Reverse transcription recombinase-aided amplification assay for H5 subtype avian influenza virus.

BACKGROUND: The H5 subtype avian influenza virus (AIV) has caused huge economic losses to the poultry industry and is a threat to human health. A rapid and simple test is needed to confirm infection in suspected cases during disease outbreaks. METHODS: In this study, we developed a reverse transcription recombinase-aided amplification (RT-RAA) assay for the detection of H5 subtype AIV. Assays were performed at a single temperature (39 °C), and the results were obtained within 20 min. RESULTS: The assay showed no cross-detection with Newcastle disease virus or infectious bronchitis virus. The analytical sensitivity was 103 RNA copies/µL at a 95% confidence interval according to probit regression analysis, with 100% specificity. Compared with published reverse transcription quantitative real-time polymerase chain reaction assays, the κ value of the RT-RAA assay in 420 avian clinical samples was 0.983 (p < 0.001). The sensitivity for avian clinical sample detection was 97.26% (95% CI, 89.56-99.52%), and the specificity was 100% (95% CI, 98.64-100%). CONCLUSIONS: These results indicated that our RT-RAA assay may be a valuable tool for detecting H5 subtype AIV.

Modeling the outbreak and control of African swine fever virus in large-scale pig farms.

African swine fever virus (ASFV) leads to a highly contagious, lethal and economically devastating disease among pigs. Since no effective treatment for the disease, it is crucial to investigate its transmission mechanism and control strategies in large-scale pig farms. We first established a toy model to explore ASFV spread in one pig unit. Then a switching patch model was developed to capture its spread from one initial epidemic pig house consecutively to others, even the whole farm. Assessing innocent culling rates of three large-scale epidemic pig farms in Jiangsu Province showed that it is unnecessary to slaughter all pigs in the farms compulsively. Then we explored how the disinfection and fixation of employees impact ASFV spread in the farms. To control ASFV, we can block or slow down its spreading by improving the efficiency of disinfection and decreasing employee population to some extend. We can also shrink potential areas to be infected by properly improving the matching refinement degree among employees and houses. Some essential requirements for large-scale pig farms are presented to reduce their ASFV spreading risk, which can be helpful for animal health authorities in establishing regulation to standardize large-scale pig farms.

Effectiveness of Market-Level Biosecurity at Reducing Exposure of Poultry and Humans to Avian Influenza: A Systematic Review and Meta-Analysis.

Background: In this study, we aimed to identify the effect of market-level risk factors on avian influenza (AI) infection in poultry and humans and generate evidence that will inform AI prevention and control programs at live bird markets (LBMs). Methods: We performed a systematic literature review in both English and Chinese search engines. We estimated the pooled odds ratios of biosecurity indicators relating to AI infections at market level using a quality effects (QE) meta-analysis model. Results: Biosecurity measures effective at reducing AI market contamination and poultry infection at LBMs include smaller market size, selling single poultry species and separating different species, performing cleaning and disinfection and market closures, ban on overnight storage, and sourcing poultry from local areas. Our meta-analysis indicates that higher risk of exposure to AI infection occurs in workers at retail LBMs, female workers, and those who contact ducks, conduct cleaning, slaughtering, defeathering, or evisceration. Conclusions: The most effective strategies to reduce AI market contamination identified in this study should target larger LBMs that are located at noncentral city areas and sell and slaughter multispecies of live poultry. Live bird market workers directly involved in cleaning and poultry processing tasks should participate in occupational health and safety programs.

Characterization of Streptococcus suis isolates from slaughter swine.

The characterization of 61 Streptococcus suis strains isolated from Chinese slaughter pigs was investigated. S. suis serotypes 1, 2, 3, 4, 7, 9, 10, 11, 12, 13, 14, 15, 16, 22, 23, 25, 26, 28, 29, and 1/2 were found in the isolates by serum agglutination. Of all the prevalent serotypes, S. suis serotype 7 is the most predominant circulating in Chinese slaughter pigs. The virulence-associated genes profile and multilocus sequence typing scheme of the isolates were analyzed. The mrp-/epf-/sly- virulence-associated genes type is the most prevalent in the isolates from slaughter pigs. It is the first time to find S. suis serotypes 7 and 9 isolates with epf. The serotypes 7 and 9 isolates with mrp and/or epf genes did not express MRP and/or EF in the present research. Thirteen new ST types were identified for the first time. ST1 complex and ST27 complex of S. suis are prevalent in China. This paper supplied information to understand the characteristics, such as capsular serotypes, virulence factors, and gene backgrounds of S. suis carried by slaughter pigs.

Prevalence and genetic characterization of avian polyomavirus and psittacine beak and feather disease virus isolated from budgerigars in Mainland China.

Budgerigar fledgling disease (BFD) and psittacine beak and feather disease (PBFD) are caused by avian polyomavirus (APV) and psittacine beak and feather disease virus (PBFDV), respectively. These diseases frequently infect psittacine birds and result in similar clinical manifestations. In this study, we observed the prevalence of PBFDV infection and a dual infection of APV and PBFDV in a budgerigar (Melopsittacus undulatus) in Mainland China for the first time. One PBFDV isolate and two APV isolates were harvested using chicken embryos. Genetic characterization and phylogenetic analysis of the complete genome of the two APV isolates revealed nucleotide similarity ranging from 99.0% to 99.6% to other sequences in GenBank, and a 14-bp insertion was observed in the genome of one APV isolate. The results of complete genome analysis of the PBFDV isolate showed nucleotide similarity ranging from 83.0% to 95.0% with other PBFDV sequences in GenBank. Genetic characterization and phylogenetic analysis of the APV and PBFDV strains isolated in this study indicated that the isolates from China were closely related to their Japanese counterparts. The results of this study will help to identify molecular determinants and will aid further research on the prevention and control of APV and PBFD infection.

Data-driven dynamical modelling of the transmission of African swine fever in a few places in China.

Since the outbreak of African swine fever (ASF) in Shengyang, it has continued spreading in China. In the early stage of the epidemic, multi-point and concentrated outbreaks were mainly in the swill feeding areas. In this paper, we developed compartmental models to investigate the transmission of ASF in several raising units including Guquan, Jinba and Liancheng. Using the data collected from these three infected premises, we calibrated the models to estimate that the average incubation period was between 8 and 11 days, the onset period was about 2-3 days and the basic reproductive number was about 4.83-11.90. We also estimated the infection on the day before culling to be 45.24% (Guquan), 89.20% (Jinba) and 16.35% (Liancheng), respectively. The infection rate of Guquan could reach about 74.8% if culling were postponed by 2 days. We found that the infection was significantly higher than the morbidities (22.11% (Guquan), 49.35% (Jinba) and 12.94% (Liancheng)) calculated by actual statistical data. Besides, we simulated and compared the control effect of stopping transport, disinfecting, stopping swill and culling. Our findings suggest that any single measure was not enough to prevent the spread of ASF on a regional level but the combined measures is the key. Under the current situation, fully culling was recognized as most effective in controlling the epidemic, despite the culling of uninfected pigs.

Benefit-cost analysis of a H7N9 vaccination program in poultry in Guangxi, China.

China launched a H7N9 vaccination program in poultry, starting from the Guangxi and Guangdong provinces in July 2017, followed by other provinces in September 2017, as a response to a steep increase of H7N9 influenza human infections from September 2016. Since then, H5-H7 bivalent vaccine has been used in the nationwide avian influenza compulsory vaccination program to replace the existing H5N1 vaccine. However, the economic returns of the H7N9 vaccination program in China have never been adequately assessed. This study was designed to evaluate the economic value of the H7N9 vaccination program in Guangxi by assessing the benefits and costs of the program compared to not vaccinating against H7N9. A benefit-cost analysis (BCA) was undertaken to evaluate the adoption of a vaccination program against H7N9 in each of three consecutive years from July 2017 to June 2020 with the baseline scenario (the absence of H7N9 vaccination in the 12-month period July 2016 to June 2017). Both animal and public health perspectives were included in the BCA framework and took account of both the private and public sectors. Benefit-Cost Ratio (BCR) of the three-year H7N9 vaccination program was 18.6 (90 %PI: 15.4; 21.8), and total Net Present Values reached to CNY 1.63 billion (90 %PI: 1.37 billion; 1.89 billion). The extra revenue generated by the yellow broiler industry comprised 93.8 % of the total benefits after adoption of H7N9 vaccination program in Guangxi. While cost-savings in public health and animal health expenditure avoided were 3.6 % and 2.6 %, respectively. Total costs arising from adoption of the revised vaccination program over the three years were CNY 12.46 million (90 %PI: 11.49 million; 14.14 million), CNY 34.87 million (90 %PI: 31.88 million; 40.06 million), and CNY 44.28 million (90 %PI: 39.66 million; 52.27 million), respectively. Sensitivity analysis found the yellow broiler wholesale prices contributed 97.7 % of the variance of the total NPV of three vaccination years. The study results demonstrate the significant economic advantage of implementing a vaccination program against H7N9 in Guangxi. It also offers a new set of evidence to China's H7N9 vaccination policy and debates around economic values of conducting routine avian influenza vaccination.

Analysis of the movement of live broilers in Guangxi, China and implications for avian influenza control.

Most Chinese provinces have a daily-updated database of live animal movements; however, the data are not efficiently utilized to support interventions to control H7N9 and other avian influenzas. Based on official records, this study assessed the spatio-temporal patterns of live broilers moved out of and within Guangxi in 2017. The yearly and monthly networks were analyzed for inter- and intra-provincial movements, respectively. Approximately 200,000 movements occurred in 2017, involving the transport of 200 million live broilers from Guangxi. Although Guangxi exported to 24 out of 32 provinces of China, 95% of inter-provincial movements occurred with three bordering provinces. Within Guangxi, counties were highly connected through the live broiler movements, creating conditions for rapid virus spreading throughout the province. Interestingly, a peak in movements during the Chinese Lunar New Year celebrations, late January in 2017, was not observed in this study, likely due to H7N9-related control measures constraining live bird trading. Both intra- and inter-provincial movements in March 2017 were significantly higher than in other months of that year, suggesting that dramatic price changes may influence the movement's network and reshape the risk pathways. However, despite these variations, the same small proportion of counties (less than 20%) exporting/importing more than 90% of inter- and intra-provincial movements remains the same throughout the year. Interventions, particularly surveillance and improving biosecurity, targeted to those counties are thus likely to be more effective for avian influenza risk mitigation than implemented indiscriminately. Additionally, simulations further demonstrated that targeting counties according to their degree or betweenness in the movement network would be the most efficient way to limit disease transmission via broiler movements. The study findings provide evidence to support the design of risk-based control interventions for H7N9 and all other avian influenza viruses in broiler value chains in Guangxi.

A mixed methods study of stakeholders' practices and attitudes on avian influenza H7N9 vaccination for the yellow broiler industry in Guangxi, China.

In response to a sudden increase in H7N9 human infections, China introduced an H5/H7 bivalent inactivated vaccine for poultry in Guangxi and Guangdong provinces in July 2017, which subsequently became integrated into the existing compulsory national H5N1 vaccination programme from September 2017. Although the vaccination programme effectively reduced H7N9 infections in humans and poultry, there are ongoing arguments against continuing this long-term vaccination. These discussions have drawn policymakers to think about the possibility of stopping routine vaccination for H7N9 avian influenza viruses (AIVs) in China; however, they have not considered the poultry industry stakeholders' practices on and attitudes towards this vaccination. This study investigated H7N9 vaccination practices in the yellow broiler industry in Guangxi and stakeholders' attitudes on H7N9 vaccination, using a mixed methods design. The study found H7N9 vaccination was well adopted in the yellow broiler industry in Guangxi regardless of the source of the vaccines. Most stakeholders believed vaccination was the best measure to control H7N9 and H5N1 AIVs, and they showed a strong willingness to continue with vaccination even without government subsidies or freely provided vaccines. The motivations by stakeholders for using vaccines to control H7N9 and H5N1 were different due to the epidemiological differences between the two strains. Understanding poultry industry stakeholders' practices and attitudes on H7N9 vaccination has important practical implications in planning vaccination policies, particularly when considering the possibility of vaccination withdrawal.

Cross-sectional study on risk factors associated with porcine epidemic diarrhea virus infection in pig farms in Junan county, China.

Porcine epidemic diarrhea (PED) is a highly contagious, intestinal infectious disease in pigs, characterized by severe diarrhea, vomiting and dehydration. PED is widely epidemic in China as well as in many eastern Asian and America countries, causing tremendous losses in pig industry. However, little was known about the disease frequency and the associated risk factors of PED in pig farms. A cross-sectional study was conducted to estimate the herd prevalence and to identify the potential risk factors of porcine epidemic diarrhea virus (PEDV) infection of pig farms (≥100 pigs) in Junan county, China. A two-stage random sampling strategy was adopted, and a total of 751 fecal samples from suckling piglets of 82 farms were collected and tested by RT-PCR and sequencing for PEDV. Meanwhile, information on the putative risk factors of PEDV infection of those farms were collected in forms of questionnaires, followed by a descriptive analysis, univariable and multivariable logistic regression analysis. The results showed that the herd-level true prevalence of PEDV infection of pig farms in Junan was 35.16 % (95 %CI: 22.91-53.89); there were two variables significantly associated with PEDV infection, which were 'having more than 1000 slaughter pigs per annum' (OR = 5.42, 95 %CI: 1.19-24.72), and 'Weaning at 21-25 days' old' (OR = 4.50, 95 %CI:1.25-16.20). The research suggested that PED was highly endemic in pig farms in Junan county; larger herd size and weaning at an earlier age were potential risk factors associated with PEDV infection in pig farms in Junan. This study set an example in the research on herd-level prevalence of PEDV infection and risk factors associated with PEDV infection, and the results were of practical significance for the future planning of prevention and control of PED in Junan or other areas of China.

Epidemic situation and control measures of African Swine Fever Outbreaks in China 2018-2020.

As of 21 April 2020, 176 ASF outbreaks have occurred in China. For each outbreak, an investigation was conducted, including historical data retrieval and traceability of potential contacts. The purpose of this study is to conduct a preliminary analysis of the data obtained from the outbreak investigations, including an investigation of the possible contributing factors of the spread of ASF in China. Based on the epidemic situation and the policies issued, the entire epidemic can be divided into three phases. 71 outbreaks were reported between 3 August 2018 and 17 November 2018; 44 outbreaks between 19 November 2018 and 30 March 2019; and 61 outbreaks between 4 April 2019 and 12 April 2020. Based on the reported outbreaks, the proportional rate of outbreaks in small farms (livestock ≤ 500, 127/168) is significantly higher than that of medium (501 ≤ livestock < 2,000, 14/168; 2001 ≤ livestock ≤ 5,000, 9/168) and large farms (livestock ≥ 5,001, 18/168). The odds of infection related to swill feeding (OR = 2.5, 95% CI, 1.5-4.3) and the mechanical dissemination of vehicles and personnel (OR = 2.7, 95% CI, 1.6-4.5) are significantly higher than those of pigs and pig production transportation. Swill feeding is the major contributing factor for small farms while mechanical dissemination of vehicles and personnel is the major contributing factor for large farms. The average duration from the beginning of the infection to the official outbreak report is gradually decreasing, which means that response speed of industry entities and the animal husbandry and veterinary departments from the beginning of the infection to the outbreak report is gradually increasing. Based on the analysis for ASF outbreaks, some policies and suggestions were put forward, such as improving the biosecurity level of the farms, as well as strengthening the supervision of breeding, transportation and slaughter.

Value chain analysis of yellow broiler industry in Guangxi, China to inform H7N9 influenza control strategies.

Yellow broilers are the primary source of poultry consumption in China and the predominant trade of live poultry. However, knowledge of the value chain is limited, which is vital evidence for the effective control of H7N9 and other zoonotic avian influenzas. The aim of the study was to map the yellow broiler value chain in Guangxi Zhuang Autonomous Region, China and investigate its governance structure and practices relevant to the risk of H7N9 transmission. A value chain analysis was conducted in five areas of Guangxi from May to August 2018. To map the value chain, three focus group discussions (FGDs) were conducted and stakeholders, products and premises involved and their interactions were identified. Then, 55 key informant interviews (KIIs) collected qualitative data on stakeholders' profile, practices and interactions with other stakeholders and rules/norms that exist along the value chain. On-site observations were also carried out at different types of premises along the value chain to complement and validate findings of KIIs and FGDs. Participants were also asked to provide proportional estimates of each component in the value chain where possible. The qualitative data from FGDs, KIIs and on-site observations were analysed to create stakeholder profiles and a diagram of product flows and stakeholders' interactions. Thematic analysis was used to identify the governance structure of the value chains and practices relevant to the risk of H7N9 transmission. The stakeholders and premises involved in Guangxi yellow broiler production, wholesale and retail were described, as well as their interactions. Contract farming is extensively adopted in Guangxi; consequently yellow broiler grower companies are the dominant stakeholders. The trading platform was identified as a key premise linking farms and live bird markets. The thematic analysis highlighted poor biosecurity practices in different premises along the value chain, which was supported by on-site observations. The operation of trading platforms reported in this study presents a disease risk but is not considered in the current H7N9 control programs. The study suggested that biosecurity management gaps need to be addressed through government-industry partnerships that require engagement with private stakeholders in the planning and implementation of H7N9 control strategies incentivising participation of grower companies, wholesalers and retailers.

Infection and risk factors of human and avian influenza in pigs in south China.

The coinfection of swine influenza (SI) strains and avian/human-source influenza strains in piggeries can contribute to the evolution of new influenza viruses with pandemic potential. This study analyzed surveillance data on SI in south China and explored the spatial predictor variables associated with different influenza infection scenarios in counties within the study area. Blood samples were collected from 7670 pigs from 534 pig farms from 2015 to 2017 and tested for evidence of infection with influenza strains from swine, human and avian sources. The herd prevalences for EA H1N1, H1N1pdm09, classic H1N1, HS-like H3N2, seasonal human H1N1 and avian influenza H9N2 were 88.5, 64.5, 60.3, 57.8, 12.9 and 10.3 %, respectively. Anthropogenic factors including detection frequency, chicken density, duck density, pig density and human population density were found to be better predictor variables for three influenza infection scenarios (infection with human strains, infection with avian strains, and coinfection with H9N2 avian strain and at least one swine strain) than were meteorological and geographical factors. Predictive risk maps generated for the four provinces in south China highlighted that the areas with a higher risk of the three infection scenarios were predominantly clustered in the delta area of the Pearl River in Guangdong province and counties surrounding Poyang Lake in Jiangxi province. Identification of higher risk areas can inform targeted surveillance for influenza in humans and pigs, helping public health authorities in designing risk-based SI control strategies to address the pandemic influenza threat in south China.

Characterization and influencing factors of the pig movement network in Hunan Province, China.

In terms of pig production in China, Hunan was the third largest province where the number of hogs accounted for 9.0 % of the national number of hogs in 2017. To propose the precise strategy for supervision of pig movements in Hunan Province, a weighted directed one-mode network was constructed using the data from the electronic animal health certificate platform in 2017. The nodes were designed as districts in Hunan and edges as flows of pig movement between districts. Social network analysis was used to analyse network characteristics and generalized linear models were performed to ascertain the socioeconomic factors that affect the pig movement network. During 2017, the pig movement network within the Hunan Province was composed of 122 nodes and 8562 directed connections, with a total of 510,973 shipments and 17,815,040 pigs moved. The network displayed a small-world topology, which had a higher clustering coefficient (0.4 vs. 0.1) and shorter average shortest path length (1.8 vs. 3.7) compared with equivalent random networks. The degree centrality positively correlated with closeness centrality (r = 0.99, P < 0.001) as well as betweenness centrality (r = 0.91, P < 0.001). After restricting the cross-regional pig movements in areas with the top 10 % of degree centrality, the number of pigs was reduced by nearly 50 % in the network, whereas the number of pigs was reduced by 94.0 % when movement restrictions were implemented in areas with the top 50 % of degree centrality. Observed network metrics showed an upward trend during the months of 2017, peaking in November and December. Generalized linear models showed that the size of the human population and per capita gross domestic product were the most important socioeconomic drivers of pig movements. The pig movement network in Hunan Province is a small-world network in which the introduction and spread of diseases may be quicker. More human, material, and financial resources should be allocated to areas with higher centrality. Swine movements were seasonal, and the inspection and quarantine work should be reinforced in the fourth quarter, especially in November and December. Pig movements were more active in areas with larger populations and advanced economy, and stricter supervision in these areas should be implemented. Our findings contribute to understanding the movement of pigs and the associated influencing factors in a big pig producing province in China, and the supervision strategies proposed in this study can be extended to other regions in China if proved to be viable.

Assessment of regional vulnerability to Africa swine fever in China during 2018/8-2019/7 based on data envelopment analysis method.

In this study, we introduce a vulnerability index to measure the regional ASF epidemic and present the ASF severity ratings of the 31 provinces of mainland China. The index is defined based on the data from the investigation, national statistical yearbook and reports. The data to be used include pig breeding, financial resources, human resources, epidemic information of ASF and price fluctuation from the 31 provinces. Then, we use the data envelopment analysis (DEA) method to define the vulnerability index, the relative severity value for each region, which quantitatively reflects the damage degree caused by the epidemic of ASF. The method allows us to provide a systematic classification for the regional vulnerability level of ASF in China. Using this index, we find that the vulnerability of the whole country is at a high level, and there is no regional aggregation phenomenon. The vulnerability level of the 31 provinces is quite different and the provinces with high vulnerability level are dispersive geographically. For the five major prevention and control zones for ASF in China, the northern region has the highest vulnerability level, while the eastern zoon level is the lowest.

Traceable surveillance and genetic diversity analysis of coronaviruses in poultry from China in 2019.

Coronavirus disease 2019 (COVID-19), caused by Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first reported in Wuhan, China, and rapidly spread throughout the world. This newly emerging pathogen is highly transmittable and can cause fatal disease. More than 35 million cases have been confirmed, with a fatality rate of about 2.9% to October 9, 2020. However, the original and intermediate hosts of SARS-CoV-2 remain unknown. Here, 3160 poultry samples collected from 14 provinces of China between September and December 2019 were tested for SARS-CoV-2 infection. All the samples were SARS-CoV-2 negative, but 593 avian coronaviruses were detected, including 485 avian infectious bronchitis viruses, 72 duck coronaviruses, and 36 pigeon coronaviruses, with positivity rates of 15.35%, 2.28%, and 1.14%, respectively. Our surveillance demonstrates the diversity of avian coronaviruses in China, with higher prevalence rates in some regions. Furthermore, the possibility that SARS-CoV-2 originated from a known avian-origin coronavirus can be preliminarily ruled out. More surveillance of and research into avian coronaviruses are required to better understand the diversity, distribution, cross-species transmission, and clinical significance of these viruses.

Molecular epidemiological surveys of H5 subtype highly pathogenic avian influenza viruses in poultry in China during 2007-2009.

To investigate the prevalence and evolution of the H5 subtype highly pathogenic avian influenza (HPAI) viruses circulating in poultry in China during 2007-2009, five molecular epidemiological surveys were carried out. A total of 21, 591 swab samples were collected, and from them 55 H5 HPAI viruses were isolated. None of the 55 viruses carried any known mutations, which can render the virus binding to human SAa2,6Gal receptors. The surveys indicated that live-bird markets, backyard flocks and slaughtering sites were at greater risk of being infected with the viruses during winter, and Clades 2.3.2, 2.3.4 and 7 of the viruses co-circulated in poultry in China during 2007-2009. Viruses within Clades 2.3.2 and 7 have become genetically distinguishable from the viruses isolated before 2007 and antigenically distinguishable from the vaccine strains used in China. Viruses within Clade 2.3.2 have been circulating widely in China and caused a new wave of cross-continental spreading from Asia to Europe.

African Swine Fever in a commercial pig farm: Outbreak investigation and an approach for identifying the source of infection.

African Swine Fever (ASF) is a contagious disease of domestic and wild pigs caused by the African Swine Fever Virus (ASFV). The disease has spread globally in recent years with serious economic consequences to pork production. This report describes an ASF outbreak that occurred in a large-scale Chinese commercial pig farm. The outbreak started in 2018 and presents the spatial and temporal spread of infection in an intensive pig farm. Pig houses adjacent to exit rooms had a higher risk of infection (Odds ratio = 14.4, 95%CI: 1.5-140). Introduction of disease is presumed to have occurred through a contaminated vehicle used in the sale of pigs with poor productivity. This investigation shows the process of ASFV infection and spread in a facility with presumed adequate biosecurity measures. These findings may benefit others in the control of ASF in large-scale pig farms.

Risk of zoonotic transmission of swine influenza at the human-pig interface in Guangdong Province, China.

A cross-sectional survey was conducted from 2015 to 2018 to assess the risk of zoonotic influenza to humans at the human-pig interface in Guangdong Province, south China. One hundred and fifty-three pig farmers, 21 pig traders and 16 pig trade workers were recruited using convenience sampling and surveyed at local pig farms, live pig markets and slaughterhouses, respectively. Questionnaires were administered to collect information on the biosecurity and trading practices adopted and their knowledge and beliefs about swine influenza (SI). Most (12 of 16) trade workers said they would enter piggeries to collect pigs and only six of 11 said they were always asked to go through an on-farm disinfection procedure before entry. Only 33.7% of the interviewees believed that SI could infect humans, although pig farmers were more likely to believe this than traders and trade workers (p < .01). Several unsafe practices were reported by interviewees. 'Having vaccination against seasonal flu' (OR = 3.05, 95% CI: 1.19-8.93), 'Believe that SI can cause death in pigs' (no/yes: OR = 8.69, 95% CI: 2.71-36.57; not sure/yes: OR = 4.46, 95% CI: 1.63-14.63) and 'Keep on working when getting mild flu symptoms' (OR = 3.80, 95% CI: 1.38-11.46) were significantly and positively correlated to 'lacking awareness of the zoonotic risk of SI'. 'Lacking awareness of the zoonotic risk of SI' (OR = 3.19, 95% CI: 1.67-6.21), 'Keep on working when getting mild flu symptoms' (OR = 3.59, 95% CI: 1.57-8.63) and 'Don't know SI as a pig disease' (OR = 3.48, 95% CI: 1.02-16.45) were significantly and positively correlated to 'not using personal protective equipment when contacting pigs'. The findings of this study would benefit risk mitigation against potential pandemic SI threats in the human-pig interface in China.

Pig trade networks through live pig markets in Guangdong Province, China.

This study used social network analysis to investigate the indirect contact network between counties through the movement of live pigs through four wholesale live pig markets in Guangdong Province, China. All 14,118 trade records for January and June 2016 were collected from the markets and the patterns of pig trade in these markets analysed. Maps were developed to show the movement pathways. Evaluating the network between source counties was the primary objective of this study. A 1-mode network was developed. Characteristics of the trading network were explored, and the degree, betweenness and closeness were calculated for each source county. Models were developed to compare the impacts of different disease control strategies on the potential magnitude of an epidemic spreading through this network. The results show that pigs from 151 counties were delivered to the four wholesale live pig markets in January and/or June 2016. More batches (truckloads of pigs sourced from one or more piggeries) were traded in these markets in January (8,001) than in June 2016 (6,117). The pigs were predominantly sourced from counties inside Guangdong Province (90%), along with counties in Hunan, Guangxi, Jiangxi, Fujian and Henan provinces. The major source counties (46 in total) contributed 94% of the total batches during the two-month study period. Pigs were sourced from piggeries located 10 to 1,417 km from the markets. The distribution of the nodes' degrees in both January and June indicates a free-scale network property, and the network in January had a higher clustering coefficient (0.54 vs. 0.39) and a shorter average pathway length (1.91 vs. 2.06) than that in June. The most connected counties of the network were in the central, northern and western regions of Guangdong Province. Compared with randomly removing counties from the network, eliminating counties with higher betweenness, degree or closeness resulted in a greater reduction of the magnitude of a potential epidemic. The findings of this study can be used to inform targeted control interventions for disease spread through this live pig market trade network in south China.