African Swine Fever In Wild Boar Research Articles

Epidemiological analysis of African swine fever in the European Union during 2022.

This report presents the epidemiological analysis of African swine fever (ASF) during 2022 based on the surveillance and pig population data submitted by the European Union (EU) affected countries and one neighbouring country. Coinciding with regulatory changes and an important decrease in ASF outbreaks in 2022 in the EU, the number of domestic pig samples tested as part of active surveillance decreased by 80%, while the number of samples from passive surveillance almost doubled compared with 2021. Most outbreaks among domestic pigs in the EU were detected by testing clinical suspicions (93% of outbreaks), followed by tracing activities (5%) and weekly testing of the first two dead pigs per establishment (2%). Although most of the wild boar samples came from hunted animals, the probability of detecting PCR-positive animals was much higher in wild boar found dead. The ASF outbreaks among domestic pigs in the EU decreased by 79% while a decrease of 40% in the wild boar cases was observed in comparison with 2021. This was strongly marked in Romania, Poland and Bulgaria, with a reduction of 50-80% compared with 2021. In many countries, an important decrease in the number of pig establishments was observed, especially of small establishments with fewer than 100 pigs. The regional between farm incidence and proportion of pigs lost due to ASF in the EU was in general very low (average of 1%) apart from some regions in Romania. The impact of ASF on wild boar populations was variable, with a decline in wild boar abundance observed in certain countries versus a stable or even increased population after ASF introduction. This supports the negative relationship observed in this report between the proportion of the country with restricted zones due to ASF in wild boar and wild boar hunting bags.

Eco-Sanitary Regionalization of Wild Boar (Sus scrofa) in the Western Palearctic Realm as a Tool for the Stewardship of African Swine Fever

African swine fever (ASF) is a viral hemorrhagic disease affecting domestic and wild suids, with catastrophic socioeconomic impact worldwide. In the European scenario, wild boar (Sus scrofa) actively contributes to the maintenance and spread of the disease. In this study, we applied a multivariate clustering method to define ecoregions in the western Palearctic realm based on ecological and sanitary aspects of ASF in wild boar. Beforehand, we performed a principal components analysis for the eight selected variables. An analysis of the countries was carried out in terms of the extent of ecoregions and ASF notifications. After clustering, we identified nine eco-regions that showed important differences based on the used eco-sanitary variables. Several ecoregions stand out in the country and notification analysis for retaining the most ASF cases and being present in their surrounding locations. Here, we developed a cartographical tool to understand patterns in the distribution and spread of ASF in wild boar at the European level, as well as improve prevention, control, surveillance plans, and eradication strategies, especially future vaccination programs once a safe and effective vaccine is available.

A Novel Tool to Assess the Risk for African Swine Fever in Hunting Environments: The Balkan Experience.

In Europe, African swine fever (ASF) can be sustained within wild boar populations, thus representing a constant source of virus and a huge challenge in the management of the disease. Hunters are the key stakeholders for the prevention, detection and control of ASF in wild boar. Their behavior and the biosecurity standards applied in infected or at-risk hunting grounds have a huge impact on disease dynamics and management. The Food and Agriculture Organization (FAO) has developed a semi-quantitative survey-based novel tool to assess the risk of ASF in hunting grounds (namely the risks of introduction and spread into and between hunting grounds, and the risk of not detecting the infection) and how such risks could be reduced if mitigation or corrective measures were applied at low, medium and high effort. The weight of risk factors was determined through an expert knowledge elicitation (EKE). The surveys for each hunting ground were filled in by their respective managers. The tool's outputs allow users to visualize the different ASF risks of hunting grounds, whether as numerical values or color-coded maps, at sub-national, national and regional levels. These outputs can be used to guide policy makers, highlighting gaps or geographical areas to prioritize. The tool was used to assess hunting grounds in Kosovo1 (1 As per United Nations Security Council resolution 1244). Montenegro and Serbia, showing overall a high risk.

Disease surveillance in England and Wales, June 2022.

Veterinary RecordVolume 191, Issue 1 p. 20-24 SurveillanceFree Access Disease surveillance in England and Wales, June 2022 First published: 08 July 2022 https://doi.org/10.1002/vetr.2003AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Highlights from the scanning surveillance network Cattle Skin disease Cattle with skin disease were investigated in four separate herds in Powys and Herefordshire. Individual animals were affected in three of the herds, with five animals affected in the fourth. Three of these cases led to investigations for lumpy skin disease (LSD) by APHA Field Services. Following exclusion of LSD, further diagnostic sampling was undertaken by the private practitioners. None of the animals was pruritic and hence skin scrapes were not considered useful; instead, some fixed and fresh biopsy samples were obtained. Histopathological examination confirmed lymphoma in two of the cases. One was an 18-month-old Holstein-Friesian heifer, which rapidly developed many ‘spongy’ masses of varying size, some becoming ulcerated. The second was a five-year-old Limousin suckler cow which similarly had multiple masses over its entire body (Fig 1). The possibility of enzootic bovine leucosis (EBL) must be considered for lymphomas. The cases were each discussed with APHA Field Services. As EBL occurs in cattle older than three years, further testing was carried out for the five-year-old suckler cow but not the 18-month-old heifer. Tests for EBL were negative. APHA DISEASE SURVEILLANCE REPORT HEADLINES Cattle with multifocal skin lesions Mesenteric torsion and tapeworms in a lamb First outbreak this year of Klebsiella pneumoniae septicaemia in pigs Coronavirus nephritis in adult pheasants Seabird deaths along the British coastline Focus on antibiotic prescribing challenges In smallholder poultry The third case was a 12-month-old Limousin-cross bullock which over several months developed many cutaneous lesions, resembling abscesses, along the dorsal aspect of the nasal bones and over the back, varying from 5–30 mm in diameter. A chronic multifocal pyogranulomatous dermatitis with folliculitis and furunculosis was diagnosed on histopathology, although no specific aetiology was identified. A PCR test ruled out bovine viral diarrhoea virus infection. ABOUT THIS REPORT This report is produced each month by the APHA Surveillance Intelligence Unit and the six Species Expert Groups (livestock and wildlife). The international horizon-scanning summaries are produced by the Defra/APHA International Disease Monitoring (IDM) team, notifiable disease reports by the APHA Veterinary Exotic and Notifiable Disease Unit (VENDU), and threat analysis by the cross-agency Veterinary Risk Group (VRG). The report is drawn from scanning surveillance information, data and reports produced by the APHA Veterinary Investigation Centres and non-APHA partner postmortem examination providers contributing to the Veterinary Investigation Diagnosis Analysis (VIDA) database and complying with standardised diagnostic and laboratory testing criteria. Other livestock and wildlife scanning surveillance reports may also be found at https://bit.ly/3vNoHV3 Fig 1Open in figure viewerPowerPoint Lymphoma skin lesions affecting a cow The fourth case was in a suckler herd of 300 cows, where five animals exhibited caseous abscesses along the mandible and ventral neck (Fig 2). No bacteria were isolated from three needle aspirates, but histopathology confirmed severe multifocal chronic pyogranulomatous lesions with Splendore-Hoeppli inclusions. These lesions are diagnostic for actinobacillosis. Sampling for skin diseases Practitioners are encouraged to discuss skin disease cases with the APHA; if LSD or EBL is suspected, APHA Field Services should be informed (see ‘Contacting the APHA’, p 26). If notifiable disease is ruled out, the following sampling protocol is recommended. If animals are pruritic, collect skin scrapes from the edge of active lesions, for examination for ectoparasites. Bacteriology may be considered for abscessated or purulent lesions; collect swabs in charcoal, or aspirate lesion contents (it can be difficult to avoid contamination with commensal organisms). For histopathology, obtain full-thickness skin biopsies fixed in 10 per cent formalin. Fig 2Open in figure viewerPowerPoint Actinobacillosis lesions behind the mandible of a cow In all cases sampling from several sites is recommended. Small ruminants Mesenteric torsion and tapeworms in a lamb A six-week-old lamb was submitted to the APHA Carmarthen Veterinary Investigation Centre (VIC) to investigate three sudden deaths in a group of 14 ewes and 33 lambs. The lambs were housed at night with some receiving supplementary lamb milk from a bottle, including the submitted lamb. The lambs had been treated with ivermectin for gastrointestinal parasites 10 days previously. Significant postmortem findings included torsion of the mesentery affecting a 30-cm segment of the distal small intestine, with dark-red haemorrhages on the affected serosa and mesentery and fibrin strands on the serosa (Fig 3). A large number of tapeworms were present in the small intestine (Fig 4). The submitted lamb also had 200 Teladorsagia/Ostertagia species identified in the abomasum, indicating a light worm burden, although no worm eggs were detected in the faeces, likely resulting from the recent worming treatment. A coccidial count of 2050 oocysts per gram of faeces was also identified; of those that were successfully sporulated, 52 per cent were of the pathogenic species Eimeria ovinoidalis. Coccidiosis due to Eimeria species typically affects young lambs, four to eight weeks of age, producing diarrhoea, illthrift and death. The significance of the large number of tapeworms within the small intestinal tract is not clear in this case. Adult tapeworms (Moniezia species) are common parasites in the intestines of first-season grazing lambs but the pathogenicity of infection is yet to be conclusively demonstrated, although unthriftiness or diarrhoea have sometimes been attributed to Moniezia.1 Fig 3Open in figure viewerPowerPoint Distension of the small intestines in a lamb with a mesenteric torsion A similar case of small intestinal torsion in a five-week-old lamb has previously been reported.2 Intestinal torsions occurring in older lambs are usually associated with dietary changes, such as access to readily fermentable crops, including lush pasture. Fermentation occurs in the large intestine and results in gas production, which causes the gut to shift, resulting in a twist. Access to a milk replacer diet could have predisposed both lambs to a small intestinal torsion. However, the presence of such a large Moniezia burden in the present case may have also been a contributory factor. In older, larger sheep, large burdens are unlikely to physically block the intestines; however, this has been anecdotally reported in young lambs.3 This case report suggests that parasite attachment to the intestinal mucosa might cause altered local intestinal motility as described in cases of Anoplocephala perfoliata infections inducing colic in horses. Clearly there is a need for further research into the epidemiology of Moniezia species. Fig 4Open in figure viewerPowerPoint Tapeworms removed from the small intestine of the lamb in Fig 3 In the case submitted to the APHA, it was advised to review the husbandry practice of keeping lambs in at night and out in the day, as changes between feed types may have increased the risk of intestinal torsion. Additionally, a review of gastrointestinal parasite control was recommended and further testing to assess coccidial oocyst burden in the lambs could be helpful to establish how widespread infection is within the group. More information on parasite control in sheep can be obtained from the Sustainable Control of Parasites in Sheep (SCOPS) website, www.scops.org.uk Pigs Klebsiella pneumoniae septicaemia Sudden deaths of good pigs were reported in June among 19-day-old piglets from three litters in a large farrowing batch on an outdoor breeding unit in East Anglia. Most piglets within the three litters were affected, with a total of 30 deaths at the time of submission. All four piglets submitted to the APHA Bury St Edmunds VIC showed diffuse purple skin discolouration. They had dark, congested livers, congested meninges and the scant milky contents in their stomachs suggested they had been inappetent before death. Initial examination raised suspicion of bacterial septicaemia, and the isolation of heavy, often pure, growths of Klebsiella pneumoniae subspecies pneumoniae (Kpp) from multiple internal sites in several piglets confirmed a diagnosis of Kpp septicaemia. The isolate involved was resistant to ampicillin by disc diffusion antimicrobial sensitivity testing, and sensitive to other antimicrobials tested. Ampicillin resistance is innate and not acquired in Kpp. This is the first outbreak of Kpp septicaemia in pigs diagnosed in 2022. Interestingly, these outbreaks show a marked seasonal pattern, with almost all occurring between May and October each year (Fig 5). Outbreaks of septicaemia in piglets due to Kpp have been diagnosed by the APHA every year since the summer of 2011, when the first outbreaks were seen in pigs. Molecular analysis of isolates has identified that the same emerging strain of Kpp (sequence type 25) has been involved in all but one of the outbreaks. Outbreaks almost exclusively affect preweaned pigs from 10 days of age to weaning, and most, but not all, have been in outdoor pig herds, as in this case. Herds experiencing outbreaks in consecutive years have used autogenous vaccine in sows to control disease in piglets, reportedly to good effect. The clinical signs of sudden death are non-specific and further investigation, including postmortem examination and culture, is essential to confirm a diagnosis of Kpp septicaemia. The case definition for an outbreak of Kpp septicaemia is ‘Pigs found dead with lesions consistent with septicaemia and pure/predominant growths of Klebsiella pneumoniae subspecies pneumoniae isolated from internal sites in multiple pigs.‘ More information about Kpp septicaemia is available at https://bit.ly/3NmBpB3 and https://bit.ly/3u9CDsF Birds Gamebirds Coronavirus nephritis in adult pheasants At the beginning of May 2022, APHA Lasswade received fixed kidneys and a pool of swabs from fresh kidneys from a flock of pheasants. Seventy deaths had been reported in this flock of 500 breeding birds. The birds had not been vaccinated against coronaviruses. At gross examination, visceral gout with pale and enlarged kidneys was observed. Histopathology revealed a marked subacute multifocal tubular interstitial nephritis in two of the samples (Figs 6, 7). Non-specific nephropathy was observed in the other two kidney samples received. PCR for infectious bronchitis virus (IBV) and IBV-like γ coronaviruses was positive, but the genotype could not be determined. A similar submission received from another part of the country showed a subacute to chronic tubular interstitial nephritis in all three samples received and PCR testing for IBV and IBV-like γ coronaviruses was weakly positive. In both cases, the epidemiology, gross and microscopic findings, and the molecular analysis were consistent with coronavirus nephritis of pheasants. Coronavirus nephritis of pheasants has been described since the 1980s in Great Britain.4–6 Initial molecular analysis of the British pheasant coronaviruses showed a similarity to coronaviruses derived from poultry, though differences could be identified.7 A recent publication from China has looked more closely at the molecular characteristics of pheasant-derived coronaviruses, concluding that the pheasant coronavirus in China and IBV detected in poultry have the same ancestor.8 Fig 5Open in figure viewerPowerPoint Klebsiella pneumoniae septicaemia outbreaks in piglets by month of diagnosis, 2011–mid-June 2022 There are no recent data on the strains currently circulating in British pheasants, and the APHA is interested in collecting material to investigate this further. Any suspect cases can be discussed with APHA Lasswade. Wildlife Wild birds Seabird deaths along the British coastline There has been a recent increase in reports of large numbers of seabirds dying along the British coastline. A variety of species have been reported, including gannets, great skuas, puffins, eider ducks, herring gulls, guillemots, and Arctic, Sandwich and common terns. APHA investigations are ongoing but highly pathogenic avian influenza (HPAI) has been detected in birds from most affected sites and in a range of species. Fig 6Open in figure viewerPowerPoint Kidney histology sample showing tubulointerstitial nephritis with a multifocal mononuclear and granulocytic infiltration of the cortical interstitium (arrows) Fig 7Open in figure viewerPowerPoint Kidney histology sample showing tubulointerstitial nephritis with dense granulocytic infiltrations into distended tubules in the medulla (arrows), which are associated with disruption of the epithelium. There is mononuclear and granulocytic infiltration the adjacent cortical interstitium (stars) Transmission of HPAI may be occurring more readily as seabirds are currently congregating at their breeding colonies. This mass mortality event poses a threat to biodiversity as most of the aforementioned species have either an amber- or red-listed conservation status.9 Britain is an important site for some of the affected species, such as the great skua (approximately 60 per cent of the global population breeds in Britain). In addition to large numbers of birds dying reducing overall population sizes, it is unclear what effect HPAI may have on breeding success due to possible effects on egg viability or loss of parents. Many of these species also take a number of years to reach sexual maturity, further affecting recovery following these mortality events. The APHA Diseases of Wildlife Scheme continues to take an interest in these events and has investigated several accounts of seabird deaths over the past few years.10,11 Anyone finding a dead wild bird should contact the APHA (see ‘Contacting the APHA’, p 26). International disease monitoring International Disease Monitoring (IDM) horizon-scanning activities monitor for major, notifiable or new and re-emerging animal disease outbreaks worldwide. This is done to provide an early warning and to assess the risks they may pose to the UK, in particular those diseases that impact on animal health and welfare, international trade, public health or wider society. IDM also assesses the risk that animal diseases might come into the UK through the trade in animals or animal products (legal or illegal), through movements of wildlife, or through the movement of fomites and vectors such as insects, which may carry infectious disease. These outbreak assessments are used to guide decisions on how to manage or reduce the risks and are published online at https://bit.ly/3ul7r6U “This mass mortality event poses a threat to biodiversity • Poultry and non-commercial non-poultry are defined in the World Organisation for Animal Health's Terrestrial Animal Health Code at https://bit.ly/32yIjlA The following summarises outbreaks during May 2022. Highly pathogenic avian influenza In May, in Europe, outbreaks of HPAI H5N1 were reported in poultry in Czech Republic (one), France (196), Hungary (142), Iceland (one), Netherlands (two) and Slovakia (one). HPAI H5N1 was reported in non-commercial non-poultry in Czech Republic (one), France (13), Germany (one) and Iceland (one). HPAI H5N1 was reported in wild birds in Austria (one), Czech Republic (two), Finland (four), France (two), Germany (19), Greece (one), Iceland (one), Lithuania (two), Netherlands (33), Spain (two) and Sweden (three). HPAI H5N5 was reported in wild birds in Norway (four). HPAI H5 (serotype not typed) was reported in poultry in Bulgaria (12) and Moldova (one). In Asia, HPAI H5N1 was reported in poultry in Japan (three), Nepal (one) and Philippines (13), and in wild birds in Japan (11). HPAI H5N2 was reported in poultry in Chinese Taipei (one). HPAI H5N8 was reported in wild birds in Israel (two). In Africa, HPAI H5N1 was reported in poultry in Gabon (one), Nigeria (two) and South Africa (one), and in wild birds in South Africa (one). In the Americas, HPAI H5N1 was reported in poultry in Canada (34) and the USA (52); in non-commercial non-poultry in Canada (11) and the USA (69); and in wild birds in Canada (20) and the USA (nine). The risk of an incursion of HPAI H5 in wild birds in Great Britain has reduced from high to medium. The risk of exposure of poultry across Great Britain is maintained at low (with low uncertainty) where good biosecurity is applied, and at medium (with low uncertainty) where biosecurity is suboptimal. The housing measures that were implemented across the UK on 29 November 2021 were lifted on 2 May 2022. Mandatory enhanced biosecurity requirements remain along with the Avian Influenza Prevention Zone imposed in Great Britain on 3 November 2021 and in Northern Ireland on 17 November 2021. All poultry keepers (including those who keep gamebirds or pet poultry) should follow the biosecurity best practice advice available at https://bit.ly/2Ziz3jU Poultry keepers are requested to remain vigilant for any signs of disease in their flock and report any sign of avian influenza to the appropriate contact number (see ‘Contacting the APHA’, p 26). Details of the latest situation can be found at https://bit.ly/2SqJf5Y African swine fever In May, in Europe, outbreaks of African swine fever (ASF) in domestic pigs were reported in Germany (one), Moldova (two), Romania (17) and Russia (two). Outbreaks of ASF in wild boar have been reported in Germany (24), Hungary (74), Italy (43), Latvia (25), Poland (113), Romania (32) and Russia (two). Elsewhere, outbreaks of ASF in domestic pigs were reported in Nepal (10), South Africa (three), South Korea (one) and Thailand (seven). Cases of ASF in wild boar were reported in South Korea (14). There is a medium risk of incursion of ASF virus to the UK, and this is being kept under review. More information on the situation in Europe is available at https://bit.ly/34hYoJq, while information on the situation in Asia can be found at https://bit.ly/34kvokc As the travel restrictions observed over the past two years as a result of Covid-19 ease, it remains a critical time for the potential spread of the virus throughout Europe as well as into other regions through human-mediated routes such as introduction from personal imports (including illegal imports) or fomites. Although the UK has now left the EU, the rules for passengers travelling into Great Britain from the EU with products of animal origin have not yet changed, but Great Britain will be bringing in controls in late 2023. All travellers are strongly advised to avoid bringing any pork products – for example, dried or cured meats, sausages, salamis or pâté – back to the UK from ASF-affected parts of Europe. Travellers from Asia and other third country areas who bring meat or dairy products can face prosecution and a large fine. Everyone should observe the swill feeding ban. It remains illegal to feed catering waste, kitchen scraps, meat or meat products to farmed animals, including those kept as pets. This is to prevent the introduction and spread of potentially devastating notifiable animal diseases, such as ASF, classical swine fever (CSF) and foot-and-mouth disease (FMD). Outbreaks of these diseases can cause significant animal health and welfare problems and damage to the economy (https://bit.ly/3fLcbgV). Information on how to spot ASF, including photos of clinical signs, and how to report suspect cases is available at https://bit.ly/2SkQFHX Classical swine fever In May, Japan reported one outbreak of CSF in domestic pigs. There is a very low risk of incursion of CSF virus to the UK, and this is being kept under review. Foot-and-mouth disease In May, the following outbreaks of FMD were reported: serotype O in Algeria (four), Israel (24) and Palestine (two); serotype SAT 2 in South Africa (19) and Zimbabwe (10); serotype SAT 3 in South Africa (six); and untyped in Indonesia (80). There remains a low risk of FMD incursion into the UK from any affected region. Newcastle disease In May, Newcastle disease was reported in Israel (12) and Colombia (seven). The risk level for exposure to poultry in the UK remains at low. References 1Elliott DC. Tapeworm (Moniezia expansa) and its effect on sheep production: the evidence reviewed. N Z Vet J 1986; 34: 61– 5CrossrefCASPubMedWeb of Science®Google Scholar 2Kelly RF, Evans M, Sargison ND. Identifying knowledge gaps in Moniezia expansa epidemiology: a report of a small intestinal torsion in a 5-week-old lamb. N Z Vet J 2021; 69: 186– 9CrossrefCASPubMedWeb of Science®Google Scholar 3Burnell M. Tapeworm control in sheep. Vet Rec 2005; 157: 180Wiley Online LibraryPubMedWeb of Science®Google Scholar 4Pennycott TW. Causes of mortality and culling in adult pheasants. Vet Rec 2000; 146: 273– 8Wiley Online LibraryCASPubMedWeb of Science®Google Scholar 5Lister SA. Diseases of game birds. In Pract 1989; 11: 170– 4Wiley Online LibraryGoogle Scholar 6Gough RE, Cox WJ, Winkler CE, et al. Isolation and identification of infectious bronchitis virus from pheasants. Vet Rec 1986; 138: 208– 9Wiley Online LibraryGoogle Scholar 7Cavanagh D, Mawditt K, Welchman D de B, et al. Coronaviruses from pheasants (Phasianus colchicus) are genetically closely related to coronaviruses of domestic fowl (infectious bronchitis virus) and turkeys. Avian Pathol 2002; 31: 81– 93CrossrefCASPubMedWeb of Science®Google Scholar 8Han Z, Liwen X, Ren M, et al. Genetic, antigenic and pathogenic characterization of avian coronaviruses isolated from pheasants (Phasianus colchicus) in China. Vet Microbiol 2020; 240: 108513CrossrefCASPubMedGoogle Scholar 9Stanbury A, Eaton M, Aebischer N, et al. The status of our bird populations: the fifth Birds of Conservation Concern in the United Kingdom, Channel Islands and Isle of Man and second IUCN Red List assessment of extinction risk for Great Britain. British Birds 2021; 114: 723– 74Google Scholar 10Duff JP, Thurston L, Holmes JP, et al. Botulism and Bisgaard taxon implicated in Arctic tern deaths in the UK. Vet Rec 2021; 189: 77– 8Wiley Online LibraryCASPubMedWeb of Science®Google Scholar 11Fullick E, Bidewell CA, Duff JP, et al. Mass mortality of seabirds in GB. Vet Rec 2022; 190: 129– 30Wiley Online LibraryCASPubMedWeb of Science®Google Scholar Volume191, Issue19/16 July 2022Pages 20-24 FiguresReferencesRelatedInformation

Eight Years of African Swine Fever in the Baltic States: Epidemiological Reflections

African swine fever (ASF) was first detected in Lithuania, Latvia, and Estonia in 2014 and has since been circulating in the Baltic States with a similar epidemiological course characterized by persistence of the disease in the wild boar population and occasional spill-over infections in domestic pigs. The aim of the present study was to evaluate surveillance data on ASF in wild boar from the three countries to improve our understanding of the course of the disease. ASF surveillance and wild boar population data of the countries were analyzed. In all three countries, a decrease in the prevalence of ASF virus-positive wild boar was observed over time. Although somewhat delayed, an increase in the seroprevalence was seen. At the same time, the wild boar population density decreased significantly. Towards the end of the study period, the wild boar population recovered, and the prevalence of ASF virus-positive wild boar increased again, whereas the seroprevalence decreased. The decreasing virus prevalence has obviously led to virus circulation at a very low level. Together with the decreasing wild boar population density, the detection of ASF-infected wild boar and thus ASF control has become increasingly difficult. The course of ASF and its continuous spread clearly demonstrate the necessity to scrutinize current ASF surveillance and control strategies fundamentally and to consider new transdisciplinary approaches.

The Role of the Wild Boar Spreading African Swine Fever Virus in Asia: Another Underestimated Problem

African swine fever (ASF) is a highly lethal infectious disease in naive populations of domestic pigs and wild boar. In Asia, from the first outbreak in August 2018 until the end of November 2021, ASF has been reported in 16 Asian countries. The ASF virus (ASFV) circulation in domestic pigs is considered the main problem in Asia. On the other hand, there are very few reports of ASF in wild boar in this region. However, considering the high wild boar density within the same area of smallholder domestic pig farms in Asia, the occurrence of ASFV infection in wild boar may be underestimated. The role of the wild boar in other ASF epidemiological scenarios, such as Europe, is a key for the maintenance and transmission of the disease. Hence, we performed a preliminary study estimating the extent of ASFV infection in the Asian wild boar population. The potential risk area of ASF-infected wild boar was calculated based on the habitat suitability for wild boar, the kernel density of ASF notification in smallholder farms and wild boar, and the ASFV transmission rate of wild boar. As a result of the analysis, high-, medium-, and low-risk areas were identified throughout Southeast and East Asia. The highest risk area was detected in China, followed by Myanmar, Far East Russia, Thailand, Vietnam, Laos, Cambodia, and the Philippines. Additionally, another risk area was detected from northeastern China to the Korean Peninsula, including Far East Russia. This study shows hot spots where a high risk of infection in wild boar is most likely to occur, helping to control ASF.

African Swine Fever Survey in a European Context

African swine fever (ASF) is currently the most threatening disease for domestic and wild pigs worldwide. Wild boar has been the main affected species in all EU countries except for Romania, where most notifications occur in domestic pigs. The spread of ASF in wild boar is challenging to control; risk factors are harder to identify and establish than in domestic pigs, which, together with an underestimation of the disease and the lack of treatment or an effective vaccine, are hindering control and eradication efforts. We distributed two online questionnaires, one for domestic pigs and one for wild boar, to experts of different background and countries in Europe, to explore risk factors in relation to ASF control connected to farming, hunting, trade, the environment, and domestic pig and wild boar populations. Overall, wild boar movements were estimated to pose the highest risk of ASF introduction and spread. The movement of pork and pork products for own consumption also ranked high. Here we explored, in addition to the assessment of risk pathways, the identification of risks of transmission at the domestic/wild boar interface, the importance of biosecurity practices and improved control efforts, and controversial opinions that require further attention.

Safety of African Swine Fever Vaccine Candidate Lv17/WB/Rie1 in Wild Boar: Overdose and Repeated Doses.

African swine fever (ASF) is a highly lethal infectious disease that affects domestic pigs and wild boar. Outbreaks of ASF have grown considerably in the last decade causing important economic consequences for the swine industry. Its control is hampered by the lack of an effective treatment or vaccine. In Europe, the wild boar is a key wild reservoir for ASF. The results of the oral vaccination trial of wild boar with Lv17/WB/Rie1 are hope for this problem. However, this vaccine candidate has certain safety concerns, since it is a naturally attenuated vaccine. Therefore, the current study aims to evaluate the safety of this vaccine candidate in terms of overdose (high dose) and repeated doses (revaccination) in wild boar. Low-dose orally vaccinated animals developed only a slight transient fever after vaccination and revaccination. This was also the case for most of the high-dose vaccinated wild boar, except for one of them which succumbed after revaccination. Although this fatality was related to hierarchical fights between animals, we consider that further studies are required for clarification. Considering these new results and the current epidemiological situation of ASF in wild boar, this vaccine prototype is a promising tool for the control of the disease in these wild populations, although further studies are needed.

African Swine Fever in Wild Boar in Europe-A Review.

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.

Research priorities to fill knowledge gaps in wild boar management measures that could improve the control of African swine fever in wild boar populations

The European Commission asked EFSA to provide study designs for the investigation of four research domains (RDs) according to major gaps in knowledge identified by EFSA in a report published in 2019: (RD 1) African swine fever (ASF) epidemiology in wild boar; (RD 2) ASF transmission by vectors; (RD 3) African swine fever virus (ASFV) survival in the environment, and (RD 4) the patterns of seasonality of ASF in wild boar and domestic pigs in the EU. In this Scientific Opinion, the second RD on ASF epidemiology in wild boar is addressed. Twenty‐nine research objectives were proposed by the working group and broader ASF expert networks and 23 of these research objectives met a prespecified inclusion criterion. Fourteen of these 23 research objectives met the predefined threshold for selection and so were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time‐frame study (< 1 year); (5) the novelty of the study; and (6) if it was a priority for risk managers. Finally, after further elimination of three of the proposed research objectives due to overlapping scope of studies published during the development of this opinion, 11 research priorities were elaborated into short research proposals, considering the potential impact on ASF management and the period of one year for the research activities.

Research objectives to fill knowledge gaps in African swine fever virus survival in the environment and carcasses, which could improve the control of African swine fever virus in wild boar populations.

The European Commission requested that EFSA provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: i) the patterns of seasonality of African Swine Fever (ASF) in wild boar and domestic pigs in the EU; ii) the epidemiology of ASF in wild boar; iii) survival of ASF virus (ASFV) in the environment and iv) transmission of ASFV by vectors. In this Scientific Opinion, the third research domain on ASFV survival is addressed. Nine research objectives were proposed by the working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the nine research objectives, only one was prioritised and elaborated into a general protocol/study design research proposal, pertaining ASFV survival in feed and bedding. To investigate the survival of ASFV in feed, bedding and roughage, laboratory survival studies are proposed. To investigate possible risk mitigation measures, proof‐of‐concept approaches should be investigated.

Research priorities to fill knowledge gaps in the control of African swine fever: possible transmission of African swine fever virus by vectors.

The European Commission requested that EFSA provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: (i) the patterns of seasonality of African Swine Fever (ASF) in wild boar and domestic pigs in the EU; (ii) the epidemiology of ASF in wild boar; (iii) survival of ASF virus (ASFV) in the environment and (iv) transmission of ASFV by vectors. In this Scientific Opinion, the fourth research domain on ASFV transmission by vectors is addressed. Eleven research objectives were proposed by the EFSA working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the 11 research objectives, six were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time‐frame study (< 1 year); (5) the novelty of the study and (6) if it was a priority for risk managers. The prioritised research objectives were: (I) Studies on the potential vector fauna at the pig–wild boar interface and the feeding preference of blood‐feeding potential vectors in ASF‐affected areas; (II) Assessment of the efficacy of insect screens on indoor/outdoor pig holdings to prevent the entry of blood‐sucking vectors (i.e. Stomoxys) in ASF endemic areas; (III) Assess the role of mechanical vectors in the virus transmission in ASF‐affected areas; (IV) Distribution of the potential mechanical transmission vectors in ASF‐affected areas of the EU; (V) ASFV transmission by synanthropic birds; and (VI) Assessment on the presence/absence of the soft tick Ornithodoros erraticus in ASF‐affected areas in Europe. For each of the selected research objectives, a research protocol has been proposed considering the potential impact on ASF management and the period of 1 year for the research activities.

Epidemiological analysis of African swine fever in the European Union (September 2019 to August 2020).

An update on the African swine fever (ASF) situation in the 10 affected Member States (MS) in the EU and in two neighbouring countries from the 1 September 2019 until the 31 August 2020 is provided. The dynamics of the proportions of PCR‐ and ELISA‐positive samples since the first ASF detection in the country were provided and seasonal patterns were investigated. The impact of the ASF epidemic on the annual numbers of hunted wild boar in each affected MS was investigated. To evaluate differences in the extent of spread of ASF in the wild boar populations, the number of notifications that could be classified as secondary cases to a single source was calculated for each affected MS and compared for the earliest and latest year of the epidemic in the country. To evaluate possible risk factors for the occurrence of ASFV in wild boar or domestic pigs, a literature review was performed. Risk factors for the occurrence of ASF in wild boar in Romanian hunting grounds in 2019 were identified with a generalised linear model. The probability to find at least one PCR‐confirmed ASF case in wild boar in a hunting ground in Romania was driven by environmental factors, wild boar abundance and the density of backyard pigs in the hunting ground area, while hunting‐related variables were not retained in the final model. Finally, measures implemented in white zones (ASF‐free zones that are geographically adjacent to an area where ASF is present in wild boar) to prevent further spread of ASF were analysed with a spatially, explicit stochastic individual‐based model. To be effective, the wild boar population in the white zone would need to be drastically reduced before ASF arrives at the zone and it must be wide enough. To achieve the necessary pre‐emptive culling targets of wild boar in the white zone, at the start of the establishment, the white zone should be placed sufficiently far from the affected area, considering the speed of the natural spread of the disease. This spread is faster in denser wild boar populations. After a focal ASF introduction, the white zone is always close to the infection hence pre‐emptive culling measures in the white zone must be completed in short term, i.e. in a few months.

What Do Lithuanian Hunters Think of African Swine Fever and Its Control-Perceptions.

Simple SummaryEffectiveness and successful implementation of control measures greatly depend on hunters’ willingness and motivation to carry out these measures. Therefore, assessing their opinions regarding the current system is paramount in order to achieve the best possible results. The present study provides insights of hunters’ attitudes and perceptions about measures to control African swine fever (ASF) in wild boar in Lithuania. This study highlights several measures that are not supported by hunters (i.e., restriction of hunting, selective female hunting, ban of supplementary feeding, involvement of additional forces in ASF control) and possible motivational options (i.e., reduction of work, financial incentives and improved feedback and relationships with government officials). Considering these findings when planning and altering control measures for ASF could improve their successful implementation in the field.After the introduction of African swine fever (ASF) into Lithuania in 2014, continuous spread of the disease resulted in infection of the wild boar populations in most parts of Lithuania. The virus has been moving closer to other Western European countries where pig density is high. An efficient surveillance system detecting ASF cases early in domestic and wild animals is necessary to manage this disease. To make surveillance appropriate and effective, it is critical to understand how key players perceive the implemented control measures. This study investigated the attitudes and beliefs of hunters in Lithuania regarding currently implemented or proposed measures for the control of ASF in the wild boar population. Study data were collected through questionnaires distributed via the internet and by hunting associations in Lithuania. In total, 621 fully completed questionnaires were received and analyzed. All measures interfering with extensive hunting, like ban of driven or individual hunting or ban of supplementary feeding were considered as unacceptable and as ineffective measures to control ASF in wild boar. However, selective hunting of female wild boar was generally considered as an unethical act and therefore rejected. Some measures that seem to have been successful in other countries, like involvement of additional forces, were rejected by Lithuanian hunters, thus implementation of these measures could be difficult. The study highlighted that there is a need for improving important relationships with other stakeholders, since many hunters expressed a lack of trust in governmental institutions and regarded cooperation with them as insufficient. Hunters emphasized that their motivation to support passive surveillance measures could be improved with financial compensation and reduction of workload. The present study provides insights into hunters’ perceptions, which may be used as a foundation for additional discussions with these important stakeholders and for adapting measures to improve their acceptance if appropriate.

Detection of African swine fever virus in free-ranging wild boar in Southeast Asia.

African Swine Fever (ASF) is a highly contagious and fatal viral disease affecting both domestic and wild suids. The virus was introduced to Southeast Asia in early 2019 and has since spread rapidly throughout the region. Although significant efforts have been made to track and diagnose the disease in domestic pigs, very little is known about ASF in free‐ranging wild boar and their potential role in maintaining the disease within Southeast Asia. Through a collaboration between government and non‐government actors in Laos, Viet Nam, and Cambodia, investigations were conducted to (a) characterize the interface between domestic pigs and wild boar, (b) document risk factors for likely ASF spillover into wild boar populations by way of this interface, and (c) determine whether ASF in wild boar could be detected in each country. An extensive overlap between wild boar habitat and domestic pig ranging areas was found around villages bordering forests in all three countries, creating a high‐risk interface for viral spillover between domestic pig and wild boar populations. Fifteen and three wild boar carcasses were detected through passive reporting in Laos and Viet Nam, respectively, in 2019 and early 2020. Four of five carcasses screened in Laos and two of three in Viet Nam were confirmed positive for African swine fever virus using real‐time PCR. There were no confirmed reports of wild boar carcasses in Cambodia. This is the first confirmation of ASF in wild boar in Southeast Asia, the result of a probable viral spillover from domestic pigs, which highlights the importance of early reporting and monitoring of ASF in wild boar to enable the implementation of appropriate biosecurity measures.

Hunters’ view on the control of African swine fever in wild boar. A participatory study in Latvia

African swine fever (ASF) has massively spread in recent years and threatens the global pig industry. ASF has been present in Latvia since 2014. Hunters play a major role in the implementation of measures to control ASF and in passive disease surveillance. The probability to detect an ASF-positive wild boar is much higher in animals found dead than in hunted animals. Thus, the willingness and the motivation of hunters to support passive surveillance is of utmost importance. Using participatory methods, this study aimed to assess the acceptability of control measures for ASF in wild boar among hunters. In addition, new approaches to increase hunters’ motivation to report wild boar found dead were investigated.A total of ten focus group discussions with hunters from different regions in Latvia were conducted. To assess the quantity and quality of contacts between hunters and stakeholders involved in the control of ASF, relation diagrams were used. Using ranking tools, the trust of the participants in stakeholders to implement control measures successfully was evaluated. Defined control measures were presented to the hunters and their acceptability investigated. An impact diagram and a list of defined motivation options for passive surveillance were offered to identify new ways to increase the willingness of hunters to support passive surveillance actively.A satisfactory and regular relationship was identified between the hunters, the Food and Veterinary Service (FVS) and the State Forest Service (SFS). The hunters’ trust in these authorities was high. Although there is no vaccine against ASF, hunters were convinced of the potential of vaccination in controlling ASF. However, building fences was considered as useless and ineffective. To increase the willingness of hunters to support passive surveillance, reducing the infection pressure in the forests was regarded as most motivating. Furthermore, hunters would appreciate a decrease in their costs and workload.The study provides new insight into the concerns and experiences of hunters. Including their views and expectations in the further design and implementation of control and surveillance activities may help to improve current efforts to control ASF in wild boar populations. Although representing the perceptions of Latvian hunters, the main conclusions may be adaptable to adjust ASF control and surveillance in other countries.

Joining the club: First detection of African swine fever in wild boar in Germany.

African swine fever (ASF) has spread across many countries in Europe since the introduction into Georgia in 2007. We report here on the first cases of ASF in wild boar detected in Germany close to the border with Poland. In addition to the constant risk of ASF virus (ASFV) spread through human activities, movements of infected wild boar also represent a route of introduction. Since ASF emerged in Western Poland in November 2019, surveillance efforts, in particular examination of wild boar found dead, were intensified in the regions of Germany bordering with Poland. The first case of ASF in wild boar in Germany was therefore detected by passive surveillance and confirmed on 10 September 2020. By 24 September 2020, 32 cases were recorded. Testing of samples from tissues of carcasses in different stages of decomposition yielded cycle threshold values from 18 to 36 in the OIE-recommended PCR, which were comparable between the regional and national reference laboratory. Blood swabs yielded reliable results, indicating that the method is suitable also under outbreak conditions. Phylogenetic analysis of the ASFV whole-genome sequence generated from material of the first carcass detected in Germany, revealed that it groups with ASFV genotype II including all sequences from Eastern Europe, Asia and Belgium. However, some genetic markers including a 14bp tandem repeat duplication in the O174L gene were confirmed that have so far been detected only in sequences from Poland (including Western Poland). Epidemiological investigations that include estimated postmortem intervals of wild boar carcasses of infected animals suggest that ASFV had been introduced into Germany in the first half of July 2020 or even earlier.

Predicting spread and effective control measures for African swine fever-Should we blame the boars?

An ongoing, continually spreading, outbreak of African swine fever (ASF), following its identification in Georgia in 2007, has resulted in 17 European and 12 Asian countries reporting cases by April 2020, with cases occurring in both wild boar and domestic pigs. Curtailing further spread of ASF requires understanding of the transmission pathways of the disease. ASF is self-sustaining in the wild boar population, and they have been implicated as one of the main drivers of transmission within Europe. We developed a spatially explicit model to estimate the risk of infection with ASF in wild boar and pigs due to natural movement of wild boar that is applicable across the whole of Europe. We demonstrate the model by using it to predict the probability that early cases of ASF in Poland were caused by wild boar dispersion. The risk of infection in 2015 is computed due to wild boar cases in Poland in 2014, compared against reported cases in 2015, and then the procedure is repeated for 2015-2016. We find that long- and medium-distance spread of ASF (i.e. >30km) is unlikely to have occurred due to wild boar dispersal, due in part to the generally short distances wild boar will travel (<20km on average). We also predict the relative success of different control strategies in 2015, if they were implemented in 2014. Results suggest that hunting of wild boar reduces the number of new cases, but a larger region is at risk of ASF compared with no control measure. Alternatively, introducing wild boar-proof fencing reduces the size of the region at risk in 2015, but not the total number of cases. Overall, our model suggests wild boar movement is only responsible for local transmission of disease; thus, other pathways are more dominant in medium- and long-distance spread of the disease.

Stability of African swine fever virus on heat-treated field crops.

African swine fever (ASF) is an infectious disease of pigs and represents a massive threat to animal health and the pig industry worldwide. The ASF virus (ASFV) is efficiently transmitted via blood and meat from infected animals and can be highly stable in the environment. There is therefore great concern about the potential role of contaminated raw materials used for feed or bedding in the spread of ASFV. Especially crops and derived products originating from areas with ASF in wild boar and thus with high environmental ASFV contamination may be a risk for virus introduction into domestic pig herds. However, little is known about the stability of ASFV on contaminated crops and possible inactivation methods. In this study, we tested the effect of drying and heat treatment on the inactivation of ASFV on six different types of field crops, namely wheat, barley, rye, triticale, corn, and peas, contaminated with infectious blood. Samples were analysed for the presence of viral DNA and infectious virus after 2hr drying at room temperature or after drying and 1hr exposure to moderate heat at a specific temperature between 40°C and 75°C. ASFV genome was detected in all samples by real-time polymerase chain reaction (PCR), including samples that had been dried for 2hr and incubated for 1hr at 75°C. On the other hand, no infectious virus could be detected after 2hr drying using virus isolation in porcine macrophages in combination with the detection of ASFV by the haemadsorption test (HAT). We therefore conclude that the risk of ASFV transmission via contaminated crops is most likely low, if they are incubated for at least 2hr minimum at room temperature. Nonetheless, to minimize the risk of transmission as much as possible crops from ASF-affected zones should not be used for pig feed.

First Occurence of African Swine Fever in Serbia

Abstract Until July 30th, 2019 when the first case of African swine fever (ASF) was confirmed, Serbia was a country free from ASF. After the owner reported atypical illness and death of a sow, the local veterinarian submitted the organ samples to the National Reference Laboratory for Classical Swine Fever (CSF) and African Swine Fever within the Institute of Veterinary Medicine of Serbia in Belgrade. Observed gross lesions included splenomegaly, serous edema of the wall of the gallbladder and hemorrhages in the enlarged portal lymph nodes, petechial hemorrhages on the kidney and epicardium, and petechial and echymotic hemorrhages on the mucosa of the urinary bladder. Results of real-time PCR confirmed that the cause of illness and death of the swine was African swine fever virus. The samples were sent for confirmation to the EU Reference Laboratory where it was confirmed that Serbian domestic pig virus isolates based on p72 belong to genotype II. In total, 270 pigs from 18 affected holdings were killed in the infected zones. According to the on-record data, mortality was 6.89%, whereas lethality reached 64.5%. Currently, an extensive surveillance program is being conducted, aiming to force passive surveillance. ASF in wild boar has not been confirmed so far.