Spread Of African Swine Fever Research Articles

Spatio-temporal clustering of African swine fever virus (Asfarviridae: Asfivirus) circulating in the Kaliningrad region based on three genome markers.

The rapid spread of African swine fever in the Kaliningrad region makes it necessary to use the methods of molecular epidemiology to determine the dynamics and direction of ASF spread in this region of Russia. The aim of the study was to determine single nucleotide polymorphisms within molecular markers K145R, O174L and MGF 505-5R of ASFVs isolated in Kaliningrad region and to study the circulating of the pathogen in European countries by subgenotyping and spatio-temporal clustering analysis. Blood samples from living domestic pigs and organs from dead domestic pigs and wild boars, collected in the Kaliningrad region between 2017 and 2022 were used. Virus isolation was carried out in porcine bone-marrow primary cell culture. Amplicons of genome markers were amplified by PCR with electrophoretic detection and subsequent extraction of fragments from agarose gel. Sequencing was performed using the Sanger method. The circulation of two genetic clusters of ASFV isolates on the territory of the Kaliningrad has been established: epidemic (K145R-III, MGF 505-5R-II, O174L-I - 94.3% of the studied isolates) and sporadic (K145R-II, MGF 505-5R-II, O174L-I - 5.7%). The broaden molecular genetic surveillance of ASFV isolates based on sequencing of genome markers is necessary in the countries of the Eurasian continent to perform a more detailed analysis of ASF spread between countries and within regions.

An analysis of the social, cultural, and ecological factors that affect the implementation of biosecurity measures on smallholder commercial swine farms in Italy in the context of an emerging African Swine Fever outbreak

African Swine Fever (ASF) is a contagious viral disease that infects wild and domesticated swine. In early 2022, the virus was found in wild boar in the Apennine mountains of mainland Italy.22https://storymaps.arcgis.com/stories/9fe6aa3980ca438cb9c7e8d656358f35 Since then, it has spread from wild boar to domesticated swine. To control the spread of ASF, an effective surveillance system and the implementation of strict biosecurity measures on farms are required yet are unevenly implemented across husbandry systems. Smallholder farms in particular are known to have low levels of biosecurity. In the Apennine mountains of Italy, small commercial farms have been found to have low levels of biosecurity despite being located in areas with high densities of wild boar, and, hence, being high-risk sites for potential ASF incursion and subsequent diffusion. To address the question as to why the level of biosecurity is low, interviews and participant observation were conducted with smallholder commercial farmers. The interviews identified the social, cultural, and ecological factors that affect the implementation of biosecurity measures in small commercial swine farms in the Apennines. Farmers expressed knowledge of priority biosecurity measures and an overall willingness to follow rules and regulations; however, the application of the measures in practice was uneven across farms. Economic, political, and ecological factors as well as farmer beliefs about biosecurity emerged as important factors affecting the implementation of biosecurity measures. These include economic constraints, challenges posed by the mountain environment, a shifting regulatory environment, and ideas about animal welfare. Other important factors include cultural factors such as the use of traditional agricultural methods and norms about customer access to animals, time constraints and the perceived hassle of implementing the measures, farmer age, farmer relationships with government officials and veterinarians, and the role of pigs in reducing farm waste. The study confirmed that wild boar are present in high numbers and in close proximity to smallholder commercial farms in the Apennines.

Resource‐driven changes in wild boar movement and their consequences for the spread of African Swine Fever in the Russian Far East

Knowledge of animal movement patterns is invaluable to understanding the spread of diseases among wildlife populations. One example is the recent African swine fever (ASF) outbreak among wild boar Sus scrofa populations across East Asia, where there is a lack of information on movements of this species. During a wild boar tracking project to inform abundance estimation methods in the Russian Far East's Sikhote‐Alin Biosphere Zapovednik, the combination of high variability in pulsed resources of acorns and pine nuts between fall 2019 and fall 2020, and the outbreak of ASF during the latter year, offered the unique opportunity to investigate the relationship between wild boar movements to exploit pulsed resources and the potential for disease spread. We analyzed relocation data from GPS‐collared wild boar in fall 2019 and 2020 and compared them to reference data in Belgium, representative of western Europe. We found remarkable differences in movement patterns, with Far East wild boar travelling large distances in fall 2020 (maximum observed of 77 km in four days) when the availability of acorns was low. In our resource selection analysis, we found clear selection for mast‐producing forest types that corresponded with the species of greater mast production (oak or pine) for that year. Comparing the displacement of individual wild boar along a moving window of 1–7 days (time between infection and the onset ASF symptoms) highlighted the potential of rapid ASF spread over long distances when wild boar are in search of pulsed resources. This work demonstrates the capacity of wild boar to move long distances to exploit resources and emphasizes the need to consider resource availability when predicting the speed and extent to which diseases such as ASF can spread.

African swine fever in wild boar: investigating model assumptions and structure

African swine fever (ASF) is a highly virulent viral disease that affects domestic pigs and wild boar. Current ASF transmission in Europe is in part driven by wild boar populations, which act as a disease reservoir. Wild boar are abundant throughout Europe and are highly social animals with complex social organization. Despite the known importance of wild boar in ASF spread and persistence, knowledge gaps remain surrounding wild boar transmission. We developed a wild boar modelling framework to investigate the influence of contact-density functions and wild boar social structure on disease dynamics. The framework included an ordinary differential equation model, a homogeneous stochastic model and various network-based stochastic models that explicitly included wild boar social grouping. We found that power-law functions (transmission ∝ density 0.5 ) and frequency-based contact-density functions were best able to reproduce recent Baltic outbreaks; however, power-law function models predicted considerable carcass transmission, while frequency-based models had negligible carcass transmission. Furthermore, increased model heterogeneity caused a decrease in the relative importance of carcass-based transmission. The transmission pathways predicted by each model type affected the efficacy of idealized interventions, which highlights the importance of evaluating model type and structure when modelling systems with significant uncertainties.

Epidemiological analysis of African swine fever in the European Union during 2023.

In 2023, 14 Member States were affected by African swine fever (ASF), including Croatia and Sweden where ASF emerged (wild boar outbreaks only) and Greece where ASF re-emerged after being free since 2021. The number of ASF outbreaks among domestic pigs in the EU was five times higher than in 2022, reaching a similar magnitude to that in 2019. This was predominantly driven by the introduction and subsequent spread of ASF in Croatia and its resurgence in Romania, representing 96% of the EU outbreaks. ASF outbreaks in domestic pigs were clearly seasonal in all countries, with 88% of outbreaks reported between July and October. Most of the ASF outbreaks among domestic pigs were detected through clinical suspicion (94%), followed by tracing from affected establishments (3%), and the weekly testing of at least two dead pigs in establishments (3%). In wild boar, a 10% increase in the number of notified outbreaks was observed in the EU in comparison with 2022, with considerable variations between countries. A winter peak was observed only in Poland, Slovakia and Hungary. The epidemiological situation in wild boar improved in Germany and Hungary, as suggested by the decrease in the number of outbreaks and in the proportions of PCR-positive samples from dead wild boar. Overall, 31% of wild boar carcasses found during passive surveillance tested positive by PCR, representing 69% of the ASF outbreaks in wild boar in the EU. In contrast, 0.4% of hunted wild boar tested positive, representing 31% of the outbreaks. Despite the introduction of ASF into new countries and the increase in the number of outbreaks, the size of restricted zones in the EU remained stable, due to the highly clustered outbreaks in Croatia, and the reduction of restricted zones in Poland, Slovakia and Bulgaria (in domestic pigs), and Hungary (in wild boar).

An integrated fuzzy multi-criteria decision-making model for determining the interdependencies among the african swine fever spread factors

African swine fever (ASF) is a disease outbreak that has substantially impacted agriculture, public health, and food security. This study tackles the lack of knowledge regarding the interactions between multiple factors causing the spread of ASF. We also present a potential for cross-fertilization between applying soft computing to nonmeasurable factors of different natures through investigating the relationships and significance of ASF spread factors in the Philippine setting using Multi-criteria Decision Making (MCDM) methodologies and fuzzy logic. We develop a list of ASF spread factors through a literature review. Fuzzy Analytic Hierarchy Process (AHP)-VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) is used for the dimensionality reduction of factors. These elements are then classified as either net causes or net effects using the Fuzzy Decision Making Trial and Evaluation Laboratory (DEMATEL), which also shows their interdependencies. The results show how socioeconomic characteristics, particularly those connected to biosecurity lapses, significantly influence other parameters through a causal graph. This knowledge can be used to develop effective ASF preventive and management methods as it provides a systematic and unbiased decision-making framework for policymakers, breeders, and manufacturers.

African Swine Fever Diagnosis in Africa: Challenges and Opportunities.

The global spread of African swine fever (ASF) in recent decades has led to the need for technological advances in sampling and diagnostic techniques. The impetus for these has been the need to enable sampling by lay persons and to obtain at least a preliminary diagnosis in the field for early control measures to be put in place before final laboratory confirmation. In rural Africa, rapid diagnosis is hampered by challenges that include lack of infrastructure as well as human and financial resources. Lack of animal health personnel, access to affordable means to transport field samples to a laboratory, and lack of laboratories with the capacity to make the diagnosis result in severe under-reporting of ASF, especially in endemic areas. This review summarizes the challenges identified in gap analyses relevant to low- and middle-income countries, with a focus on Africa, and explore the opportunities provided by recent research to improve field diagnosis and quality of diagnostic samples used. Sampling techniques include invasive sampling techniques requiring trained personnel and non-invasive sampling requiring minimal training, sampling of decomposed carcass material, and preservation of samples in situations where cold chain maintenance cannot be guaranteed. Availability and efficacy of point-of-care (POC) tests for ASF has improved considerably in recent years and their application, as well as advantages and limitations, are discussed. The adequacy of existing laboratory diagnostic capacity is evaluated and opportunities for networking amongst reference and other laboratories offering diagnostic services are discussed. Maintaining laboratory diagnostic efficiency in the absence of samples during periods of quiescence is another issue that requires attention, and the role of improved laboratory networking is emphasized. Early diagnosis of ASF is key to managing the disease spread. Therefore, the establishment of the Africa Chapter of the Global African Swine Fever Research Alliance (GARA) increases opportunities for collaboration and networking among the veterinary diagnostic laboratories in the region.

Risk factors for African swine fever spread in wild boar in the Russian Federation

The analysis and assessment of risk factors associated with the occurrence, spread and persistence of African swine fever (ASF) virus in wild boar population are an important tool in determining the strategic measures aimed at eradicating epizootics and mitigating their consequences. A thorough examination of foreign and domestic literature revealed that wild boar population management factors, socio-economic and environmental ones, that mainly account for the density and number of animals were the most significant and associated with the risk of ASF outbreak occurrence in wild animals. In order to identify risk factors for the spread of the disease in wild boar in the Russian Federation Subjects, a regression model was built to examine the relationship between the annual number of ASF outbreaks in wild boar at the municipal raion level, wild boar population density and some other factors for the period between 2007 and 2022. Based on the Subject-level regression modelling results, a positive association between the intensity of the disease outbreaks and wild boar population density was identified in 42.5% of the model regions of the Russian Federation. Other significant factors were the length of roads, the presence of forest cover and outbreaks in domestic pigs. However, on the whole, for all the infected Subjects, the regression model demonstrated the failure of the wild boar population density factor to explain the observed ASF outbreak distribution, and this may be indicative of the existence of other epizootic drivers of the disease spread in the wild. One of such mechanisms may be the persistence of infectious potential in the external environment and in the formed stationary local foci of African swine fever, despite the anti-epizootic measures taken, including the measures aimed at regulating the number of susceptible population – depopulation.

Seroprevalence of African swine fever in pigs for slaughter in Leyte, Philippines.

This study aims to determine the seroprevalence of African swine fever (ASF) in pigs for slaughter in Leyte, Philippines. It underpins the concept that recovered and infected pigs from ASF are likely sent for slaughter to avoid perceived economic losses. A cross-sectional study was conducted from March to June 2023 in eight abattoirs, each representing both a city and a municipality in Leyte province. A total of 218 blood samples from 78 farms were examined for ASF virus (ASFV) (VP72) antibodies using a blocking enzyme-linked immunosorbent assay (ELISA) method. Descriptive and seroprevalence analyses were performed. ASF antibodies were detected in pigs for slaughter from abattoirs in Baybay and Ormoc cities, showing a seroprevalence of 3.57% (1/28 pigs) and 2.27% (1/44 pigs), respectively. An apparent absence of ASF antibodies was observed among pigs for slaughter in Isabel, Villaba, Abuyog, Kananga, Dulag, and Macarthur. The farm-level seroprevalence was 2.56% (95% CI: 0.71%-8.88%), while the pig-level seroprevalence was 0.91% (95% CI: 0.25%-3.27%). Detecting ASF antibodies among pigs for slaughter implies exposure to the virus from the farm of origin. This means that, on some farms, ASF remains unreported or undiagnosed. Active surveillance is needed for early case detection and rapid response to control the spread of ASF in the country.

Identification of High-Priority Wild Boar (Sus scrofa) Control Areas by Predicting Potential Habitat and Crop Damage

Background and objective: The wild boar (Sus scrofa) is a highly mobile, fertile, clever, stealthy, and adaptable animal. It is distributed around the world and inhabits a fairly wide range of habitats, which results in frequent friction and conflict with humans. Disturbances caused by wild boars, such as crop damage on agricultural land and the spread of African swine fever, has recently been increasing in Korea, making it necessary to confirm the habitat range of wild boars and to predict the possibility of future crop damage.Methods: The locations of Gapyeong-gun, Namyangju-si, Yangpyeong-gun, and Gwangju-si in Gyeonggi-do, where crop damage caused by wild boars is confirmed to be serious, were selected as the study area. Data from 2nd to 4th National Natural Environment Surveys (covering three periods of respectively 8, 8, and 5 years) were used to analyze the continuity of potential boar habitat, and data from point samples of crop damage were used to identify areas with a high probability of future crop damage. The MaxEnt model was used to analyze potential habitats and crop-damage areas based on 15 environmental variables selected through literature research.Results: The average area under the receiver operating curve (AUC) of the resulting potential habitat models for the three survey periods was 0.644, and the AUC of the crop damage prediction model was relatively high at 0.850. The resulting key crop-damage priority management areas were Seorak-myeon, Gapyeong-gun; Sudong-myeon, Namyangju-si; Joan-myeon, Namyangju-si; Sang-myeon and Gapyeong-gun; Gapyeong-eup, Gapyeong-gun.Conclusion: This study illustrates changes in the spatial distribution of wild boars in Korea based on time-series survey records from 1997 to 2018. These findings are expected to be useful as reliable reference data for setting priorities when establishing future measures to prevent crop damage, such as managing the number of wild boars in Gyeonggi-do.

Generation of High-Quality African Swine Fever Virus Complete Genome from Field Samples by Next-Generation Sequencing.

African swine fever (ASF) is a lethal contagious viral disease of domestic pigs and wild boars caused by the African swine fever virus (ASFV). The pandemic spread of ASF has caused severe effects on the global pig industry. Whole-genome sequencing provides crucial information for virus strain characterization, epidemiology analysis and vaccine development. Here, we evaluated the performance of next-generation sequencing (NGS) in generating ASFV genome sequences from clinical samples. Thirty-four ASFV-positive field samples including spleen, lymph node, lung, liver and blood with a range of Ct values from 14.73 to 25.95 were sequenced. For different tissue samples collected from the same sick pigs, the proportion of ASFV reads obtained from the spleen samples was 3.69-9.86 times higher than other tissues. For the high-viral-load spleen samples (Ct < 20), a minimum of a 99.8% breadth of ≥10× coverage was revealed for all the samples. For the spleen samples with Ct ≥ 20, 6/12 samples had a minimum of a 99.8% breadth of ≥10× coverage. A high average depth of sequencing coverage was also achieved from the blood samples. According to our results, high-quality ASFV whole-genome sequences could be obtained from the spleen or blood samples with Ct < 20. The high-quality ASFV genome sequence generated in this study was further used for the high-resolution phylogenetic analysis of the ASFV genomes in the early stage of the ASF epidemic in China. Our study demonstrates that NGS may act as a useful tool for efficient ASFV genome characterization, providing valuable information for disease control.

African Swine Fever and Its Control Measures in Wild Boar: A "De Iure Condito" Analysis in the European Union.

Recently, the African swine fever (ASF) epizootic has been reported in domestic pigs and wild boars in several European Union Member States (EU MS) and epidemiological evidence has accumulated which indicates that wild boar play a key role in maintaining and spreading the disease. Thanks to the experience gained when managing ASF outbreaks in Sardinia (Italy) and Eastern Europe, Directive 2002/60 CE was issued. This directive represented an important step forward in controlling the disease, particularly the risk of spreading the virus to wild animals. Since 2021, according to Regulation (EU) 2016/429, which is also called "Animal Health Law-AHL", when the MS competent authority suspects or confirms ASF (a cat. A listed disease) in wild animals, it is mandatory to conduct surveillance in the wild boar population and implement the necessary control measures. Within AHL, Regulations (EU) 2020/687 and 2023/594 established special ASF control measures in kept and wild porcine animals, and their products and by-products, focusing on and underlying old and new responsibilities that vets (both public and private ones) have to accomplish under the new regulations. The new change in the legal framework deals with specific measures to be applied in the wild and represents a great challenge for MS veterinary services. Some of these measures have been well established in the last two decades, particularly those related to application in the farming system, while other measures are still new to veterinary health management and require a holistic approach in terms of intensity, considering all geographical, ecological, productive, cultural and social features of the involved EU MS. In this contribution, the authors intend to focus on specific measures which have been issued in order to limit or stop the spread of ASF in a wild, "boundless" ecosystem. These measures expand the field of competence of the official veterinary service to wild areas in addition to farm activity.

Epidemiological Assessment of African Swine Fever Spread in the Dominican Republic.

Since African Swine Fever (ASF) was detected in the Dominican Republic in July 2021, it has negatively impacted the country's swine industry. Assessing the epidemiological situation is crucial to helping local authorities and industry stakeholders control the disease. Here, data on 155 reported outbreaks in the Dominican Republic from November 2022 to June 2023 were evaluated. Descriptive spatiotemporal analysis was performed to characterize disease distribution and spread, and between-herd R0 was calculated for the study period. The Knox test and a space-time permutation model were used to evaluate clustering. Data on clinical presentation, biosecurity measures, and suspected reasons for introduction were categorized and summarized. The majority (78%) of outbreaks occurred on backyard farms which generally had low biosecurity. Across farm types, the majority of pigs were still alive at the time of depopulation. Spatiotemporal findings and R0 estimates suggest an endemic pattern of disease geographically located centrally within the country. Clustering was detected even at small temporal and spatial distances due to outbreaks amongst neighboring backyard farms. These results provide critical information on the current state of the ASF epidemic in the Dominican Republic and will aid government officials and swine industry leaders in developing effective ASF control strategies.

Nine Years of African Swine Fever in Poland.

(1) Background: African swine fever (ASF) is a highly contagious and fatal haemorrhagic disease in domestic pigs and wild boars, causing significant economic loss to the swine industry in the European Union. The genotype II of African swine fever has spread in many European countries since the virus was detected in 2007 in Georgia. In Poland, the genotype II of the ASF virus was confirmed on 17 February 2014 in the eastern part of the country and appeared to have been transmitted to Poland from Belarus. Poland has been particularly affected by ASF epidemics in the last decade, resulting in a significant decline in the Polish pig population. Wild boars are the main reservoir of the African swine fever virus (ASFV), but human activities such as transportation and illegal animal trade are the primary reasons for the long-distance transmission of the disease. (2) Conclusions: During the nine years of ASF in Poland, multiple measures have been taken to prevent the spread of the virus among the wild boar population via the passive and active surveillance of these animals. With regard to pig farms, the only effective measure for preventing the spread of ASF is the efficient enforcement by state authorities of the biosecurity standards and the farmers' compliance with them.

The emergence and spread of African Swine Fever in Western Europe

African swine fever (ASF) is the most dangerous viral disease of domestic pigs and wild boars, causing huge economic damage. It is characterized by acute, subacute, chronic course with high (up to 100%) mortality. The causative agent of ASF has been isolated into a separate family Asfarviridae, the genus Asfivirus. The disease is widespread in Africa, Europe, Asia. The purpose of the review article is to analyze the literature data on the occurrence and spread of epizootic foci of African swine fever in Western Europe. The materials of the article are based on the results of numerous epizootological and diagnostic studies by scientists from Spain, Portugal, Belgium, France, Italy, the Netherlands, Malta, Germany, Sweden.Due to the complex seroimmune structure of the pathogen and the impossibility of forming viral neutralizing antibodies, there are difficulties in creating effective vaccines against ASF. The main tools for preventing the spread of the disease are due to the use of strict quarantine measures. Early diagnosis is an important component of ASF control and eradication.Preventive and liquidation measures for ASF in Western European countries are considered. The recommendations of the OIE/WOAH-OIE on the diagnosis of ASF using a combination of tests are given: determination of the viral genome by PCR in national reference laboratories; detection of viral antigens and antibodies by ELISA or fluorescent test; detection of the pathogen by virus isolation. The explanation of the observed interspecific interaction during the watering of wild boars and free-range domestic pigs is given, which explains the endemicity of ASF on the island of Sardinia in Italy for more than forty years.Given the virulence of the ASF virus and the many ways of transmission throughout Europe, diagnostic and epizootological monitoring of this disease should be a priority in the fight against ASF.

Spatiotemporal Patterns of African Swine Fever in Wild Boar in the Russian Federation (2007-2022): Using Clustering Tools for Revealing High-Risk Areas.

African swine fever (ASF) is an infectious disease that affects both domestic pigs (DPs) and wild boar (WB). The WB population plays an important role in the spread of ASF as the WB acts as a natural reservoir of the virus and transmits it to other susceptible wild and domestic pigs. Our study was aimed at revealing the areas with a high concentration of the WB population, and their potential relationships with the grouping of ASF cases in WB during the course of the ASF spread in the Russian Federation (2007-2022). We collected the annual data on WB numbers by municipalities within the regions of the most intensive ASF spread. We then conducted spatiotemporal analysis to identify clustering areas of ASF cases and compare them with the territories with a high density of WB population. We found that some of the territories with elevated ASF incidence in WB demonstrated spatial and temporal coincidence with the areas with a high WB population density. We also visualized the zones ("emerging hot spots") with a statistically significant rise in the WB population density in recent years, which may be treated as areas of paramount importance for the application of surveillance measures and WB population control.

Understanding the interface between European wild boar (Sus scrofa) and domestic pigs (Sus scrofa domesticus) in Sweden through a questionnaire study

BackgroundIn recent years, the wildlife/livestock interface has attracted increased attention due to disease transmission between wild and domestic animal populations. The ongoing spread of African swine fever (ASF) in European wild boar (Sus scrofa) emphasize the need for further understanding of the wildlife/livestock interface to prevent disease spill-over between the wild and domestic populations. Although wild boar may also act as a potential source for other infectious disease agents, ASF is currently the most severe threat from wild boar to domestic pigs. To gather information on the wild boar situation at commercial pig producing farms in Sweden, a digital questionnaire survey was distributed through the animal health services.ResultsMost pigs produced for commercial purposes in Sweden are raised without outdoor access. Of the 211 responding pig producers, 80% saw wild boar or signs of wild boar activity in the vicinity of their farm at least once during the year. Observations were significantly correlated with geographical region, but there was no correlation between farm characteristics (farm size, main type of production, outdoor access) and observed wild boar presence or proximity. However, a reported higher frequency of wild boar observations was positively correlated with the observations being made in closer proximity to the farm.Hunting and strategic baiting were the most common mitigation strategies used to keep wild boar at bay. Of the 14 farms raising pigs with outdoor access, 12 responded that these pigs could be raised solely indoors if needed.Pigs with outdoor access are required to be fenced in, but double fencing in these outdoor pig enclosures was not practiced by all. A perimeter fence surrounding any type of pig farm was very rare. More than half of the producers that grew crops with intended use for pigs reported crop damage by wild boar.ConclusionThis study shows that although pigs raised for commercial purposes in Sweden are, to a large extent, kept indoors the potential for indirect contact with wild boar exists and must be considered. Variable local situations regarding wild boar abundance may require an adaptive approach regarding biosecurity efforts.

Investigation of Risk Factors Associated with the African Swine Fever Outbreaks in the Nizhny Novgorod Region of Russia, 2011–2022

African swine fever (ASF) is a transboundary viral disease that affects both domestic pigs and wild boar, causing enormous damage to the pig production. Numerous studies are devoted to elucidating the role of domestic and wild pigs in ASF outbreaks. The identification of the risk factors contributing to the spread of disease in previously unaffected regions is of special interest. We conducted a retrospective analysis of sporadic ASF outbreaks in the Nizhny Novgorod region of the Russian Federation from 2011 to 2022 among both domestic pig and wild boar populations. Methods of spatiotemporal cluster analysis, mathematical modeling with logistic and negative binomial regressions, as well as the cross-correlation analysis of time series, were used to identify the most significant factors associated with the ASF outbreaks’ presence and intensity. Regression analysis did not reveal a statistically significant correlation between ASF outbreaks in wild boar and their population density over the entire study period. However, the spatial and temporal coincidence between outbreaks and increased wild boar density was observed at the beginning of the ASF epidemic in the region. We identified the significant environmental and sociodemographic factors contributing to the spread of ASF in both domestic pig and wild boar populations. The number of small-scale farms (backyards) and summary road length were determined as the main factors contributing to the spread of ASF among domestic pigs in the Nizhny Novgorod region. The regression model for ASF outbreaks in the wild boar population revealed the presence of water bodies, number of hunting farms, and the occurrence of ASF outbreaks in the domestic pig population to be the main explanatory factors. A statistically significant coincidence was identified between the monthly volume of pork products imported to the region from the rest of Russia and the occurrence of ASF outbreaks in both domestic and wild populations. Thus, the identified spatiotemporal patterns may be useful to determine areas with an elevated risk of ASF outbreaks emergence for better resource management, disease control, and prevention. The importance of intensified monitoring and control measures in the pig products supply chain is strongly needed. The obtained models can be applied not only by the veterinary service of the Nizhny Novgorod region but to other regions with similar environmental and sociodemographic conditions.

The diffusion metrics of African swine fever in wild boar

To control African swine fever (ASF) efficiently, easily interpretable metrics of the outbreak dynamics are needed to plan and adapt the required measures. We found that the spread pattern of African Swine Fever cases in wild boar follows the mechanics of a diffusion process, at least in the early phase, for the cases that occurred in Germany. Following incursion into a previously unaffected area, infection disseminates locally within a naive and abundant wild boar population. Using real case data for Germany, we derive statistics about the time differences and distances between consecutive case reports. With the use of these statistics, we generate an ensemble of random walkers (continuous time random walks, CTRW) that resemble the properties of the observed outbreak pattern as one possible realization of all possible disease dissemination patterns. The trained random walker ensemble yields the diffusion constant, the affected area, and the outbreak velocity of early ASF spread in wild boar. These methods are easy to interpret, robust, and may be adapted for different regions. Therefore, diffusion metrics can be useful descriptors of early disease dynamics and help facilitate efficient control of African Swine Fever.

Identification of seropositive wild boars in Eurasia as a sign of possible formation of African swine fever-endemic areas (review)

The continued spread of African swine fever (ASF) in Eurasia remains a global problem for the world pig industry. The disease is characterized by high mortality (up to 100 %) and acute course - domestic and wild animals die within the first two weeks after infection. However, active surveillance on ASF in Eastern Europe had been showing regular detection of seropositive susceptible animals, especially among wild boar populations which may indicate chronic, asymptomatic infection and even the survival of individual animals. At the same time, the persistence of the virus in the wild boar population creates constant risks of sporadic outbreaks of ASF in infected areas, and the infection can become endemic. The aim of the study was a systematic review of the available data on seroprevalence among wild boars in relation to the possible establishment of ASF endemicity in Eurasia. In these animals, there was a change in the dynamics of the disease, which is manifested by self-sustaining cycles of infection. Seropositive wild boars are being found in the Baltic countries, Hungary, Poland, Romania, Slovakia, and Russia. Seroprevalence rates among wild boars hunted in ASF-infected areas of European countries range from 0.3 to 3.8 %. In the Baltic countries, the number of seropositive samples from wild boars exceeds the number of samples positive for ASF virus in polymer chain reaction (PCR). A similar trend persists in those regions where the ASF virus has been present for a long time (Poland, Lithuania, Latvia, Estonia), which may indicate the endemic nature of ASF. In the Russian Federation, ASF-endemic territories in the wild have not yet been registered, although isolated cases of seropositive wild boars have been detected in some regions since 2013. In the future, in order to understand the dynamics of the disease in the wild, it is necessary to conduct a comprehensive diagnosis of the ASF virus genome and antibodies in wild boar samples, which eventually will allow choosing the right strategy to combat ASF.