African swine fever from Kenya to five continents: the role of wild boar.

The article presents the results of the analysis of the epizootic situation in Ukraine regarding African swine fever among domestic and wild pigs from 2012 to 2020 and identifies the main sources of virus spread as well as weak links in the biological safety system of farms. When studying the statistical material of the Food and Agriculture Organization of the United Nations (FAO) and the State Service of Ukraine on Food Safety and Consumer Protection regarding animal morbidity, revealed a territorial pattern between the outbreaks of African swine fever among wild boars and domestic pigs of private farms and pig-breeding complexes, and proved the involvement of the European boar in the epizootic process as a natural reservoir and mobile focus of infection. Calculated the number of outbreaks of African swine fever among wild boars and domestic pigs within the same region and district, and studied the sequence of the emergence of foci on limited territories. Analyzed the natural focality of the disease, the probability of infection transmission to the domestic pig farm sector, and the role of infected objects in the spread of the virus among wild animal populations. From 2012 to 2020 inclusive, according to FAO statistics, 537 cases of African swine fever were recorded in Ukraine, 21.7 % of which were associated with wild boars. In 2017 and 2018, the role of the European wild boar in the epizootic process is best reflected, when 10.9 % (2017) and 20.4 % (2018) of outbreaks of African swine fever among domestic animals recorded in the same administrative districts, where during a year this desiase was detected among wild pigs. When analyzing statistical data of the recent years, the effectiveness of introducing more detailed monitoring of African swine fever among wild boars using modern laboratory methods and improving biosafety measures in the private sector and directly on hunting grounds has been proved. Further research is based on predicting the dynamics of the spread of African swine fever in Ukraine and the role of wild boar in this epizootic process. In addition, the role of wild boar in the spread of African swine fever in other countries and the most effective foreign methods of disease control and prevention will be analyzed.

African swine fever (ASF) is a highly contagious and deadly swine disease, causing a lot of damage to farmers and smallholder village farms, as well as pork production worldwide. Unfortunately, the disease has spread significantly in recent years and is now a major concern in many countries. ASF was first identified in a Black Sea harbour in Georgia in 2007, and since then, it has spread to the European Union (EU), including Romania. In Romania, the disease was first diagnosed in Satu Mare County in 2017 and then in Constanta County in July 2018. Since then, ASF has been reported among pig farms with generally low biosecurity and in wild boar populations. Considering the role of wild boars in the maintenance and transmission of ASF virus, the occurrence of ASF in wild boar should not be underestimated. The study involved surveillance actions carried out by official veterinarians and hunters who collected a total of 6820 samples for PCR analysis and 4248 samples were analysed using ELISA method, from 2018-2013. The data obtained from these tests were statistically analysed using IBM SPSS Statistics for Windows, version 29.0 emphasizing the advantage of using reliable and advanced statistical tools that can lead to a better understanding and management of ASF disease. This extensive collection of data improves the robustness of the study and allows for a more thorough analysis of health trends over time. The detailed breakdown of samples collected each year on each species in which the disease was confirmed, the number of susceptible animals or showing clinical signs of the disease provides valuable information on temporal changes in ASF disease status data. The methodology and findings presented can serve as a reference for future studies that increase understanding of trends and can lay the foundations for future efforts that can influence decisions and interventions in the field.

The introduction of genotype II African swine fever (ASF) virus (ASFV) into the Caucasus in 2007 resulted in unprecedented disease propagation via slow geographical expansion through wild boar populations, short- and long-distance human-mediated translocations, and incursions into naive wild boar and domestic pig populations. The disease is now widespread in eastern and central Europe as well as in Asia, including China. The global dimension of the current epidemic shows that all countries need to be prepared for an introduction. In its natural habitat in Africa, ASFV is maintained within an ancient cycle between soft argasid ticks and the common warthog. Once introduced to the domestic pig population, direct and indirect virus transmission occurs with or without involvement of the tick vector in the pig-tick and domestic pig epidemiological cycles respectively. In the domestic pig cycle, human activities involving pigs or pig derived products are the dominating driver of virus transmission. ASF epidemiology in the presence of wild boar and northern European climates has proved to have specific characteristics, described in the wild boar-habitat epidemiological cycle. In this cycle wild boar carcasses and the resulting contamination of the environment play key roles in virus persistence. In both the wild boar-habitat and the domestic pig epidemiological cycle, fully implemented biosecurity is the key for stopping virus transmission and controlling the disease. Positive examples from the Czech Republic and Belgium show that control and eradication of ASF from the wild boar-habitat cycle can be achieved. Both these cases, as well as the example of Sardinia, where ASFV genotype I now seem very close to eradication after more than 40 years presence, further underline the importance of involving, engaging and understanding all stakeholders in the value chains from farm and forest to fork in order to accomplish ASF control and eradication.

Exosomes derived from African swine fever virus-infected pigs mediate immune responses through NF-κB and JAK-STAT signaling pathways.

The introduction of genotype II African swine fever (ASF) virus, presumably from Africa into Georgia in 2007, and its continuous spread through Europe and Asia as a panzootic disease of suids, continues to have a huge socio-economic impact. ASF is characterized by hemorrhagic fever leading to a high case/fatality ratio in pigs. In Europe, wild boar are especially affected. This review summarizes the currently available knowledge on ASF in wild boar in Europe. The current ASF panzootic is characterized by self-sustaining cycles of infection in the wild boar population. Spill-over and spill-back events occur from wild boar to domestic pigs and vice versa. The social structure of wild boar populations and the spatial behavior of the animals, a variety of ASF virus (ASFV) transmission mechanisms and persistence in the environment complicate the modeling of the disease. Control measures focus on the detection and removal of wild boar carcasses, in which ASFV can remain infectious for months. Further measures include the reduction in wild boar density and the limitation of wild boar movements through fences. Using these measures, the Czech Republic and Belgium succeeded in eliminating ASF in their territories, while the disease spread in others. So far, no vaccine is available to protect wild boar or domestic pigs reliably against ASF.

Introduction. Effective measures for African swine fever outbreak prevention and early detection are required in view of global spread of African swine fever, fatal viral hemorrhagic disease of domestic pigs and wild boars. Wild boar population managing and search for the wild boars died of African swine fever and being the virus source are considered priority measures for the disease control in wildlife.Objective. Generalization of currently available knowledge about advanced technologies for the use of unmanned aerial vehicles (drones) in combination with artificial intelligence-based methods in the wild.Materials and methods. Analytical research methods including search in the following databases were used: PubMed, Springer, Wiley Online Library, Google Scholar, CrossRef, Russian Science Citation Index (RSCI), еLIBRARY, CyberLeninka.Results. Potential of using unmanned aerial vehicles (drones) and artificial intelligence (neural network) for detection of wild boars and their remnants in the context of combating African swine fever is described in the review. The role of wild boars in the disease spread and the need for wild boar population regulation are discussed in detail. Also, the importance of timely wild boar carcass removal and use of modern technologies for wild boar population recording and its density estimation are underlined. Data on the use of drones equipped with various technical devices for study of large animal populations in the wild are analyzed, advantages and peculiarities of unmanned aerial vehicle use are indicated. Experience gained in using neural networks-based techniques for automatic processing of animal images acquired from drones is also summarized.Conclusion. Artificial intelligence-integrated unmanned aerial vehicles appear to be a key tool for managing wild boar populations and the rapid detection of African swine fever dead wild boars that allows improvement of overall effectiveness of the measures taken against this disease.

In 2007 African swine fever (ASF) arrived at a Black Sea harbour in Georgia and in 2014 the infection reached the European Union (EU), where it still expands its territory. ASF is a fatal viral disease affecting domestic pigs and wild boar of all ages with clinical presentations ranging from per-acute to chronic disease, including apparently asymptomatic courses. Until the detection of the first case inside the EU, infections in the current epidemic were mainly seen among pig farms with generally low biosecurity, and with incidental spill over to the wild boar population. In the EU, however, the infection survived locally in the wild boar population independently from outbreaks in domestic pigs, with a steady and low prevalence. Apart from the wild boar population and the habitat, the current epidemic recognizes humans as the main responsible for both long distance transmission and virus introduction in the domestic pig farms. This underlines the importance to include social science when planning ASF-prevention, −control, or -eradication measures.Based on experiences, knowledge and data gained from the current epidemic this review highlights some recent developments in the epidemiological understanding of ASF, especially concerning the role of wild boar and their habitats in ASF epidemiology. In this regard, the qualities of three epidemiological traits: contagiousity, tenacity, and case fatality rate, and their impact on ASF persistence and transmission are especially discussed.

African swine fever virus (ASFV) is an economically devastating pathogen that can cause fatal infections in both domestic pigs and wild boar, with monocytes and macrophages as its target cells. For macrophages, phagocytosis is a fundamental and crucial process, which is usually suppressed by the virus, impeding pathogen clearance and antigen presentation. However, it was unexpectedly found that ASFV infection enhances the phagocytic ability of primary porcine alveolar macrophages (PAMs), as evaluated using an EGFP-labeled bacterial phagocytosis model. The phagocytic processes, including cell migration, bacterial adhesion, pseudopod extension, and pattern recognition receptor (PRR) expression, in ASFV-infected PAMs were systematically investigated. In addition, the upregulated PRRs were knocked down to analyze their role in enhanced phagocytosis. CD14, a receptor of LPS and phospholipid, was identified as being upregulated by ASFV, leading to enhanced bacterial uptake. Further exploration revealed that ASFV's genomic nucleic acid in infected PAMs activates the cGAS/STING/NF-κB pathway to increase CD14 expression. Meanwhile, the free ASFV nucleic acid released from infected PAMs can also activate CD14 expression in bystander PAMs via the TLR9 pathway, facilitating ASFV transmission via apoptotic bodies (ApoBDs). Moreover, the boosted bacterial phagocytosis in the early stages of ASFV infection potentially creates a more inflamed environment with more intense cytokine production. Here, it reveals a critical mechanism by which ASFV enhances CD14-dependent bacterial uptake in PAMs via the cGAS/STING/NF-κB and TLR9 pathways, promoting viral transmission through ApoBDs and amplifying inflammatory responses to bacterial co-infections, providing vital insights into ASFV pathogenesis and host immune manipulation.IMPORTANCEPorcine alveolar macrophages (PAMs) are the target cells of African swine fever virus (ASFV), but how ASFV impacts their phagocytic function is less known. Here, it was discovered that the nucleic acids of ASFV can enhance the expression of CD14, a receptor of LPS and phospholipid, in infected PAMs via the cGAS/STING/NF-κB pathway, or in bystander PAMs via the TLR9 pathway. Consequently, enhanced CD14 expression facilitates the uptake of bacteria and apoptotic bodies (ApoBDs), promoting the inflammatory response and ASFV cell-to-cell transmission. It provides new insights into the innate immunity response following ASFV infection and the transmission of ASFV.

BackgroundRecently moderate-virulence classical swine fever virus (CSFV) strains have been proven capable of generating postnatal persistent infection (PI), defined by the maintenance of viremia and the inability to generate CSFV-specific immune responses in animals. These animals also showed a type I interferon blockade in the absence of clinical signs. In this study, we assessed the infection generated in 7-week-old CSFV PI wild boars after infection with the African swine fever virus (ASFV). The wild boars were divided in two groups and were infected with ASFV. Group A comprised boars who were CSFV PI in a subclinical form and Group B comprised pestivirus-free wild boars. Some relevant parameters related to CSFV replication and the immune response of CSFV PI animals were studied. Additionally, serum soluble factors such as IFN-α, TNF-α, IL-6, IL-10, IFN-γ and sCD163 were analysed before and after ASFV infection to assess their role in disease progression.ResultsAfter ASFV infection, only the CSFV PI wild boars showed progressive acute haemorrhagic disease; however, the survival rates following ASFV infection was similar in both experimental groups. Notwithstanding, the CSFV RNA load of CSFV PI animals remained unaltered over the study; likewise, the ASFV DNA load detected after infection was similar between groups. Interestingly, systemic type I FN-α and IL-10 levels in sera were almost undetectable in CSFV PI animals, yet detectable in Group B, while detectable levels of IFN-γ were found in both groups. Finally, the flow cytometry analysis showed an increase in myelomonocytic cells (CD172a+) and a decrease in CD4+ T cells in the PBMCs from CSFV PI animals after ASFV infection.ConclusionsOur results showed that the immune response plays a role in the progression of disease in CSFV subclinically infected wild boars after ASFV infection, and the immune response comprised the systemic type I interferon blockade. ASFV does not produce any interference with CSFV replication, or vice versa. ASFV infection could be a trigger factor for the disease progression in CSFV PI animals, as their survival after ASFV was similar to that of the pestivirus-free ASFV-infected group. This fact suggests a high resistance in CSFV PI animals even against a virus like ASFV; this may mean that there are relevant implications for CSF control in endemic countries. The diagnosis of ASFV and CSFV co-infection in endemic countries cannot be ruled out and need to be studied in greater depth.

Feral pigs (Sus scrofa) were introduced to Australia following European settlement and are now widely distributed in a variety of habitats (Figure 1). High-density populations are found particularly in north-eastern Australia. Feral pigs are commonly viewed as a valued hunting or commercial resource, occasionally as an important cultural resource, but overwhelmingly as a devastating agricultural and environmental pest.1, 2 Their wide-ranging impacts demand intervention through control programs on many production and conservation lands. Feral pigs also carry pathogens of human health significance and contribute to the persistence and transmission of a range of endemic diseases or pathogens of livestock and wildlife. Feral pigs are the invasive species of most concern in Australia as potential vectors of exotic disease.2 The 2022 outbreak of Japanese Encephalitis (JE) on 79 pig farms in South Australia, Victoria, New South Wales and Queensland together with cases in feral pigs in the Northern Territory and Queensland highlights the importance of both feral and domestic pigs as important amplifying hosts of the JE virus.4-6 In addition, the recent African swine fever (ASF) epizootic in Europe and Asia has focused attention in Australia on the potentially devastating implications of ASF to the domestic pork industry. Data following outbreaks in Europe have demonstrated that there is an ASF epidemiological cycle involving wild boar and their habitat, and that wild boar is an important reservoir of the disease. In Australia, this 'feral pig-habitat' cycle would involve direct transmission of the disease between infected and susceptible feral pigs, and indirect transmission arising from infected carcases in the habitat.5-8 Of particular concern is the potential spread to the 'domestic-cycle' via direct or indirect contact between domestic pigs and feral pigs, or their habitat. Tools to manage the ASF 'feral pig-habitat' cycle and interactions with domestic pigs are available. They include poisoning, trapping, aerial shooting, and recreational and commercial harvesting. Poisoning is typically seen as the most effective and cost-efficient technique for managing pig populations, with population reductions greater than 80% commonly recorded.2, 9 Poisoning is still reliant upon the toxin 1080 (sodium fluoroacetate), although sodium nitrite-dosed baits have recently become available.10 In some jurisdictions 1080 can be added to different bait substrates (e.g., grain, meat) to help tailor acceptability to local pig population dietary preferences. Sodium nitrite is available in commercially manufactured baits which offer advantages in shelf-stability and ease of use. Generally, the most effective applications of poisoning rely on prefeeding of bait substrates (e.g., grains without toxin added) to increase uptake of the bait when the toxin is added, increasing the proportion of the population encountering and ingesting toxic material. However, aerial applications of bait are more efficient for pig control over extensive or inaccessible areas. There are restrictions on toxin use, particularly to safeguard wildlife, pets, and domestic stock, and use in closely settled environments is difficult. Given the generally long period following between consumption and death, carcases can be difficult to locate following poisoning operations, making disposal difficult. Trapping can be effective at population reduction but 'catchability' can vary widely among individual pigs and environments.9 Trapping can often be applied in situations where other control techniques cannot (e.g., closely settled areas) and there are trap designs that ensure target-specificity. Trapping is often applied as ongoing or maintenance control at a local scale, with traps activated following pig activity. Trapping is generally considered labour-intensive and costly compared to other control like poisoning and shooting9, 11 although the increasing availability of various technologies to remotely monitor traps and activate feeders and traps have reduced labour requirements. Shooting or hunting of pigs is common. Aerial (helicopter) shooting remains a useful technique for rapid population knockdown when used over a number of adjacent properties.2 However, it can be difficult to efficiently remove a large proportion of the population with these techniques as the effort (time/costs) of finding and destroying pigs disproportionately increases as density declines. Capture success is usually group-size dependent, with individuals becoming increasingly difficult to capture with increasing group size, particularly during ground shooting or hunting operations. However, small, or isolated pig groups may be difficult to detect when encounter rates are low. The use of hunting dogs is legal in some states and territories but remains controversial.2, 12 Like recreational hunting, commercial harvesting of pigs is often seen as a 'free' form of control for pest managers. However, harvest offtake rates are highly variable, usually well below population replacement levels, and restricted in spatial extent, allowing populations to quickly recover.13 There is also a risk of deliberate introductions by hunters to seed new populations. Nonlethal techniques are also used to manage pig populations or their impacts. Exclusion fencing is used to restrict pigs from small, high-value areas (e.g., horticultural cropping, intensive livestock) where the economic benefits exceed the construction and maintenance costs. Fencing is also used to protect highly sensitive environmental areas (e.g., mound springs, freshwater lagoons) where total exclusion is required to mitigate impacts. Fencing is a commonly used asset protection biosecurity measure to restrict contact between feral pigs and domestic livestock in livestock production settings (e.g., commercial piggeries). Electric fencing is cost-effective to restrict pig movements, but more robust and expensive designs are required for total exclusion.14 Temporary, panel-style fences have also been effective at containing pig movements. Fertility and biological control are not currently viable ways to manage feral pig populations. Fertility control applications remain unlikely until target-specific, oral delivery mechanisms are developed, and results are proven in wild pig populations.1 Furthermore, impacts from treated animals would remain, including as reservoirs or agents of disease transmission. The use of any biological control agents to manage feral pig populations is considered problematic given the susceptibility of domestic pigs. The cost and effectiveness of removal techniques vary widely and not all pigs are susceptible to each control technique. Therefore, combinations of techniques are recommended2, 9 and should ideally be applied at a landscape or population-scale to reduce repopulation from uncontrolled areas. Pig populations subjected to control may also compensate with increased fecundity or survival, assisting population recovery. When populations are reduced to low levels, and the environmental conditions are favourable (i.e., food and resources are not limiting), population growth can be unrestricted and can reach maximum rates (rmax). For a population potentially growing at rmax, 60%–70% of the population needs to be removed continuously throughout the year to hold it stable.13 This is difficult to achieve without continual control efforts (i.e., removals). Hunting or commercial harvesting of pig populations cannot consistently achieve these levels of reduction, particularly across landscapes,13 a problem shared by most other lethal control programs. In most circumstances, eradication of feral pigs is not considered feasible,9 thus management should target reducing damage or risk, not necessarily pig abundance, although these are inextricably linked.15 For example, the relationship between damage and pig-density for fruit and vegetable crops is likely to be curvilinear at high pig densities2 (i.e., once pigs reach a certain density, no more damage is expected with further increases in pig density). This translates to an unlikely reduction in damage/impacts until pig numbers are greatly reduced. A similar relationship is expected for many disease management scenarios where densities may need to be significantly reduced to below density thresholds required for disease persistence or transmission. Control programs should aim to reduce impacts to acceptable levels, and continue as necessary to inhibit recovery.1 Therefore, continued monitoring of the impacts (or benefits) of control is required to ensure that the strategic aims are being met. There has been significant work completed on developing strategies on biosecurity preparedness for porcine exotic disease in Australia.8 Review of recent mitigation strategies used to manage European wild boar populations during ASF outbreaks are also essential to guide local developments.16 External to managing ASF transmission in the 'domestic pig cycle', a challenge with ASF in the 'feral pig-habitat' cycle involves managing disease transmission between feral pigs and indirect transmission arising from contact with infected carcases in habitat.7 ASF has been positively associated with wild boar population density in Europe.7, 17 A major risk factor for JE also includes populations of pigs (feral or domestic) particularly where the climate supports the mosquito vectors. Unfortunately, detailed information on current feral pig densities and habitat distribution (and influences of climatic or seasonal conditions) across their range in Australia is lacking. This is needed to identify where and when feral pigs may overlap with domestic pigs and the likelihood of disease transmission. This in turn will identify key locations for emergency animal disease preparedness, surveillance, and likely response. Detailed pig distribution can also be used to inform and refine decision support modelling tools, including the Australian Animal Disease spread model,18 adapted to ASF. ASF virus can persist in infected carcases and nearby soil for extended periods despite high wild suid depopulation,7, 19 making carcase removal and site management critical to avoid cannibalism and oral transmission.20, 21 Although local data are lacking under Australian conditions, ASF virus persistence in the environment is likely to be greater in the southern, cooler areas than the more northern, warmer regions. Conventional control methods that allow for carcase retrieval (e.g., trapping, shooting, hunting, harvesting), are required for active surveillance and sanitary carcase disposal. Poison baiting is considered efficient for population control, but is problematic for carcase retrieval and site management, and may thus be less effective to reduce ASF prevalence or spread in feral pig populations. Regulatory changes will limit the use of different bait substrates (e.g., fruit, vegetables, meat) in poisoning campaigns, potentially reducing baiting efficiency in some areas.22 Exclusion fencing has obvious applications in ASF management to reduce the likelihood of contact between domestic and feral pig populations and restrict the movement of feral pigs. Secondary fences may further mitigate the potential for domestic pig, feral pig and pig habitat interactions. The resources and maintenance required are prohibitive for landscape scale deployment, but suitable for targeted applications (e.g., excluding feral pig access to domestic pig production or, processing facilities). Fencing (including electric and 'odour' fencing) has been successfully used to manage wild boar dispersal and ASF spread from high-risk zones in Europe.16 Aerial shooting is popular and effective for rapid knockdown of pig populations, particularly useful for exotic disease management, and can be applied in some areas where ground access is limited.2 However, sanitary carcase disposal needs to be considered for ASF. Intensive control programs using more 'aggressive' techniques such as intensive hunting with dogs may possibly disperse or alter pig behaviour and are obviously problematic for limiting disease spread.23 However, such potential effects on pig behaviour require further assessment. Hunting with dogs may be particularly useful to target pigs that survive other control techniques.24 Hunting or commercial harvesting may be applicable for passive surveillance, particularly to assist in early detection, or to supplement more intensive, restrictive sampling in higher risk areas. Passive and active surveillance, particularly through testing wild boar carcases has been critical in early detection and effective responses to ASF outbreaks in Europe.16 Processing depots or facilities used for game meat processing13 may also offer initial sampling points for ASF or JE surveillance where domestic pigs cannot be used as sentinels. All surveillance and control measures need to mitigate the potential for movement of infected material, using measures such as bans on feral pig hunting or entry to infected areas by the public.16 Conflicting values between stakeholders (e.g., feral pigs perceived as either a resource or pest) can lead to difficulties in implementing or agreement on objectives of control programs. At worst, conflicts could result in accidental or deliberate breaches of biosecurity measures. Anthropogenic factors are often associated with long-distance spread of ASF in Europe,7 and will be important locally given human interactions with feral pigs through hunting and commercial harvesting are common.13 The cooperation of hunters, harvesters, land and pest managers and other members of the public will be essential for an effective, cohesive ASF response. ASF control options adapted to and accepted in local contexts – as informed through social science approaches – are required to ensure their high acceptance and success.25 Understanding the 'human element' of ASF, through behaviour study, community engagement and consultation, is thus critical to successfully develop, implement and monitor ASF management plans, particularly where conflicting values are apparent. The wide distribution and habitat range of feral pigs in Australia offers challenges to developing and implementing effective disease management strategies. A variety of methods (including shooting, trapping, poisoning, exclusion fencing, recreational and commercial harvesting) of variable efficacy are available as part of surveillance and control options for application in the event of a potential future ASF outbreak affecting feral pigs in Australia. Detailed information on feral pig distribution, habitat use and the likely epidemiology of an ASF incident in Australian feral pig populations is needed to collectively inform or refine the type, intensity and location of surveillance and interventions required to manage risk to acceptable level. Understanding the 'human element' of managing ASF in feral pigs is also essential to ensure management approaches are successfully adapted to local contexts. The assistance of Carmel Kerwick, Malcolm Kennedy, Tony Pople, Robyn Grob and Mark Cozens is acknowledged. Support for this work was provided by Biosecurity Queensland. Open access publishing facilitated by Queensland Department of Agriculture and Fisheries, as part of the Wiley - Queensland Department of Agriculture and Fisheries agreement via the Council of Australian University Librarians. The authors declare no conflicts of interest or sources of funding for the work presented here.

This thesis investigates risk factors shaping the occurrence of African Swine Fever (ASF) in domestic pigs and wild boar. ASF is a contagious viral disease with severe economic and environmental consequences due to high mortality, trade restrictions, and the costs of control and eradication. The research addresses three overarching questions: (i) which farm-level risk factors for ASF are actionable by farmers; (ii) what explains the consistent seasonal pattern of ASF outbreaks in domestic pigs across Europe; and (iii) whether arthropods may contribute to the mechanical transmission of African Swine Fever virus (ASFV). Chapter 1 introduces ASF, summarising its aetiology, epidemiology, distribution, transmission pathways, seasonal dynamics, and control measures. Chapter 2 presents a systematic literature review identifying variables associated with ASF occurrence. In domestic pigs, reported factors most frequently relate to local infection pressure, socio-economic conditions, production system characteristics, and proximity to wild boar habitats. In wild boar, ASF occurrence is driven by local virus circulation, habitat features, and socio-economic indicators. The review highlights a lack of quantitative observational studies focusing on manageable farm-level biosecurity measures. Chapter 3 examines ASF incursion risks in Romanian pig farms using a matched case–control design. Proximity to infected domestic farms was a key predictor for both commercial and backyard systems. Additional risk factors for backyard farms included larger herd size, higher wild boar abundance, closer proximity to infected wild boar, frequent visits by external professionals, and environmental and management factors such as nearby wild-boar-attracting crops and the use of forage from ASF-affected areas. Chapter 4 extends the analysis to commercial farms in Poland, Romania, and Lithuania, integrating entomological surveillance. ASF risk was again associated with proximity to recent outbreaks and crops attractive to wild boar. Several biosecurity practices influenced risk: off-site carcass collection and sealed carcass storage were protective, whereas machinery sharing and non-routine events increased risk. Farms with insect screens showed reduced risk, while higher numbers of captured Culicoides midges were associated with increased risk. Manure application sourced from other farms also emerged as a risk factor. Chapter 5 presents targeted entomological surveillance assessing the potential role of stable flies (Stomoxys calcitrans) and Culicoides midges in ASFV transmission. Although viable virus was not isolated, ASFV DNA was detected in several Culicoides species and in S. calcitrans. No association was observed between farm outbreak status and viral DNA detection; however, both insect groups were strongly attracted to pig farms, creating opportunities for virus acquisition and transfer. Chapter 6 synthesises the findings, identifying consistent actionable biosecurity gaps, plausible drivers of ASF seasonality, and evidence supporting a potential role for arthropod-mediated mechanical transmission. ASF outbreaks in domestic pigs peak from May to October across Europe, coinciding with increased arthropod activity and ripening crops that attract wild boar. While insect involvement cannot be confirmed conclusively, multiple epidemiological lines of evidence support its plausibility. Overall, this work highlights the importance of strengthening core biosecurity measures—particularly vehicle disinfection, functional disinfection barriers, pest control, visitor management, preventing contact with wild boar—while integrating vector control into ASF prevention strategies.

This study represents the first report on the detection and whole-genome sequencing of African swine fever (ASF) viruses in wild boar in Hong Kong in 2021–2023. Wild boar samples collected via an ASF surveillance program by the Agriculture, Fisheries, and Conservation Department were tested for ASF viruses (ASFVs) using real-time polymerase chain reaction. ASF-positive carcasses were detected in four cases and hemadsorption, virus isolation, and whole-genome sequencing were conducted. The B646L gene, E183L gene, central variable region within the B602L gene, intergenic region between the I73R and I329L genes, EP420R gene, and multigene family members of the four ASFV strains were compared. The whole-genome phylogenetic relationships were studied. The comparative analysis of the genomes indicates that the ASFVs in these four cases have genetic similarities to Asian genotype II ASFVs, but are genetically distinct from each other, as well as the ASFV previously identified in a domestic pig farm in Hong Kong in 2021.

ABSTRACTAfrican swine fever virus (ASFV) is a highly pathogenic swine DNA virus with high mortality that causes African swine fever (ASF) in domestic pigs and wild boars. For efficient viral infection, ASFV has developed complex strategies to evade key components of antiviral innate immune responses. However, the immune escape mechanism of ASFV remains unclear. Upon ASFV infection, cyclic GMP-AMP (2′,3′-cGAMP) synthase (cGAS), a cytosolic DNA sensor, recognizes ASFV DNA and synthesizes the second messenger 2′,3′-cGAMP, which triggers interferon (IFN) production to interfere with viral replication. In this study, we demonstrated a novel immune evasion mechanism of ASFV EP364R and C129R, which blocks cellular cyclic 2′,3′-cGAMP-mediated antiviral responses. ASFV EP364R and C129R with nuclease homology inhibit IFN-mediated responses by specifically interacting with 2′,3′-cGAMP and exerting their phosphodiesterase (PDE) activity to cleave 2′,3′-cGAMP. Particularly notable is that ASFV EP364R had a region of homology with the stimulator of interferon genes (STING) protein containing a 2′,3′-cGAMP-binding motif and point mutations in the Y76S and N78A amino acids of EP364R that impaired interaction with 2′,3′-cGAMP and restored subsequent antiviral responses. These results highlight a critical role for ASFV EP364R and C129R in the inhibition of IFN responses and could be used to develop ASFV live attenuated vaccines.IMPORTANCE African swine fever (ASF) is a highly contagious hemorrhagic disease in domestic pigs and wild boars caused by African swine fever virus (ASFV). ASF is a deadly epidemic disease in the global pig industry, but no drugs or vaccines are available. Understanding the pathogenesis of ASFV is essential to developing an effective live attenuated ASFV vaccine, and investigating the immune evasion mechanisms of ASFV is crucial to improve the understanding of its pathogenesis. In this study, for the first time, we identified the EP364R and C129R, uncharacterized proteins that inhibit type I interferon signaling. ASFV EP364R and C129R specifically interacted with 2′,3′-cGAMP, the mammalian second messenger, and exerted phosphodiesterase activity to cleave 2′,3′-cGAMP. In this study, we discovered a novel mechanism by which ASFV inhibits IFN-mediated antiviral responses, and our findings can guide the understanding of ASFV pathogenesis and the development of live attenuated ASFV vaccines.

The Russian Federation is suffering from African swine fever since november 2007. The main problem with African swine fever on the territory of the Russian Federation is determined by the formed enzootic zones and partially external cases of the disease on the administrative territories of the non-enzootic zones. Despite the measures taken, the disease tends to spread annually. For the period 2007-2020, 1840 outbreaks of this disease were registered in Russia, including 1077 domestic pigs and 737 wild boars. From our opinion, Russia has a unique opportunity in natural conditions to study the stages of the formation of the enzootic zone in the North Caucasus region. This territory is compactly located: the Chechen Republic, the Republic of Ingushetia, the Kabardino-Balkar Republic, the Republic of Dagestan, the Republic of North Ossetia-Alania, the Karachay-Cherkess Republic, the Republic of Adygea, where population, with the exception of the Republic of North Ossetia-Alania, confess the Islamic religion, which prohibits pork consumption. In this article, based on the analysis of the epizootic situation from 2007-2020. an opinion was expressed on the mechanism of the formation of enzootic zones for African swine fever, as well as on the establishment of zones where the disease appears in order to introduce restrictive and prohibitive measures. The position on the role of wild boars in the formation of enzootic zones and the spread of infection was determined. The understanding of the mechanism of formation of enzootic zones is the basis for the development of effective measures to eradicate African swine fever in Russia.

Since the first detection of African swine fever (ASF)-infected wild boar in October 2019, the ASF virus has been circulating among wild boars in the Republic of Korea. The priority for ASF control is to understand the epidemic situation correctly. The basic reproduction number (R0) can be used to describe the contagious disease epidemic situation since it can assess the contagiousness of infectious agents by presenting the average number of new cases generated by an infected case. The current study estimated R0 for the 2019/20 ASF epidemics in wild boars in the Republic of Korea using the reported number of ASF cases and a serial interval of the ASF virus. The estimated mean R0 was 2.10 (range: 0.06 – 10.24) for the 2019/20 ASF epidemics, 2.94 (range: 0.43 – 9.89) for the 2019 ASF epidemics, and 2.00 (range: 0.06 – 11.10) for the 2020 ASF epidemics. In addition, the estimated mean R0 was 3.82 (range: 1.16 – 8.78) in winter, 1.39 (range: 0.16 – 6.30) in spring, 4.82 (range: 0.26 – 17.08) in summer, and 2.21 (range: 0.51 – 5.86) in fall. Even though the Korean government has applied ASF control measures, including hunting or fencing, the ASF epidemic situation in wild boars has intensified. For ASF control in wild boars, tailor-made hunting, wild boar management, or active searching for carcasses are required to reduce the ASF virus. For ASF prevention in domestic pigs, no contact between wild boars and domestic pigs and a biosecurity plan by veterinarians are needed to decrease the risk of ASF virus transmission from wild boars to domestic pigs.