African swine fever in the Lithuanian wild boar population in 2018: a snapshot

Abstract The first cases of African swine fever (ASF) were detected in the Lithuanian wild boar population in 2014. Since then, the disease spread slowly through the whole country, affecting both, wild boar and domestic pigs. In the other Baltic states, which both are also affected by ASF since 2014, the recent course of ASF prevalence suggests that the countries might be well under way of disease elimination. In contrast, in Lithuania the epidemic seems to be still in full progress. In the present study, we aimed to extend a previous prevalence study in Lithuania. Looking at ASF virus (ASFV) and seroprevalence estimates of wild boar in all months of 2018 and in all affected municipalities in Lithuania, the course of ASF was evaluated on a temporal and spatial scale. A non-spatial beta-binomial model was used to correct for under- or overestimation of the average prevalence estimates. Within 2018 no big differences between the prevalence estimates were seen over time. Despite of the lower sample size, highest ASFV prevalence estimates were found in dead wild boar, suggesting higher detection rates through passive surveillance than through active surveillance. Accordingly, with the maximum prevalence of 87.5% in May 2018, the ASFV prevalence estimates were very high in wild boar found dead. The number of samples originating from hunted animals (active surveillance) predominated clearly. However, the ASFV prevalence in those animals was lower with a maximum value of 2.1%, emphasizing the high value of passive surveillance. A slight increase of the seroprevalence in hunted wild boar could be seen over time. In the center of Lithuania, a cluster of municipalities with high ASFV and seroprevalence estimates was found. The results of the study indicate that ASFV is still circulating within the Lithuanian wild boar population, constituting a permanent risk of disease transmission into domestic pig holdings. However, additional, more recent data analyses are necessary to re-evaluate the course of ASF in Lithuania and thus, to be able to make a statement about the stage of the ASF epidemic in the country. This is of huge importance for Lithuania for evaluating control measures and their efficacy, but also for neighbouring countries to assess the risk of disease spread from Lithuania.

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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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The African Swine Fever Epidemic in Wild Boar (Sus scrofa) in Lithuania (2014–2018)

Veterinary Sciences ◽

10.3390/vetsci7010015 ◽

2020 ◽

Vol 7 (1) ◽

pp. 15 ◽

Cited By ~ 1

Author(s):

Petras Mačiulskis ◽

Marius Masiulis ◽

Gediminas Pridotkas ◽

Jūratė Buitkuvienė ◽

Vaclovas Jurgelevičius ◽

...

Keyword(s):

Wild Boar ◽

Population Decline ◽

African Swine Fever ◽

Control Measures ◽

Disease Spread ◽

Wild Boar Population ◽

Baltic States ◽

Long Distance ◽

First Case ◽

The Baltic

In January 2014 the first case of African swine fever (ASF) in wild boar of the Baltic States was reported from Lithuania. It has been the first occurrence of the disease in Eastern EU member states. Since then, the disease spread further affecting not only the Baltic States and Poland but also south-eastern Europe, the Czech Republic and Belgium. The spreading pattern of ASF with its long-distance spread of several hundreds of kilometers on the one hand and the endemic situation in wild boar on the other is far from being understood. By analyzing data of ASF cases in wild boar along with implemented control measures in Lithuania from 2014–2018 this study aims to contribute to a better understanding of the disease. In brief, despite huge efforts to eradicate ASF, the disease is now endemic in the Lithuanian wild boar population. About 86% of Lithuanian’s territory is affected and over 3225 ASF cases in wild boar have been notified since 2014. The ASF epidemic led to a considerable decline in wild boar hunting bags. Intensified hunting might have reduced the wild boar population but this effect cannot be differentiated from the population decline caused by the disease itself. However, for ASF detection sampling of wild boar found dead supported by financial incentives turned out to be one of the most effective tools.

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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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A Comparison of Perceptions of Estonian and Latvian Hunters With Regard to the Control of African Swine Fever

Frontiers in Veterinary Science ◽

10.3389/fvets.2021.642126 ◽

2021 ◽

Vol 8 ◽

Author(s):

Nico Urner ◽

Carola Sauter-Louis ◽

Christoph Staubach ◽

Franz Josef Conraths ◽

Katja Schulz

Keyword(s):

Wild Boar ◽

Group Discussion ◽

African Swine Fever ◽

Control Measures ◽

Disease Spread ◽

Successful Implementation ◽

Participatory Methods ◽

The European Union ◽

Passive Surveillance ◽

Participatory Epidemiology

Since the first detected African swine fever (ASF) cases in Lithuanian wild boar in 2014, the virus has occurred in many other member states of the European Union (EU), most recently in Belgium in 2018 and in Germany in 2020. Passive surveillance and various control measures are implemented as part of the strategy to stop disease spread in the wild boar population. Within this framework, hunters perform important activities, such as the removal of carcasses, fencing or hunting. Therefore, the successful implementation of these measures largely depends on their acceptability by hunters. Methods of participatory epidemiology can be used to determine the acceptance of control measures. The use of participatory methods allows the involvement of key stakeholders in the design, the implementation and the analysis of control and surveillance activities. In the present study, two studies that had been conducted using participatory epidemiology with hunters in Estonia and Latvia were compared on the topics recruitment, participants, facilitators, focus group discussion (FGDs) and their contents. The aim was to evaluate similarities and differences in the two studies and to identify a broader spectrum of possibilities to increase the willingness of hunters supporting the fight against ASF. Evaluating all conducted FGDs in both countries showed primarily similarities in the perceptions and opinions of the hunters in Estonia and Latvia. One notable difference was that passive surveillance in Latvia was perceived mostly as topic of duty and ethics rather than an issue driven by incentives. Participatory methods have proven to be an effective tool in the evaluation of the acceptance of established ASF control systems. The results of this study point out further chances for improving the cooperation with hunters in the future. Nevertheless, the importance of gathering and analyzing the opinions of hunters in all ASF affected countries individually is highlighted.

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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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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 Status in Europe

Viruses ◽

10.3390/v11040310 ◽

2019 ◽

Vol 11 (4) ◽

pp. 310 ◽

Cited By ~ 34

Author(s):

Przemyslaw Cwynar ◽

Jane Stojkov ◽

Klaudia Wlazlak

Keyword(s):

Eastern Europe ◽

Wild Boar ◽

Western Europe ◽

African Swine Fever ◽

Disease Spread ◽

Wild Boar Population ◽

Domestic Pig ◽

Domestic Pigs ◽

In The Wild ◽

Virus Spreading

African Swine Fever (ASF) is a highly contagious disease that affects the domestic pig and wild boar population. The aim of this study was to describe the introduction and spread of the ASF virus in Western Europe (1960–1995) and in Eastern Europe (2007–2018), with particular emphasis on the current ASF situation in Poland and its challenges and future perspectives. The first ASF outbreak in Europe was reported in Portugal in 1957, with the virus spreading over most of Western Europe over the next 30 years. In Eastern Europe, the virus was first observed in Georgia in 2007, from where the disease spread quickly to other neighboring countries, reaching Poland in 2014. Since then, there have been 3341 confirmed cases in the wild boar population in Poland. Although there have been no confirmed cases of wild boars coming into contact with domestic pigs, the first notified case concerning domestic pigs was reported in July 2014. Since then, there have been a total of 213 confirmed outbreaks of ASF on Polish pig farms. Given the virulence of the ASF virus and the myriad of transmission routes across Europe, the monitoring of this disease must be a priority for Europe.

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African Swine Fever: Disease Dynamics in Wild Boar Experimentally Infected with ASFV Isolates Belonging to Genotype I and II

Viruses ◽

10.3390/v11090852 ◽

2019 ◽

Vol 11 (9) ◽

pp. 852 ◽

Cited By ~ 11

Author(s):

Sánchez-Cordón ◽

Nunez ◽

Neimanis ◽

Wikström-Lassa ◽

Montoya ◽

...

Keyword(s):

Immune Response ◽

Wild Boar ◽

Western Europe ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Relevant Information ◽

Disease Spread ◽

Wild Boar Population ◽

Disease Pathogenesis ◽

Genotype I

After the re-introduction of African swine fever virus (ASFV) genotype II isolates into Georgia in 2007, the disease spread from Eastern to Western Europe and then jumped first up to Mongolian borders and later into China in August 2018, spreading out of control and reaching different countries of Southeast Asia in 2019. From the initial incursion, along with domestic pigs, wild boar displayed a high susceptibility to ASFV and disease development. The disease established self-sustaining cycles within the wild boar population, a key fact that helped its spread and that pointed to the wild boar population as a substantial reservoir in Europe and probably also in Asia, which may hinder eradication and serve as the source for further geographic expansion. The present review gathers the most relevant information available regarding infection dynamics, disease pathogenesis and immune response that experimental infections with different ASFV isolates belonging to genotype I and II in wild boar and feral pigs have generated. Knowledge gaps in areas such as disease pathogenesis and immune response highlights the importance of focusing future studies on unravelling the early mechanisms of virus-cell interaction and innate and/or adaptive immune responses, knowledge that will contribute to the development of efficacious treatments/vaccines against ASFV.

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African Swine Fever in Wild Boar in Europe—A Review

Viruses ◽

10.3390/v13091717 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1717

Author(s):

Carola Sauter-Louis ◽

Franz J. Conraths ◽

Carolina Probst ◽

Ulrike Blohm ◽

Katja Schulz ◽

...

Keyword(s):

Wild Boar ◽

Case Fatality ◽

African Swine Fever ◽

Hemorrhagic Fever ◽

Spatial Behavior ◽

Control Measures ◽

Disease Spread ◽

Domestic Pigs ◽

In The Wild ◽

Socio Economic Impact

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

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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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