Dinh Ng-Nguyen

Dogs are key reservoirs of zoonotic infections, including Toxocara canis, a widely distributed parasite of major public health concern. In Vietnam, the parasite is highly prevalent in dog populations and humans. Epidemiological studies assessing infection and associated factors are essential to better understand transmission and to inform effective control strategies. We conducted a cross-sectional baseline survey to assess Toxocara infection in dogs in rural Vietnam. Fecal samples from 371 dogs were examined using centrifugal flotation (Sheather’s solution, specific gravity 1.2) and conventional polymerase chain reaction (PCR), alongside structured questionnaires on dog demographics and management. Using combined copromicroscopic and molecular methods, the overall prevalence of Toxocara infection was 44.7% (95% CI: 39.6–50.0). By microscopy alone, 29.9% (95% CI: 25.4–34.9) of samples were positive, while PCR detected Toxocara DNA in 41.2% (95% CI: 36.2–46.5) of dogs. Molecular analysis identified T. canis in 35.9% (95% CI: 31.0–41.0) and T. cati in 10.5% (95% CI: 7.7–14.2) of tested dogs. Dog age and deworming status were independently associated with PCR-detected T. canis infection. The elevated likelihood of infection among dogs that have never been dewormed highlights the importance of canine deworming. Questionnaire findings indicating suboptimal dog care and management highlight the need for community public health education to promote responsible ownership and reduce transmission risk. This baseline assessment provides essential evidence to inform targeted interventions and improve understanding of Toxocara transmission in endemic settings.

Background and Aim: Pasteurella multocida is a primary cause of hemorrhagic septicemia (HS) in buffaloes across tropical regions, leading to rapid deaths and significant economic losses. In Vietnam, recurrent HS outbreaks have been reported, yet most studies have solely focused on bacterial isolation or species-level identification. Comprehensive molecular data, including capsular typing, lipopolysaccharide (LPS) genotyping, virulence–associated genes (VAGs), and antimicrobial resistance genes (ARGs), remain limited for buffalo-derived strains. This molecular gap hampers understanding of strain diversity, epidemiology, and vaccine development. Notably, no previous Vietnamese study has concurrently characterized capsule, LPS, VAG, and ARG profiles or reported atypical serogroups in buffaloes. Therefore, integrated molecular surveillance is crucial to detect emerging lineages and guide One Health–oriented disease management. This study aimed to provide the first comprehensive molecular characterization of P. multocida strains isolated from buffaloes in Vietnam’s Central Highlands, incorporating capsular typing, LPS genotyping, virulence gene profiling, and antimicrobial resistance detection. Materials and Methods: Sixty-seven P. multocida isolates were recovered from lungs, bone marrow, and nasal swabs of clinically affected buffaloes (2022–2025). Species confirmation and molecular screening for capsular types (A, B, D), LPS genotypes (L1–L8), 12 VAGs, and seven ARGs were performed using polymerase chain reaction-based assays. Three representative isolates underwent 16S rRNA sequencing for phylogenetic analysis. Prevalence estimates, along with their 95% confidence intervals, were calculated, and chi-square tests were performed. Results: Capsular type B was the most common (62.7%), followed by type A (31.3%). Importantly, capsular type D (5.9%) was identified for the first time in Vietnamese buffaloes. LPS genotyping showed L2 as the predominant genotype (56.7%), with L6 (19.4%), L1 (16.4%), and L3 (7.5%) also present. All isolates contained eight conserved VAGs, while pfhA (58.2%) and hgbB (34.3%) showed variable presence. ToxA and nanH were not detected. Four ARGs, floR (22.3%), tetB (11.9%), blaROB1 (10.4%), and tetH (4.4%), were observed. Phylogenetic analysis clustered all isolates within the P. multocida group, with the type D isolate forming a minor diverging sub-branch. Conclusion: This study establishes the first multilocus molecular profile of P. multocida in Vietnamese buffaloes, highlighting the emergence of capsular type D and the dominance of L2 genotypes. These findings support better diagnostics, vaccine antigen selection, and antimicrobial stewardship. Future work using multilocus sequence typing/whole–genome sequencing across livestock species will improve understanding of regional transmission dynamics within a One Health framework. Keywords: antimicrobial resistance genes, buffalo, capsular typing, hemorrhagic septicemia, lipopolysaccharide genotype, molecular epidemiology, One Health, Pasteurella multocida, Vietnam, virulence–associated genes.

: Quantitative polymerase chain reaction (qPCR) is an increasingly recognized diagnostic tool for soil-transmitted helminths (STHs), overcoming limitations of microscopy. We compared qPCR with Kato–Katz (KK) and sodium nitrate flotation (SNF; specific gravities 1.2 and 1.3) in determining STH prevalence and infection intensity using samples from a community survey of 351 people in Dak Lak province, Vietnam. Established correlation formulas were used to convert qPCR cycle threshold values to eggs per gram to compare infection intensity. Sensitivity, specificity, and agreement between methods were also investigated. Hookworm was the predominant STH detected, with prevalences of 70.3% (95% CI: 63.6–76.9) by qPCR, 59.1% (95% CI: 46.3–72.4) by 1.2SNF, 56.5% (95% CI: 43.2–69.4) by 1.3SNF, and 47.8% (95% CI: 34.6–57.6) by KK. Detection of Ascaris lumbricoides and Trichuris trichiura was low across methods. Prevalences of zoonotic hookworm Ancylostoma ceylanicum and Strongyloides species by qPCR were 3.0% (95% CI: 1.3–6.4) and 17.3% (95% CI: 8.1–22.3), respectively. qPCR detected higher prevalence of moderate- (8.3% versus Strongyloides spp. supports the role of qPCR to inform control strategies, particularly for zoonotic reservoirs and use of macrocyclic lactones.

Toxocara canis is a globally distributed zoonotic parasite. The parasite has recently become a concern for public health in Vietnam. This cross-sectional study aimed to identify and quantify the risk factors associated with T. canis infection in dogs in Dak Lak province in the Central Highlands of Vietnam. The risk factors were identified using a mixed-effects logistic regression model and quantified using population attributable fractions. Examination of fecal samples collected from 1455 dogs using the sodium nitrate flotation technique showed 37.32% (95% CI: 34.83–39.86) of dogs infected with T. canis. The factors, including study location, multiple dogs living in a household, dog age, dog breed, and places keeping dogs were associated with a dog’s likelihood of being T. canis infection. The household and individual dog levels contributed 17% and 82%, respectively, to the prevalence of T. canis in dogs. The adjusted population attributable fraction for confining dogs and raising an individual dog per household was 52% and 27%, respectively. The result of this study indicated that to minimize the burden of T. canis, intervention measures should target individual dogs and household levels.

Background: Soil-transmitted helminth (STH) infection is driven by a complex interaction of demographic, socioeconomic and behavioural factors, including those related to water, sanitation and hygiene (WASH). Epidemiological studies that measure both infection and potential risk factors associated with infection help to understand the drivers of transmission in a population and therefore can provide information to optimise STH control programmes.Methods: During October and November 2019, we conducted a cross-sectional survey of the prevalence and intensity of STH infection and associated risk factors among 7710 primary-school-age children from 64 primary schools across 13 districts in Dak Lak province, Vietnam. Quantitative PCR (qPCR) was used to detect and quantify STH infections.Results: The predominant STH species was the hookwormNecator americanus(overall cluster-adjusted prevalence of 13.7%), and its prevalence was heterogeneously distributed across surveyed schools (0% to 56.3%). All other STH species had a prevalence of less than 1%. Using mixed-effects logistic regression, we found that the adjusted odds ratio (aOR) was significantly higher for both infection and moderate-to-heavy-intensity infection withN. americanusamong children from multiple ethnic minority groups, compared to children from the majority group (Kinh). Adjusted odds of infection withN. americanuswere also higher in children who reported practising open defecation at school (aOR 1.42, 95% CI 1.05, 1.93,P = 0.02) and in those who had an unimproved household water supply (aOR 1.28, 95% CI 1.04, 1.57,P = 0.02). Conversely, children with a flushing household toilet had a reduced risk of infection (aOR 0.58, 95% CI 0.47, 0.70,P < 0.01), as did those whose primary female carer attended secondary (aOR 0.65, 95% CI 0.51, 0.84,P < 0.01) or tertiary education (aOR 0.39, 95% CI 0.24, 0.63,P < 0.01).Conclusions: This study is the largest reported prevalence survey of STH infections conducted using qPCR as a diagnostic technique. The findings of higher adjusted odds of infection amongst ethnic minority children highlight that STH control programmes may not be reaching certain population groups and that additional culturally appropriate approaches may be required. Additionally, the associations between specific WASH factors and infection indicate potential programmatic targets to complement preventive chemotherapy programmes.Graphical

Taenia hydatigena is a globally distributed canine tapeworm. The canine tapeworm results in economic impacts for farmers owing to organ condemnation. T. hydatigena utilizes dogs and other carnivores as definitive hosts while swine and ruminants serve as intermediate hosts. T. hydatigena is endemic in Vietnam; however, information on the prevalence and risk factors associated with infection is scarce. This cross-sectional study aims to identify the prevalence of T. hydatigena taeniasis in dogs and T. hydatigena cysticercosis in pigs and cattle. The risk factors associated with taeniasis in dogs were identified using a fixed effects logistic regression model and quantified using population attributable fractions. The prevalence of T. hydatigena taeniasis in dogs and T. hydatigena cysticercosis in pigs and cattle was 10.31% (95% CI 8.21 to 12.84%), 7.60% (95% CI 6.34 to 9.08%), and 11.11% (95% CI 7.63 to 11.81%), respectively; these levels were lower than those reported in other regions of Vietnam. The population attributable fraction of risk factors associated with T. hydatigena taeniasis in dogs for dogs living in proximity of an abattoir, those having access to raw pork or beef viscera, and those living in multi-dog households were 80%, 19%, and 7%, respectively. This current study identified and quantified the risk factors for taeniasis in dogs thus advocating for targeted community intervention programs to break the lifecycle of T. hydatigena in Dak Lak province.