Passive surveillance of African Swine Fever (ASF) in wild boars as an effective tool for prevention, control and eradication of ASF: A new approach

The latest recommendations of the European Commission and the scientific opinions of the EFSA and other bodies define the passive surveillance of ASF in wild boars as a key means of epidemiological surveillance and a basic tool for the eradication of the ASF virus from the natural environment in the areas where this disease occurs, especially in the early stage of its development. The key to eradication is the management of the wild boar population and its reduction to a low and controlled number, so as to diminish the virus pressure in the environment and lessen the risk to pig farms. Wild boar hunting should take place in a planned manner that is adapted to the epizootic situation (as part of centrally managed hunting and sanitary culling). The most intensive hunting should take place in ASF-free areas, with the use of tailored methods and the latest technologies. Periodic hunting moratoria and restrictions on any activity in newly infected zones are necessary. This approach provides for phased eradication of the infectious agent by culling or capturing wild boars, as well as identifying and safely removing their carcasses and remains. When passive ASF surveillance in wild fauna is undertaken, data on the incidence of the disease in wild boars are obtained by the Veterinary Inspectorate without its active participation. The inspectorate is notified of any suspicion or occurrence of the disease, including discoveries of carcasses of animals of susceptible species. Then it acts according to an established plan including clinical examination of suspected or sick animals, anatomopathological examinations and sample collection for laboratory tests. The article describes the use of passive ASF surveillance in wild boars as a tool to prevent, control and combat ASF in Poland.

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African Swine Fever Virus (ASFV) in Poland in 2019—Wild Boars: Searching Pattern

Agriculture ◽

10.3390/agriculture11010045 ◽

2021 ◽

Vol 11 (1) ◽

pp. 45

Author(s):

Maciej Frant ◽

Anna Gal ◽

Łukasz Bocian ◽

Anna Ziętek-Barszcz ◽

Krzysztof Niemczuk ◽

...

Keyword(s):

Wild Boar ◽

Logistic Regression Model ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Passive Surveillance ◽

Domestic Pig ◽

Wild Boars ◽

Preventive Actions ◽

Control And Prevention ◽

Epidemiological Situation

African swine fever (ASF) was introduced to Poland in 2014. Despite the implementation of preventive actions focused on the reduction of wild boar populations and the introduction of biosecurity rules in domestic pig farms, the disease has been continuously spreading to new areas. The aim of this paper was to analyze the dynamics of ASFV spread in wild boar populations in Poland and to summarize the 2019 epidemiological situation. Using a logistic regression model, it has been shown that there is a significant correlation between the month, ASF affected area and ASF prevalence among wild boars. According to EU definitions, Part II and Part III zones had a total of 3065 (65.2%) ASF-positive death wild boars. In addition, there were 36 post-accident (road-killed) wild boars (2.6%) and 612 hunted animals (1.5%) in this area. These results showed the importance of passive surveillance and its advantages overactive surveillance in ASF control and prevention. The data indicated a greater chance of a positive result in the winter months (January, February, March) than in reference September, where the ASF prevalence was the lowest. This observation confirms the preliminary theory about the seasonality of the disease in wild boar populations and its connection with winter.

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African swine fever virus (ASFV) in Poland: Prevalence in a wild boar population (2017–2018)

Veterinární Medicína ◽

10.17221/105/2019-vetmed ◽

2020 ◽

Vol 65 (No. 4) ◽

pp. 143-158 ◽

Cited By ~ 1

Author(s):

MP Frant ◽

M Lyjak ◽

L Bocian ◽

A Barszcz ◽

K Niemczuk ◽

...

Keyword(s):

Wild Boar ◽

Active Surveillance ◽

African Swine Fever Virus ◽

Winter Season ◽

African Swine Fever ◽

Disease Spread ◽

Passive Surveillance ◽

Wild Boar Population ◽

Wild Boars ◽

In The Wild

African swine fever (ASF) was first described in 1921 in Kenya. The latest epidemic of ASF started in 2007 in Georgia. The virus was introduced to Poland in 2014. Since the beginning of the epidemics, the National Veterinary Research Institute in Pulawy (NVRI) has been testing wild boar samples from restricted areas and other parts of Poland to conduct passive and active surveillance for ASFV in these groups of animals. The aim of this study was to summarise the last two years of the ASF epidemiological status in Poland and the attempt to find disease patterns in the wild boar population. The period between 2017 and 2018 brought a massive number of new ASF cases in Poland. The number of ASF-positive wild boars jumped from 91 in 2016 to 1 140 in 2017 (approximately a 12 × increase), and 2018 was even worse, with the disease affecting 4 083 animals (2 435 cases; one case could even be 10 animals or more if they are found in one place next to each other). The percentage of positive wild boars found dead (passive surveillance) in the restricted area increased in 2018 to 73.1% from 70.8% in 2017. The chance of obtaining positive results in this group was six times higher in December and 4.5 times higher in January than in August and September. The percentage of positive wild boars detected through active surveillance reached 1.5% in 2018. The data suggested that, not only in Poland, but also in other ASF-affected countries, during the epizootic stage of the disease spread the most important measure is an effective passive surveillance of dead wild boars especially, in the winter season rather than in the summer.

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African Swine Fever in Two Large Commercial Pig Farms in LATVIA—Estimation of the High Risk Period and Virus Spread within the Farm

Veterinary Sciences ◽

10.3390/vetsci7030105 ◽

2020 ◽

Vol 7 (3) ◽

pp. 105 ◽

Cited By ~ 1

Author(s):

Kristīne Lamberga ◽

Edvīns Oļševskis ◽

Mārtiņš Seržants ◽

Aivars Bērziņš ◽

Arvo Viltrop ◽

...

Keyword(s):

High Risk ◽

Wild Boar ◽

Early Stage ◽

African Swine Fever ◽

Control Measures ◽

Virus Spread ◽

Passive Surveillance ◽

Early Disease Detection ◽

Risk Period ◽

Commercial Farms

African swine fever (ASF) was first detected in Latvia in wild boar at the Eastern border in June 2014. Since then ASF has continued to spread in wild boar populations covering almost whole territory of the country. Sporadic outbreaks occurred at the same time in domestic pig holdings located in wild boar infected areas. Here we present the results of the epidemiological investigation in two large commercial farms. Several parameters were analyzed to determine the high risk period (HRP) and to investigate the ASF virus spread within the farm. Clinical data, mortality rates and laboratory results proved to be good indicators for estimating the HRP. The measures for early disease detection, particularly the enhanced passive surveillance that is targeting dead and sick pigs, were analyzed and discussed. Enhanced passive surveillance proved to be a key element to detect ASF at an early stage. The study also showed that ASF virus might spread slowly within a large farm depending mainly on direct contacts between pigs and the level of internal biosecurity. Findings suggest improvements in outbreak prevention, control measures and may contribute to a better understanding of ASF spreading patterns within large pig herds. Culling of all pigs in large commercial farms could be reconsidered under certain conditions.

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Modelling the Spatial Distribution of ASF-Positive Wild Boar Carcasses in South Korea Using 2019–2020 National Surveillance Data

Animals ◽

10.3390/ani11051208 ◽

2021 ◽

Vol 11 (5) ◽

pp. 1208

Author(s):

Jun-Sik Lim ◽

Timothée Vergne ◽

Son-Il Pak ◽

Eutteum Kim

Keyword(s):

Spatial Distribution ◽

Risk Factor ◽

South Korea ◽

Wild Boar ◽

African Swine Fever Virus ◽

Significant Risk ◽

African Swine Fever ◽

Credible Interval ◽

Imperfect Detection ◽

Wild Boars

In September 2019, African swine fever (ASF) was reported in South Korea for the first time. Since then, more than 651 ASF cases in wild boars and 14 farm outbreaks have been notified in the country. Despite the efforts to eradicate ASF among wild boar populations, the number of reported ASF-positive wild boar carcasses have increased recently. The purpose of this study was to characterize the spatial distribution of ASF-positive wild boar carcasses to identify the risk factors associated with the presence and number of ASF-positive wild boar carcasses in the affected areas. Because surveillance efforts have substantially increased in early 2020, we divided the study into two periods (2 October 2019 to 19 January 2020, and 19 January to 28 April 2020) based on the number of reported cases and aggregated the number of reported ASF-positive carcasses into a regular grid of hexagons of 3-km diameter. To account for imperfect detection of positive carcasses, we adjusted spatial zero-inflated Poisson regression models to the number of ASF-positive wild boar carcasses per hexagon. During the first study period, proximity to North Korea was identified as the major risk factor for the presence of African swine fever virus. In addition, there were more positive carcasses reported in affected hexagons with high habitat suitability for wild boars, low heat load index (HLI), and high human density. During the second study period, proximity to an ASF-positive carcass reported during the first period was the only significant risk factor for the presence of ASF-positive carcasses. Additionally, low HLI and elevation were associated with an increased number of ASF-positive carcasses reported in the affected hexagons. Although the proportion of ASF-affected hexagons increased from 0.06 (95% credible interval (CrI): 0.05–0.07) to 0.09 (95% CrI: 0.08–0.10), the probability of reporting at least one positive carcass in ASF-affected hexagons increased from 0.49 (95% CrI: 0.41–0.57) to 0.73 (95% CrI: 0.66–0.81) between the two study periods. These results can be used to further advance risk-based surveillance strategies in the Republic of Korea.

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Evaluation of the Efficiency of Active and Passive Surveillance in the Detection of African Swine Fever in Wild Boar

Veterinary Sciences ◽

10.3390/vetsci7010005 ◽

2019 ◽

Vol 7 (1) ◽

pp. 5 ◽

Cited By ~ 5

Author(s):

Vincenzo Gervasi ◽

Andrea Marcon ◽

Silvia Bellini ◽

Vittorio Guberti

Keyword(s):

Wild Boar ◽

Active Surveillance ◽

Disease Surveillance ◽

Virus Detection ◽

African Swine Fever ◽

First Year ◽

Passive Surveillance ◽

European Wild Boar ◽

Absolute Probability ◽

Host Parasite

African swine fever (ASF) is one of the most severe diseases of pigs and has a drastic impact on pig industry. Wild boar populations play the role of ASF genotype II virus epidemiological reservoir. Disease surveillance in wild boar is carried out either by testing all the wild boar found sick or dead for virus detection (passive surveillance) or by testing for virus (and antibodies) all hunted wild boar (active surveillance). When virus prevalence and wild boar density are low as it happens close to eradication, the question on which kind of surveillance is more efficient in detecting the virus is still open. We built a simulation model to mimic the evolution of the host-parasite interaction in the European wild boar and to assess the efficiency of different surveillance strategies. We constructed a deterministic SIR model, which estimated the probability to detect the virus during the 8 years following its introduction, using both passive and active surveillance. Overall, passive surveillance provided a much larger number of ASF detections than active surveillance during the first year. During subsequent years, both active and passive surveillance exhibited a decrease in their probability to detect ASF. Such decrease, though, was more pronounced for passive surveillance. Under the assumption of 50% of carcasses detection, active surveillance became the best detection method when the endemic disease prevalence was lower than 1.5%, when hunting rate was >60% and when population density was lower than 0.1 individuals/km2. In such a situation, though, the absolute probability to detect the disease was very low with both methods, and finding almost every carcass is the only way to ensure virus detection. The sensitivity analysis shows that carcass search effort is the sole parameter that increases proportionally the chance of ASF virus detection. Therefore, an effort should be made to promote active search of dead wild boar also in endemic areas, since reporting wild boar carcasses is crucial to understand the epidemiological situation in any of the different phases of ASF infection at any wild boar density.

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Clinical Course and Gross Pathological Findings in Wild Boar Infected with a Highly Virulent Strain of African Swine Fever Virus Genotype II

Pathogens ◽

10.3390/pathogens9090688 ◽

2020 ◽

Vol 9 (9) ◽

pp. 688 ◽

Cited By ~ 1

Author(s):

Antonio Rodríguez-Bertos ◽

Estefanía Cadenas-Fernández ◽

Agustín Rebollada-Merino ◽

Néstor Porras-González ◽

Francisco J. Mayoral-Alegre ◽

...

Keyword(s):

Wild Boar ◽

Clinical Course ◽

African Swine Fever Virus ◽

Virulent Strain ◽

African Swine Fever ◽

Pathological Findings ◽

Wild Boars ◽

Gross Pathology ◽

Highly Virulent ◽

Genotype Ii

African swine fever (ASF) is a notifiable disease that in recent years has spread remarkably in Europe and Asia. Eurasian wild boar (Sus scrofa) plays a key role in the maintenance and spread of the pathogen. Here we examined gross pathology of infection in wild boar with a highly virulent, hemadsorbing genotype II ASF virus (ASFV) strain. To this end, six wild boars were intramuscularly inoculated with the 10 HAD50 Arm07 ASFV strain, and 11 wild boars were allowed to come into direct contact with the inoculated animals. No animals survived the infection. Clinical course, gross pathological findings and viral genome quantification by PCR in tissues did not differ between intramuscularly inoculated or contact-infected animals. Postmortem analysis showed enlargement of liver and spleen; serosanguinous effusion in body cavities; and multiple hemorrhages in lungs, endocardium, brain, kidneys, urinary bladder, pancreas, and alimentary system. These results provide detailed insights into the gross pathology of wild boar infected with a highly virulent genotype II ASFV strain. From a didactic point of view, this detailed clinical course and macroscopic description may be essential for early postmortem detection of outbreaks in wild boar in the field and contribute to disease surveillance and prevention efforts.

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Selected aspects related to epidemiology, pathogenesis, immunity, and control of African swine fever

Journal of Veterinary Research ◽

10.1515/jvetres-2016-0017 ◽

2016 ◽

Vol 60 (2) ◽

pp. 119-125 ◽

Cited By ~ 3

Author(s):

Grzegorz Woźniakowski ◽

Magdalena Frączyk ◽

Krzysztof Niemczuk ◽

Zygmunt Pejsak

Keyword(s):

Wild Boar ◽

Viral Infections ◽

Specific Treatment ◽

African Swine Fever ◽

New Era ◽

Wild Boars ◽

Domestic Pigs ◽

Rate Of Spread ◽

International Transport ◽

Socio Economic Impact

Abstract African swine fever (ASF) is currently one of the most severe viral infections of domestic pigs, wild boars, and other hosts belonging to Suidae family. ASF is also considered as the most complex and devastating infectious and haemorrhagic disease of swine due to its severe socio-economic impact and transboundary character. ASF it is a notifiable disease and due to the lack of specific treatment and vaccine, the disease can be only limited by the administrative measures comprising wild boar hunting and stamping out of affected pigs. ASF occurred for the first time in Kenya in 1921 while in Europe (Portugal) the virus was detected at the end of the 1950s. In spite of successful eradication of this threat in a number of affected regions, the virus remains endemic in both feral and domestic pigs in Africa and Sardinia. The ‘new era’ of ASF started in 2007 after its re-introduction to Georgia. Following its intensive expansion, the virus spread to other Caucasian countries, including the territory of the Russian Federation. In 2014 the virus reached Ukraine, Belarus, and, consequently, European Union countries: Lithuania, Latvia, Estonia, and Poland. The occurrence of ASF in wild boars and pigs had a severe impact on both epidemiology and economy because of the national and international transport and trade consequences. Up to date, starting from the February 2014, eighty ASF cases in wild boar and three outbreaks in domestic pigs have been diagnosed. Taking into account the diverse rate of spread in Poland, this review aims to present and discuss the current state of knowledge on ASF including its epidemiology, pathology, transmission, and perspectives of control.

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R0 Estimation for the African Swine Fever Epidemics in Wild Boar of Czech Republic and Belgium

Veterinary Sciences ◽

10.3390/vetsci7010002 ◽

2019 ◽

Vol 7 (1) ◽

pp. 2 ◽

Cited By ~ 4

Author(s):

Andrea Marcon ◽

Annick Linden ◽

Petr Satran ◽

Vincenzo Gervasi ◽

Alain Licoppe ◽

...

Keyword(s):

Czech Republic ◽

Wild Boar ◽

African Swine Fever ◽

Reliable Data ◽

Control Measures ◽

Passive Surveillance ◽

Wild Populations ◽

Wild Pigs ◽

Eradication Strategy ◽

Growth Method

African swine fever (ASF) is a contagious haemorrhagic fever that affects both domesticated and wild pigs. Since ASF reached Europe wild boar populations have been a reservoir for the virus. Collecting reliable data on infected individuals in wild populations is challenging, and this makes it difficult to deploy an effective eradication strategy. However, for diseases with high lethality rate, infected carcasses can be used as a proxy for the number of infected individuals at a certain time. Then R0 parameter can be used to estimate the time distribution of the number of newly infected individuals for the outbreak. We estimated R0 for two ASF outbreaks in wild boar, in Czech Republic and Belgium, using the exponential growth method. This allowed us to estimate both R0 and the doubling time (Td) for those infections. The results are R0 = 1.95, Td = 4.39 for Czech Republic and R0 = 1.65, Td = 6.43 for Belgium. We suggest that, if estimated as early as possible, R0 and Td can provide an expected course for the infection against which to compare the actual data collected in the field. This would help to assess if passive surveillance is properly implemented and hence to verify the efficacy of the applied control measures.

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African swine fever (ASF) in wild boar

Medycyna Weterynaryjna ◽

10.21521/mw.6148 ◽

2018 ◽

Vol 74 (12) ◽

pp. 6148-2018

Author(s):

ZYGMUNT PEJSAK ◽

MARIAN TRUSZCZYŃSKI ◽

KAZIMIERZ TARASIUK

Keyword(s):

Early Detection ◽

Wild Boar ◽

Large Scale ◽

Current Knowledge ◽

African Swine Fever ◽

The European Union ◽

Passive Surveillance ◽

Surveillance Strategy ◽

Feral Pigs ◽

Scientific Opinion

This paper contains main points of the scientific opinion prepared by EFSA in 2018 on the request of the European Commission on the ASF epidemic in wild boar in Eastern – Central Europe, which started in 2014 and is existing and increasing until the present time. The first point is providing an estimate of the wild boar density in the European Union (EU). The next item is presenting the opinion on the latest epidemiological data to identify thresholds in wild boar density that do not allow sustaining the disease in different settings. The third question and answer concerns wild boar and feral pigs depopulation methods or population reduction methods. The fourth chapter is reviewing fencing methods demonstrating to temporarily protect crops from damage, caused by wild boar or feral swine. Currently there is no evidence , that large –scale fences have been effective for the containment of wild boar or feral pigs. The answer to the fifth question on surveillance strategy contains information on sample size, frequency of sampling and identification of possible risk groups for early detection of ASFV in naïve wild boar population. Passive surveillance is according to the opinion of EFSA the most effective and efficient method of surveillance for early detection of ASF in wild boar. For early detection through passive surveillance , the aim is to test as many “found dead” animals as possible. Based on current knowledge and experiences for an intervention to be successful, there is a need to detect an ASF incursion while it is spatially contained. The sixth topic of the EFSA scientific opinion requests to review successful methodologies used in the past, as for example the mentioned passive surveillance. It is recommended that this should be done in discussion among specialists from the UE countries. Good collaborations with hunters is recommended.

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

Animals ◽

10.3390/ani11020525 ◽

2021 ◽

Vol 11 (2) ◽

pp. 525

Author(s):

Evelina Stončiūtė ◽

Katja Schulz ◽

Alvydas Malakauskas ◽

Franz J. Conraths ◽

Marius Masiulis ◽

...

Keyword(s):

Wild Boar ◽

Surveillance System ◽

African Swine Fever ◽

Study Data ◽

Control Measures ◽

Attitudes And Beliefs ◽

Passive Surveillance ◽

Wild Boar Population ◽

In The Wild ◽

Governmental Institutions

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.

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