Camellia annamensis (Theaceae): phytochemical analysis, cytotoxic, antioxidative, and antimicrobial activities

Cytotoxic, antioxidative, and antimicrobial activities of Camellia annamensis, and its chemical compositions were first provided in the current study. Phenolic contents in the methanol extracts of its leaves and flowers were 222.73 ± 0.09 and 64.44 ± 0.08 mg GAE/g extract, whereas flavonoid contents in these parts were 108.80 ± 0.28 and 131.26 ± 0.39 mg rutin/g extract, respectively. By using HPLC-DAD analysis, gallic acid (43.72 ± 0.09 - 81.89 ± 1.83 mg/g) and (-)-epigallocatechin gallate (67.31 ± 1.26 - 70.68 ± 7.82 mg/g) were identified as the major compounds. C. annamensis leaf and flower extracts were moderately cytotoxic against A549, HT-29, SK-Mel-2, MCF-7, HepG2, HeLa, and MKN-7. Particularly, they are better than the standards trolox (IC50 7.57 ± 0.23 µg/mL) in lipid peroxidation inhibitory evaluation, and streptomycin (IC50/MIC = 45.34-50.34/128-256 µg/mL) in antimicrobial assay against the Gram-positive bacteria Enterococcus faecalis ATCC299212, Staphylococcus aureus ATCC25923, and the Gram-negative bacterium Salmonella enterica ATCC13076.

Fruit and Vegetable Intake of Females Before, During, and After Introduction of 3 Bundled Food System Interventions in Urban Vietnam and Nigeria

Background

Low fruit and vegetable (FV) intake in low- and middle-income countries, which is associated with noncommunicable diseases and micronutrient deficiencies, requires food system interventions addressing FV accessibility, affordability, and acceptability. Periodic FV intake monitoring during interventions informs progress toward achieving increased intakes and contributes to understanding the effectiveness of these interventions.

Objectives

This study evaluates the trend in FV intake before, during, and after implementation of a set of nutrition-sensitive food system interventions addressing accessibility, affordability, and acceptability to increase FV consumption over a 1-y period in Vietnamese and Nigerian low-income urban and periurban females.

Methods

We used the Diet Quality Questionnaire to assess FV food group consumption among 600 Vietnamese (Hanoi) and 610 Nigerian (Ibadan) females before, during, and after the interventions (Vietnam: July 2020-September 2021; Nigeria: November 2020-December 2021). A FV score was compared between exposure groups with (mixed) count modeling. The trend in consumption of individual FV groups was analyzed with mixed logistic regression.

Results

The FV score was stable over time, and a small increase was observed after the intervention period especially in Nigeria and in urban Vietnam. A decrease in the total score was observed in periurban Vietnam. Fluctuations were detected in the probability of consumption of individual FV groups over time especially within the fruit groups, probably due to seasonal availability. The degree of exposure could not explain differences in FV intake.

Conclusions

We found a marginal increase in the proportion of females consuming FV during the interventions in both countries. The FV score appeared to be a simple, quick, and easy-to-use indicator for monitoring diversity, variety, and consumption.

Essential Oils of Five Syzygium Species Growing Wild in Vietnam: Chemical Compositions and Antimicrobial and Mosquito Larvicidal Potentials

The essential oils of five Vietnamese Syzygium species (Syzygium levinei, S. acuminatissimum, S. vestitum, S. cumini, and S. buxifolium) were first hydro-distilled and analyzed using GC-FID/MS (gas chromatography-flame ionization detection/mass spectrometry). Monoterpene hydrocarbons, sesquiterpene hydrocarbons, and oxygenated sesquiterpenoids were the main chemical classes in these oils. All these essential oils showed good-excellent antimicrobial activities against Gram-positive bacteria Enterococcus faecalis, Staphylococcus aureus, and Bacillus cereus, and the yeast Candida albicans. S. levinei leaf essential oil, rich in bicyclogermacrene (25.3%), (E)-β-elemene (12.2%), (E)-caryophyllene (8.2%), and β-selinene (7.4%), as well as S. acuminatissimum fruit essential oil containing (E)-caryophyllene (14.2%), α-pinene (12.1%), caryophyllene oxide (10.9%), β-selinene (10.8%), α-selinene (8.0%), and α-humulene (5.7%), established the same MIC value of 8 µg/mL against E. faecalis and B. cereus, which were much better than the positive control streptomycin (MIC 128-256 µg/mL). The studied essential oils showed the potential to defend against mosquitoes since they caused the 24 and 48 h LC50 values of less than 50 µg/mL against the growth of Culex quinquefasciatus and Aedes aegypti larvae. Especially, S. buxifolium leaf essential oil strongly inhibited Ae. aegypti larvae with 24 and 48 h LC50 values of 6.73 and 6.73 µg/mL, respectively, and 24 and 48 h LC90 values of 13.37 and 10.83 µg/mL, respectively. These findings imply that Vietnamese Syzygium essential oils might have potential for use as supplemental antibacterial agents or as "green" alternatives for the control of mosquitoes.

Essential oils of the ginger plants Meistera caudata and Conamomum vietnamense: chemical compositions, antimicrobial, and mosquito larvicidal activities

The current study describes the chemical identification, antimicrobial, and mosquito larvicidal activities of essential oils from Meistera caudata and Conamomum vietnamense, growing in Vietnam. Essential oils were extracted from the leaves and rhizomes, and characterized by the GC-FID/MS (gas chromatography-flame ionization detection/mass spectrometry) analysis. Monoterpenes (33.1-89.2 %) were the main chemical class found in these oils. β-Pinene (30.8 %) and α-pinene (23.8 %) were two major compounds in M. caudata leaf oil. C. vietnamense leaf and rhizome essential oils were dominated by 1,8-cineole (47.9-62.0 %) and limonene (10.3-16.2 %). With the same MIC (minimum inhibitory concentration) value of 25 μg/mL, C. vietnamense leaf and rhizome essential oils strongly inhibited the growth of Gram-positive bacteria Staphylococcus aureus ATCC 29213 and Bacillus subtilis ATCC 6501, respectively. For 24 and 48-h treatments, C. vietnamense leaf essential oil strongly controlled the growth of mosquito Aedes aegypti with the respective LC50 values of 7.67 and 6.73 μg/mL, and the respective LC90 values of 13.37 and 10.83 μg/mL. In the same manner, C. vietnamense rhizome essential oil also showed strong mosquito larvicidal activity against Aedes albopictus with the LC50 values of 12.37 and 12.00 μg/mL, and the LC90 values of 20.56 and 18.58 μg/mL, respectively. C. vietnamense essential essential oils containing a high amount of 1,8-cineole are generally better than M. caudata essential essential oils in both two biological assays.

A simple fruit and vegetable score is a valid tool to assess actual fruit and vegetable intake

With the recent growing interest in improving fruit and vegetable intake for better health and limited research resources in many settings, simple-to-administer and low-priced indicators are essential tools for monitoring fruit and vegetable intake at the population level. A potential candidate indicator is the fruit and vegetable component of the Global Dietary Recommendation score (FV-GDR) based on data collected using the Diet Quality Questionnaire (DQQ). We investigated the relative validity of FV-GDR collected with the DQQ to measure fruit and vegetable intake by comparison with a 24-h recall (24hR) as a reference collected from 620 Vietnamese and 630 Nigerian adults in 2021. We found proportional differences in the prevalence of intake of vitamin A-rich vegetables, other vegetables and other fruits in Vietnam and all vegetable food groups in Nigeria. In both countries, we found a small difference in the total FV-GDR from DQQ compared with the 24hR, and the percentage of agreement between the two methods was quite high for the majority of the food groups. The FV-GDR calculated from the DQQ correlated with the actual intake, although less strongly than the FV-GDR from 24hR. The DQQ is a promising low-burden, low-cost and simple tool to calculate FV-GDR and to monitor fruit and vegetable consumption at the population level. This provides the possibility of evaluating an important aspect of diet quality in low-resource settings.

Environmentally-Friendly Pesticidal Activities of Callicarpa and Karomia Essential Oils from Vietnam and Their Microemulsions

There is an ongoing interest to identify alternative pesticidal agents to avoid the chronic problems associated with synthetic pesticides. Essential oils have shown promise as botanical pest control agents. In the present study, the essential oils of four members of the Lamiaceae (Callicarpa candicans, C. erioclona, C. macrophylla, and Karomia fragrans; Vietnamese names: Nàng nàng, Tu châu lông mem, Tu châu lá to and Cà diện, respectively), obtained from wild populations in Vietnam, have been obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The essential oils were formulated into microemulsions and the essential oils and their microemulsions were screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and for molluscicidal activity against Pomacea canaliculata. Atractylone and (E)-caryophyllene dominated the volatiles of C. candicans (CCEO) and C. erioclona (CEEO), while the major component in C. macrophylla (CMEO) and K. fragrans (KFEO) was (E)-caryophyllene. The essential oils and microemulsions of both C. candicans and C. erioclona exhibited excellent larvicidal activity against all three mosquito species (Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus) with LC₅₀ values <10 μg/mL. Additionally, the larvicidal activity of the microemulsions were significantly improved compared with their free essential oils, especially for C. candicans and C. erioclona. All four essential oils and their microemulsions showed excellent molluscicidal activity with LC₅₀ <10 μg/mL. In most cases, the essential oils and microemulsions showed greater pesticidal activity against target organisms than the non-target freshwater fish, Oreochromis niloticus. The in silico studies on physicochemical and ADMET properties of the major components in the studied essential oils were also investigated and most of the compounds possessed a favorable ADMET profile. Computational modeling studies of the studied compounds demonstrated a favorable binding interaction with the mosquito odorant-binding protein target and support atractylone, β-selinene, and caryophyllene oxide as potential inhibitors. Based on the observed pesticidal activities of the essential oils and their microemulsions, the Callicarpa species and K. fragrans should be considered for potential cultivation and further exploration as botanical pesticidal agents.

Chemical composition, antimicrobial and larvicidal activities of essential oils of two Syzygium species from Vietnam

The present study is the first to investigate the chemical composition, antimicrobial and larvicidal activities of the essential oils from the leaves of Syzygium attopeuense (Gagnep.) Merr. & L.M.Perry and Syzygium tonkinense (Gagnep.) Merr. & L.M.Perry collected in Vietnam. The essential oils were extracted by hydrodistillation and analyzed by GC and GC-MS. The study indicated the presence of a high percentage of sesquiterpenes in both investigated essential oils. The major components of S. attopeuense essential oil were bicyclogermacrene (24.26%), (E)-caryophyllene (11.72%), and (E)-β-ocimene (6.75%), whereas S. tonkinense essential oil was dominated by (E)-caryophyllene (80.80%). The antimicrobial activity of essential oils was evaluated by broth microdilution assay to determine the minimum inhibitory concentration (MIC) and median inhibitory concentration (IC50). Both essential oils exhibited remarkable inhibitory activity against all tested Gram-positive bacteria and yeast than Gram-negative bacteria. Among them, essential oils of S. attopeuense and S. tonkinense possessed the strongest activity against Enterococcus faecalis (MIC = 4.00 μg/mL; IC50 = 1.69 μg/mL) and Candida albicans (MIC = 16.00 μg/mL; IC50 = 8.67 μg/mL), respectively. Furthermore, the larvicidal activity of essential oils was tested using fourth-instar larvae of Aedes aegypti. Results from the larvicidal test revealed that both essential oils had an excellent inhibitory effect against A. aegypti larvae with LC50 values from 25.55 to 30.18 μg/mL and LC90 values from 33.00 to 39.01 μg/mL. Our findings demonstrate that the essential oil extracted from S. attopeuense and S. tonkinense are potential sources of natural antimicrobials and can act as inexpensive mosquito larvicidal agents.

Chemical Compositions and Antimicrobial Activity of Essential Oils From the Leaves of 4 Vietnamese Zingiberaceae Species

Essential oils of the leaves of 4 Vietnamese Zingiberaceae species were first obtained by hydro-distilled, and their chemical compositions were identified by gas chromatography-flame ionization detection/mass spectrometry . β-Pinene (21.7%), sabinene (12.8%), and α-pinene (8.0%) were the main compounds in Wurfbainia tenella leaf oil. The essential oil of Hedydium villosum var. tenuifolium leaf was dominated by β-pinene (23.7%), β-caryophyllene (21.6%), and 1,8-cineole (14.0%). β-Pinene (27.4%), α-pinene (21.2%), limonene (12.1%), and myrcene (8.6%) were the characteristic components of Meistera sudae leaf oil, and β-pinene (32.8%) and ( E)-methyl cinnamate (15.8%) of Alpinia hongiaoensis leaf oil. The 4 oil samples exhibited antimicrobial activity against Bacillus subtilis (American Type Culture Collection [ATCC] 27212), Staphylococcus aureus (ATCC 12222), Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 25923), Aspergillus niger (ATCC 9763), Fusarium oxysporum (ATCC 48112), Candida albicans (ATCC 10231), and Saccharomyces cerevisiae (ATCC 2601) at different levels. Especially, the leaf oil of M sudae showed strong activity against B subtilis, S aureus, and S cerevisiae with a minimum inhibitory concentration (MIC) value of 25.0 µg/mL.

Essential Oils from Vietnamese Asteraceae for Environmentally Friendly Control of Aedes Mosquitoes

Mosquitoes, in addition to being a biting nuisance, are vectors of several pathogenic viruses and parasites. As a continuation of our work identifying abundant and/or invasive plant species in Vietnam for use as ecologically friendly pesticidal agents, we obtained the essential oils of Blumea lacera, Blumea sinuata, Emilia sonchifolia, Parthenium hysterophorus, and Sphaeranthus africanus; analyzed the essential oils using gas chromatographic techniques; and screened the essential oils for mosquito larvicidal activity against Aedes aegypti and Aedes albopictus. The most active larvicidal essential oils were B. sinuata, which was rich in thymohydroquinone dimethyl ether (29.4%), (E)-β-caryophyllene (19.7%), α-pinene (8.8%), germacrene D (7.8%), and α-humulene (4.3%), (24-h LC₅₀ 23.4 and 29.1 μg/mL) on Ae. aegypti and Ae. albopictus, respectively, and Emilia sonchifolia, dominated by 1-undecene (41.9%) and germacrene D (11.0%), (24-h LC₅₀ 30.1 and 29.6 μg/mL) on the two mosquito species. The essential oils of P. hysterophorus and S. africanus were also active against mosquito larvae. Notably, B. sinuata, P. hysterophorus, and S. africanus essential oils were not toxic to the non-target water bug, Diplonychus rusticus. However, E. sonchifolia essential oil showed insecticidal activity (24-h LC₅₀ 48.1 μg/mL) on D. rusticus. Based on these results, B. sinuata, P. hysterophorus, and S. africanus essential oils appear promising for further investigations.

A brief review on the validation of biology methods for COVID-19 detection

The COVID-19 global pandemic has been going on for more than two years, and the evolution of SARS-CoV-2 with many variants of concern still poses a risk to public health. Sufficient access to qualified and validated testing plays an important role in detecting and alerting trends of the pandemic and provides evidence for making decisions in preventive strategies and policies. Depending on the method of testing and laboratory conditions, validation parameters (i.e., analytical sensitivity, limit of detection, diagnostic sensitivity, analytical specificity, diagnostic specificity, repeatability, reproducibility, robustness, positive predictive value, negative predictive value, applicability, practicability, and time to results) can be very different. With three main types of COVID-19 detection kits available, comprising nucleic acid, serological, and antigen detection, the kind of validation parameters that should be used becomes a complicated consideration and takes time to assess. Our review provides valuable and comprehensive information for laboratories in the assessment and selection of the optimal parameters to validate new COVID-19 test kits.

Acetylcholinesterase Inhibitory Activities of Essential Oils from Vietnamese Traditional Medicinal Plants

Essential oils are promising as environmentally friendly and safe sources of pesticides for human use. Furthermore, they are also of interest as aromatherapeutic agents in the treatment of Alzheimer’s disease, and inhibition of the enzyme acetylcholinesterase (AChE) has been evaluated as an important mechanism. The essential oils of some species in the genera Callicarpa, Premna, Vitex and Karomia of the family Lamiaceae were evaluated for inhibition of electric eel AChE using the Ellman method. The essential oils of Callicarpa candicans showed promising activity, with IC₅₀ values between 45.67 and 58.38 μg/mL. The essential oils of Callicarpa sinuata, Callicarpa petelotii, Callicarpa nudiflora, Callicarpa erioclona and Vitex ajugifolia showed good activity with IC₅₀ values between 28.71 and 54.69 μg/mL. The essential oils Vitex trifolia subsp. trifolia and Callicarpa rubella showed modest activity, with IC₅₀ values of 81.34 and 89.38, respectively. trans-Carveol showed an IC₅₀ value of 102.88 µg/mL. Molecular docking and molecular dynamics simulation were performed on the major components of the studied essential oils to investigate the possible mechanisms of action of potential inhibitors. The results obtained suggest that these essential oils may be used to control mosquito vectors that transmit pathogenic viruses or to support the treatment of Alzheimer’s disease.

Nutritional Intervention Improves Nutrition Outcomes in Stomach and Colon Cancer Patients Receiving Chemotherapy: Finding from a Quasi-Experiment in Vietnam

Background: Evidence on the effects of nutritional interventions on gastrointestinal cancer patients receiving chemotherapy is not well documented. This study aims to assess the effects of nutritional intervention in patients diagnosed with stomach and colon cancer receiving chemotherapy in Vietnam. Methods: A quasi-experiment with intervention and control groups for pre- and post-intervention was carried out in cancer patients receiving chemotherapy in a university hospital in Vietnam. Patients in the intervention group were provided nutritional counseling, personalized specific dietary advice, and received oral nutrition supplements (ONSs) while patients in the control group only received nutrition counseling. Results: The weight in the intervention and control group after 2 months increased significantly by 1.4 ± 2.6 kg and 0.4 ± 2.3 kg, respectively. Muscle mass increased by 1.2 ± 4.1 cm in the intervention group, while those in the control group decreased by 0.55 ± 2.77 cm. There was no statistical significance between two groups after intervention in terms of Mid–Upper Arm Circumference (MUAC) and percentage of fat. The percentage of malnutrition based on the Scored Patient-Generated Subjective Global Assessment (PG-SGA) and Body Mass Index (BMI) declined after the intervention in both groups. According to the average treatment effect on the treated (ATT) using the propensity score matching and DiD method, participants receiving the intervention were more likely to have a higher score of weight (Coef = 0.84; 95%CI = 0.47; 2.16) and muscle mass (Coef = 1.08; 95%CI = 0.09; 2.06) between pre- and post-intervention. By contrast, the PG-SGA scores on treated participants were more likely to decrease after the intervention (Coef = −1.28; 95%CI = −4.39; −0.84). After matching, being female, living in rural areas, or having stomach cancer were still positively related to being moderately/severely malnourished by the PG-SGA, and these findings were statistically significant (p < 0.05). Conclusion: The nutritional interventions had a positive effect on weight gain, muscle mass, and reduced malnutrition. Further studies with a longer follow-up duration are needed to confirm the effects of the intervention.

Lantana camara Essential Oils from Vietnam: Chemical Composition, Molluscicidal, and Mosquito Larvicidal Activity

Lantana camara is a troublesome invasive plant introduced to many tropical regions, including Southeast Asia. However, the plant does hold promise as a source of essential oils that may be explored for potential use. Fresh water snails such as Pomacea canaliculata, Gyraulus convexiusculus, and Tarebia granifera can be problematic agricultural pests as well as hosts for parasitic worms. Aedes and Culex mosquitoes are notorious vectors of numerous viral pathogens. Control of these vectors is of utmost importance. In this work, the essential oil compositions, molluscicidal, and mosquito larvicidal activities of four collections of L. camara from north-central Vietnam have been investigated. The sesquiterpene-rich L. camara essential oils showed wide variation in their compositions, not only compared to essential oils from other geographical locations (at least six possible chemotypes), but also between the four samples from Vietnam. L. camara essential oils showed molluscicidal activities comparable to the positive control, tea saponin, as well as other botanical agents. The median lethal concentrations (LC₅₀ ) against the snails were 23.6-40.2 μg/mL (P. canaliculata), 7.9-29.6 μg/mL (G. convexiusculus), and 15.0-29.6 μg/mL (T. granifera). The essential oils showed good mosquito larvicidal activities with 24-h LC₅₀ values of 15.1-29.0 μg/mL, 26.4-53.8 μg/mL, and 20.8-59.3 μg/mL against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus, respectively. The essential oils were more toxic to snails and mosquito larvae than they were to the non-target water bug, Diplonychus rusticus (24-h LC₅₀ =103.7-162.5 μg/mL). Sesquiterpene components of the essential oils may be acting as acetylcholinesterase (AChE) inhibitors. These results suggest that the invasive plant, L. camara, may be a renewable botanical pesticidal agent.

Acoustic Cell Patterning in Hydrogel for Three-Dimensional Cell Network Formation

In the field of engineered organ and drug development, three-dimensional network-structured tissue has been a long-sought goal. This paper presents a direct hydrogel extrusion process exposed to an ultrasound standing wave that aligns fibroblast cells to form a network structure. The frequency-shifted (2 MHz to 4 MHz) ultrasound actuation of a 400-micrometer square-shaped glass capillary that was continuously perfused by fibroblast cells suspended in sodium alginate generated a hydrogel string, with the fibroblasts aligned in single or quadruple streams. In the transition from the one-cell stream to the four-cell streams, the aligned fibroblast cells were continuously interconnected in the form of a branch and a junction. The ultrasound-exposed fibroblast cells displayed over 95% viability up to day 10 in culture medium without any significant difference from the unexposed fibroblast cells. This acoustofluidic method will be further applied to create a vascularized network by replacing fibroblast cells with human umbilical vein endothelial cells.

Premna Species in Vietnam: Essential Oil Compositions and Mosquito Larvicidal Activities

Essential oils have emerged as viable alternatives to synthetic insecticides for control of mosquito-borne pathogens. The leaf essential oils of eight species of Premna (Lamiaceae) growing in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Sesquiterpene hydrocarbons dominated most of the Premna essential oils, with the notable exception of Premnamekongensis from Ngoc Linh Nature Reserve, which had α-pinene as the major component. Larvicidal activities against Aedes aegypti have been determined and all of the Premna essential oils showed larvicidal activity with 24-h LC50 < 65 μg/mL. The leaf essential oils of Premnacambodiana from Chu Mom Ray National Park and Premnamekongensis from Ngoc Linh Nature Reserve showed the best larvicidal activities with 24-h LC50 of 16.8 and 18.0 μg/mL, respectively. The essential oil compositions and larvicidal activities of P. cambodiana, Premna flavescens, Premnamaclurei, P. mekongensis, and Premnapuberula are reported for the first time. Although the larvicidal activities of Premna leaf essential oils are promising, the essential oil yields are relatively low (0.10-0.25%).

Knowledge of Cervical Cancer and Human Papillomavirus Vaccines among Child-Bearing Aged Women in Hanoi, Vietnam

Objectives:

The study sought to examine knowledge of cervical cancer and human papillomavirus (HPV) vaccines among child-bearing aged women in Hanoi, Vietnam.

Methods:

In 2016, 807 women aged 18 to 49 years were recruited from one urban area and one rural area in 2016 and were examined through face-to-face paper-based interviews. Pearson’s chi-square test and an independent t-test were utilized to compare awareness of cervical cancer and HPV vaccination among women according residential status.

Results:

Overall, 83.8% and 71.3% women had heard about cervical cancer and HPV vaccination, respectively. Mean knowledge scores for cervical cancer and HPV vaccination were 4.60±1.43 out of 7 and 1.53±1.35 out of 5, respectively. Women living in an urban area were more likely to be aware of cervical cancer and to be more knowledgeable of HPV vaccination than women in a rural area.

Conclusions:

Despite strong awareness, we found knowledge on cervical cancer and HPV vaccination to be alarmingly insufficient among Vietnamese women.

Chemical Compositions, Mosquito Larvicidal and Antimicrobial Activities of Leaf Essential Oils of Eleven Species of Lauraceae from Vietnam

The Lauraceae is a family rich in aromatic and medicinal plants. Likewise, essential oils derived from members of this family have demonstrated a myriad of biological activities. It is hypothesized that members of the Lauraceae from Vietnam will yield essential oils that may be useful in controlling mosquito populations and treating microbial infections. In this work, the leaf essential oils of eleven species of Lauraceae (Beilschmiedia erythrophloia, B. robusta, B. yunnanensis, Cryptocarya concinna, C. impressa, C. infectoria, Litsea viridis, Machilus balansa, M. grandifolia, Neolitsea ellipsoidea, and Phoebe angustifolia) have been obtained by hydrodistillation and the chemical compositions analyzed by gas chromatography – mass spectrometry (GC-MS) and gas chromatography with flame ionization detection (GC-FID). The essential oils were screened for larvicidal activity against Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans. The leaf essential oil of N. ellipsoidea, rich in (E)-β-ocimene (87.6%), showed excellent larvicidal activity against Ae. aegypti with a 24 h LC₅₀ of 6.59 μg/mL. The leaf essential oil of C. infectoria, dominated by germacrene D (55.5%) and bicyclogermacrene (11.4%), exhibited remarkable larvicidal activity against Cx. quinquefasciatus (48 h LC₅₀ = 0.40 μg/mL). N. ellipsoidea leaf essential oil also demonstrated notable antibacterial activity against E. faecalis and B. cereus with minimum inhibitory concentration (MIC) values of 16 μg/mL, while the leaf essential oil of C. impressa showed excellent anticandidal with an MIC of 16 μg/mL. Leaf essential oils from the Lauraceae should be considered for utilization as alternative agents for controlling mosquito populations and as antimicrobial agents.

Mosquito Larvicidal Activity, Antimicrobial Activity, and Chemical Compositions of Essential Oils from Four Species of Myrtaceae from Central Vietnam

Mosquitoes are important vectors of several diseases, and control of these insects is imperative for human health. Insecticides have proven useful in controlling mosquito populations, but insecticide resistance and environmental concerns are increasing. Additionally, emerging and re-emerging microbial infections are problematic. Essential oils have been shown to be promising mosquito larvicidal agents as well as antimicrobial agents. In this work, the essential oils from four species of Myrtaceae (Baeckea frutescens, Callistemon citrinus, Melaleuca leucadendra, and Syzygium nervosum) growing wild in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The essential oils have been screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. Callistemon citrinus fruit essential oil, rich in α-pinene (35.1%), 1,8-cineole (32.4%), limonene (8.2%), and α-terpineol (5.8%) showed good larvicidal activity with 24-h LC₅₀ = 17.3 μg/mL against both Ae. aegypti and Cx. quinquefasciatus, and good antibacterial activity against E. faecalis (minimum inhibitory concentration (MIC) = 16 μg/mL) The 48-h larvicidal activities of M. leucadendra leaf essential oil, rich in α-eudesmol (17.6%), guaiol (10.9%), linalool (5.1%), (E)-caryophyllene (7.0%), and bulnesol (3.6%) were particularly notable, with LC₅₀ of 1.4 and 1.8 μg/mL on Ae. aegypti and Cx. quinquefasciatus. Similarly, M. leucadendra bark essential oil, with α-eudesmol (24.1%) and guaiol (11.3%), showed good antibacterial activity against. E. faecalis. Both B. frutescens and C. citrinus leaf essential oils demonstrated anti-Candida activities with MIC values of 16 μg/mL. The results of this investigation suggest that essential oils derived from the Myrtaceae may serve as "green" alternatives for the control of mosquitoes and/or complementary antimicrobial agents.

Chemical Composition of Actinodaphne pilosa Essential Oil From Vietnam, Mosquito Larvicidal Activity, and Antimicrobial Activity

Leaves of Actinodaphne pilosa were collected at 2 different seasons from the Pù Hoạt Nature Reserve, Vietnam. The leaf samples were hydrodistilled to give essential oils, which were analyzed by gas chromatography (GC)–mass spectrometry and GC-flame ionization detection. The major components in the essential oils were α-pinene, ( Z)-β-ocimene, ( E)-β-ocimene, β-caryophyllene, germacrene D, bicyclogermacrene, and spathulenol. The essential oils were screened for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans, as well as mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus. Actinodaphne pilosa leaf essential oils showed broad antimicrobial activity (minimum inhibitory concentration = 32, 64, 64, 16, and 16 μg/mL against E. faecalis, S. aureus, B. cereus, P. aeruginosa, and C. albicans, respectively) and excellent larvicidal activity (24-hour 50% lethal concentration = 19.0, 24.7, and 48.1 μg/mL against A. aegypti, A. albopictus, and C. quinquefasciatus, respectively).

Mosquito Larvicidal Activity of the Essential Oils of Erechtites Species Growing Wild in Vietnam

Mosquito-borne infections are a constant problem in Vietnam, and mosquito vector control is a primary approach to control these infections. Essential oils represent environmentally friendly alternatives to synthetic pesticides for mosquito control. The essential oils of two weedy species in Vietnam, Erechtites hieraciifolius and E. valerianifolius, have been obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry. The essential oils have been screened for mosquito larvicidal activity against Aedes albopictus, Ae. aegypti, and Culex quinquefasciatus. The essential oil from the aerial parts of E. hieraciifolius was rich in α-pinene (14.5%), limonene (21.4%), and caryophyllene oxide (15.1%), while E. valerianifolius essential oil was dominated by myrcene (47.8%) and α-pinene (30.2%). Both essential oils showed good larvicidal activity against Ae. albopictus (24-h LC₅₀ 10.5 and 5.8 μg/mL, respectively) and Ae. aegypti (24-h LC₅₀ 10.6 and 12.5 μg/mL, respectively). The essential oil of E. valerianifolius also showed good activity against Cx. quinquefasciatus larvae (24-h LC₅₀ = 40.7 μg/mL). Thus, Erechtites essential oils may serve as low-cost vector control agents for mosquito-borne infections.

Internet addiction and sleep quality among Vietnamese youths

INTRODUCTION

Internet addiction has been a major behavioral disorder over the past decade. Prior meta-analytic review has demonstrated the association between Internet addiction and psychiatric disorders, as well as sleep related disorders.

AIMS AND OBJECTIVES

There remains a paucity of literature about Internet addiction and sleep related disorders in low and middle income countries like Vietnam. It is the aim of this exploratory study to determine the association.

METHODOLOGY

An online cross-sectional study was conducted between August through to October 2015. Respondent drive sampling technique was utilized in the recruitment of participants. The short form version of the Young's Internet addiction test was administered and sleep related disorders was ascertained by means of a self-report questionnaire. Chi-squared, t-test and ANOVA were used to determine whether there were any significant differences amongst the variables considered. Multivariate logistic regressions were also used in the analysis, in order to identify factors associated with Internet addiction.

RESULTS

21.2% Of the participants were diagnosed with Internet addiction. 26.7% of those with Internet addiction also reported that they have had sleep related difficulties. 77.2% of these participants were receptive towards seeking medical treatment. Our current study also highlighted that being single and those who were using tobacco products were not at heightened risk of developing associated sleep related issues.

CONCLUSIONS

Our current study is largely a cross-sectional exploratory study that has shown that there is a significant prevalence of both Internet addiction and sleep related disorders amongst Vietnamese youth.

A study on the influence of internet addiction and online interpersonal influences on health-related quality of life in young Vietnamese

Background

Internet addiction (IA) is a common problem found in young Asians. This study aimed to study the influence of IA and online activities on health-related quality of life (HRQOL) in young Vietnamese. This study also compared the frequencies of anxiety, depression and other addiction of young Vietnamese with and without IA.

Methods

This study recruited 566 young Vietnamese (56.7% female, 43.3% male) ranging from 15 to 25 years of age via the respondent-driven sampling technique. Chi-squared, t-test and analysis of variance were used to compare young Vietnamese with and without IA. Regression analyses were used to examine the association between internet usage characteristics and HRQOL.

Results

Results from this cross-sectional study showed that 21.2% of participants suffered from IA. Online relationship demonstrated significantly higher influences on behaviors and lifestyles in participants with IA than those without IA. Participants with IA were more likely to have problems with self-care, difficulty in performing daily routine, suffer from pain and discomfort, anxiety and depression. Contrary to previous studies, we found that there were no differences in gender, sociodemographic, the number of participants with cigarette smoking, water-pipe smoking and alcohol dependence between the IA and non-IA groups. IA was significantly associated with poor HRQOL in young Vietnamese.

Conclusion

IA is a common problem among young Vietnamese and the prevalence of IA is the highest as compared to other Asian countries. Our findings suggest that gender may not play a key role in IA. This can be an emerging trend when both genders have equal access to the internet. By studying the impact of IA on HRQOL, healthcare professionals can design effective intervention to alleviate the negative consequences of IA in Vietnam.

Cigarette Smoking among Adolescents aged 13-15 in Viet Nam and Correlates of Current Cigarette Smoking: Results from GYTS 2014 Data

The aim of this paper is to report the rate of current and ever cigarette smoking and explore correlates of current cigarette smoking among adolescents aged 13-15 in Viet Nam. This analysis was derived from GYTS survey, which comprised of 3,430 adolescents aged 13-15, conducted in 2014 in 13 cities and provinces of Viet Nam. We calculated the weighted rates of current and ever cigarette smoking and reported patterns of smoking behavior. We also performed logistic regression to explore correlates of current cigarette smoking behavior. The weighted rate of ever cigarette smoking was 9.5% (95% confidence interval (CI): 8.5 %-10.5%), in which the weighted rate among males (15.4%; 95% CI: 13.6%-17.0%) was higher than that among females (4.2%; 95% CI: 3.3%-5.1%). The weighted rate of current cigarette smoking was relatively low at 2.5% (95%CI: 2.0%- 3.0%) with higher weighted rate among males (4.9%; 95% CI: 3.8%-5.9%) compared to the corresponding figure among females (0.2%; 95% CI: 0.0 %-0.5%). Current cigarette smoking was significantly higher among males than females, in students aged 15 versus 13 years old, and in students who had several or all close friends smoking and students with daily observation of smoking at school. For greater smoking reduction outcomes, we recommend that tobacco interventions for adolescents should consider targeting more male students at older ages, establish stricter adherence to school-based banning of cigarette smoking, engage both smoking and nonsmoking adolescents and empower adolescents to resist peer smoking influence as well as changing their norms or beliefs towards smoking benefits.

Diet and nutritional status among children 24-59 months by seasons in a mountainous area of Northern Vietnam in 2012

Background

Seasonal variation affects food availability. However, it is not clear if it affects dietary intake and nutritional status of children in Vietnam.

Objectives

This paper aims at examining the seasonal variation in nutrition status and dietary intake of children aged 24–59 months.

Design

A repeated cross-sectional study design was used to collect data of changes in nutritional status and diets of children from 24 to 59 months through four seasons in Chiem Hoa district, Tuyen Quang province, a predominately rural mountainous province of northern Vietnam. The quantitative component includes anthropometric measurements, 24 hours dietary recall and socio-economic characteristics. The qualitative component was conducted through focus group discussions (FGDs) with mothers of the children surveyed in the quantitative component. The purpose of FGDs was to explore the food habits of children during the different seasons and the behaviours of their mothers in relation to the food that they provide during these seasons.

Results

The prevalence of underweight among children aged 24–59 months is estimated at around 20–25%; it peaked in summer (24.9%) and reached a low in winter (21.3%). The prevalence of stunting was highest in summer (29.8%) and lowest in winter (22.2%). The prevalence of wasting in children was higher in spring and autumn (14.3%) and lower in summer (9.3%). Energy intake of children was highest in the autumn (1259.3 kcal) and lowest in the summer (996.9 kcal). Most of the energy and the nutrient intakes during the four seasons did not meet the Vietnamese National Institute of Nutrition recommendation.

Conclusions

Our study describes some seasonal variation in nutrition status and energy intake among children in a mountainous area northern Vietnam. Our study indicated that the prevalence of stunting and underweight was higher in summer and autumn, while the prevalence of wasting was higher in spring and autumn. Energy intake did not always meet national recommendations, especially in summer.

Seasonality in mortality and its relationship to temperature among the older population in Hanoi, Vietnam

BACKGROUND

Several studies have established a relationship between temperature and mortality. In particular, older populations have been shown to be vulnerable to temperature effects. However, little information exists on the temperature-mortality relationship in Vietnam.

OBJECTIVES

This article aims to examine the monthly temperature-mortality relationship among older people in Hanoi, Vietnam, over the period between 2005 and 2010, and estimate seasonal patterns in mortality.

METHODS

We employed Generalized Additive Models, including smooth functions, to model the temperature-mortality relationships. A quasi-Poisson distribution was used to model overdispersion of death counts. Temporal trends, seasonality, and population size were adjusted for while estimating changes in monthly mortality over the study period. A cold month was defined as a month with a mean temperature below 19°C.

RESULTS

This study found that the high peak of mortality coincided with low temperatures in the month of February 2008, during which the mean temperature was the lowest in the whole study period. There was a significant relationship between mean monthly temperature and mortality among the older people (p<0.01). Overall, there was a significant decrease in the number of deaths in the year 2009 during the study period. There was a 21% increase in the number of deaths during the cold season compared to the warm season. The increase in mortality during the cold period was higher among females compared to males (female: IRR [incidence relative risk] =1.23; male: IRR=1.18).

CONCLUSIONS

Cold temperatures substantially increased mortality among the older population in Hanoi, Vietnam, and there were gender differences. Necessary preventive measures are required to mitigate temperature effects with greater attention to vulnerable groups.

In vivo analysis of Aicda gene regulation: a critical balance between upstream enhancers and intronic silencers governs appropriate expression

The Aicda gene encodes activation-induced cytidine deaminase (AID). Aicda is strongly transcribed in activated B cells to diversify immunoglobulin genes, but expressed at low levels in various other cells in response to physiological or pathological stimuli. AID’s mutagenic nature has been shown to be involved in tumor development. Here, we used a transgenic strategy with bacterial artificial chromosomes (BACs) to examine the in vivo functions of Aicda regulatory elements, which cluster in two regions: in the first intron (region 2), and approximately 8-kb upstream of the transcription start site (region 4). Deleting either of these regions completely abolished the expression of Aicda-BAC reporters, demonstrating these elements’ critical roles. Furthermore, we found that selectively deleting two C/EBP-binding sites in region 4 inactivated the enhancer activity of the region despite the presence of intact NF-κB-, STAT6- and Smad-binding sites. On the other hand, selectively deleting E2F- and c-Myb-binding sites in region 2 increased the frequency of germinal-center B cells in which the Aicda promoter was active, indicating that E2F and c-Myb act as silencers in vivo. Interestingly, the silencer deletion did not cause ectopic activation of the Aicda promoter, indicating that Aicda activation requires enhancer-specific stimulation. In summary, precise regulation of the Aicda promoter appears to depend on a coordinated balance of activities between enhancer and silencer elements.

Knowledge of the health consequences of tobacco smoking: a cross-sectional survey of Vietnamese adults

BACKGROUND

Although substantial efforts have been made to curtail smoking in Vietnam, the 2010 Global Adult Tobacco Survey (GATS) revealed that the proportion of male adults currently smoking remains high at 47.4%.

OBJECTIVES

To determine the level of, and characteristics associated with, knowledge of the health consequences of smoking among Vietnamese adults.

DESIGN

GATS 2010 was designed to survey a nationally representative sample of Vietnamese men and women aged 15 and older drawn from 11,142 households using a two-stage sampling design. Descriptive statistics were calculated and multivariate logistic regression was used to examine associations between postulated exposure factors (age, education, access to information, ethnic group etc.) and knowledge on health risks.

RESULTS

General knowledge on the health risks of active smoking (AS) and exposure to second hand smoke (SHS) was good (90% and 83%, respectively). However, knowledge on specific diseases related to tobacco smoking (stroke, heart attack, and lung cancer) appeared to be lower (51.5%). Non-smokers had a significantly higher likelihood of demonstrating better knowledge on health risks related to AS (OR 1.6) and SHS (OR 1.7) than smokers. Adults with secondary education, college education or above also had significantly higher levels knowledge of AS/SHS health risks than those with primary education (AS: ORs 1.6, 1.7, and 1.9, respectively, and SHS: ORs 2.4, 3.9, and 5.7 respectively). Increasing age was positively associated with knowledge of the health consequences of SHS, and access to information was significantly associated with knowledge of AS/SHS health risks (ORs 2.3 and 1.9 respectively). Otherwise, non-Kinh ethnic groups had significantly less knowledge on health risks of AS/SHS than Kinh ethnic groups.

CONCLUSIONS

It may be necessary to target tobacco prevention programs to specific subgroups including current smokers, adults with low education, non-Kinh ethnics in order to increase their knowledge on health risks of smoking. Comprehensive messages and/or images about specific diseases related to AS/SHS should be conveyed using of different channels and modes specific to local cultures to increase knowledge on smoking health consequences for general population.

Costing of clinical services in rural district hospitals in northern Vietnam

OBJECTIVES

This study aimed to estimate and analyse the "actual" unit cost of providing key clinical services in selected rural district hospitals in the North of Vietnam. It also examined the relationship between actual costs and the levels of cost covered by the corresponding user fees paid by patients.

METHODS

This was a facility-based costing study which estimates the costs of health care services from the perspective of the service providers. Three rural district hospitals from three provinces in the North of Vietnam were purposively selected for this study. The "step-down" approach was applied.

RESULTS

There was little difference in the costs of an outpatient visit across the hospitals, but the costs of an operation and an inpatient day varied considerably. In terms of cost structure, personnel costs accounted for the highest share of total cost of the clinical services. The shares of operating cost were considerable while depreciation of buildings/equipments made up a small "proportion". The study results revealed that the user fee levels were much lower than the actual costs of providing the corresponding services. The present study highlights the importance of costing data for hospital planning and management.

Prevalence of Sarcocystis spp. in water buffaloes in Vietnam

Muscles from heart, tongue, oesophagus, neck and abdomen from 502 adult water buffaloes (Bubalus bubalis) slaughtered in Ho Chi Minh City, Vietnam, between 1996 and 1997 were examined for Sarcocystis cysts by a combination of ocular and histological examination. Sarcocysts were present in 396 (79%) of the animals and the prevalence increased with age from a 57% infection rate among 2-3 year old animals to 93% among 6-7 year olds. The prevalence was higher in animals originating from the northern part (89%) than in those from the southern part (69%) of the country. Four species of Sarcocystis were identified. S. levinei (74%) was the most common species found, followed by S. fusiformis (41%), S. buffalonis (33%) and S. dubeyi (12%). All four species were present in 8% of the infected animals. The most common site for sarcocyst location was oesophagus, followed by cervical muscles, tongue and heart.

Sarcocystis dubeyi n. sp. (Protozoa: Sarcocystidae) in the water buffalo (Bubalus bubalis)

Sarcocystis dubeyi n. sp. is proposed for a species forming thick-walled, microscopic sarcocysts in striated muscular tissues of the water buffalo (Bubalus bubalis). Sarcocysts of S. dubeyi were found in histological sections of skeletal muscles and esophagus, but not in heart and tongue, of 8 (13%) of 60 water buffaloes examined in Ho Chi Minh City, Vietnam. Sarcocysts of S. dubeyi were up to 600 microns long and up to 200 microns wide. The cyst wall was 4.5-9 microns thick and was composed of tightly packed, cylindrical villar protrusions (Vp) that had a uniform width of up to 3 microns, a length of up to 8 microns, and a blunt, often flattened tip. The Vp contained microfilaments but no prominent electron-dense granules. The definitive host of S. dubeyi was not determined, but it could possibly be humans or other primates. By the present description, 4 Sarcocystis species are recognized in the water buffalo: the macrocyst-forming Sarcocystis fusiformis and S. buffalonis and the microcyst-forming S. levinei and S. dubeyi.

Evolution of ruminant Sarcocystis (Sporozoa) parasites based on small subunit rDNA sequences

We present an evolutionary analysis of 13 species of Sarcocystis, including 4 newly sequenced species with ruminants as their intermediate host, based on complete small subunit rDNA sequences. Those species with ruminants as their intermediate host form a well-supported clade, and there are at least two major clades within this group, one containing those species forming microcysts and with dogs as their definitive host and the other containing those species forming macrocysts and with cats as their definitive host. Those species with nonruminants as their intermediate host form the paraphyletic sister group to these clades. Most of the species have considerable genotypic differences (differing in more than 100 nucleotide positions), except for S. buffalonis and S. hirsuta. There is a large suite of genotypic differences indicating that those species infecting ruminant and nonruminant hosts have had very different evolutionary histories, and similarly for the felid- and canid-infecting species. Furthermore, the rDNA sequences that represent the different structural regions of the rRNA molecule have very different genotypic behavior within Sarcocystis. The evolution of these regions should be functionally constrained, and their differences can be explained in terms of the importance of the nucleotide sequences to their functions.

Prevalence of antibodies to Neospora caninum and Toxoplasma gondii in cattle and water buffaloes in southern Vietnam

Serum samples from 200 dairy cattle and 200 beef water buffaloes were collected in southern Vietnam during May to September 1995. The sera were analysed for antibodies to Neospora caninum by an enzyme-linked immunosorbent assay and the indirect fluorescent antibody test, and for antibodies to Toxoplasma gondii by the direct agglutination test. Significant levels of N. caninum antibodies were detected in 5.5% of the cattle sera and in 1.5% of the water buffalo sera. 10.5% of the cattle sera and 3% of the water buffalo sera were found to contain T. gondii antibodies. Two of the cattle sera had both T. gondii and N. caninum antibodies. The present communication is the first to report serological evidence of N. caninum infection in the water buffalo.

Redescription of Sarcocystis levinei Dissanaike and Kan, 1978 (Protozoa: Sarcocystidae) of the water buffalo (Bubalus bubalis)

Sarcocystis levinei Dissanaike and Kan, 1978, is redescribed because the original description was a mixture of 2 species, the amended S. levinei and the newly recognized S. buffalonis Huong, Dubey, Nikkilä, and Uggla, 1997. In histological sections, S. levinei sarcocysts are microscopic, up to 640 microm long and up to 95 microm wide. Ultrastructurally, the cyst wall is thin (< 1.0 microm thick) with a minute undulating surface and smooth, hairlike villar protrusions arising at irregular distances from the cyst wall. The villar protrusions have a dome-shaped base (approximately 0.5 microm thick), a fingerlike middle part, and a tapering distal end (<0.1 microm thick). The morphological features of the sarcocyst resemble those of S. cruzi (Hasselman, 1926) Wenyon, 1926, of cattle. Sarcocystis levinei sarcocysts were found in striated muscles including heart, esophagus, tongue, and skeletal muscle. The buffalo myocardium is parasitized exclusively by S. levinei, whereas >1 Sarcocystis species may occur concurrently in other muscular tissues of water buffaloes. Two dogs, but not 2 cats, fed water buffalo hearts infected with S. levinei sarcocysts shed sporocysts measuring 9.5-10.5 x 14.0-16.5 microm starting from days 16 and 18, respectively.

Sarcocystis buffalonis n.sp. (Protozoa: Sarcocystidae) from the water buffalo (Bubalus bubalis) in Vietnam

Sarcocystis buffalonis n. sp. is proposed for a species forming thick-walled, macroscopic sarcocysts in skeletal muscles and the esophagus of the water buffalo (Bubalus bubalis). Sarcocysts of S. buffalonis were found in 68 (10.5%) of 647 buffalo carcasses examined grossly at slaughter in Ho Chi Minh City in southern Vietnam. Sarcocystis buffalonis sarcocysts were 1-8 mm long and 0.1-0.5 mm wide. The cyst wall was 3-7.7 microns thick and had palisadelike villar protrusions that were constricted at the base, expanded laterally in the mid-region, and tapered distally. The villar protrusions contained microfilaments and electron-dense granules. Sarcocysts of Sarcocystis fusiformis, the other well-known macroscopic species occurring in water buffalo, were also found in 60 of the 68 animals infected with S. buffalonis. Sarcocysts of S. fusiformis were thin walled and had characteristic cauliflowerlike villar protrusions. Two of 7 cats fed isolated S. buffalonis sarcocysts were found to have 12 x 8 microns sporocysts in their intestine or feces 10 days after inoculation.

Plague foci in Viet Nam: zoological and parasitological aspects

Reported are the results of studies over the period 1989-94 on host-flea complexes in small mammals and their flea ectoparasites in and around a number of human settlements in Viet Nam in which human cases of plague had been found. Collections were also made in savanna and tropical forest areas within a 10-km radius of the settlements. The greatest numbers of small mammals, for the most part Rattus spp., and of the flea ectoparasite Xenopsylla cheopis were found in inhabited areas. X. cheopis was not found on any feral or sylvan mammal further than 0.6 km from settlements. A possible link between wild and commensal mammals may be provided by the flea Lentistivalius klossi, a specific parasite of squirrels and tree-shrews but also found in very small numbers on commensal rats. No zoonotic foci of plague were found in the immediate vicinity of the villages studied and it is most likely that plague persists in a commensal rat-X. cheopis cycle in and around human settlements in Viet Nam.

[Notes on fleas (Siphonaptera) in plague foci on the Tay Nguyen plateau (Vietnam)]

The fleas of wild and commensal small mammals, domestic animals (dogs, cats) and free-living flea forms in houses have been collected in plague nidi of Tay Nguyen plate, Dak-Lak province, Vietnam. Pulex irritans, Ctenocephalides felis felis, Ct. felis orientis were found in the houses on dogs, cats and on the ground floor. Commensal rats in populated areas were infested by Xenopsylla cheopis and rarely by Lentistivalius klossi. The agricultural zone was inhabited by both home and wild animals such as commensal, savannah and forest-dwelling small mammals. The flea fauna of this zone is presented by X. cheopis and L. klossi. In the tropical forest surrounding villages four of the flea species were found: X. vexabilis, a specific parasite of the forest-dwelling rat Berylmys berdmorei, L. klossi found on six species of forest small mammals, Acropsylla girshami from Berylmys bowersii and Pariodontis subjugis from Hystrix brachyura. The agricultural zone is the most possible place of commensal and forest-dwelling small mammals contact, where the latter can get plague microbe.