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.

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).

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.

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

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.

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

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.

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

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.

An investigation into aflatoxin M 1 in slaughtered fattening pigs and awareness of aflatoxins in Vietnam.

BACKGROUND: Aflatoxin M1 (AFM1) is a hydroxylated metabolite formed after aflatoxin B1 (AFB1) is consumed by humans and animals; it can be detected in urine, milk and blood. It is well recognized that AFB1 is toxic to humans and other animals. The International Agency for Research on Cancer (IARC) classifies aflatoxins as group 1 carcinogens and AFM1 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 AFM1 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 AFM1. 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.

Transboundary viral diseases of pigs, poultry and ruminants in Southeast Asia: a systematic review.

Livestock is a strategic part of the small-farm economy in Southeast Asia's society, providing food income, clothing, fertilizer, and draught power. However, incidences or outbreaks of transboundary animal diseases (TADs) are due to converging factors such as the natural hazards' aftermath, climate change, deforestation, urban growth, changing production conditions, and market chains. Therefore, this affects productivity and impacts farmers' livelihoods with small holdings. The literature review was carried out to understand the current situation of TADs in Southeast Asia, identifying knowledge gaps to provide actions for disease control and prevention in the region. We have attempted to summarise the scientific literature in English on the prevalence data of TADs in Southeast Asia between 2011 and March 2022. Relatively few studies evaluated the distribution of TAD, where most of the studies focused on diseases that are important for international trade, such as avian influenza (AI), African swine fever (ASF), classical swine fever (CSF), foot-and-mouth disease (FMD) and Newcastle disease (ND). Traditional production systems have received little attention in such studies as they belonged to mainly smallholders. The outbreaks of ASF and lumpy skin disease (LSD) in 2019 resulted in increased research activity between 2019-2022, while the other TADs were ignored in this period. For new emerging TADs diseases such as ASF and LSD, there is only information about the first detection without prevalence information. Therefore, further epidemiological investigations are necessary to reduce the gaps in disease surveillance reporting systems and support the prevention and reduction of further outbreaks.

Emerging zoonotic diseases in Southeast Asia in the period 2011-2022: a systematic literature review.

As COVID-19 has shown, pandemics and outbreaks of emerging infections such as Zika, Nipah, monkeypox and antimicrobial-resistant pathogens, especially emerging zoonotic diseases, continue to occur and may even be increasing in Southeast Asia. In addition, these infections often result from environmental changes and human behaviour. Overall, public health surveillance to identify gaps in the literature and early warning signs are essential in this region. A systematic review investigated the prevalence of emerging zoonotic diseases over 11 years from 2011 to 2022 in Southeast Asia to understand the status of emerging zoonotic diseases, as well as to provide necessary actions for disease control and prevention in the region. During the 2011-2022 period, studies on pigs, poultry, ruminants, companion animals and wildlife in Southeast Asia were reviewed thoroughly to assess the quality of reporting items for inclusion in the systematic review. The review was performed on 26 studies of pigs, 6 studies of poultry, 21 studies of ruminants, 28 studies of companion animals and 25 studies of wildlife in Southeast Asia, which provide a snapshot of the prevalence of the emerging zoonotic disease across the country. The findings from the review showed that emerging zoonotic diseases were prevalent across the region and identified a few zoonotic diseases associated with poultry, mainly stemming from Cambodia and Vietnam, as high priority in Southeast Asia.Clinical relevance: Appropriate prevention and control measures should be taken to mitigate the emerging zoonotic diseases in Southeast Asia.

Transcriptome profiles of organ tissues from pigs experimentally infected with African swine fever virus in early phase of infection.

African swine fever, caused by African swine fever virus (ASFV), is a highly contagious and fatal disease that poses a significant threat to the global pig industry. The limited information on ASFV pathogenesis and ASFV-host interactions has recently prompted numerous transcriptomic studies. However, most of these studies have focused on elucidating the transcriptome profiles of ASFV-infected porcine alveolar macrophages in vitro. Here, we analyzed dynamic transcriptional patterns in vivo in nine organ tissues (spleen, submandibular lymph node, mesenteric lymph node, inguinal lymph node, tonsils, lungs, liver, kidneys, and heart) obtained from pigs in the early stages of ASFV infection (1 and 3 d after viremia). We observed rapid spread of ASFV to the spleen after viremia, followed by broad transmission to the liver and lungs and subsequently, the submandibular and inguinal lymph nodes. Profound variations in gene expression patterns were observed across all organs and at all time-points, providing an understanding of the distinct defence strategies employed by each organ against ASFV infection. All ASFV-infected organs exhibited a collaborative response, activating immune-associated genes such as S100A8, thereby triggering a pro-inflammatory cytokine storm and interferon activation. Functional analysis suggested that ASFV exploits the PI3K-Akt signalling pathway to evade the host immune system. Overall, our findings provide leads into the mechanisms underlying pathogenesis and host immune responses in different organs during the early stages of infection, which can guide further explorations, aid the development of efficacious antiviral strategies against ASFV, and identify valuable candidate gene targets for vaccine development.

Analysis of patterns of livestock movements in the Cattle Corridor of Uganda for risk-based surveillance of infectious diseases.

Introduction: The knowledge of animal movements is key to formulating strategic animal disease control policies and carrying out targeted surveillance. This study describes the characteristics of district-level cattle, small ruminant, and pig trade networks in the Cattle Corridor of Uganda between 2019 and 2021. Methodology: The data for the study was extracted from 7,043 animal movement permits (AMPs) obtained from the Ministry of Agriculture, Animal Industry and Fisheries (MAAIF) of Uganda. Most of the data was on cattle (87.2%), followed by small ruminants (11.2%) and pigs (1.6%). Two types of networks representing animal shipments between districts were created for each species based on monthly (n = 30) and seasonal (n = 10) temporal windows. Measures of centrality and cohesiveness were computed for all the temporal windows and our analysis identified the most central districts in the networks. Results: The median in-degree for monthly networks ranged from 0-3 for cattle, 0-1 for small ruminants and 0-1 for pigs. The highest median out-degrees for cattle, small ruminant and pig monthly networks were observed in Lira, Oyam and Butambala districts, respectively. Unlike the pig networks, the cattle and small ruminant networks were found to be of small-world and free-scale topologies. Discussion: The cattle and small ruminant trade movement networks were also found to be highly connected, which could facilitate quick spread of infectious animal diseases across these networks. The findings from this study highlighted the significance of characterizing animal movement networks to inform surveillance, early detection, and subsequent control of infectious animal disease outbreaks.

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.

Development of a Duplex Insulated Isothermal PCR Assay for Rapid On-Site Detection and Differentiation of Genotypes 1 and 2 of African Swine Fever Virus.

Genotype II African swine fever virus (ASFV) has been plaguing Asian pig industry since 2018. Recently, genotype I ASFV was reported for the first time in China. Since there is no commercial vaccine available against ASFV, early onsite detection and quick culling procedures are commonly used by many countries all over the world. It is important that the above two genotypes of ASFV could be quickly differentiated during onsite detection at the same time. In this study, we established a sensitive and simple Fluorescent Probe Hydrolysis-Insulated isothermal PCR (iiPCR) that can detect and differentiate two genotypes of ASFV within 40 minutes. The positive or negative results of tested samples were displayed on the screen of the device automatically after PCR amplification was complete. The detection limit of the iiPCR was tested to be 20 copies for both genotype I and genotype II ASFVs. There was no cross-reactivity with other swine viruses by using the established iiPCR. Fifty-eight ASFV positive samples confirmed by National ASF Reference Laboratory were subjected to the established duplex iiPCR for genotype differentiation. The results showed that all these ASFV-positive samples belong to genotype II. At last, we found serum samples could be directly used as the templates for iiPCR without comprising sensitivity and specificity. Therefore, the duplex iiPCR established in study provide a useful tool for ASFV onsite detection and genotype differentiation.

High Pathogenicity of a Chinese NADC34-like PRRSV on Pigs.

NADC34-like porcine reproductive and respiratory syndrome virus (PRRSV) has been reported to be prevalent in China since 2018 and became one of the main epidemic strains in some areas of China. Yet, the pathogenicity of NADC34-like PRRSV tested by experimental infection has seldomly been investigated. In this study, we infected pigs with JS2021NADC34 PRRSV, a Chinese NADC34-like PRRSV isolated in Jiangsu province in 2021, to study the pathogenicity of this virus strain. Pigs infected with this virus had lasting fever and reduced body weight with high morbidity and mortality. Histopathological changes, including interstitial pneumonia, lymphocyte depletion, acute hemorrhage, and infiltration of neutrophils in the lymphoid tissues, were observed with the viral proteins detected by immunohistochemistry staining using PRRSV-specific antibody. These results suggested that JS2021NADC34 PRRSV is highly pathogenic to pigs. As it is the latest emerging PRRSV strain in China, the prevalence and pathogenicity of NADC34-like PRRSV need to be further investigated. IMPORTANCE NADC34 PRRSV was initially reported in the United States in 2018. Subsequently, this virus strain spread to other countries, including Peru, South Korea, and China. The virus was first found circulating in Northeast China and then spread to more than 10 provinces in China. NADC34 PRRSV causes severe abortion of sows and high mortality of piglets, which lead to huge economic losses to the Chinese pig industry. However, the pathogenicity of NADC34 PRRSV was rarely experimentally evaluated on pigs. In this study, pigs were infected with JS2021NADC34 PRRSV, a Chinese NADC34-like PRRSV isolated in Jiangsu province in 2021. The infected pigs had lasting fever and reduced body weight with high morbidity and mortality. Interstitial pneumonia, lymphocyte depletion, acute hemorrhage, and infiltration of neutrophils were observed in the lymphoid tissues, and high virus load was proved by immunohistochemistry staining. The above results indicated that NADC34 PRRSV has high pathogenicity on pigs.

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.

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.

Modeling the Spread of Porcine Reproductive and Respiratory Syndrome Among Pig Farms in Lira District of Northern Uganda.

Porcine Reproductive and Respiratory Syndrome (PRRS) is a viral swine disease that causes reproductive failure in breeding sows and respiratory distress in growing pigs. The main objectives were to simulate the transmission patterns of PRRS in Uganda using North American Animal Disease Spread Model (NAADSM) and to evaluate the potential effect of prevention and control options such as vaccination and movement control. The median number of infectious farms at the end of 52 weeks for the baseline scenario was 735 (36.75% of the 2,000 farms). The best effects of vaccination were observed in scenarios 60% farm coverage and 80% farm coverage, which resulted in 82 and 98.2% reduction in the median number of infectious farms at the end of the simulation, respectively. Vaccination of all medium and large farms only (33% of the farms) resulted in a 71.2% decrease in the median number of infectious farms at the end of 52 weeks. Movement control (MC) results showed that the median number of infectious farms at the end of 52 weeks decreased by 21.6, 52.3, 79.4, and 92.4% for scenarios MC 20, MC 40, MC 60, and MC 80%, respectively. This study provides new insights to the government of Uganda on how PRRS can be controlled. The large and medium farms need to be prioritized for vaccination, which would be a feasible and effective way to limit the spread of PRRS in Uganda. Scavenging pigs should be confined at all times, whether in the presence or absence of any disease outbreaks.

Skewness in the literature on infectious livestock diseases in an emerging economy - the case of Vietnam.

Livestock production has increased in many emerging economies, but productivity is often substantially impaired by infectious diseases. The first step towards improved livestock health and productivity is to map the presence of livestock diseases. The objective of this review was to summarize studies conducted on such diseases in an emerging economy, Vietnam, and thereby identifying knowledge gaps that may inform the design of surveillance and control programs. Few studies were found to evaluate the distribution of infectious livestock diseases other than avian influenza. Also, many regions with dense livestock populations had received little attention in terms of disease investigation. A large proportion of the studies dealt with zoonoses and food-borne infections which might be due to funding agencies priorities. On the contrary, studies targeting infections that affect livestock and their productivity were few. We think that this limitation in scientific reports on infectious diseases that only affect livestock productivity is a common phenomenon in low and lower middle income countries. More science-based data on such diseases would help policymakers to prioritize which livestock diseases should be subject to animal health programs aimed to support rural livelihoods and economic development.

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.

An Assessment of the Economic Impacts of the 2019 African Swine Fever Outbreaks in Vietnam.

The 2019 African swine fever (ASF) outbreaks in Vietnam imposed considerable impacts on the pig sector in Vietnam, resulting in the death or culling of nearly six million pigs, or more than 20% of the country's pig population. In order to assess the magnitude of the outbreak at sector level (both on farm and at value chain level), on livelihoods, and on the broader national economy, a comprehensive impact assessment was conducted using a mixed methods approach that integrated a value chain assessment with the use of quantitative modeling tools at sector and national levels. The results showed that the outbreak caused severe direct and indirect economic losses among farmers, particularly medium- and large-farmers whose livelihoods are largely derived from pig production. The outbreaks also affected other value chain actors due to a halving in the volume of pigs traded. At sector level, the outbreaks posed adverse impacts on the domestic supply and demand for pork, especially in the traditional sector. Meanwhile, the modern sector with higher levels of biosecurity and high technology growth was less likely to be affected and even benefited from the outbreak, which was evidenced by increased supply and income throughout the simulation period in this sector. At national level, different model simulation scenarios showed a sharp reduction in total gross domestic product (GDP) and a substantial loss of jobs. Improvements in the system of ASF compensation scheme are needed, both in terms of its administration, but also in its targeting, with greater emphasis needed on developing improved risk-sharing and funding mechanisms across national and local levels.