Clustering broiler farmers based on their behavioural differences towards biosecurity to prevent highly pathogenic avian influenza

Highly pathogenic avian influenza (HPAI) is an important zoonotic disease. The study aims to identify farmer behaviour types to inform the design of behaviour change programmes for mitigating the transmission of HPAI. Therefore, the study utilised multivariate statistical analysis for gaining a better understanding of the relationships among farmers' 30 biosecurity behaviours, the risk of HPAI infection, and distinct features of commercial broiler farmers, which is different from using simple and few binary biosecurity measures. Convenience sampling was used to collect data from 303 Taiwan's farmers among which 40 farmers (13.2%) self-reported having had a HPAI outbreak in the study year while 16 farmers (5.3%) self-reported having had a HPAI outbreak in the past two years. Using categorical principal components analysis and a two-stage cluster analysis, four farmer clusters were identified with distinct features: 1)'Reserved' (4.6%) tended to choose 'No idea' for answering specific questions about HPAI; 2)'Secure' (76.3%) had a higher biosecurity status than the other farms; 3) 'Jeopardised' (16.8%) had a lower biosecurity status than the other farms; 4) 'No-response' (2.3%) tended to skip specific questions about HPAI. The biosecurity status of the 'Reserved' and 'No-response' clusters was undetermined, placing these farms at risk of HPAI infection. Compared to the 'Secure' cluster, the 'Jeopardised' cluster exhibited higher odds of self-reported HPAI in the study year (OR: 2.61, 95% CI: 1.22-5.58) and in the past two years (OR: 4.28, 95% CI: 1.39-13.19). Additionally, the 'Jeopardised' cluster showed increased odds of HPAI recurrence (OR: 4.01, 95% CI: 1.41-11.43). Our study demonstrates that inadequate biosecurity practices can elevate the occurrence or recurrence of HPAI outbreaks. The findings underscore the importance of distinguishing between these clusters to accurately assess the risk of HPAI infection across farms. Furthermore, understanding farmers' behaviours can inform the development of strategies aimed at behaviour change among farmers.

Lessons for cross-species viral transmission surveillance from highly pathogenic avian influenza Korean cat shelter outbreaks

In this Comment, the authors describe recent outbreaks of highly pathogenic avian influenza in cat shelters in Seoul, South Korea. They discuss potential routes of transmission and describe implications for surveillance of spillover infections in animals in non-agricultural settings.

H9N2 avian influenza virus dispersal along Bangladeshi poultry trading networks

Avian influenza virus subtype H9N2 is endemic in Bangladesh's poultry population. The subtype affects poultry production and poses a potential zoonotic risk. Insufficient understanding of how the poultry trading network shapes the dissemination of avian influenza viruses has hindered the design of targeted interventions to reduce their spread. Here, we use phylodynamic analyses of haemagglutinin sequences to investigate the spatial spread and dispersal patterns of H9N2 viruses in Bangladesh's poultry population, focusing on its two largest cities (Dhaka and Chattogram) and their poultry production and distribution networks. Our analyses suggest that H9N2 subtype avian influenza virus lineage movement occurs relatively less frequently between Bangladesh's two largest cities than within each city. H9N2 viruses detected in single markets are often more closely related to viruses from other markets in the same city than to each other, consistent with close epidemiological connectivity between markets. Our analyses also suggest that H9N2 viruses may spread more frequently between chickens of the three most commonly sold types (sunali-a cross-bred of Fayoumi hen and Rhode Island Red cock, deshi-local indigenous, and exotic broiler) in Dhaka than in Chattogram. Overall, this study improves our understanding of how Bangladesh's poultry trading system impacts avian influenza virus spread and should contribute to the design of tailored surveillance that accommodates local heterogeneity in virus dispersal patterns.

The attitude-behaviour gap in biosecurity: Applying social theories to understand the relationships between commercial chicken farmers' attitudes and behaviours

Introduction

Traditionally, it is believed that people's behaviours align with their attitudes; however, during COVID-19 pandemic, an attitude-behaviour gap in relation to preventive measures has been observed in recent studies. As such, the mixed-methods research was used to examine the relationships between farmers' biosecurity attitudes and behaviours in Taiwan's chicken industry based on the cognitive consistency theory.

Methods

Content analysis of face-to-face interviews with 15 commercial chicken farmers identified their biosecurity responses to infectious disease threats.

Results

The results indicated the mismatch of farmers' attitudes and behaviours towards specific biosecurity measures, in that they act differently than they think. The findings of the qualitative research allowed the research team to conduct the subsequent quantitative, confirmatory assessment to investigate the mismatch of farmers' attitudes and behaviours in 303 commercial broiler farmers. Survey data were analyzed to discover the relationships between farmers' attitudes and behaviours in relation to 29 biosecurity measures. The results show a mixed picture. The percentage of the farmers who had the attitude-behaviour gap towards 29 biosecurity measures ranged from 13.9 to 58.7%. Additionally, at the 5% significant level, there is an association between farmers' attitudes and behaviours for 12 biosecurity measures. In contrast, a significant association does not exist for the other 17 biosecurity measures. Specifically, out of the 17 biosecurity measures, the disconnection of farmers' attitudes and behaviours was observed in three specific biosecurity measures such as using a carcass storage area.

Discussion

Based on a fairly large sample of farmers in Taiwan, this study confirms the existence of an attitude-behaviour gap in context and applies social theories to provide an in-depth understanding of how infectious diseases are managed in the animal health context. As the results demonstrate the necessity of tailoring biosecurity strategies to address the gap, it is time to reconsider the current approach by understanding farmers' real attitudes and behaviours in relation to biosecurity for the success of animal disease prevention and control at the farm level.

The challenges of pig farming in Hong Kong: a study of farmers' perceptions and attitudes towards a pig health and production management service

BACKGROUND

Pig farming in Hong Kong differs markedly from other places in the world, with a highly urbanised population, the majority of pigs being imported for slaughter, and limited on-farm veterinary support. Little is known about the barriers and attitudes of pig farmers in Hong Kong and their expectations of a new pig health and production management service provided by veterinarians. We collected qualitative and quantitative data to 1) describe pig farms, 2) identify barriers to pig farming in Hong Kong and 3) describe the perceptions of the new service. Thematic analysis was conducted to identify barriers and attitudes.

RESULTS

Eight and nine out of 38 pig farmers agreed to participate in the qualitative and quantitative components, respectively. All farms were farrow-to-finish farms with a median of 2800 (range 950 to 7000) pigs per farm. Three themes were identified during the interview analysis and could be ranked based on their importance to the farmers: the regulatory environment (Theme 1), veterinary support structures (Theme 2), and the sustainability of the pig industry (Theme 3). Farmers expressed dissatisfaction with the regulation of the industry and veterinary services on offer within Hong Kong. However, farmers did note that the provision of a new pig health and production management service was as a positive development. The public perception of pig farming, market forces, and competition from mainland pig farmers have resulted in sustainability challenges for the industry.

CONCLUSIONS

Farmers identified very specific local systems and challenges unique to pig farming in Hong Kong. The lack of veterinary support was one of these challenges and although a certain level of scepticism towards the new pig health and production service was expressed, farmers indicated their interest and listed areas where they would benefit from improved veterinary support. Prior experiences of veterinary services clouded farmers perceptions of the usefulness of a new service. To be successful in this environment, clear communication about the goals, role and limitations of the new on farm service is crucial, as is the alignment with the needs of farmers. Despite the small sample size, the qualitative methodology used allows us to assume that these themes give a general idea of what Hong Kong farmers' concerns and attitudes are.

Sequestration and Destruction of Rinderpest Virus-Containing Material 10 Years after Eradication

In 2021, the world marked 10 years free from rinderpest. The United Nations Food and Agriculture Organization and World Organisation for Animal Health have since made great strides in consolidating, sequencing, and destroying stocks of rinderpest virus-containing material, currently kept by only 14 known institutions. This progress must continue.

Exploring the hurdles that remain for control of African swine fever in smallholder farming settings

To honour the 100 years anniversary of the first publication about African swine fever (ASF) a webinar with a particular focus on disease control in the smallholder sector was organized. This article is based on the webinar, summarizing the early history of ASF research, reflecting on the current global disease situation and bringing forward some suggestions that could contribute towards achieving control of ASF. The first description of ASF by R. Eustace Montgomery in 1921 laid the foundations for what we know about the disease today. Subsequent research confirmed its association with warthogs and soft ticks of the Ornithodoros moubata complex. During the latter half of the 21st century, exponential growth of pig production in Africa has led to a change in the ASF-epidemiology pattern. It is now dominated by a cycle involving domestic pigs and pork with virus spread driven by people. In 2007, a global ASF epidemic started, reaching large parts of Europe, Asia and the Americas. In Europe, this epidemic has primarily affected wild boar. In Asia, wild boar, smallholders and industrialized pig farms have been affected with impact on local, national and international pig value chains. Globally and historically, domestic pigs in smallholder settings are most frequently affected and the main driver of ASF virus transmission. Awaiting a safe and efficacious vaccine, we need to continue focus on other measures, such as biosecurity, for controlling the disease. However, smallholders face specific challenges linked to poverty and other structural factors in implementing biosecurity measures that can prevent spread. Improving biosecurity in the smallholder sector thus remains an important tool for preventing and controlling ASF. In this regard, interdisciplinary research can help to find new ways to promote safe practices, facilitate understanding and embrace smallholders' perspectives, engage stakeholders and adjust prevention and control policies to improve implementation.

Determinants of farmers' biosecurity mindset: A social-ecological model using systems thinking

Commercial poultry is often farmed in high-density facilities, therefore, predisposing exposure to threats of infectious diseases. Studies suggest that it is likely that farmers have little motivation to practise on-farm biosecurity. In Taiwan, where high-density intensive poultry production is commonplace, unfortunately, several avian influenza outbreaks have occurred over the past decade despite the establishment of biosecurity procedures. To develop effective interventions, it is essential to understand the determinants of farmers' biosecurity mindset through systems thinking. In this qualitative study, we directly explored the opinions of Taiwan's chicken farmers, and a grounded theory analysis was performed. The study revealed that farmers allocate resources based on their justification for the optimisation of resource utilisation, and biosecurity is the most concerning challenge. Farmers focus on the economic aspects of their production systems, particularly when the implementation of biosecurity increases production costs, and there are multifaceted, complex barriers to implementing on-farm biosecurity. Although the participant farmers accepted to take major responsibility for disease management, paradoxically, some farmers blamed the practicality of government regulations and government employees' attitudes. Additionally, the farmers rejected the government's intentions to ask farmers to take major responsibility for the outbreaks of avian influenza while some of them intended to ignore the perceived risks. Government interventions that were considered not directly related to biosecurity also negatively influenced farmers' willingness to improve biosecurity. Using the interview results together with information in the scientific literature, we constructed a modified six-level social-ecological model to explain the complex influences of macro socio-economic conditions on farmers' biosecurity mindset. The novelty of this research lies in its wider relevance to Taiwan's chicken production industry in that it provides first-hand evidence-based knowledge to demonstrate a wide number of determinants of farmers' biosecurity mindset. This social-ecological model highlights the importance of systems thinking for the development of behavioural interventions and allows adaptation to the local context. The findings of this study have relevance to Taiwan's chicken production industry and potentially to similar systems in other countries in the wider region and should result in more effective animal health management at the farm level.

Quality Assessment of Day-Old Chickens on the Broiler Farms of Hong Kong

Simple Summary

Assessing the quality and determining maternal antibodies against regional pathogens in day-old chickens is important to optimize the production performance and management of flocks. So far, such information in Hong Kong is lacking. The present study was conducted to assess abnormalities in appearance, navel, crop filling, dehydration, body weight, and length uniformity in day-old chicks. In addition, the maternally derived antibody levels against relevant infectious diseases were measured. This study was the first in Hong Kong to provide a baseline for the quality of day-old chicks, and results in evidence-based management advice tailored to the farms. We advise the establishment of a well-managed broiler breeder farm and hatchery, in order to improve the health and productivity of the local broiler chicken industry.

Abstract

The present study aimed to investigate the quality of newly hatched broiler chicks delivered to Hong Kong (imported or local), and to develop tailored recommendations to improve their management. During 2019–2021, 70 batches (34 imported from mainland China and 36 local) of one/three day old chicks on 11 broiler farms were studied. From each batch, 23 or 24 chicks (1647 in total) were assessed for abnormalities in appearance, navel, crop filling, dehydration, body weight, and length uniformity. Chicks were sacrificed, and yolk sac residues in three day old chicks were measured. Maternally derived antibody levels against Newcastle disease virus (NDV), infectious bursal disease virus (IBDV), and avian reovirus (ARV) were measured in all chicks using an enzyme-linked immunosorbent assay (ELISA). The proportion of abnormal navel in most batches is high (median: 59%), ranging between 0 and 100%. The average length of chicks within batches ranges between 16.3 and 20.7 cm, and their average weights are 31–38.5 g upon delivery to the farms. On average, imported batches have a higher body weight and length than their local counterparts. The average yolk-free weight varies between 45 and 55 g, which is significantly lower in local batches (33–43 g). The mean antibody titers against NDV and ARV are higher in imported batches than in the local ones. In contrast, the mean antibody titer against IBDV is significantly lower in the imported batches. Concerning the overall lower quality of local chicks compared to the imported batches, establishing a well-managed broiler breeder farm and a hatchery in Hong Kong is highly recommended to enhance the health and productivity of the local broiler chicken industry.

First Study to Describe the Prevalence of Porcine Reproductive and Respiratory Syndrome Virus and Porcine Circovirus Type 2 among the Farmed Pig Population in the Hong Kong Special Administrative Region

Infection of pig farms with porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) causes substantial economic losses globally. However, little epidemiological data of PRRSV and PCV2 in the Hong Kong Special Administrative Region (HKSAR) were available. This pilot study aimed to provide baseline information of the prevalences of PPRSV and PCV2 in the HKSAR. A complex survey was conducted from 3 February 2020 to 11 March 2021 on 29 of the 40 pig farms in the HKSAR, with five pigs each from seven age groups (representing key production stages) tested using a real-time PCR. Evidence of presence of PRRSV European strain (PRRSV-1), PRRSV North American strain (PRRSV-2) and PCV2 was confirmed on 48%, 86% and 79% of farms, with overall prevalences of 7.6% (95% CI: 4.8–10.3%), 12.2% (95% CI: 9.6–14.7%) and 20.3% (95% CI: 14.3–26.2%) in the HKSAR pig population based on pooling results from all pigs across all farms. PRRSV-1 and PRRSV-2 were more prevalent in younger pigs, with the highest prevalences of 32.1% (95% CI: 20.8–45.0%) and 51.5% (95% CI: 38.9–64.0%) for 8-week-old pigs. In contrast, the distribution of PCV2 prevalence across age groups appeared to be more symmetrical, with higher prevalences reported in pigs from 12 weeks old to 24 weeks old but lower prevalences in younger pigs and sows. The results of this study demonstrate that PRRSV-1, PRRSV-2 and PCV2 are widely spread across pig farms in the HKSAR, which indicates that the current farm management and control protocols should be improved. We recommend the implementation of on-farm intervention strategies combined with ongoing surveillance to reduce these viruses, and their consequences, in the HKSAR pig population.

Trait-Based Vaccination of Individual Meerkats (Suricata suricatta) against Tuberculosis Provides Evidence to Support Targeted Disease Control

Simple Summary

There is evidence to show that, within a population, some individuals are more likely to spread infections than others. When trying to protect a population against infection, most strategies aim to vaccinate as many individuals as possible. However, vaccinating wildlife is difficult because individuals are difficult to find and capture. For wildlife therefore, the ideal strategy would involve targeting vaccinations at those individuals most likely to transmit infection, thus gaining maximum benefit from capturing a small number of individuals. Whilst this seems a very attractive solution, very few studies have attempted to provide evidence to support this theory. This study focuses on a population of meerkats with a history of tuberculosis. Previous work has suggested that socially dominant individuals are most likely to transmit infection, with subordinates most likely to become infected. Therefore, whilst some social groups were left untreated as a baseline, in others, either dominants or subordinates were vaccinated. All groups were monitored for two years, after which time the infection data was analysed. Groups in which vaccinations had been used showed reduced infection rates suggesting that the targeted approach had reduced transmission. A targeted approach may therefore offer an efficient option for vaccinating wildlife in the future.

Abstract

Individuals vary in their potential to acquire and transmit infections, but this fact is currently underexploited in disease control strategies. We trialled a trait-based vaccination strategy to reduce tuberculosis in free-living meerkats by targeting high-contact meerkats (socially dominant individuals) in one study arm, and high-susceptibility individuals (young subordinates) in a second arm. We monitored infection within vaccinated groups over two years comparing the results with untreated control groups. Being a member of a high-contact group had a protective effect on individuals’ survival times (Hazard Ratio = 0.5, 95% Confidence Interval, CI: 0.29–0.88, p = 0.02) compared to control groups. Over the study, odds of testing positive for tuberculosis increased more than five-fold in control groups (Odds Ratio = 5.40, 95% CI = 0.94–30.98, p = 0.058); however, no increases were observed in either of the treatment arms. Targeted disease control approaches, such as the one described in this study, allow for reduced numbers of interventions. Here, trait-based vaccination was associated with reduced infection rates and thus has the potential to offer more efficient alternatives to traditional mass-vaccination policies. Such improvements in efficiency warrant further study and could make infectious disease control more practically achievable in both animal (particularly wildlife) and human populations.

Combining Analytical Approaches and Multiple Sources of Information to Improve Interpretation of Diagnostic Test Results for Tuberculosis in Wild Meerkats

Diagnostic tests are used to classify individual animals' infection statuses. However, validating test performance in wild animals without gold standard tests is extremely challenging, and the issue is further complicated in chronic conditions where measured immune parameters vary over time. Here, we demonstrate the value of combining evidence from different diagnostic approaches to aid interpretation in the absence of gold standards, large sample sizes, and controlled environments. Over a two-year period, we sampled 268 free-living meerkats (Suricata suricatta) longitudinally for Mycobacterium suricattae (a causative agent of tuberculosis), using three ante-mortem diagnostic tests based on mycobacterial culture, and antigen-specific humoral and cell-mediated immune responses, interpreting results both independently and in combination. Post-mortem cultures confirmed M. suricattae infection in 22 animals, which had prior ante-mortem information, 59% (13/22) of which were test-positive on a parallel test interpretation (PTI) of the three ante-mortem diagnostic assays (95% confidence interval: 37-79%). A similar ability to detect infection, 65.7% (95% credible interval: 42.7-84.7%), was estimated using a Bayesian approach to examine PTI. Strong evidence was found for a near doubling of the hazard of death (Hazard Ratio 1.75, CI: 1.14-2.67, p = 0.01), associated with a positive PTI result, thus demonstrating that these test results are related to disease outcomes. For individual tests, small sample sizes led to wide confidence intervals, but replication of conclusions, using different methods, increased our confidence in these results. This study demonstrates that combining multiple methodologies to evaluate diagnostic tests in free-ranging wildlife populations can be a useful approach for exploiting such valuable datasets.

Absence of serological or molecular evidence of Leptospira infection in farmed swine in the Hong Kong Special Administrative Region

Leptospirosis is an important zoonotic disease with several maintenance host species including swine. A cross sectional survey was undertaken between January to October 2020 to investigate the prevalence of leptospirosis in farmed swine in the Hong Kong Special Administrative Region (HKSAR) of China. Serum samples were collected from swine on seven farms (15 swine per farm; ten multiparous sows and five twelve-week-old weaners), while kidney samples were collected from 64 swine submitted for routine post-mortem (26 farms; average 2.4 swine per farm, range 1-6). Microscopic agglutination tests (MAT) to a panel of 24 Leptospira antigens did not reveal any evidence of seroconversion at a titre of 1:100. Polymerase chain reaction (PCR) testing of the kidney samples for Leptospira DNA did not detect any evidence of infection. Bayesian methods were used to compute the probability that the leptospirosis prevalence in farmed swine in the HKSAR was <3%, given none of the 105 swine sampled were positive on the MAT. The results of this study demonstrate no serological or molecular evidence of leptospirosis in farmed swine in the HKSAR. Subsequent statistical analysis supports the conclusion that the prevalence of leptospirosis in farmed swine in the HKSAR is negligible at present.

Epidemic disease risks and implications for Veterinary Services

Growth in the livestock sector is associated with heightened risk for epidemic diseases. The increasing spillover of new diseases from wildlife is being driven by wide-scale anthropogenic changes allowing for more frequent and closer wildlife-human and wildlife-livestock contacts. An increasing number of epidemics in livestock are associated with rapid transition of livestock systems from extensive to intensive, and local to global movement of livestock and their products through value chain networks with weak biosecurity. Major livestock epidemics in the past two decades have had substantial economic impacts, and the COVID-19 pandemic highlights the devastating socio-economic consequences that spillovers can have when not identified and controlled early in the process of emergence. This highlights the importance of Veterinary Services to integrated, whole-of-society efforts to control infectious diseases in animals. Emphasis within Veterinary Services must be placed on prevention and preparedness. The authors suggest four areas for continued improvement in Veterinary Services to meet this challenge. These are a) continued development of staff capacity for risk assessment and value chain analysis, together with improved policies and communication, b) appropriate adaptation of approaches to prevention and control in resource-poor settings, c) improved multi-sectoral and transboundary cooperation, which enables the sharing of resources and expertise, and d) systematic approaches that enable Veterinary Services to influence decisionmaking for trade, markets, business, public health, and livelihood development at the national and regional levels.

Avian Influenza Risk Environment: Live Bird Commodity Chains in Chattogram, Bangladesh

In this paper, we identify behaviours in live bird commodity chains in Chattogram, Bangladesh, which may influence the risk of pathogen emergence and transmission: the nature of poultry trade, value appropriation and selling sick or infected birds. Examining the reasons why actors engage in these behaviours, we emphasise the politics of constraints within a context of real-world decisions, governed by existential and pragmatic agency. Focusing on contact zones and entanglement, analysing patron-client relationships and precarious circumstances, we argue that agency and structure specific to the Bangladeshi context produce a risk environment. Structural constraints may reinforce risky occupational practises and limit individual agency. Structural constraints need to be addressed in order to tackle animal and zoonotic disease risk along live animal commodity chains.

Transmission Dynamics of African Swine Fever Virus, South Korea, 2019

African swine fever (ASF) is a substantial concern for global food production and security. However, lack of epidemiologic data in affected areas has limited the knowledge of the main drivers of ASF virus (ASFV) transmission. To assess the role of vehicle movements and wild boar populations in spreading ASFV to pig farms in South Korea, we combined data generated by ASF surveillance on pig farms and of wild boars with nationwide global positioning system–based tracking data for vehicles involved in farming activities. Vehicle movements from infected premises were associated with a higher probability of ASFV incursion into a farm than was geographic proximity to ASFV-infected wild boar populations. Although ASFV can spill over from infected wild boars into domestic pigs, vehicles played a substantial role in spreading infection between farms, despite rapid on-farm detection and culling. This finding highlights the need for interventions targeting farm-to-farm and wildlife-to-farm interfaces.

Undetected Circulation of African Swine Fever in Wild Boar, Asia

African swine fever is a growing threat to the livestock industry. We examined data indicating that in most countries in Asia, most notified events were related to farm outbreaks; meanwhile, only a few wild boar cases were reported. We hypothesize the virus circulates unnoticed in wild boar populations in Asia.

A tool for rapid assessment of wildlife markets in the Asia-Pacific Region for risk of future zoonotic disease outbreaks

Decades of warnings that the trade and consumption of wildlife could result in serious zoonotic pandemics have gone largely unheeded. Now the world is ravaged by COVID-19, with tremendous loss of life, economic and societal disruption, and dire predictions of more destructive and frequent pandemics. There are now calls to tightly regulate and even enact complete wildlife trade bans, while others call for more nuanced approaches since many rural communities rely on wildlife for sustenance. Given pressures from political and societal drivers and resource limitations to enforcing bans, increased regulation is a more likely outcome rather than broad bans. But imposition of tight regulations will require monitoring and assessing trade situations for zoonotic risks. We present a tool for relevant stakeholders, including government authorities in the public health and wildlife sectors, to assess wildlife trade situations for risks of potentially serious zoonoses in order to inform policies to tightly regulate and control the trade, much of which is illegal in most countries. The tool is based on available knowledge of different wildlife taxa traded in the Asia-Pacific Region and known to carry highly virulent and transmissible viruses combined with relative risks associated with different broad categories of market types and trade chains.

Demand-driven spreading patterns of African swine fever in China

African swine fever (ASF) is a highly contagious hemorrhagic viral disease of domestic and wild pigs. ASF has led to major economic losses and adverse impacts on livelihoods of stakeholders involved in the pork food system in many European and Asian countries. While the epidemiology of ASF virus (ASFV) is fairly well understood, there is neither any effective treatment nor vaccine. In this paper, we propose a novel method to model the spread of ASFV in China by integrating the data of pork import/export, transportation networks, and pork distribution centers. We first empirically analyze the overall spatiotemporal patterns of ASFV spread and conduct extensive experiments to evaluate the efficacy of a number of geographic distance measures. These empirical analyses of ASFV spread within China indicate that the first occurrence of ASFV has not been purely dependent on the geographical distance from existing infected regions. Instead, the pork supply-demand patterns have played an important role. Predictions based on a new distance measure achieve better performance in predicting ASFV spread among Chinese provinces and thus have the potential to enable the design of more effective control interventions.

The role of livestock movements in the spread of Rift Valley fever virus in animals and humans in Mayotte, 2018-19

Rift Valley fever (RVF) is a vector-borne viral disease of major animal and public health importance. In 2018–19, it caused an epidemic in both livestock and human populations of the island of Mayotte. Using Bayesian modelling approaches, we assessed the spatio-temporal pattern of RVF virus (RVFV) infection in livestock and human populations across the island, and factors shaping it. First, we assessed if (i) livestock movements, (ii) spatial proximity from communes with infected animals, and (iii) livestock density were associated with the temporal sequence of RVFV introduction into Mayotte communes’ livestock populations. Second, we assessed whether the rate of human infection was associated with (a) spatial proximity from and (b) livestock density of communes with infected animals. Our analyses showed that the temporal sequence of RVFV introduction into communes’ livestock populations was associated with livestock movements and spatial proximity from communes with infected animals, with livestock movements being associated with the best model fit. Moreover, the pattern of human cases was associated with their spatial proximity from communes with infected animals, with the risk of human infection sharply increasing if livestock in the same or close communes were infected. This study highlights the importance of understanding livestock movement networks in informing the design of risk-based RVF surveillance programs.

Rift Valley fever (RVF) is a vector-borne zoonotic disease, endemic in many sub-Saharan Africa regions with substantial outbreaks. RVF virus (RVFV) is transmitted to animals primarily by the bite of infected mosquitos, whereas direct or indirect contact with infected animals forms the primary route of RVFV transmission to humans. In 2018–19, Mayotte, an archipelago in the Indian Ocean between Madagascar and the coast of Eastern Africa, experienced an RVF epidemic in both livestock and humans. In this study, we investigated factors shaping the spatio-temporal pattern of RVFV infection in livestock and human populations across Mayotte. The diffusion of RVFV through Mayotte’s livestock population was associated with livestock movements and, potentially to a lesser extent, spatial proximity from communes with infected animals. Moreover, the pressure of infection on humans was the highest if nearby livestock were infected. This study highlights the value of accounting for the structure of livestock movement networks in the surveillance of zoonotic diseases at the human-animal interface, and the need for One Health approaches.

African Swine Fever Epidemiology and Control

African swine fever is a devastating disease that can result in death in almost all infected pigs. The continuing spread of African swine fever from Africa to Europe and recently to the high-pig production countries of China and others in Southeast Asia threatens global pork production and food security. The African swine fever virus is an unusual complex DNA virus and is not related to other viruses. This has presented challenges for vaccine development, and currently none is available. The virus is extremely well adapted to replicate in its hosts in the sylvatic cycle in East and South Africa. Its spread to other regions, with different wildlife hosts, climatic conditions, and pig production systems, has revealed unexpected epidemiological scenarios and different challenges for control. Here we review the epidemiology of African swine fever in these different scenarios and methods used for control. We also discuss progress toward vaccine development and research priorities to better understand this complex disease and improve control.

Non-ambulatory dogs with cervical intervertebral disc herniation: single versus multiple ventral slot decompression

OBJECTIVE

To evaluate the proportion of non-ambulatory dogs with cervical intervertebral disc herniation (IVDH) in a private clinic and to compare signalment and outcome between those that underwent single or multiple ventral slot decompression (VSD).

DESIGN

Retrospective cohort study.

METHODS

After screening 43,378 medical records (January 2010-September 2016), those of 185 dogs with non-ambulatory tetraparesis or tetraplegia along with cervical IVDH that had undergone single (123) or multiple (62) VSD were included in this study. Data on signalment, preoperative neurological status, location of affected intervertebral disc(s), time to ambulation and short-term outcome were compared between single and multiple VSD groups.

RESULTS

The proportion of non-ambulatory dogs with IVDH was 35.3%. The prevalence of non-ambulation was higher in male dogs (0.56%) than in female dogs (0.26%; P < 0.001) and in neutered dogs than in unneutered dogs (0.51% and 0.27%, respectively, P < 0.001). After surgery, 96.2% of the dogs reached ambulatory status. Dogs with multiple IVDH were older than those with single IVDH. Sex, neutering status or size did not affect the outcome or ambulation status postsurgery. The Pekingese was the most commonly affected breed in both groups. There was no difference in the time to reach ambulation and the presence of neurological deficits after surgery between dogs that underwent single and multiple VSD.

CONCLUSIONS

In this cohort, dogs undergoing multiple VSD had a good postoperative outcome, and their short-term functional recovery was equal to that of dogs undergoing single ventral slot compression.

Antibiotic resistance gene sharing networks and the effect of dietary nutritional content on the canine and feline gut resistome

BACKGROUND

As one of the most densely populated microbial communities on Earth, the gut microbiota serves as an important reservoir of antibiotic resistance genes (ARGs), referred to as the gut resistome. Here, we investigated the association of dietary nutritional content with gut ARG diversity and composition, using publicly available shotgun metagenomic sequence data generated from canine and feline fecal samples. Also, based on network theory, we explored ARG-sharing patterns between gut bacterial genera by identifying the linkage structure between metagenomic assemblies and their functional genes obtained from the same data.

RESULTS

In both canine and feline gut microbiota, an increase in protein and a reduction in carbohydrate in the diet were associated with increased ARG diversity. ARG diversity of the canine gut microbiota also increased, but less strongly, after a reduction in protein and an increase in carbohydrate in the diet. The association between ARG and taxonomic composition suggests that diet-induced changes in the gut microbiota may be responsible for changes in ARG composition, supporting the links between protein metabolism and antibiotic resistance in gut microbes. In the analysis of the ARG-sharing patterns, 22 ARGs were shared among 46 genera in the canine gut microbiota, and 11 ARGs among 28 genera in the feline gut microbiota. Of these ARGs, the tetracycline resistance gene tet(W) was shared among the largest number of genera, predominantly among Firmicutes genera. Bifidobacterium, a genus extensively used in the fermentation of dairy products and as probiotics, shared tet(W) with a wide variety of other genera. Finally, genera from the same phylum were more likely to share ARGs than with those from different phyla.

CONCLUSIONS

Our findings show that dietary nutritional content, especially protein content, is associated with the gut resistome and suggest future research to explore the impact of dietary intervention on the development of antibiotic resistance in clinically-relevant gut microbes. Our network analysis also reveals that the genetic composition of bacteria acts as an important barrier to the horizontal transfer of ARGs. By capturing the underlying gene-sharing relationships between different bacterial taxa from metagenomes, our network approach improves our understanding of horizontal gene transfer dynamics.