Pathobiological analysis of african swine fever virus contact-exposed pigs and estimation of the basic reproduction number of the virus in Vietnam.

BACKGROUND: African swine fever (ASF), caused by African swine fever virus (ASFV), is a fatal disease affecting wild and domestic pigs. Since China reported the first ASF outbreak in August 2018, ASFV has swept over the neighbouring Asian countries. However, studies involving experimental pig-to-pig ASFV transmission in Vietnam are lacking. The main objective of this experimental study was to demonstrate the pathobiological characteristics of ASFV contact-exposed pigs and estimate their basic reproduction number (R0) in Vietnam. Fifteen pigs were randomly divided into two groups: experimental (n = 10) and negative control (n = 5) groups. One pig in the experimental group was intramuscularly inoculated with ASFV strain from Vietnam in 2020 and housed with the uninoculated pigs during the study period (28 days). RESULTS: The inoculated pig died 6 days post-inoculation, and the final survival rate was 90.0%. We started observing viremia and excretion of ASFV 10 days post-exposure in contact-exposed pigs. Unlike the surviving and negative control pigs, all necropsied pigs showed severe congestive splenomegaly and moderate-to-severe haemorrhagic lesions in the lymph nodes. The surviving pig presented with mild haemorrhagic lesions in the spleen and kidneys. We used Susceptible-Infectious-Removed models for estimating R0. The R0 values for exponential growth (EG) and maximum likelihood (ML) were calculated to be 2.916 and 4.015, respectively. In addition, the transmission rates (ß) were estimated to be 0.729 (95% confidence interval [CI]: 0.379-1.765) for EG and 1.004 (95% CI: 0.283-2.450) for ML. CONCLUSIONS: This study revealed pathobiological and epidemiological information in about pig-to-pig ASFV transmission. Our findings suggested that culling infected herds within a brief period of time may mitigate the spread of ASF outbreaks.

Long-Term Epidemiology and Evolution of Swine Influenza Viruses, Vietnam.

Influenza A viruses are a One Health threat because they can spill over between host populations, including among humans, swine, and birds. Surveillance of swine influenza virus in Hanoi, Vietnam, during 2013-2019 revealed gene pool enrichment from imported swine from Asia and North America and showed long-term maintenance, persistence, and reassortment of virus lineages. Genome sequencing showed continuous enrichment of H1 and H3 diversity through repeat introduction of human virus variants and swine influenza viruses endemic in other countries. In particular, the North American H1-δ1a strain, which has a triple-reassortant backbone that potentially results in increased human adaptation, emerged as a virus that could pose a zoonotic threat. Co-circulation of H1-δ1a viruses with other swine influenza virus genotypes raises concerns for both human and animal health.

SARS-CoV-2 Infection in a Hippopotamus, Hanoi, Vietnam.

While investigating the death of a hippopotamus at a zoo in Hanoi, Vietnam, we isolated SARS-CoV-2 and sequenced the RNA-dependent RNA polymerase gene from different organs. Phylogenetic analysis showed that the SARS-CoV-2 strain was closely related to 3 human SARS-CoV-2 strains in Vietnam.

Blood parameters and pathological lesions in pigs experimentally infected with Vietnam's first isolated African swine fever virus.

African swine fever virus (ASFV) is a notable virus and one of the most serious global threats to the pig industry. Improving awareness about host-virus interactions could facilitate the understanding of the disease pathogenesis. Therefore, we investigated changes in blood parameters, viral loads, and pathological changes in ASFV-inoculated pigs according to the time of death after the onset of viremia. For the analyses, the ASFV-infected pigs (n = 10) were divided into two groups (five pigs/group) according to their time of death after the onset of viremia. The blood cell count dynamics and serum biochemistry profiles were similar between the groups; however, viral load distribution was different. A comparison of the histopathological changes and immunohistochemistry results between the two groups indicated that the lymphoid system, particularly the spleen, was more damaged in the early stage of the disease than in the last stage. Additionally, the virus-induced lesions in other organs (liver and kidney) were more severe in the late stage than in the early stage. Our findings provide invaluable information on the characteristics of blood parameters and pathological lesions in pigs infected with the Asia-epidemic ASFV strain and the course of ASF, targeting internal organs in pigs. Overall, this study characterizes the host-pathogen interaction in ASFV infection, offering insight for the establishment of ASF control strategies.

Duck circovirus in northern Vietnam: genetic characterization and epidemiological analysis.

In the present study, tissue samples collected from 130 ducks from clinically suspected commercial flocks and diseased birds in six provinces of northern Vietnam were tested for duck circovirus (DuCV) infection. The DuCV genome was detected in 56 out of 130 (43.08%) duck samples by PCR. Of 38 tested farms, 26 (68.42%) were positive for the DuCV genome. The rate of the DuCV genome detection in ducks at 3-4 weeks of age (54.17%) was significantly higher (p < 0.05) than that at <3 (32.43%) and >7 (33.33%) weeks of age and insignificantly higher than that at 5-7 weeks of age (43.33%) (p = 0.11). The genomes of six Vietnamese DuCV isolates were determined. They ranged in length from 1,988 to 1,995 nucleotides, and their nucleotide sequences were 83.24% to 99.69% identical to each other. Phylogenetic analysis based on the complete genome sequences indicated that the DuCV strains circulating in northern Vietnam can be divided into two main genotypes (I and II) and several subgenotypes. The Vietnamese DuCV isolates were closely related to Chinese, Taiwanese, and Korean strains. One positively selected site was detected in the capsid protein.

Zoonotic Flavivirus Exposure in Peri-Urban and Suburban Pig-Keeping in Hanoi, Vietnam, and the Knowledge and Preventive Practices of Pig Farmers.

Mosquito-borne diseases (MBDs), including those caused by flaviviruses, remain human health problems for developing and urbanizing economies. This cross-sectional study examined risks of flavivirus exposure through a survey regarding knowledge and practices of pig farmers, and serological analysis of pigs in peri-urban and suburban Hanoi city. A total of 636 pig sera from 179 pig farms in 4 districts, namely, Chuong My, Dan Phuong, Ha Dong, and Bac Tu Liem, were analyzed by a competitive ELISA designed for flavivirus antibody detection. The results indicated a low level of awareness about MBDs among pig farmers, and a high seroprevalence in pigs at 88.5% (95%CI = 85.8-90.9%). Moreover, common practices of pig owners to prevent mosquitoes at home and farm did not show a significant reduction in flavivirus exposure in pigs. At animal level, significant associations between seropositive pigs and the farms with more than 60 pigs, and the district location were found. Farm-level multivariable analysis did not identify significant risk factors for flavivirus exposure. The study suggests that improving awareness of pig owners about MBDs in Hanoi city may be warranted to reduce the risk for MBD flavivirus infections in both humans and pigs.

Characterization of Lumpy skin disease virus isolated from a giraffe in Vietnam.

While investigating a giraffe's death in a Vietnamese zoo, we successfully identified and isolated Lumpy skin disease virus (LSDV) from skin nodule biopsies and ruptured nodule wound swab samples. Phylogenetic analysis indicated that the isolate obtained in this study was closely related to the previous Vietnamese and Chinese LSDV strains from cattle. This is the first report on the genome detection and isolation of LSDV in a diseased giraffe in Vietnam. Further study is needed to better understand the epidemiology of this disease in wildlife.

Spatiotemporal Analysis and Assessment of Risk Factors in Transmission of African Swine Fever Along the Major Pig Value Chain in Lao Cai Province, Vietnam.

African swine fever (ASF) is a contagious and lethal hemorrhagic disease with a case fatality rate approaching 100% in domestic pigs. The main objectives of this study were to describe the spatiotemporal analysis as well as to assess the potential risk factors along the pig value chain in Lao Cai province, Vietnam. A total of 925 outbreaks were reported from 2019 to 2020. The three clusters (primary, secondary and 5th) were observed near the Chinese border. The most temporal clusters were detected between May and August during the study period. In addition, we evaluated the association between ASF outbreak locations to the nearest main roads and elevation. For ASF outbreak locations to the nearest main roads, compared with the reference (<5,000 m), <1,000 m (10.22 times) and 1,000-2,000 m (1.98 times) were significantly higher occurrences of ASF. For elevation, compared to the reference (>1,500 m), the farm locations with <500 m (55.31 times) showed a significantly increased risk of ASF outbreaks. Farmers perceived that the highest risk of ASF transmission may come from collectors and slaughterers, intermediaries inside and outside the commune, feed agents and maize agents in the commune, and pig retailers. Both commercial and household pig producers considered minimizing the number of people going in and out of pig stables and improving healthcare and husbandry procedures to be both very important and feasible. There is a need for compliance by all pig producers and other actors in the pig value chain to adopt biosecurity practices. Therefore, awareness, knowledge and understanding of infection and risks of ASF need to be improved. Veterinary officials at the provincial and district levels need to improve capacity and resources to perform laboratory analysis for ASF and need to coordinate with local actors on the control and prevention of ASF in the community.

Age-dependent immune response in pigs against foot-and-mouth disease virus in vitro.

Foot-and-mouth disease, one of the most contagious diseases in cloven-hoofed animals, causes significant economic losses. The pathogenesis of foot-and-mouth disease virus (FMDV) infection is known to differ with age of the animals. In this study, we aimed to reveal the difference in immunological response in the initial stage of FMDV infection between piglets and adult pigs. Peripheral blood mononuclear cells (PBMCs) were isolated from 3 piglets (8 weeks old) and 3 pigs (35 weeks old) that were not vaccinated against FMDV. O-type FMDV (2 × 102 median tissue culture infectious dose) was inoculated into porcine PBMCs and the cells were incubated at 37.0°C under 5% CO2 for various time periods (0, 1, 3, 6, 12, 24, and 48 h). The total RNA was obtained from the FMDV-inoculated PBMCs after each time point, and the virus titer was investigated in these RNA samples. Furthermore, dynamics of mRNA expression of the six tested cytokines (interferon [IFN]-α, IFN-γ, interleukin [IL]-6, IL-8, IL-10, and tumor necrosis factor [TNF]-α) in FMDV-inoculated porcine PBMCs were evaluated by time-series analysis to determine the differences, if any, based on the age of the pigs. The PBMCs of piglets contained the highest quantity of FMDV mRNA at 6 hours post-inoculation (hpi), and the PBMCs of pigs had the highest quantity of FMDV mRNA at 3 hpi. The mean cycle threshold-value in the PBMCs steadily decreased after the peak time point in the piglets and pigs (6 and 3 hpi, respectively). The dynamics of mRNA expression of all cytokines except TNF-α showed age-dependent differences in FMDV-inoculated PBMCs. The mRNA expression of most cytokines was more pronounced in the piglets than in the pigs, implying that the immune response against FMDV showed an age-dependent difference in pigs. In conclusion, within 48 hpi, the 8-week-old piglets responded more rapidly and were more sensitive to FMDV infection than the 35-week-old pigs, which could be associated with the difference in the pathogenesis of FMDV infection among the pigs. These results provide valuable insights into the mechanisms underlying the age-dependent differences in immune response in pigs against FMDV infection.

The Distribution and Composition of Vector Abundance in Hanoi City, Vietnam: Association with Livestock Keeping and Flavivirus Detection.

BACKGROUND: Dengue virus and Japanese encephalitis virus are two common flaviviruses that are spread widely by Aedes and Culex mosquitoes. Livestock keeping is vital for cities; however, it can pose the risk of increasing the mosquito population. Our study explored how livestock keeping in and around a large city is associated with the presence of mosquitoes and the risk of them spreading flaviviruses. METHODS: An entomological study was conducted in 6 districts with 233 households with livestock, and 280 households without livestock, in Hanoi city. BG-Sentinel traps and CDC light traps were used to collect mosquitoes close to animal farms and human habitats. Adult mosquitoes were counted, identified to species level, and grouped into 385 pools, which were screened for flaviviruses using a pan-flavivirus qPCR protocol and sequencing. RESULTS: A total of 12,861 adult mosquitoes were collected at the 513 households, with 5 different genera collected, of which the Culex genus was the most abundant. Our study found that there was a positive association between livestock keeping and the size of the mosquito population-most predominantly between pig rearing and Culex species (p < 0.001). One pool of Cx. tritaeniorhynchus, collected in a peri-urban district, was found to be positive for Japanese encephalitis virus. CONCLUSIONS: The risk of flavivirus transmission in urban areas of Hanoi city due to the spread of Culex and Aedes mosquitoes could be facilitated by livestock keeping.

Dynamic Variations in Infrared Skin Temperature of Weaned Pigs Experimentally Inoculated with the African Swine Fever Virus: A Pilot Study.

African swine fever (ASF) is a devastating viral disease in pigs and is therefore economically important for the swine industry. ASF is characterized by a short incubation period and immediate death, making the early identification of ASF-infected pigs essential. This pilot-scale study evaluates whether the infrared thermography (IRT) technique can be used as a diagnostic tool to detect changes in skin temperature (Tsk) during the early stages of disease development in experimentally ASF-infected pigs. Clinical symptoms and rectal temperatures (Tcore) were recorded daily, and IRT readings during the experimental ASF infection were analyzed. All infected pigs died at 5-8 days post inoculation (dpi), and the incubation period was approximately 4 dpi. The average Tcore increased from 0 dpi (38.9 ± 0.3 °C) to 7 dpi (41.0 ± 0.5 °C) and decreased by 8 dpi (39.8 ± 0 °C). The maximum Tsk of ASF-infected pigs increased from 2 (35.0 °C) to 3 dpi (38.5 °C). The mean maximum Tsk observed from three regions on the skin (ear, inguinal, and neck) significantly increased from 2 to 3 dpi. This study presents a non-contact method for the early detection of ASF in infected pigs using thermal imaging at 3 days after ASF infection.

Molecular characterization of bovine foamy virus and its association with bovine leukemia virus infection in Vietnamese cattle.

The detection of bovine foamy virus (BFV) in Vietnamese cattle was performed using conventional PCR targeting pol and gag genes. Out of 243 tested samples, ten (4.1%) and eight (3.3%) samples were positive for BFV gag and pol DNA, respectively. The prevalence of bovine leukemia virus (BLV) estimated by detection of proviral DNA using nested PCR targeting env gene was 26.7% (65/243). The results of nucleotide sequence alignment and the phylogenetic analysis suggested that Vietnamese BFV strains showed high homology to isolates belonging to either European or non-European clades. There was no significant correlation between BLV and BFV. This study provides information regarding BFV infection and confirms the existence of two BFV clades among Vietnamese cattle for the first time.

An epidemiological study of Streptococcus suis prevalence among swine at industrial swine farms in Northern Vietnam.

INTRODUCTION: Streptococcus suis is a zoonotic pathogen found in swine that may cause systemic infection in humans. S. suis is endemic in Southeast Asia and is the leading cause of adult meningitis in Vietnam. Given Vietnam's increasing centralization of the swine industry, we sought to estimate the prevalence of S. suis on large swine farms in Northern Vietnam. METHODS: A cross-sectional, one-health-oriented, surveillance study for S. suis was conducted between October 2019-March 2020. Swine oral, swine worker nasal, and bioaerosol samples were collected from four large-scale swine farms (>500 swine) in three provinces in Northern Vietnam: Lao Cai, Bac Giang, and Quang Ninh. Samples were evaluated for presence of S. suis growth on blood agar plates and confirmed with conventional polymerase chain reaction. RESULTS: The authors found that 4/174 (2.3%, 95% CI: 0.6-5.8%) of swine oral samples and 1/58 (1.7%, 95% CI: 0-9.2%) bioaerosol samples were positive for S. suis by bacterial culture and conventional PCR. S. suis was not detected in any swine worker nasal wash samples. There was no significant relationship between sampling location and month of sample collection with results of swine oral or bioaerosol samples. CONCLUSION: Compared to previous reports from slaughterhouses in Vietnam, the lower than expected prevalence of S. suis, supports the notion that that recent efforts to centralize Vietnam's pork industry through establishment of large-scale farms with better biosecurity may have been effective in limiting S. suis prevalence on these large farms.

Pathogenicity of an African swine fever virus strain isolated in Vietnam and alternative diagnostic specimens for early detection of viral infection.

BACKGROUND: African swine fever (ASF), caused by the ASF virus (ASFV), was first reported in Vietnam in 2019 and spread rapidly thereafter. Better insights into ASFV characteristics and early detection by surveillance could help control its spread. However, the pathogenicity and methods for early detection of ASFV isolates from Vietnam have not been established. Therefore, we investigated the pathogenicity of ASFV and explored alternative sampling methods for early detection. RESULTS: Ten pigs were intramuscularly inoculated with an ASFV strain from Vietnam (titer, 103.5 HAD50/mL), and their temperature, clinical signs, and virus excretion patterns were recorded. In addition, herd and environmental samples were collected daily. The pigs died 5-8 days-post-inoculation (dpi), and the incubation period was 3.7 ± 0.5 dpi. ASFV genome was first detected in the blood (2.2 ± 0.8) and then in rectal (3.1 ± 0.7), nasal (3.2 ± 0.4), and oral (3.6 ± 0.7 dpi) swab samples. ASFV was detected in oral fluid samples collected using a chewed rope from 3 dpi. The liver showed the highest viral loads, and ear tissue also exhibited high viral loads among 11 tissues obtained from dead pigs. Overall, ASFV from Vietnam was classified as peracute to acute form. The rope-based oral fluid collection method could be useful for early ASFV detection and allows successful ASF surveillance in large pig farms. Furthermore, ear tissue samples might be a simple alternative specimen for diagnosing ASF infection in dead pigs. CONCLUSIONS: Our data provide valuable insights into the characteristics of a typical ASFV strain isolated in Vietnam and suggest an alternative, non-invasive specimen collection strategy for early detection.

A stochastic network-based model to simulate farm-level transmission of African swine fever virus in Vietnam.

African swine fever virus is highly contagious, and mortality rates reach up to 100% depending on the host, virus dose, and the transmission routes. The main objective of this study was to develop a network-based simulation model for the farm-level transmission of ASF virus to evaluate the impact of changes in farm connectivity on ASF spread in Vietnam. A hypothetical population of 1,000 pig farms was created and used for the network-based simulation, where each farm represented a node, and the connection between farms represented an edge. The three scenarios modelled in this way (baseline, low, and high) evaluated the impact of connectivity on disease transmission. The median number of infected farms was higher as the connectivity increased (low: 659, baseline: 968 and high: 993). In addition, we evaluated the impact of the culling strategy on the number of infected farms. A total of four scenarios were simulated depending on the timing of culling after a farm was infected. We found that the timing of culling at 16, 12, 8, and 6 weeks had resulted in a reduction of the number of median infected farms by 81.92%, 91.63%, 100%, and 100%, respectively. Finally, our evaluation of the implication of stability of ties between farms indicated that if the farms were to have the same trading partners for at least six months could significantly reduce the median number of infected farms to two (95th percentile: 413) than in the basic model. Our study showed that pig movements among farms had a significant influence on the transmission dynamics of ASF virus. In addition, we found that the either timing of culling, reduction in the number of trading partners each farm had, or decreased mean contact rate during the outbreaks were essential to prevent or stop further outbreaks.

Knowledge and practice on prevention of mosquito-borne diseases in livestock-keeping and non-livestock-keeping communities in Hanoi city, Vietnam: A mixed-method study.

Mosquito-borne diseases (MBDs) are causing high morbidity and mortality for humans. Urban livestock keeping is still common in cities around the world. The animals may serve as reservoirs for zoonotic MBDs, which increase the risks for humans. Here we assess the knowledge and practices related to MBDs in households with livestock and without livestock and explore the perceptions of the health care sector about MBDs and livestock keeping in Hanoi city of Vietnam in a cross-sectional study. A quantitative survey was conducted including 513 households with and without livestock-keeping in six districts and complemented with qualitative surveys with four health staff from Hanoi Center of Disease Control and three district health centers. The quantitative survey indicated that the participants possessed basic knowledge on MBDs with an average score of 18.3 out of 35, of which non-livestock-keeping households had a better knowledge than households keeping livestock (p<0.05). Both household categories had low score, 3.5 out of 11, regarding preventive practices against MBDs. The negative binomial model showed that occupation and location of living were factors associated to the knowledge on MBDs. Farmers were likely to have better preventive practices as compared to office workers (p<0.05). Those who had better knowledge also had more adequate preventive practices against MBDs (p<0.001). The qualitative survey revealed that livestock keeping was determined as increasing risks of MBDs due to the increase of mosquito population. It is recommended that community campaigns to raise the awareness and change behavior on MBDs should be organized based on collaboration between the health sector and the veterinary sector for households with and without livestock living in central urban and peri-urban areas. Further studies are needed to confirm the association between urban livestock keeping and potential increasing risks of MBDs such as dengue and Japanese encephalitis.

A stochastic simulation model of African swine fever transmission in domestic pig farms in the Red River Delta region in Vietnam.

The main objectives of this study were to model various scenarios of African swine fever (ASF) virus transmission among farms in Vietnam and to evaluate the impact of control strategies using North American Animal Disease Spread Model (NAADSM). A total of 7,882 pig farms in the Red River Delta (RRD) region were obtained from the General Statistics Office, and then, random points corresponding to the number of farms in each province were generated as exact farm locations were not available. A total of 10 models were developed, including movement control scenarios. In addition, we conducted sensitivity analysis to assess the impact of indirect contact transmission probability (TP). Overall, the indirect contact exhibited an important role in transmitting the ASF virus. In order to minimize ASF transmission between farms, we found that movement restriction needed to reach a certain level (approximately between 50% and 75%) and that the restriction had to be applied in a timely manner. This study offers valuable insight into how ASF virus can be transmitted via direct and indirect contact and controlled among farms under the various simulation scenarios. Our results suggest that the enforcement of movement restriction was an effective control measure as soon as the outbreaks were reported. In addition, this study provided evidence that high standards of biosecurity can contribute to the reduction of disease spread.

Prevalence and phylogenetic analysis of hepatitis E virus in pigs in Vietnam.

BACKGROUND: Hepatitis E virus (HEV) is a zoonotic disease and has been reported around the world. The main objective of this study was to evaluate the sero-prevalence and phylogenetic analysis of HEV in Vietnam. Pig blood and fecal pooled samples were collected to assess the prevalence of HEV. We assessed the true prevalence (TP) of HEV from apparent prevalence (AP) by taking into account the sensitivity and specificity of diagnostic tests using a Bayesian approach. For phylogenetic analysis, the data compared with worldwide HEV reference strains including all eight genotypes (G1-G8) which were identified in previous study. RESULTS: A total of 475 sera and 250 fecal pooled samples were collected at slaughterhouses and pig farms from five provinces, in Viet Nam. Overall, the sero-AP of HEV was 58.53% (95% confidence interval: 53.95-62.70) while the sero-TP was slightly higher (65.43, 95% credible interval: 47.19-84.70). In terms of pooled samples, overall, the RNA-AP was 6.80% (95% confidence interval: 4.01-10.66). One strain in Hanoi, two strains in Dak Lak, seven strains in An Giang, four strains in Son La and two strains in Nghe An were isolated. The phylogenetic tree demonstrated that 19 Vietnamese strains were clustered into HEV 3 and 4. CONCLUSIONS: This study provided evidence that HEV is circulating in domestic pigs in Vietnam. From a public health perspective, it is very important to raise public awareness for high-risk groups (e.g. slaughterhouse workers, pig traders, farmers and market sellers) who have more opportunities to come in contact with pig and contaminated meats.

Seroprevalences of multi-pathogen and description of farm movement in pigs in two provinces in Vietnam.

BACKGROUND: In Vietnam, lack of animal health information is considered a major challenge for pig production. The main objective of this study was to assess the seroprevalences of five pathogens [porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), mycoplasma hyopneumoniae (M. hyo), Japanese encephalitis virus (JEV) and leptospirosis] and to better characterize the farm movements through a survey. RESULTS: A total of 600 samples were collected from 120 farms from Bac Giang and Nghe An. Among unvaccinated herds, the highest seroprevalence was found for JE with 73.81% (95% CI: 68.39-78.74) in Bac Giang and 53.51% (95% CI 47.68-59.27) in Nghe An. Seroprevalences for PCV2 and M.hyo were 49.43% (95% CI: 45.06-53.80) and 46.06% (95% CI: 41.48-50.69) among unvaccinated animals. Accumulative co-infections for JE (86.25%) showed the highest level followed by M. hyo (66.25%) and PCV2 (62.50%). Three co-infections with JE had the highest positive rate (28.75%) followed by four co-infections (25.0%). Medium farms had relatively higher herd prevalences for all pathogens, except from leptospirosis. Overall, farmers exported/imported their pigs at the most 1-2 times every 6 months. Some respondents (5% for exportation and 20% for importation) had moved pigs more than 6 times over the last 6 months. CONCLUSIONS: Our study provided another pool of evidence that showed that PCV2, PRRS and H. hyo are endemic in pigs in Vietnam. Given the economic impacts of these pathogens elsewhere, the findings confirm the need for studies to evaluate the association between antibody response and clinical relevance as well as to assess the economic impact of co-infections at farm level. We also found that high seroprevalences of JE and leptospirosis were detected in pigs. From a pubic health point of view, it is crucial to raise public awareness especially for high risk occupations (mainly pig farm workers).

Urban livestock-keeping and dengue in urban and peri-urban Hanoi, Vietnam.

Urban livestock provides an important source of food and income, but it may increase the risks for disease transmission. Vectors, such as mosquitoes, might increase and thereby cause an enhanced transmission of infectious diseases, such as dengue fever; considered the most important mosquito-borne viral disease globally. This cross-sectional study evaluated the awareness of dengue fever and investigated how the presence of dengue vectors is affected by the keeping of livestock in urban households in the city of Hanoi, Vietnam. From February to March 2018, during the season of lowest occurrence of dengue in Hanoi, 140 households were interviewed, of which 69 kept livestock. A general trend was observed; respondents living in the Dan Phuong district, a peri-urban district, had better knowledge and practice regarding dengue as compared to the urban Ha Dong district. In total, 3899 mosquitoes were collected and identified, of which 52 (1.33%) were Aedes species. A significant difference between the two districts was observed, with more households in Ha Dong having Aedes spp. mosquitoes (p = 0.02) and a higher incidence of dengue fever (p = 0.001). There was no significant association between livestock-rearing and the presence of Aedes spp. mosquitoes (p = 0.955), or between livestock-rearing and the incidence of dengue fever (p = 0.08). In conclusion, this study could not find any indication that households keeping livestock were at higher risk of dengue virus infections in Hanoi during the season of lowest occurrence of dengue, but clearly indicated the need of more information provided to urban inhabitants, particularly on personal protection.