, how and by whom villagers were informed was critical for participation. There was a strong association between sensitization by an informant such as a member of the local health team with participation in the intervention. CONCLUSIONS: The study suggests several approaches to increase participation in mass drug administration campaigns. Training trustworthy informants to sensitize the study population is critical to maximize village participation in this setting. To achieve high coverage the entire community must understand and agree with the intervention.

The prevalence, incidence and prevention of Plasmodium falciparum infections in forest rangers in Bu Gia Map National Park, Binh Phuoc province, Vietnam: a pilot study.

BACKGROUND: Prophylaxis for high-risk populations, such as forest workers, could be one component for malaria elimination in the Greater Mekong Sub-region. A study was conducted to assess the malaria incidence in forest rangers and the feasibility of malaria prophylaxis for rangers sleeping in forest camps. METHODS: Forest rangers deployed in the Bu Gia Map National Park, Vietnam were invited to participate in the study. Plasmodium infections were cleared using presumptive treatment, irrespective of malaria status, with a 3-day course dihydroartemisinin/piperaquine (DP) and a 14-day course of primaquine. Before returning to the forest, study participants were randomly allocated to a 3-day course of DP or placebo. Fifteen days after returning from their forest deployment the participants were tested for Plasmodium infections using uPCR. RESULTS: Prior to treatment, 30 of 150 study participants (20%) were found to be infected with Plasmodium. Seventeen days (median) after enrolment the rangers were randomized to DP or placebo 2 days before returning to forest camps where they stayed between 2 and 20 days (median 9.5 days). One ranger in the DP-prophylaxis arm and one in the placebo arm were found to be infected with Plasmodium falciparum 15 days (median) after returning from the forest. The evaluable P. falciparum isolates had molecular markers indicating resistance to artemisinins (K13-C580Y) and piperaquine (plasmepsin), but none had multiple copies of pfmdr1 associated with mefloquine resistance. CONCLUSION: Anti-malarial prophylaxis in forest rangers is feasible. The findings of the study highlight the threat of multidrug-resistant malaria. Trial registration NCT02788864.

Large-scale screening and characterization of enteroviruses and kobuviruses infecting pigs in Vietnam.

A recent survey of pigs in Dong Thap province, Vietnam identified a high frequency of enterovirus species G (EV-G) infection (144/198; 72.7%). Amongst these was a plethora of EV-G types (EV-G1, EV-G6 and four new types EV-G8-EV-G11). To better characterize the genetic diversity of EV-G and investigate the possible existence of further circulating types, we performed a larger-scale study on 484 pig and 45 farm-bred boar faecal samples collected in 2012 and 2014, respectively. All samples from the previous and current studies were also screened for kobuviruses. The overall EV infection frequency remained extremely high (395/484; 81.6%), but with comparable detection rates and viral loads between healthy and diarrhoeic pigs; this contrasted with less frequent detection of EV-G in boars (4/45; 8.9%). EV was most frequently detected in pigs ≤ 14 weeks old (∼ 95%) and declined in older pigs. Infections with EV-G1 and EV-G6 were most frequent, whilst less commonly detected types included EV-G3, EV-G4 and EV-G8-EV-G11, and five new types (EV-G12-EV-G16). In contrast, kobuvirus infection frequency was significantly higher in diarrhoeic pigs (40.9 versus 27.6%; P = 0.01). Kobuviruses also showed contrasting epizootiologies and age associations; a higher prevalence was found in boars (42%) compared with domestic pigs (29%), with the highest infection frequency amongst pigs >52 weeks old. Although genetically diverse, all kobuviruses identified belonged to the species Aichivirus C. In summary, this study confirms infection with EV-G was endemic in Vietnamese domestic pigs and exhibits high genetic diversity and extensive inter-type recombination.

Isolation of Japanese encephalitis virus and a novel insect-specific flavivirus from mosquitoes collected in a cowshed in Japan.

Cattle do not generally appear to develop severe viremia when infected with Japanese encephalitis virus (JEV), and they can be infected without showing clinical signs. However, two cattle in Japan recently died from JEV infection. In this study, we investigated the presence of different species of mosquitoes and flavivirus in a cowshed in the southwest region of Japan. In this cowshed, the two most common species of mosquitoes collected were Culex tritaeniorhynchus (including Culex pseudovishnui) and Anopheles sinensis. We performed virus isolation from the collected mosquitoes and obtained two flaviviruses: JEV and a novel insect-specific flavivirus, tentatively designated Yamadai flavivirus (YDFV). Phylogenetic analysis revealed that all three JEV isolates belonged to JEV genotype I and were closely related to a JEV strain that was isolated from the brains of cattle exhibiting neurological symptoms in Japan. Genetic characterization of YDFV revealed that the full genome RNA (10,863 nucleotides) showed homology with the Culex-associated insect-specific flaviviruses Quang Binh virus (79% identity) and Yunnan Culex flavivirus (78% identity), indicating that YDFV is a novel insect-specific flavivirus.

Severe malaria not responsive to artemisinin derivatives in man returning from Angola to Vietnam.

Resistance to artemisinin derivatives, the most potent antimalarial drugs currently used, has emerged in Southeast Asia and threatens to spread to Africa. We report a case of malaria in a man who returned to Vietnam after 3 years in Angola that did not respond to intravenous artesunate and clindamycin or an oral artemisinin-based combination.

Prevalence, genetic diversity and recombination of species G enteroviruses infecting pigs in Vietnam.

Picornaviruses infecting pigs, described for many years as 'porcine enteroviruses', have recently been recognized as distinct viruses within three distinct genera (Teschovirus, Sapelovirus and Enterovirus). To better characterize the epidemiology and genetic diversity of members of the Enterovirus genus, faecal samples from pigs from four provinces in Vietnam were screened by PCR using conserved enterovirus (EV)-specific primers from the 5' untranslated region (5' UTR). High rates of infection were recorded in pigs on all farms, with detection frequencies of approximately 90% in recently weaned pigs but declining to 40% in those aged over 1 year. No differences in EV detection rates were observed between pigs with and without diarrhoea [74% (n = 70) compared with 72% (n = 128)]. Genetic analysis of consensus VP4/VP2 and VP1 sequences amplified from a subset of EV-infected pigs identified species G EVs in all samples. Among these, VP1 sequence comparisons identified six type 1 and seven type 6 variants, while four further VP1 sequences failed to group with any previously identified EV-G types. These have now been formally assigned as EV-G types 8-11 by the Picornavirus Study Group. Comparison of VP1, VP4/VP2, 3D(pol) and 5' UTRs of study samples and those available on public databases showed frequent, bootstrap-supported differences in their phylogenies indicative of extensive within-species recombination between genome regions. In summary, we identified extremely high frequencies of infection with EV-G in pigs in Vietnam, substantial genetic diversity and recombination within the species, and evidence for a much larger number of circulating EV-G types than currently described.

Mycobacterium fortuitum skin infections after subcutaneous injections with Vietnamese traditional medicine: a case report.

BACKGROUND: Iatrogenic skin and soft tissue infections by rapidly growing mycobacteria are described with increasing frequency, especially among immunocompromised patients. CASE PRESENTATION: Here, we present an immunocompetent patient with extensive Mycobacterium fortuitum skin and soft tissue infections after subcutaneous injections to relieve joint pains by a Vietnamese traditional medicine practitioner. Moreover, we present dilemmas faced in less resourceful settings, influencing patient management. CONCLUSION: This case illustrates the pathogenic potential of rapid growing mycobacteria in medical or non-medical skin penetrating procedures, their world-wide distribution and demonstrates the dilemmas faced in settings with fewer resources.

Novel chitosan-zeolite X composite beads prepared by phase-inversion method for CO2 adsorptive capture.

The urgent need to mitigate carbon emissions from industrial heat production has led to the exploration of novel carbon-based materials for carbon capture. Chitosan, a versatile framework, has been widely utilized for embedding many materials such as grafted graphene oxide, zeolite, and activated carbon to enhance the carbon capture capacity of diverse carbon-based materials. Remarkably, the combination of chitosan and zeolite overcomes the inherent drawbacks of powdery zeolite, resulting in improved stability and efficiency in carbon capture applications. In this study, zeolite X-chitosan composite was successfully synthesized using phase inversion method followed by solvent exchange and air drying. The synthesis procedure described in this study presents a notable advantage in terms of simplicity and ease of fabrication. The combination of SEM and XRD analyses provided evidence that the composite exhibited a uniform arrangement of zeolite within the chitosan framework and maintained the original properties of the powdered zeolite. The adsorption capacity of the composite was first investigated by varying mass ratio of zeolite per chitosan. The composite with mass ratio that gave the best adsorption capacity were then tested under various temperatures (-20 °C, 0 °C, 30 °C, and 50 °C) and pressures (1 kPa, 3 kPa, 5 kPa, and 30 kPa). The application of different adsorption models was also employed to simulate the breakthrough curves. Furthermore, the material also underwent multiple continuous adsorption-desorption cycles showing its potential for repeated rechargeability. In contrast, the synthesis and characterization of copper ion-exchanged composite yielded significant drop in adsorption capacity, likely due to the formation of ligands or the inherent reactivity of Cu2+ ions towards hydroxide.

Reduction in Plasmodium falciparum Pfk13 and pfg377 allele diversity through time in southern Vietnam.

BACKGROUND: Plasmodium falciparum has acquired resistance to artemisinin in Southeast Asia, with mutations in the P. falciparum Kelch-13 (Pfk13) gene associated with the resistance phenotype. The widespread use of Artemisinin-based combination therapy (ACT)s in Southeast Asia has led to the selection and spread of parasites carrying mutations in Pfk13. We characterised the allele diversity of Pfk13 and pfg377, an artemisinin-resistance neutral polymorphic gene, in parasite DNA extracted human blood from in southern Vietnam in 2003, 2012, 2015 and 2018. METHOD: This study was conducted in Bu Gia Map commune, Binh Phuoc province, Vietnam, from May 2018 to January 2019. Twenty-four samples from 2018 to 2019, 30 from 2003, 24 from 2012 and 32 from 2015 were analysed. Malaria-infected human blood was collected by finger-prick and used for molecular analysis. A nested-PCR targeting the small subunit ribosomal RNA gene was used for Plasmodium species identification, followed by amplification and nucleotide sequencing of Pfk13 and region 3 of pfg377. Archived blood samples collected in the same region in 2012 and 2015 were also analysed as above for comparison. RESULTS: The genetic diversity of Pfk13 and pfg377 was lower in 2018-2019 compared to 2012 and 2015. The number of distinct Pfk13 mutants decreased from three in 2012 and 2015, P553L, V568G and C580Y, to one, C580Y in 2018-2019. In 2018-2019, the frequency of C580Y mutant strains was 71% (17/24 isolates). All samples were wild type in 2003. In 2012 and 2015, there were single-strain infections as well as co-infections with two mutant strains or with mutant and wild strains, whereas there were no co-infections in 2018. pfg377 allele diversity decreased from five alleles in 2012 to two alleles in 2018-2019. CONCLUSION: The genetic diversity of P. falciparum was reduced at the two genetic loci surveyed in this study, Pfk13 and pfg377. In the case of the former gene, we observed an increase in the prevalence of parasites carrying the C580Y gene, known to confer reduced susceptibility to ACTs. The reduction in the diversity of pfg377 may be linked to the clonal expansion of parasite strains carrying the C580Y mutation, leading to an overall reduction in parasite genetic diversity across the population.

Genetic diversity and cross-species transmission of kobuviruses in Vietnam.

Cross-species transmission of viruses poses a sustained threat to public health. Due to increased contact between humans and other animal species the possibility exists for cross-species transmissions and ensuing disease outbreaks. By using conventional PCR amplification and next generation sequencing, we obtained 130 partial or full genome kobuvirus sequences from humans in a sentinel cohort in Vietnam and various mammalian hosts including bats, rodents, pigs, cats, and civets. The evolution of kobuviruses in different hosts was analysed using Bayesian phylogenetic methods. We estimated and compared time of origin of kobuviruses in different host orders; we also examined the cross-species transmission of kobuviruses within the same host order and between different host orders. Our data provide new knowledge of rodent and bat kobuviruses, which are most closely related to human kobuviruses. The novel bat kobuviruses isolated from bat roosts in Southern Vietnam were genetically distinct from previously described bat kobuviruses, but closely related to kobuviruses found in rodents. We additionally found evidence of frequent cross-species transmissions of kobuviruses within rodents. Overall, our phylogenetic analyses reveal multiple cross-species transmissions both within and among mammalian species, which increases our understanding of kobuviruses genetic diversity and the complexity of their evolutionary history.

Evolution and phylogeographic dissemination of endemic porcine picornaviruses in Vietnam.

Members of the Picornaviridae are important and often zoonotic viruses responsible for a variety of human and animal diseases. However, the evolution and spatial dissemination of different picornaviruses circulating in domestic animals are not well studied. We examined the rate of evolution and time of origin of porcine enterovirus G (EV-G) and porcine kobuvirus species C lineages (PKV-C) circulating in pig farms in Vietnam and from other countries. We further explored the spatiotemporal spread of EV-G and PKV-C in Southwest Vietnam using phylogeographic models. Multiple types of EV-G are co-circulating in Vietnam. The two dominant EV-G types among isolates from Vietnam (G1 and G6) showed strong phylogenetic clustering. Three clades of PKV-C (PKV-C1-3) represent more recent introductions into Vietnam; PKV-C2 is closely related to PKV-C from Southwest China, indicating possible cross-border dissemination. In addition, high virus lineage migration rates were estimated within four districts in Dong Thap province in Vietnam for both EV-G types (G1, G6) and all PKV-C (C1-3) clades. We found that Chau Thanh district is a primary source of both EV-G and PKV-C clades, consistent with extensive pig trading in and out of the district. Understanding the evolution and spatial dissemination of endemic picornaviruses in pigs may inform future strategies for the surveillance and control of picornaviruses.

Tomographic density imaging using modified DF–DBIM approach

Ultrasonic computed tomography based on back scattering theory is the most powerful and accurate tool in ultrasound based imaging approaches because it is capable of providing quantitative information about the imaged target and detects very small targets. The duple-frequency distorted Born iterative method (DF–DBIM), which uses density information along with sound contrast for imaging, is a promising approach for imaging targets at the level of biological tissues. With two frequencies f₁ (low) and f₂ (high) through Nf₁ and Nf₂ iterations respectively, this method is used to estimate target density along with sound contrast. The implications of duple-frequency fusion for the image reconstruction quality of density information along with sound contrast based ultrasound tomography have been analyzed in this paper. In this paper, we concentrate on the selection of parameters that is supposed to be the best to improve the reconstruction quality of ultrasound tomography. When there are restraints imposed on simulated scenarios to have control of the computational cost, the iteration number Nf₁ is determined resulting in giving the best performance. The DF–DBIM is only effective if there are a moderate number of iterations, transmitters and receivers. In case that the number of transducers is either too large or too small, a result of reconstruction which is better than that of the single frequency approach is not produced by the implementation of DF–DBIM. A fixed sum N(iter) of Nf₁ and Nf₂ was given, the investigation of simulation results shows that the best value of Nf₁ is [N(iter)/2 − 1]. The error, when applying this way of choosing the parameters, will be normalized with the reduction of 56.11%, compared to use single frequency as used in the conventional DBIM method. The target density along with sound contrast is used to image targets in this paper. It is a fact that low-frequency offers fine convergence, and high-frequency offers fine spatial resolution. Wherefore, this technique can effectively expand DBIM's applicability to the problem of biological tissue reconstruction. Thanks to the usage of empirical data, this work will be further developed prior to its application in reality.

Forest malaria in central Vietnam.

Studies were conducted in a village in central Vietnam to explain the existence of a forest malaria cycle of transmission external to the village. The findings suggested no malaria transmission in the village because of the absence of a suitable vector, but suggested evidence for transmission in villagers when attending garden plots in the forested hills surrounding the village. A sizeable population residing near these garden plots, the presence of Anopheles dirus (a highly efficient vector), and a degree of malaria immunity within the inhabitants created suitable conditions to sustain malaria transmission outside the village.