Publications by authors named "Hu Suk Lee"

20 Publications

  • Page 1 of 1

Dogs as Sentinels for Flavivirus Exposure in Urban, Peri-Urban and Rural Hanoi, Vietnam.

Viruses 2021 Mar 19;13(3). Epub 2021 Mar 19.

International Livestock Research Institute (ILRI), Hanoi 10000, Vietnam.

Diseases caused by flaviviruses, including dengue fever and Japanese encephalitis, are major health problems in Vietnam. This cross-sectional study explored the feasibility of domestic dogs as sentinels to better understand risks of mosquito-borne diseases in Hanoi city. A total of 475 dogs serum samples from 221 households in six districts of Hanoi were analyzed by a competitive enzyme-linked immunosorbent assay (cELISA) for antibodies to the pr-E protein of West Nile virus and other flaviviruses due to cross-reactivity. The overall flavivirus seroprevalence in the dog population was 70.7% (95% CI = 66.4-74.8%). At the animal level, significant associations between seropositive dogs and district location, age, breed and keeping practice were determined. At the household level, the major risk factors were rural and peri-urban locations, presence of pigs, coil burning and households without mosquito-borne disease experience ( < 0.05). Mosquito control by using larvicides or electric traps could lower seropositivity, but other measures did not contribute to significant risk mitigation of flavivirus exposure in dogs. These results will support better control of mosquito-borne diseases in Hanoi, and they indicate that dogs can be used as sentinels for flavivirus exposure.
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http://dx.doi.org/10.3390/v13030507DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003331PMC
March 2021

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

PLoS One 2021 3;16(3):e0247770. Epub 2021 Mar 3.

National Institute of Veterinary Research, Hanoi, 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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247770PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7928462PMC
March 2021

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

BMC Vet Res 2020 Sep 14;16(1):333. Epub 2020 Sep 14.

School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai, Ebetsu, Hokkaido, 069-8501, Japan.

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.
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http://dx.doi.org/10.1186/s12917-020-02537-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7489210PMC
September 2020

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

Transbound Emerg Dis 2020 Aug 18. Epub 2020 Aug 18.

International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia.

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.
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http://dx.doi.org/10.1111/tbed.13802DOI Listing
August 2020

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

BMC Vet Res 2020 Jan 14;16(1):15. Epub 2020 Jan 14.

International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia.

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).
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http://dx.doi.org/10.1186/s12917-020-2236-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958752PMC
January 2020

Spatiotemporal analysis of historical records (2001-2012) on dengue fever in Vietnam and development of a statistical model for forecasting risk.

PLoS One 2019 27;14(11):e0224353. Epub 2019 Nov 27.

National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.

Background: Dengue fever is the most widespread infectious disease of humans transmitted by Aedes mosquitoes. It is the leading cause of hospitalization and death in children in the Southeast Asia and western Pacific regions. We analyzed surveillance records from health centers in Vietnam collected between 2001-2012 to determine seasonal trends, develop risk maps and an incidence forecasting model.

Methods: The data were analyzed using a hierarchical spatial Bayesian model that approximates its posterior parameter distributions using the integrated Laplace approximation algorithm (INLA). Meteorological, altitude and land cover (LC) data were used as predictors. The data were grouped by province (n = 63) and month (n = 144) and divided into training (2001-2009) and validation (2010-2012) sets. Thirteen meteorological variables, 7 land cover data and altitude were considered as predictors. Only significant predictors were kept in the final multivariable model. Eleven dummy variables representing month were also fitted to account for seasonal effects. Spatial and temporal effects were accounted for using Besag-York-Mollie (BYM) and autoregressive (1) models. Their levels of significance were analyzed using deviance information criterion (DIC). The model was validated based on the Theil's coefficient which compared predicted and observed incidence estimated using the validation data. Dengue incidence predictions for 2010-2012 were also used to generate risk maps.

Results: The mean monthly dengue incidence during the period was 6.94 cases (SD 14.49) per 100,000 people. Analyses on the temporal trends of the disease showed regular seasonal epidemics that were interrupted every 3 years (specifically in July 2004, July 2007 and September 2010) by major fluctuations in incidence. Monthly mean minimum temperature, rainfall, area under urban settlement/build-up areas and altitude were significant in the final model. Minimum temperature and rainfall had non-linear effects and lagging them by two months provided a better fitting model compared to using unlagged variables. Forecasts for the validation period closely mirrored the observed data and accurately captured the troughs and peaks of dengue incidence trajectories. A favorable Theil's coefficient of inequality of 0.22 was generated.

Conclusions: The study identified temperature, rainfall, altitude and area under urban settlement as being significant predictors of dengue incidence. The statistical model fitted the data well based on Theil's coefficient of inequality, and risk maps generated from its predictions identified most of the high-risk provinces throughout the country.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0224353PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6881000PMC
April 2020

Temporal patterns and space-time cluster analysis of foot-and-mouth disease (FMD) cases from 2007 to 2017 in Vietnam.

Transbound Emerg Dis 2020 Mar 1;67(2):584-591. Epub 2019 Oct 1.

International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia.

In Vietnam, Foot-and-mouth disease (FMD) is endemic, but no nationwide studies have been conducted to assess the monthly variations and space-time clusters of FMD. The main objective was to identify the temporal patterns and space-time clusters of FMD from 2007 to 2017 using national surveillance data in Vietnam. A total of 163,733 cases were reported from 2007 to 2017. Among them, the proportion of buffaloes (43.31% of total reported cases; 70,909 cases) was highest followed by cattle (30.11%; 49,306 cases), pigs (26.67%; 43,662 cases) and sheep/goats (0.41%; 675 cases). The serotype O was widely distributed across the country while serotype A was observed in Northeast, Central and Southern part of Vietnam while Asia 1 has been not identified since 2007. For monthly variations, most cases were observed during the dry season (from November to March) except Central Highlands. Under the spatial window was set at 50%, a total of seven clusters were identified. The primary cluster was observed from Dec 2009 to Dec 2010 in the northwest (radius: 101.67 km), showing a ratio of 3.75. The secondary cluster was detected in the northeast region (radius: 76.54 km) with a ratio of 3.53 in Feb 2017. The 3rd cluster was the largest with a radius of 176.69 km and located in the southern part of Vietnam. Interestingly, the most temporal clusters included between December and March during the study period. Our findings provide better insight into the temporal patterns and distribution of clusters of FMD in Vietnam. This study provides useful information to policymakers on the hotspot areas and timing of outbreaks. It also identifies when and where national surveillance and control programmes could be implemented more efficiently for the prevention and control of FMD.
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http://dx.doi.org/10.1111/tbed.13370DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7079069PMC
March 2020

Seroprevalence of leptospirosis and Japanese encephalitis in swine in ten provinces of Vietnam.

PLoS One 2019 1;14(8):e0214701. Epub 2019 Aug 1.

International Livestock Research Institute, Nairobi, Kenya.

Background: Leptospirosis is an important zoonotic disease with a global distribution, affecting a wide range of mammalian animals and humans. Japanese encephalitis (JE) virus is the major vector-borne zoonotic disease in the Asia-Pacific region. The main objective of this study was to evaluate the seroprevalence of serovar-specific Leptospira and JE in swine from 10 provinces in Vietnam.

Methods: Samples were initially collected for swine influenza surveillance from March to April 2017 at large-scale farms (with at least 50 sows and/or 250 fattening pigs) with pigs that tested positive for influenza in the previous surveillance period (2015-16).

Findings: A total of 2,000 sera samples were analyzed from 10 provinces. Overall, the seroprevalence of leptospirosis was 21.05% (95% CI: 19.28-22.90) using a cut-off titer of ≥ 1:100. The apparent prevalence of JE was 73.45% (95% CI: 71.46-75.37) while the true prevalence was slightly higher (74.46%, 95% credible interval: 73.73-86.41). We found a relatively high presence of leptospirosis and JE in pigs kept on large farms. Prevalence was comparable with other studies suggesting opportunistic testing of samples collected for other surveillance purposes can be a valuable tool to better understand and prevent the potential transmission of these zoonotic diseases from pigs to people in Vietnam.

Conclusion: Our study provides evidence to veterinarians and animal health professionals for evidence-based practice such as diagnosis, vaccination and zoonotic control. Further investigation into the possible role of different domestic animals, wildlife species or environmental factors is needed to identify the potential risk factors and transmission routes in Vietnam.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0214701PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6675114PMC
March 2020

Simulation of control scenarios of porcine reproductive and respiratory syndrome in Nghe An Province in Vietnam.

Transbound Emerg Dis 2019 Nov 7;66(6):2279-2287. Epub 2019 Jul 7.

International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia.

The main objective of this study was to develop various models using North American Animal Disease Spread Model (NAADSM) to simulate the transmission of Porcine reproductive and respiratory syndrome (PRRS) virus between farms in Nghe An Province in Vietnam in order to inform the prevention and control of this important disease. Using real data from the household survey, credible parameters for direct/indirect mean contact rates between different farms were estimated. A total of eleven models were developed, including immunization scenarios. In addition, we conducted sensitive analysis on how the mean contact rates influenced the results. The immunization scenarios showed that a high proportion of pigs in medium size farms needs to be vaccinated in order to reduce the transmission to pigs in small farms under the Vietnamese pig production system. In order to promote the use of vaccinations, incentives (such as a vaccine subsidy) for medium size farms may be needed. It could be the most cost-effective control and prevention strategy for pig diseases in Vietnam. Our study provides insights on how pig diseases can be spread between pig farms via direct and indirect contact in Nghe An under the various hypothetical scenarios. Our results suggest that medium/large farms may play an important role in the transmission of pig diseases.
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http://dx.doi.org/10.1111/tbed.13278DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6899877PMC
November 2019

Seasonal patterns and space-time clustering of porcine reproductive and respiratory syndrome (PRRS) cases from 2008 to 2016 in Vietnam.

Transbound Emerg Dis 2019 Mar 30;66(2):986-994. Epub 2019 Jan 30.

International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia.

Porcine reproductive and respiratory syndrome (PRRS) is an important disease in pig production and is endemic in Vietnam. No nationwide studies have been carried out to understand the spread of PRRS in Vietnam. The main objective of this study was to identify the seasonal patterns and space-time clusters of PRRS from 2008 to 2016 using national surveillance data in Vietnam. A total of 614,219 cases were reported during the period. There was a seasonal pattern with single peak by region (except North Central Coast, showing double peaks in March and June). The seasonal plots from the Northern regions showed a higher peak between March and April, whereas the four regions from Southern part displayed a higher peak between June and August. Overall, outbreaks from the northern part of Vietnam tended to occur 3-4 months earlier than the southern part. When the spatial window was set at 50%, space-time cluster analysis found that the first cluster occurred in the Red River Delta (RRD) (radius: 82.17 km; ratios: 5.5; period: Mar-May/2010) and the second (radius: 50.8 km; ratios: 10.61; period: Aug-Oct/2011) in the Mekong River Delta (MRD) region. Four other clusters were observed in the central and Southern parts. Our findings might provide better insight into the distribution of clusters and temporal patterns of PRRS in Vietnam. This study may provide policy makers with valuable information on the hotspot areas and timing of outbreaks. Also, it identifies when and where national control program could be implemented more efficiently by targeting resources for the prevention and control of PRRS.
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http://dx.doi.org/10.1111/tbed.13122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6850339PMC
March 2019

Bioaerosol Sampling to Detect Avian Influenza Virus in Hanoi's Largest Live Poultry Market.

Clin Infect Dis 2019 03;68(6):972-975

Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore.

Background: Newly emergent and virulent strains of H7N9 avian influenza virus are rapidly spreading in China and threaten to invade Vietnam. We sought to introduce aerosol sampling for avian influenza viruses in Vietnam.

Methods: During October 2017, National Institute for Occupational Safety and Health 2-stage aerosol samplers were assembled on a tripod and run for 4 hours. Concomitantly, up to 20 oropharyngeal (OP) swab samples were collected from chickens and ducks distanced at 0.2-1.5 m from each sampler.

Results: The 3 weeks of sampling yielded 30 aerosol samples that were 90% positive for influenza A, by quantitative reverse-transcription polymerase chain reaction, and 116 OP swab sample pools (5 samples per pool) that were 47% positive. Egg cultures yielded 1 influenza A virus (not H5 or H7) from aerosol and 25 influenza A viruses from OP swab sample pools (5 were H5 positive). The association between positive sample types (over time and position) was strong, with 91.7% of positive OP pooled swab samples confirmed by positive aerosol samples and 81% of influenza A positive aerosol samples confirmed by positive OP swab samples.

Conclusions: We posit that aerosol sampling might be used for early warning screening of poultry markets for novel influenza virus detection, such as H7N9. Markets with positive aerosol samples might be followed up with more focused individual bird or cage swabbing, and back-tracing could be performed later to locate specific farms harboring novel virus. Culling birds in such farms could reduce highly pathogenic avian influenza virus spread among poultry and humans.
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http://dx.doi.org/10.1093/cid/ciy583DOI Listing
March 2019

The importance of on-farm biosecurity: Sero-prevalence and risk factors of bacterial and viral pathogens in smallholder pig systems in Uganda.

Acta Trop 2018 Nov 24;187:214-221. Epub 2018 Jun 24.

International Livestock Research Institute, P.O. Box 5689, Addis Ababa, Ethiopia. Electronic address:

Background: The productivity of pigs in smallholder systems is affected by high disease burden, most of which might not be obvious, with their epidemiology and impact being poorly understood. This study estimated the seroprevalence and identified the risk factors of a range of bacterial and viral pathogens of potential economic and public health importance in domestic pigs in Uganda. A total of 522 clinically healthy pigs were randomly selected from 276 pig farms in Masaka (142) and Lira (134) districts of Uganda in 2015.

Results: Overall the highest animal prevalence was found for Streptococcus suis 73.0% (CI95: 67.0-78.3) in Lira and 68.2% (CI95: 62.7-73.4) in Masaka; followed by Porcine circovirus type 2 with 50.8% (CI95: 44.5-57.2) in Lira and 40.7% (CI95: 35.2-46.5) in Masaka and Actinobacillus pleuro-pneumoniae, 25.6% (CI95: 20.4-31.6) in Lira and 20.5% (CI95: 16.2-25.6) in Masaka. Mycoplasma hyopneumonia prevalence was 20.9% (CI95: 16.2-26.6) in Lira and 10.1% (CI95: 7.1-14.1) in Masaka, while Porcine parvovirus was 6.2% (CI95: 4.0-9.7) in Masaka and 3.4% (CI95: 1.7-6.6) in Lira. Less common pathogens were Influenza A, 8.5% (CI95: 5.6-12.8) in Lira and 2.0% (CI95: 0.9-4.5) in Masaka and Porcine Reproductive and Respiratory Syndrome Virus, 1.7% (CI95: 0.7-4.3) in Lira and 1.3% (CI95: 0.5-3.5) in Masaka. Even less common was Rotavirus A with 0.8% (CI95: 0.2-3.0) in Lira and 0.7% (CI95: 0.2-2.5) in Masaka; the same was for Aujeszky virus with 0.4% (CI95: 0.7-2.4) in Lira and 0.0% (CI95: 0.0-0.1) in Masaka. Co-infection with two pathogens was common and there was a significant association of M. hyo and PCV2 co-occurrence (p = 0.016). Multivariate analysis showed that for S. suis the use of disinfectant reduced odds of sero-positivitey (OR = 0.15; p = 0.017) and pigs less than 6 months were more likely to be infected than older pigs (OR = 3.35; p = 0.047). For M. hyo, crossbred pigs had higher odd of infection compared to local breeds (OR = 1.59; p < 0.001).

Conclusions: The studied pathogens have high prevalences in smallholder pig production systems and might be silent killers, thus affecting productivity and there is a possibility that some pathogens could spread to humans. Given the limited knowledge of veterinary workers and the poor diagnostic capacities and capabilities in these systems, the diseases are potentially usually under-diagnosed. These findings constitute baseline data to measure the impact of future interventions aiming to reduce disease burden in the pig production systems in Uganda.
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http://dx.doi.org/10.1016/j.actatropica.2018.06.025DOI Listing
November 2018

Geographical and temporal patterns of rabies post exposure prophylaxis (PEP) incidence in humans in the Mekong River Delta and Southeast Central Coast regions in Vietnam from 2005 to 2015.

PLoS One 2018 10;13(4):e0194943. Epub 2018 Apr 10.

International Livestock Research Institute, Hanoi, Vietnam.

Background: In Vietnam, rabies has been a notifiable disease for more than 40 years. Over the last five years, on average, more than 350,000 people per year have been bitten by dogs and cats while more than 80 human deaths have been reported yearly. No studies have been conducted to evaluate the geographical and temporal patterns of rabies in humans in Vietnam. Therefore, the main objective of this study was to assess the geographical and temporal distributions of rabies post exposure prophylaxis (PEP) incidence in humans in Vietnam from 2005 to 2015.

Methods: Average incidence rabies (AIR) PEP rates for every 3 or 4 years (2005-2008, 2009-2012 and 2013-2015) were calculated to describe the spatial distribution of rabies PEP. Hotspot analysis was implemented to identify patterns of spatial significance using the Getis-Ord Gi statistic. For temporal pattern analysis, two regions [Mekong River Delta (MRD) and Southeast Central Coast (SCC)], with the highest incidence rates, and the seasonal-decomposition procedure based on loess (STL), were compared to assess their temporal patterns of rabies PEP.

Findings: We found hotspots in southern Vietnam and coldspots in northern Vietnam during the study period. Rabies cases were limited to specific areas. In addition, the hotspot analysis showed that new risk areas were identified in each period which were not observed in incidence rate maps. The seasonal plots showed seasonal patterns with a strong peak in February/July and a minor peak in October/December in the MRD region. However, in the SCC, a small peak was detected at the early part of each year and a strong peak in the middle of each year.

Conclusion: Our findings provide insight into understanding the geographical and seasonal patterns of rabies PEP in Vietnam. This study provides evidence to aid policy makers when making decisions and investing resources. Such information may also be utilized to raise public awareness to prevent rabies exposures and reduce unnecessary PEP.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194943PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892892PMC
July 2018

An investigation into aflatoxin M in slaughtered fattening pigs and awareness of aflatoxins in Vietnam.

BMC Vet Res 2017 Nov 28;13(1):363. Epub 2017 Nov 28.

International Livestock Research Institute, Nairobi, Kenya.

Background: Aflatoxin M (AFM) is a hydroxylated metabolite formed after aflatoxin B (AFB) is consumed by humans and animals; it can be detected in urine, milk and blood. It is well recognized that AFB is toxic to humans and other animals. The International Agency for Research on Cancer (IARC) classifies aflatoxins as group 1 carcinogens and AFM as group 2B carcinogen. The main objective of this study was to evaluate the exposure of pigs to aflatoxins as well as to assess the public awareness of aflatoxins among people in five provinces in Vietnam.

Results: A total of 1920 urine samples were collected from slaughterhouses located in five provinces. Overall, the positive rate of AFM was 53.90% (95% confidence interval 51.64-56.15) using a cut-off of 0.15 μg/kg (range: limit of detection to 13.66 μg/kg, median: 0.2 μg/kg and mean: 0.63 μg/kg). A total of 252 people from the general population were interviewed from 5 provinces, and overall 67.86% reported being aware of aflatoxins. We also found that men and more highly educated had significantly increased awareness of aflatoxins compared to the females and primary/secondary school group. The respective odds ratios (ORs) were as follows: "male" group (OR: 2.64), "high school educated" group (OR: 3.40) and "college/university or more educated" group (OR: 10.20).

Conclusions: We can conclude that pigs in Vietnam are exposed to aflatoxins to varying degrees, and there may be a risk that pork products could contain AFM. Further investigation is needed into the possible health impacts as well as to aid in establishing regulations for animal feed to reduce the health impacts in humans and animals.
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http://dx.doi.org/10.1186/s12917-017-1297-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5706150PMC
November 2017

Seasonal and geographical distribution of bacillary dysentery (shigellosis) and associated climate risk factors in Kon Tam Province in Vietnam from 1999 to 2013.

Infect Dis Poverty 2017 Jun 21;6(1):113. Epub 2017 Jun 21.

International Livestock Research Institute (ILRI), Room 301-302, B1 Building, Van Phuc Diplomatic Compound, 298 Kim Ma Street, Ba Dinh District, Hanoi, Vietnam.

Background: Bacillary dysentery (BD) is an acute bacterial infection of the intestine caused by Shigella spp., with clinical symptoms ranging from fever to bloody diarrhoea to abdominal cramps to tenesmus. In Vietnam, enteric bacterial pathogens are an important cause of diarrhoea and most cases in children under 5 years of age are due to Shigella strains. The serogroups S. flexneri and S. sonnei are considered to be the most common. The main objective of this study was to, for the first time, assess the seasonal patterns and geographic distribution of BD in Vietnam, and to determine the climate risk factors associated with the incidence of BD in Kon Tum Province, where the highest rate of bacillary dysentery was observed from 1999 to 2013.

Methods: The seasonal patterns and geographic distribution of BD was assessed in Vietnam using a seasonal-trend decomposition procedure based on loess. In addition, negative binomial regression models were used to determine the climate risk factors associated with the incidence of BD in Kon Tum Province, from 1999 to 2013.

Results: Overall, incidence rates of BD have slightly decreased over time (except for an extremely high incidence in 2012 in the north of Vietnam). The central regions (north/south central coast and central highlands) had relatively high incidence rates, whereas the northwest/east and Red River Delta regions had low incidence rates. Overall, seasonal plots showed a high peak in the mid-rainy reason and a second smaller peak in the early or late rainy season. The incidence rates significantly increased between May and October ("wet season") across the country. In Kon Tum Province, temperature, humidity, and precipitation were found to be positively associated with the incidence of BD.

Conclusions: Our findings provide insights into the seasonal patterns and geographic distribution of BD in Vietnam and its associated climate risk factors in Kon Tum Province. This study may help clinicians and the general public to better understand the timings of outbreaks and therefore equip them with the knowledge to plan better interventions (such as improving water, sanitation, and hygiene conditions) during peak seasons. This can, in turn, prevent or reduce outbreaks and onwards transmission during an outbreak.
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http://dx.doi.org/10.1186/s40249-017-0325-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480122PMC
June 2017

Sero-prevalence of specific Leptospira serovars in fattening pigs from 5 provinces in Vietnam.

BMC Vet Res 2017 May 8;13(1):125. Epub 2017 May 8.

International Livestock Research Institute, Nairobi, Kenya.

Background: Leptospirosis is a zoonotic bacterial disease with a worldwide distribution. In Vietnam, leptospirosis is considered endemic. In pigs, leptospirosis can result in reproductive problems (such as abortion and infertility) which lead to economic loss. In addition, transmission to people presents a public health risk. In Vietnam, few national studies have been conducted on sero-prevalence of leptospirosis in pigs. The main objective of this study was to evaluate the sero-prevalence and incidence of presumptive infective leptospira serovars in fattening pigs from 5 provinces in Vietnam.

Results: Blood samples from fattening pigs were randomly collected at slaughterhouses. We collected 1959 sera samples from 5 provinces (Son La, Hanoi, Nghe An, Dak Lak and An Giang) between January and early June 2016. The microscopic agglutination test (MAT) was used to identify the serogroups/serovars. Overall, the sero-prevalence was 8.17% (95% CI: 6.99-9.47) and serovar Tarassovi Mitis (2.19%) had the highest prevalence followed by Australis (1.94%), Javanica (1.68%) and Autumnalis (1.17%) using a cutoff (≥ 1:100). The sero-prevalence among female pigs (5.28%, 95% CI: 3.94-6.93) was slightly higher than among male pigs (4.88%, 95% CI: 3.51-6.58), but this difference was not statistically significant.

Conclusions: Leptospirosis in pigs may be a useful indicator of the human/animal burden in Vietnam and a risk assessment tool. The presence of some of the identified serovars suggests that wildlife may play an important role in the transmission of leptospirosis to domesticated pigs in Vietnam. Therefore, strengthened monitoring and surveillance systems are needed to better understand the epidemiology of the disease and prevent or reduce infection in humans and animals.
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http://dx.doi.org/10.1186/s12917-017-1044-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5422963PMC
May 2017

Seasonal patterns of dengue fever and associated climate factors in 4 provinces in Vietnam from 1994 to 2013.

BMC Infect Dis 2017 03 20;17(1):218. Epub 2017 Mar 20.

International Livestock Research Institute, Nairobi, Kenya.

Background: In Vietnam, dengue fever (DF) is still a leading cause of hospitalization. The main objective of this study was to evaluate the seasonality and association with climate factors (temperature and precipitation) on the incidences of DF in four provinces where the highest incidence rates were observed from 1994 to 2013 in Vietnam.

Methods: Incidence rates (per 100,000) were calculated on a monthly basis from during the study period. The seasonal-decomposition procedure based on loess (STL) was used in order to assess the trend and seasonality of DF. In addition, a seasonal cycle subseries (SCS) plot and univariate negative binomial regression (NBR) model were used to evaluate the monthly variability with statistical analysis. Lastly, a generalized estimating equation (GEE) was used to assess the relationship between monthly incidence rates and weather factors (temperature and precipitation).

Results: We found that increased incidence rates were observed in the second half of each year (from May through December) which is the rainy season in each province. In Hanoi, the final model showed that 1 °C rise of temperature corresponded to an increase of 13% in the monthly incidence rate of DF. In Khanh Hoa, the final model displayed that 1 °C increase in temperature corresponded to an increase of 17% while 100 mm increase in precipitation corresponded to an increase of 11% of DF incidence rate. For Ho Chi Minh City, none of variables were significant in the model. In An Giang, the final model showed that 100 mm increase of precipitation in the preceding and same months corresponded to an increase of 30% and 22% of DF incidence rate.

Conclusion: Our findings provide insight into understanding the seasonal pattern and associated climate risk factors.
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http://dx.doi.org/10.1186/s12879-017-2326-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5359841PMC
March 2017

Seasonality of Viral Encephalitis and Associated Environmental Risk Factors in Son La and Thai Binh Provinces in Vietnam from 2004 to 2013.

Am J Trop Med Hyg 2017 Jan 31;96(1):110-117. Epub 2016 Oct 31.

International Livestock Research Institute, Nairobi, Kenya.

In Vietnam, Japanese encephalitis virus accounts for 12-71% of viral encephalitis (VE) cases followed by enteroviruses and dengue virus among identified pathogens. This study is the first attempt to evaluate the seasonality of VE and associated environmental risk factors in two provinces from 2004 to 2013 using a seasonal trend-decomposition procedure based on loess regression and negative binomial regression models. We found seasonality with a peak of VE in August and June in Son La and Thai Binh, respectively. In Son La, the model showed that for every 1°C increase in average monthly temperature, there was a 4.0% increase in monthly VE incidence. There was a gradual decline in incidence rates as the relative humidity rose to its mean value (80%) and a dramatic rise in incidence rate as the relative humidity rose past 80%. Another model found that a 100 mm rise in precipitation in the preceding and same months corresponded to an increase in VE incidence of 23% and 21%, respectively. In Thai Binh, our model showed that a 1°C increase in temperature corresponded with a 9% increase in VE incidence. Another model found that VE incidence increased as monthly precipitation rose to its mean value of 130 mm but declined gradually as precipitation levels rose beyond that. The last model showed that a monthly increase in duration of sunshine of 1 hour corresponded to a 0.6% increase in VE incidence. The findings may assist clinicians by improving the evidence for diagnosis.
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http://dx.doi.org/10.4269/ajtmh.16-0471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5239675PMC
January 2017

Time-series analysis of ruminant foetal wastage at a slaughterhouse in North Central Nigeria between 2001 and 2012.

Onderstepoort J Vet Res 2015 Dec 15;82(1):1010. Epub 2015 Dec 15.

International Livestock Research Institute, Regional Office for East and Southeast Asia, Hanoi.

In developing countries, foetal wastage from slaughtered ruminants and the associated economic losses appear to be substantial. However, only a limited number of studies have comprehensively evaluated these trends. In the current study, secondary (retrospective) and primary data were collected and evaluated to estimate the prevalence of foetal wastage from cattle, sheep and goats slaughtered at an abattoir in Minna, Nigeria, over a 12-year period (January 2001-December 2012). Time-series modelling revealed substantial differences in the rate of foetal wastage amongst the slaughtered species, with more lambs having been wasted than calves or kids. Seasonal effects seem to influence rates of foetal wastage and certain months in the year appear to be associated with higher odds of foetal wastage. Improved management systems are suggested to reduce the risk of foetal losses.
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http://dx.doi.org/10.4102/ojvr.v82i1.1010DOI Listing
December 2015

Time series analysis of human and bovine brucellosis in South Korea from 2005 to 2010.

Prev Vet Med 2013 Jun 29;110(2):190-7. Epub 2012 Dec 29.

Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, 725 Harrison Street, West Lafayette, IN 47907, United States.

Brucellosis is considered to be one of the most important zoonotic diseases in the world, affecting underdeveloped and developing countries. The primary purpose of brucellosis control is to prevent the spread of disease from animals (typically ruminants) to humans. The main objective of this study was to retrospectively develop an appropriate time series model for cattle-to-human transmission in South Korea using data from independent national surveillance systems. Monthly case counts for cattle and people as well as national population data were available for 2005-2010. The temporal relationship was evaluated using an autoregressive integrated moving average with exogenous input (ARIMAX) model [notated as ARIMA(p, d, q)-AR(p)] and a negative binomial regression (NBR) model. Human incidence rate was highly correlated to cattle incidence rate in the same month and the previous month (both r=0.82). In the final models, ARIMA (0, 1, 1)-AR (0, 1) was determined as the best fit with 191.5% error in the validation phase, whereas the best NBR model including lags (0, 1 months) for the cattle incidence rate yielded a 131.9% error in the validation phase. Error (MAPE) rates were high due to small absolute human case numbers (typically less than 10 per month in the validation phase). The NBR model however was able to demonstrate a marked reduction in human case immediately following a hypothetical marked reduction in cattle cases, and may be better for public health decision making.
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http://dx.doi.org/10.1016/j.prevetmed.2012.12.003DOI Listing
June 2013