Disease-Induced Mortality Outweighs Hunting in Causing Wild Boar Population Crash After African Swine Fever Outbreak

Automated Detection and Counting of Wild Boar in Camera Trap Images

Camera traps are becoming widely used for wildlife monitoring and management. However, manual analysis of the resulting image sets is labor-intensive, time-consuming and costly. This study shows that automated computer vision techniques can be extremely helpful in this regard, as they can rapidly and automatically extract valuable information from the images. Specific training with a set of 1600 images obtained from a study where wild animals approaching wild boar carcasses were monitored enabled the model to detect five different classes of animals automatically in their natural environment with a mean average precision of 98.11%, namely 'wild boar', 'fox', 'raccoon dog', 'deer' and 'bird'. In addition, sequences of images were automatically analyzed and the number of wild boar visits and respective group sizes were determined. This study may help to improve and speed up the monitoring of the potential spread of African swine fever virus in areas where wild boar are affected.

Spatio-temporal interactions between the red fox and the wolf in two contrasting European landscapes

Relationships among carnivore species are complex, potentially switching from competition to facilitation on a context-dependent basis. Negative associations are predicted to increase with latitude, due to limited resources emphasising competition and/or intra-guild predation. Accordingly, a stronger negative correlation between large- and meso-carnivore abundances should be expected at higher latitudes, with a substantial spatio-temporal partitioning favouring interspecific coexistence. Human presence may influence spatio-temporal relationships between (meso)carnivore species, as it can be perceived as a risk factor, but anthropogenic food can also provide an important additional food resource. Using camera-trap data, we studied the spatio-temporal associations between two of the most widespread carnivores in Europe, i.e., the red fox and wolf. We compared their monthly/daily spatio-temporal partitioning between two different landscapes: Białowieża Primeval Forest (Poland) and the Mediterranean Maremma Regional Park (Italy). We predicted a stronger interspecific partitioning, as well as more attraction of red foxes to humans in the northern site (Poland). Temporal activity patterns of the two carnivores overlapped in both sites, and their detection rates were positively associated, even though in weaker way in Poland. We observed a positive spatial association of red foxes with human activity in Białowieża, but not in Maremma. This association occurred only at a monthly temporal scale and disappeared at a daily scale, suggesting some disturbance in the shorter term. Our results provided partial support to our predictions and suggest that, despite the ecological differences between our study areas, only weak differences in wolf-fox relations were observed, suggesting that red fox responses to wolves may be relatively comparable over large spatial scales.

Predicting Disparity between ASF-Managed Areas and Wild Boar Habitats: A Case of South Korea

African swine fever (ASF) is a highly contagious viral disease affecting both domestic and wild boars. Since its first outbreak in South Korea in 2019, substantial efforts have been made to prevent ASF transmission by reducing the wild boar population and eliminating infected carcasses; however, the persistence of ASF transmission has posed challenges to these efforts. To improve ASF management strategies, the limitations of current management strategies must be identified by considering disparities between wild boar habitats and ASF-managed areas with environmental and anthropogenic characteristics of wild boars and their management strategies. Here, ensemble species distribution models were used to estimate wild boar habitats and potential ASF-managed areas, with elevation, distance to urban areas, and Normalized Difference Vegetation Index as important variables. Binary maps of wild boar habitats and potential ASF-managed areas were generated using the maxSSS as the threshold criterion. Disparity areas of ASF management were identified by overlying regions evaluated as wild boar habitats with those not classified as ASF-managed areas. Dense forests near urban regions like Chungcheongbuk-do, Gyeongsangbuk-do, and Gyeongsangnam-do were evaluated as disparity areas having high risk of ASF transmission. These findings hold significant potential for refining ASF management strategies and establishing proactive control measures.

Accelerometer-based detection of African swine fever infection in wild boar

Infectious wildlife diseases that circulate at the interface with domestic animals pose significant threats worldwide and require early detection and warning. Although animal tracking technologies are used to discern behavioural changes, they are rarely used to monitor wildlife diseases. Common disease-induced behavioural changes include reduced activity and lethargy ('sickness behaviour'). Here, we investigated whether accelerometer sensors could detect the onset of African swine fever (ASF), a viral infection that induces high mortality in suids for which no vaccine is currently available. Taking advantage of an experiment designed to test an oral ASF vaccine, we equipped 12 wild boars with an accelerometer tag and quantified how ASF affects their activity pattern and behavioural fingerprint, using overall dynamic body acceleration. Wild boars showed a daily reduction in activity of 10-20% from the healthy to the viremia phase. Using change point statistics and comparing healthy individuals living in semi-free and free-ranging conditions, we show how the onset of disease-induced sickness can be detected and how such early detection could work in natural settings. Timely detection of infection in animals is crucial for disease surveillance and control, and accelerometer technology on sentinel animals provides a viable complementary tool to existing disease management approaches.

Disease threats to tigers and their prey

The contraction of the global tiger population over the last 100 years into small, often isolated subpopulations has made them increasingly vulnerable to the impact of disease. Despite this, the health of wild tigers continues to be insufficiently funded and explored. For example, canine distemper virus (CDV), has been associated with localized declines and increased risk of extinction, and yet has received little research attention in most tiger range countries. The emergence of new pathogenic threats has posed fresh challenges, including African swine fever virus (ASFV), which has the potential to devastate wild boar populations, and severe acute respiratory syndrome coronavirus (SARS-CoV2) with implications for tiger conservation that remain unknown. The objective of this review is to synthesize current research on the health of tigers and their prey that impacts the conservation of tigers in the wild. Published sources are interpreted based on three mechanisms through which disease can affect the viability of tiger populations: (1) by reducing the survival of adult tigers, (2) by reducing breeding productivity, and (3) by reducing the carrying capacity of tiger habitat through decreased prey abundance. Examples of CDV, SARS-CoV2, carnivore protoparvovirus 1 and ASFV are used to illustrate these processes and inform discussion of research and mitigation priorities.

Not Just Pictures: Utility of Camera Trapping in the Context of African Swine Fever and Wild Boar Management

African swine fever (ASF) is a highly contagious disease affecting all suids and wild boar (Sus scrofa). Since 2007, ASF has spread to more than 30 countries in Europe and Asian regions, and the most recent outbreak has been in mainland Italy (reported on January 2022). When the genotype II of the ASF virus infects a population, a mortality rate close to 90% is usually reported. This drop in wild boar abundance produces a cascade effect in the entire ecosystem. In this context, effective monitoring tools for deriving management parameters are a priority aspect, and the utility of camera trapping could have been overlooked. Here, sampling the infected area in north Italy, we showed the utility of camera traps in the context of ASF infection. Specifically, we used 43 camera traps randomly distributed to (i) estimate movement parameters and population density of wild boar, roe deer (Capreolus capreolus), and wolf (Canis lupus); (ii) quantify wild boar recruitment; and (iii) assess whether the human restriction rules are being met. On the first spring after the outbreak detection, our results for wild boar indicated a density of 0.27 ind·km−2 ± 0.11 (standard error, SE), a daily activity level of 0.49 ± 0.07 (i.e., 11.76 h·day−1), a daily distance travelled of 9.07 ± 1.80 km·day−1, a litter size of 1.72 piglets·group−1, and a 72% of pregnant females. Despite human outdoor activities being restricted in the infected zone, we recorded human presence in 19 camera traps. The wide range of parameters estimated from the camera trap data, together with some intrinsic and practical advantages of this tool, allows us to conclude that camera traps are well positioned to be a reference approach to monitor populations affected by ASF. The population-specific parameters are of prime importance for optimizing ASF control efforts.

Three Years of African Swine Fever in South Korea (2019–2021): A Scoping Review of Epidemiological Understanding

African swine fever (ASF) is a highly contagious viral disease in domestic pigs and wild boar that causes tremendous socioeconomic damage in related industries. In 2019, the virus emerged in South Korea, which has since reported 21 outbreaks in domestic pig farms and over 2,600 cases in wild boar. In this review, we synthesize the epidemiological knowledge generated on ASF in South Korea during the first three years of the epidemic (2019–2021). We searched four international and one domestic Korean database to identify scientific articles published since 2019 and describing ASF epidemiology in South Korea. Fourteen articles met our selection criteria and were used to synthesize the origin of ASF in South Korea, the risk factors of disease occurrence, the effectiveness of the surveillance and intervention measures that were implemented, and the viral transmission dynamics. We found that timely intensive surveillance and interventions on domestic pig farms successfully blocked between-farm transmission. However, in wild boar, the ASF virus has spread massively towards the south primarily along the mountain ranges despite ongoing fence erection and intensive depopulation efforts, endangering domestic pig farms across the country. The current devastating epidemic is suspected to be the consequence of an ASF control strategy unaligned to the epidemiological context, the challenging implementation of control measures hindered by topological complexities, and inappropriate biosecurity by field workers. To improve our understanding of ASF epidemiology in South Korea and enhance disease management, future research studies should specify the ecological drivers of disease distribution and spread and devise effective control strategies, particularly in relation to Korean topography, and the latent spread of the virus in wild boar populations. Additionally, research studies should explore the psychosocial factors for ASF management, and develop tools to support evidence-based decision-making for managing ASFV in wild boar.

Management of a Focal Introduction of ASF Virus in Wild Boar: The Belgian Experience

African swine fever (ASF) is a fatal disease of suids that was detected in wild boar in Belgium in September 2018. The measures implemented to stop the spread and eliminate the African swine fever virus consisted of creating restriction zones, organising efficient search and removal of carcasses, constructing wire fences, and depopulating wild boar in the area surrounding the infected zone. The ASF management zone included the infected and the white zones and covered 1106 km² from which 7077 wild boar have been removed. A total of 5338 wild boars have been qPCR-tested and 833 have been detected ASF-positive. The search effort amounted to 60,631 h with a main focus on the infected zone (88%). A total of 277 km of fences have been set up. The main cause of mortality in the infected zone was the virus itself, while hunting, trapping, and night shooting were used together to reduce the wild boar density in the surrounding white zones. After continuous dispersion of the virus until March 2019, the epidemic wave stopped, and the last fresh positive case was discovered in August 2019. Hence, Belgium was declared free of the disease in November 2020.

The First Eighteen Months of African Swine Fever in Wild Boar in Saxony, Germany and Latvia-A Comparison

African swine fever (ASF) emerged in Latvia in 2014. In 2020, the virus has been detected in the German federal state, Saxony. In both regions, the virus was probably introduced by infected wild boar coming from affected neighboring countries. As the current ASF control strategy at EU level had not yet been developed at the time of ASF introduction into Latvia, disease control measures in both study areas differed over time. Assessing the course of ASF in Saxony and the implemented control strategies, the first 18 months of the ASF epidemic were epidemiologically compared between Saxony and Latvia. ASF wild boar surveillance data were analyzed and the prevalence of ASF virus-positive wild boar was estimated. For estimating the wild boar density, the numbers of wild boar per km² were calculated for the respective geographical areas. The number of samples collected from hunted wild boar and wild boar found dead was higher in Saxony. The ASF virus prevalence in Latvia was significantly higher than in Saxony, indicating that Saxony has had more time for getting prepared for dealing with an ASF incursion. Experience from other countries and the rapid implementation of new control strategies may have helped Saxony deal with ASF.

Mismatch between media coverage and research on invasive species: The case of wild boar (Sus scrofa) in Argentina

Invasive species are a pervasive driver of global change with increasing media coverage. Media coverage and framing can influence both invasive species management and policies, as well as shed light on research needs. Using the wild boar (Sus scrofa) invasion in Argentina as a case study, we conducted a content analysis of media coverage and scientific articles. Specifically, we compared news and scientific articles based on their emphasis: ecological, economic, and health impacts and the overall perception portrayed in the news: "positive" when the articles emphasized benefits from wild boar and "negative" when focused on damage and/or loss. A literature search using Google news, Web of Science, Scielo, and Google Scholar yielded a total of 194 news articles and 37 research papers on wild boar in Argentina. More than half of the news articles focused on economic impacts of wild boar (56%) such as sport hunting, illegal hunting, and road accidents; while 27% focused on ecological impacts, and 10% on health impacts. In contrast, the majority of the scientific articles (65%) focused on ecological impacts of wild boar on native species and ecosystems; while 21% were related to health impacts and only 8.3% of scientific articles were related to economic impacts. This mismatch between media and science reveals a disconnection between social and scientific interests in wild boar and their management in Argentina, and it provides insights to research needs and prevention of management conflicts. Additionally, we found that 66.8% of news articles focused on "negative" aspects of wild boar, while 33.2% of news articles portrayed "positive" perceptions. This finding is very important because the management of invasive species such as wild boar usually requires lethal techniques, and the success of the programs depend on favorable social and political support. Good science communication is therefore key to helping scientists and managers perform more effective management actions.

Changes in the Genetic Structure of Lithuania’s Wild Boar (Sus scrofa) Population Following the Outbreak of African Swine Fever

The emergence of African swine fever (ASF) in Lithuania and its subsequent persistence has led to a decline in the population of wild boar (Sus scrofa). ASF has been spreading in Lithuania since its introduction, therefore it is important to understand any genetic impact of ASF outbreaks on wild boar populations. The aim of this study was to assess how the propensity for an outbreak has shaped genetic variation in the wild boar population. A total of 491 wild boar samples were collected and genotyped using 16 STR markers. Allele richness varied between 15 and 51, and all SSR loci revealed a significant deviation from the Hardy–Weinberg equilibrium. Fixation indices indicated a significant reduction in heterozygosity within and between subpopulations. PCoA and STRUCTURE analysis demonstrated genetic differences between the western region which had had no outbreaks (restricted zone I) and the region with ASF infection (restricted zones II and III). It is concluded that environmental factors may play a particular role in shaping the regional gene flow and influence the genetic structure of the wild boar population in the region with ASF outbreaks.

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.

African Swine Fever (ASF) Trend Analysis in Wild Boar in Poland (2014–2020)

Simple Summary

African swine fever (ASF) has been present in Poland since 2014. The article describes and explains the changes in the ASF epidemic in the wild boar population in the period 2014–2020. In that relatively short time, the disease has spread to about half of the territory of Poland, affecting eastern and western provinces. Most ASF-positive animals were molecular/virus-positive, however, the observation of the increase of serologically positive animals (potential survivors) in successive years of the epidemic, especially in areas where the virus has been present for a longer time, may indicate the potential beginning of ASF endemicity in Poland.

Abstract

African swine fever (ASF) is a lethal hemorrhagic disease of Suidae, i.e., domestic pigs and wild boars. The disease was introduced to Poland in 2014 and is now present in the wild boar population. Appropriate ASF prevention requires further research for answers to fundamental questions about the importance of vectors in virus transmission, the impact of environmental factors on the presence of ASFV in wild boar habitats, and the role of survivors as potential virus carriers and their part in the potential endemicity of ASF. In order to analyze the changes in the molecular and serological prevalence of ASFV in wild boar population in Poland, real-time PCR and ELISA/IPT tests were conducted. In the analyzed period (2014–2020), most of the ASF-positive wild boars were molecular/virus-positive, however, over the years the percentage and the number of seropositive animals has increased. At the beginning of the epidemic, the disease was limited to a small area of the country. Since then, it has spread to new provinces of Poland. From the beginning and until today, most notifications of ASF-positive wild boars were for carcasses (passive surveillance), however, the number of serologically positive animals is still increasing. Despite the fact that notifications of ASF outbreaks are still being received near the eastern border of Poland, the old ASF area seems to be limited mainly to ASF serologically positive animals, which may indicate the beginning of ASF endemicity in Poland.

Emerging infectious disease triggered a trophic cascade and enhanced recruitment of a masting tree

There are several mechanisms that allow plants to temporarily escape from top-down control. One of them is trophic cascades triggered by top predators or pathogens. Another is satiation of consumers by mast seeding. These two mechanisms have traditionally been studied in separation. However, their combined action may have a greater effect on plant release than either process alone. In 2015, an outbreak of a disease (African swine fever, ASF) caused a crash in wild boar (Sus scrofa) abundance in Białowieża Primeval Forest. Wild boar are important consumers of acorns and are difficult to satiate relative to less mobile granivores. We hypothesized that the joint action of the ASF outbreak and masting would enhance regeneration of oaks (Quercus robur). Data from ungulate exclosures demonstrated that ASF led to reduction in acorn predation. Tree seedling data indicated that oak recruitment increased twofold relative to pre-epidemic period. Our results showed that perturbations caused by wildlife disease travel through food webs and influence forest dynamics. The outbreak of ASF acted synergistically with masting and removed herbivore top-down control of oaks by mobile consumers. This illustrates that the ASF epidemic that currently occurs across Europe can have broad effects on forest dynamics.

How do genetic relatedness and spatial proximity shape African swine fever infections in wild boar?

The importance of social and spatial structuring of wildlife populations for disease spread, though widely recognized, is still poorly understood in many host-pathogen systems. In particular, system specific kin relationships among hosts can create contact heterogeneities and differential disease transmission rates. Here, we investigate how distance-dependent infection risk is influenced by genetic relatedness in a novel host-pathogen system: wild boar (Sus scrofa) and African swine fever (ASF). We hypothesized that infection risk would correlate positively with proximity and relatedness to ASF-infected individuals but expected those relationships to weaken with distance between individuals due to decay in contact rates and genetic similarity. We genotyped 323 wild boar samples (243 ASF-negative and 80 ASF-positive) collected in north-eastern Poland in 2014-2016 and modeled the effects of geographic distance, genetic relatedness, and ASF virus transmission mode (direct or carcass-based) on the probability of ASF infection. Infection risk was positively associated with spatial proximity and genetic relatedness to infected individuals with generally stronger effect of distance. In the high-contact zone (0-2 km), infection risk was shaped by the presence of infected individuals rather than by relatedness to them. In the medium-contact zone (2-5 km), infection risk decreased but was still associated with relatedness and paired infections were more frequent among relatives. At farther distances, infection risk further declined with relatedness and proximity to positive individuals, and was 60% lower among unrelated individuals in the no-contact zone (33% in10-20 km) compared with among relatives in the high-contact zone (93% in 0-2 km). Transmission mode influenced the relationship between proximity or relatedness and infection risk. Our results indicate that the presence of nearby infected individuals is most important for shaping ASF infection rates through carcass-based transmission, while relatedness plays an important role in shaping transmission rates between live animals. This article is protected by copyright. All rights reserved.

African Swine Fever Re-Emerging in Estonia: The Role of Seropositive Wild Boar from an Epidemiological Perspective

African swine fever (ASF) emerged in Estonia in 2014. From February 2019 to August 2020, no pigs or wild boar tested positive for ASF virus (ASFV), only ASFV-specific antibodies could be detected in shot wild boar. However, ASF recently re-emerged in wild boar. We tested three hypotheses that might explain the current situation: (i) ASFV may have been present throughout, but at a prevalence below the detection limit; (ii) seropositive wild boar may have remained infectious (i.e., virus-carriers) and kept the epidemic going; or (iii) ASF was gone for 1.5 years, but was recently re-introduced. Using Estonian surveillance data, the sensitivity of the surveillance system and the confidence in freedom from ASF were estimated. Furthermore, the detection probability was determined and cluster analyses were performed to investigate the role of serological positive wild boar. The results suggest that the surveillance system was not able to detect virus circulation at a design prevalence below 1%. With respect to the confidence in freedom from ASF, the results indicate that circulating virus should have been detected over time, if the prevalence was ≥2%. However, the decreasing wild boar population density and ongoing surveillance activities made ASFV circulation at a low prevalence unlikely. Cluster analyses provided no evidence for a significant accumulation of serologically positive wild boar in temporal connection to the re-emergence of ASFV. Further targeted research, such as long-term experimental studies and molecular epidemiology, is necessary to improve our knowledge on the epidemiology of ASF and to control the disease more effectively.

Managing African Swine Fever: Assessing the Potential of Camera Traps in Monitoring Wild Boar Occupancy Trends in Infected and Non-infected Zones, Using Spatio-Temporal Statistical Models

The recent spreading of African swine fever (ASF) over the Eurasian continent has been acknowledged as a serious economic threat for the pork industry. Consequently, an extensive body of research focuses on the epidemiology and control of ASF. Nevertheless, little information is available on the combined effect of ASF and ASF-related control measures on wild boar (Sus scrofa) population abundances. This is crucial information given the role of the remaining wild boar that act as an important reservoir of the disease. Given the high potential of camera traps as a non-invasive method for ungulate trend estimation, we assess the effectiveness of ASF control measures using a camera trap network. In this study, we focus on a major ASF outbreak in 2018-2020 in the South of Belgium. This outbreak elicited a strong management response, both in terms of fencing off a large infected zone as well as an intensive culling regime. We apply a Bayesian multi-season site-occupancy model to wild boar detection/non-detection data. Our results show that (1) occupancy rates at the onset of our monitoring period reflect the ASF infection status; (2) ASF-induced mortality and culling efforts jointly lead to decreased occupancy over time; and (3) the estimated mean total extinction rate ranges between 22.44 and 91.35%, depending on the ASF infection status. Together, these results confirm the effectiveness of ASF control measures implemented in Wallonia (Belgium), which has regained its disease-free status in December 2020, as well as the usefulness of a camera trap network to monitor these effects.

Blastocystis occurrence and subtype diversity in wild European terrestrial mammals - The case of Białowieża Primeval Forest (NE Poland)

Blastocystis cf. Blastocystis hominis is the most common unicellular parasite found in human and animal intestines. Little is known about the life cycle, transmission and mechanisms of pathogenesis for this parasite. The aim of this study was to obtain new data on the genetic diversity of Blastocystis in selected species of mammals found in the Białowieża Primeval Forest (BPF), Poland, the best preserved lowland forest in temperate Europe. 113 faecal samples were collected in the period 2018–2020 from seven species of wild mammals occurring within the Polish part of BPF and its surroundings. Blastocystis was detected by molecular amplification and sequencing the small subunit rRNA gene. The overall prevalence of Blastocystis in animals was 8.9%. A larger number of stool samples (90) were collected from European bison and only for this species was it possible to calculate the prevalence of infection (5.6%). The isolates obtained from European bison were classified as ST1, ST3, ST5, ST7. Blastocystis was also detected in the grey wolf (Canis lupus) (ST5), wild boar (Sus scrofa) (ST5) and red deer (Cervus elaphus) (ST1). In conclusion, for the first time we have demonstrated the presence of Blastocystis in wild European bison. Preliminary studies have shown that Blastocystis is present in at least 4 species of wild mammals in the BPF area and that it exhibits great genetic diversity.

Blastocystis is present in wild mammals in the Białowieża Primeval Forest

Blastocystis in the Białowieża Primeval Forest exhibits great genetic diversity

Intra-species and interspecific transmission of Blastocystis in Białowieża Primeval Forest is highly probable.

A Review of Environmental Risk Factors for African Swine Fever in European Wild Boar

A detailed understanding of environmental risk factors for African swine fever (ASF) in wild boar will be not only essential for risk assessments but also for timely and spatially informed allocation of resources in order to manage wild boar-targeted ASF control measures efficiently. Here, we review currently known environmental risk factors that can influence the occurrence of ASF virus infection in wild boar when compared to disease occurrence in wild boar of a non-exposed reference scenario. Accordingly, the exposure of wild boar to environmental risk factors related to (1) climate, (2) land cover, (3) human activity, (4) wild boar and (5) ASF were evaluated. As key environmental risk factors in this review, increased ASF occurrence in wild boar was associated with seasonal patterns, forest coverage, presence of water, human presence, farming activities, wild boar density and ASF nearness. The review highlights inconsistencies in some of these risk factor associations with disease detection in space and time and may provide valuable insights for the investigation of ASF transmission dynamics. The examined risk information was applied to consider potential improvements of the ASF control strategy in wild boar regarding disease surveillance, hunting, wild boar carcass searches and ASF barrier implementation.

Atypical porcine pestivirus-A widespread virus in the Swedish wild boar population

The recently identified causative agent of congenital tremor in domestic piglets, atypical porcine pestivirus (APPV), was detected in serum from Swedish wild boar. A previous study from Sweden described APPV in domestic piglets suffering from congenital tremor, but the APPV situation in the wild boar population was unknown. In this study, 595 serum samples from wild boar originating from 13 counties in the south and central parts of Sweden, collected between 2000 and 2018, were analysed for the presence of the APPV-genome and for antibodies against the APPV-glycoprotein E^rns . The results revealed that APPV is highly abundant in the Swedish wild boar population; 12% (73/595) were APPV-genome positive in serum and 72% (433/595) of the tested wild boars displayed APPV-specific antibodies. The present study also shows that APPV has been present in the Swedish wild boar population since at least the year 2000. The viral sequences obtained from the wild boars were highly similar to those obtained from Swedish domestic pigs positive for APPV and suffering from congenital tremor, suggesting a viral exchange between wild boars and domestic pigs. The high proportion of viraemic and seropositive wild boar is indicative of wild boar being an important reservoir for APPV.

African Swine Fever and Its Epidemiological Course in Lithuanian Wild Boar

African swine fever (ASF) has been present in Lithuania since 2014. It is mainly the wild boar population that is affected. Currently, little is known about the epidemiological course of ASF in Lithuania. In the present study, ASF surveillance data from 2016-2021 were analyzed. The numbers of samples taken from hunted wild boar and wild boar found dead per year and month were recorded and the prevalence was estimated for each study month and administrative unit. A Bayesian space-time model was used to calculate the temporal trend of the prevalence estimates. In addition, population data were analyzed on a yearly basis. Most samples were investigated in 2016 and 2017 and originated from hunted animals. Prevalence estimates of ASF virus-positive wild boar decreased from May 2019 onwards. Seroprevalence estimates showed a slight decrease at the same time, but they increased again at the end of the study period. A significant decrease in the population density was observed over time. The results of the study show that ASF is still present in the Lithuanian wild boar population. A joint interdisciplinary effort is needed to identify weaknesses in the control of ASF in Lithuania and to combat the disease more successfully.

Indirect Effect of African Swine Fever on the Diet Composition of the Gray Wolf Canis lupus-A Case Study in Belarus

Simple Summary

The wild boar population decreased drastically in Eastern Europe after the emergence of a viral disease called African Swine Fever. We studied how the gray wolves’ diet changed in two regions in Belarus during this situation. Wolves mainly hunted wild boar, elk, red deer, roe deer and beaver. The decrease in the wild boar population caused changes in the diet of wolves, but only in Vitebsk region. After the decrease in the wild boar population, wolves in this region hunted wild boar less, but they hunted roe deer and red deer more. The more the wolves consumed wild boar, the less they consumed both deer species (roe deer and red deer). Moreover, the more the wolves consumed elk, the less they consumed beaver. In another region, Grodno, no changes in the wolves’ diet were found.

Abstract

After the emergence of African swine fever (ASF), the wild boar population numbers fell drastically in Eastern Europe. This situation made it possible to verify the changes in the wolves’ diet that occurred. The material collection was carried out in two regions, Grodno and Vitebsk, in Belarus. In total, 19 species/groups of prey were observed in the gray wolf diet, but the most important were wild boar, elk, red deer, roe deer and beaver. The decrease in the number of wild boar caused changes in the diet of wolves but only in Vitebsk region, where wolves’ diet before the ASF epidemic outbreak consisted mainly of elk and wild boar. After the decrease of wild boar numbers, wolves still mainly hunted elk, but other types of prey included roe deer, red deer and beaver. We found a negative correlation between wild boar and both deer species (roe deer and red deer) in the wolves’ diet. Moreover, the more the wolves consumed elk, the less they consumed beaver. In our opinion, only intensive hunting of wolves by humans can explain the resulting dietary fluctuations between elk and beaver, as well as the fact that wolves did not turn to other food sources.

The potential negative impacts of the classical swine fever virus on wild boar population in Gifu prefecture, Japan

There is a possibility that classical swine fever (CSF) virus outbreak has negative impacts on wild boar. To adequately manage native wild boar populations, wildlife managers need to gather the field data on wild boar and implement population management practices. We aimed to report the relative abundance index of wild boar before and after this outbreak. Our results showed that relative abundance index declined from 2017 (8.88 wild boars/100 trap days) to 2019 (2.03 wild boars/100 trap days), because of the negative impact of this virus and continuous culling programs. Although the eradication risk from the synergistic effect is low, wildlife managers need to consider the relationship between the trade-off between the risk of CSF and the conservation ecology risk of native species eradication.

Clear phylogeographic pattern and genetic structure of wild boar Sus scrofa population in Central and Eastern Europe

The wild boar Sus scrofa is one of the widely spread ungulate species in Europe, yet the origin and genetic structure of the population inhabiting Central and Eastern Europe are not well recognized. We analysed 101 newly obtained sequences of complete mtDNA genomes and 548 D-loop sequences of the species and combined them with previously published data. We identified five phylogenetic clades in Europe with clear phylogeographic pattern. Two of them occurred mainly in western and central part of the continent, while the range of the third clade covered North-Eastern, Central and South-Eastern Europe. The two other clades had rather restricted distribution. In Central Europe, we identified a contact zone of three mtDNA clades. Population genetic structure reflected clear phylogeographic pattern of wild boar in this part of Europe. The contribution of lineages originating from the southern (Dinaric-Balkan) and eastern (northern cost of the Black Sea) areas to the observed phylogeographic pattern of the species in Central and Eastern Europe was larger than those from the regions located in southern France, Iberian, and Italian Peninsulas. The present work was the first mitogenomic analysis conducted in Central and Eastern Europe to study genetic diversity and structure of wild boar population.

Development of Diagnostic Tests Provides Technical Support for the Control of African Swine Fever

African swine fever is a highly contagious global disease caused by the African swine fever virus. Since African swine fever (ASF) was introduced to Georgia in 2007, it has spread to many Eurasian countries at an extremely fast speed. It has recently spread to China and other major pig-producing countries in southeast Asia, threatening global pork production and food security. As there is no available vaccine at present, prevention and control must be carried out based on early detection and strict biosecurity measures. Early detection should be based on the rapid identification of the disease on the spot, followed by laboratory diagnosis, which is essential for disease control. In this review, we introduced the prevalence, transmission routes, eradication control strategies, and diagnostic methods of ASF. We reviewed the various methods of diagnosing ASF, focusing on their technical characteristics and clinical test results. Finally, we give some prospects for improving the diagnosis strategy in the future.

The impact of an African swine fever outbreak on endemic tuberculosis in wild boar populations: A model analysis

A mathematical model is developed and analysed to examine the impacts of African swine fever (ASF) introduction into a wild boar population that supports endemic animal tuberculosis (TB). TB is a widespread infectious disease caused by the Mycobacterium tuberculosis bacteria belonging to the Mycobacterium tuberculosis complex (MTC) that can persist in reservoir wildlife hosts. Wild boar (sus scrofa) are a key reservoir for MTC, and an increasing trend in wild boar density is expected to lead to an increase in TB prevalence with spill-over to livestock. MTC infection is presently controlled through a variety of strategies, including culling. African swine fever (ASF) is a virulent, viral infection which affects wild boar and is spreading across Eurasia and Oceania. ASF infection leads to near 100% mortality at the individual level, can cause a dramatic decrease in population density and may therefore lead to TB control. We extend an established model that captures the key demographic and infection processes for TB in wild boar to consider the impact of ASF introduction on wild boar populations that support different levels of endemic TB. Our model results indicate that an ASF infection will reduce wild boar population density and lead to a decrease in the prevalence of TB. If ASF persists in the local host population the model predicts the long-term decline of TB prevalence in wild boar. If ASF is eradicated, or fades-out in the local host population, the model predicts a slower recovery of TB prevalence in comparison to wild boar density after an ASF epidemic. This may open a window of opportunity to apply TB management to maintain low TB prevalence.

ASF Exit Strategy: Providing cumulative evidence of the absence of African swine fever virus circulation in wild boar populations using standard surveillance measures

EFSA assessed the role of seropositive wild boar in African swine fever (ASF) persistence. Surveillance data from Estonia and Latvia investigated with a generalised equation method demonstrated a significantly slower decline in seroprevalence in adult animals compared with subadults. The seroprevalence in adults, taking more than 24 months to approach zero after the last detection of ASFV circulation, would be a poor indicator to demonstrate the absence of virus circulation. A narrative literature review updated the knowledge on the mortality rate, the duration of protective immunity and maternal antibodies and transmission parameters. In addition, parameters potentially leading to prolonged virus circulation (persistence) in wild boar populations were reviewed. A stochastic explicit model was used to evaluate the dynamics of virus prevalence, seroprevalence and the number of carcasses attributed to ASF. Secondly, the impact of four scenarios on the duration of ASF virus (ASFV) persistence was evaluated with the model, namely a: (1) prolonged, lifelong infectious period, (2) reduction in the case-fatality rate and prolonged transient infectiousness; (3) change in duration of protective immunity and (4) change in the duration of protection from maternal antibodies. Only the lifelong infectious period scenario had an important prolonging effect on the persistence of ASF. Finally, the model tested the performance of different proposed surveillance strategies to provide evidence of the absence of virus circulation (Exit Strategy). A two-phase approach (Screening Phase, Confirmation Phase) was suggested for the Exit Strategy. The accuracy of the Exit Strategy increases with increasing numbers of carcasses collected and tested. The inclusion of active surveillance based on hunting has limited impact on the performance of the Exit Strategy compared with lengthening of the monitoring period. This performance improvement should be reasonably balanced against an unnecessary prolonged 'time free' with only a marginal gain in performance. Recommendations are provided for minimum monitoring periods leading to minimal failure rates of the Exit Strategy. The proposed Exit Strategy would fail with the presence of lifelong infectious wild boar. That said, it should be emphasised that the existence of such animals is speculative, based on current knowledge.

Taking a lesson from the COVID-19 pandemic: Preventing the future outbreaks of viral zoonoses through a multi-faceted approach

The pandemic of the novel coronavirus disease 2019 (COVID-19) has caused a significant burden to healthcare systems, economic crisis, and public fears. It is also a lesson to be learned and a call-to-action to minimize the risk of future viral pandemics and their associated challenges. The present paper outlines selected measures (i.e., monitoring and identification of novel viral agents in animals, limitations to wildlife trade, decreasing hunting activities, changes to mink farming and meat production), the implementation of which would decrease such a risk. The role of viral surveillance systems and research exploring the virus strains associated with different animal hosts is emphasized along with the need for stricter wild trade regulations and changes to hunting activities. Finally, the paper suggests modifications to the meat production system, particularly through the introduction of cultured meat that would not only decrease the risk of exposure to novel human viral pathogens but also strengthen food security and decrease the environmental impacts of food production.