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African swine fever (ASF) has been present in Estonia since 2014, and pigkeepers play a major role in controlling the spread of viral infection in domestic pigs. Participatory epidemiology may provide insight into livestock keepers' existing attitudes and compliance with implementing control strategies. By conducting focus group discussions and using participatory epidemiology tools, this study aimed to reveal pigkeepers' knowledge and awareness of ASF clinical signs, transmission routes, and preventive measures. Furthermore, opinions including trust in stakeholders in ASF control, acceptability of ASF eradication, and control measures by pigkeepers in Estonia were identified. The most indicative ASF signs in pigs were "increased mortality" and "fever, inappetence, lethargy". The highest risk of virus introduction into the herd was designated to "agricultural machinery, vehicles", "rodents, birds, insects", and "people". "Fencing" was the most liked ASF preventive measure, while "training of staff in biosecurity and informing the visitors" was considered the most effective measure. The least accepted ASF eradication measure was "culling of all animals on the farm". Generally, pigkeepers perceived that healthy animals should not be culled but only ASF-infected pigs. Additionally, healthy pigs could be slaughtered and used for the production of heat-treated canned meat. "Destroying the feed" of ASF-infected farms was not favoured because some pigkeepers proposed using it for other animal species. Regarding ASF territorial restrictions (zoning), "lower meat prices" and "economic losses" were regarded as consequences with the greatest impact. Pigkeepers ranked trust in "Veterinary Authority and Ministry of Rural Affairs" regarding their role in ASF prevention and control as high while perceiving themselves as the most trustworthy stakeholder within the ASF network. This study demonstrates a generally good level of awareness among the pigkeepers in Estonia concerning the clinical manifestation of ASF, the most relevant transmission routes of the virus for their farms, and preventive measures for ASF. Pigkeepers are aware of their own role in preventing ASF, and there is a high level of trust between them and government authorities. Additional efforts are needed from authorities to communicate better the purpose of some ASF control and eradication measures to the pigkeepers. Further incentives are required to support the implementation of costly biosecurity measures, assure compliance, and mitigate the consequences of these measures., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

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.

African swine fever (ASF) was first identified in Estonia in 2014, initially detected in wild boar and spreading to affect almost the whole country from late 2016 onwards. Passive surveillance and the control measures applied in Estonia are the main actions in the attempt to control the wild boar population and therefore limit the spread of ASF. Implementation and success of both activities depend mainly on the involvement and commitment of the executing force: the Estonian hunters. Thus, their acceptance of the measures is of utmost importance and with the help of participatory methods, their acceptability can be assessed. Participatory epidemiology allows the involvement of key stakeholders in planning control measures and surveillance strategies and gathering information otherwise inaccessible. By conducting focus group discussions and utilizing participatory tools, this study aimed to assess the acceptance of ASF control measures by hunters in Estonia. Furthermore, the study aimed to detect means to improve the motivation of hunters to support passive surveillance. Among hunters, the results ranked the trust in lower authorities (e.g. local official veterinarians) towards implementing control measures as high (in contrast to higher officials e.g. 'Ministry of Rural Affairs'), while perceiving themselves as the most trustworthy group among those implementing ASF control measures. Hunting and every measure supporting increased hunting, for example selective hunting, bait feeding and incentives for hunting wild boar, were deemed favourable for hunters. These measures also received the highest trust for controlling ASF. All measures hindering hunting and the movement of wildlife, for example fencing or involvement of the army in ASF control, were described as unpleasant or even unethical and trust in these measures to control the disease successfully was lacking. When assessing the perceived consequences for hunters of finding a dead wild boar, arising financial costs, additional workload and time consumption were highlighted. In line with these results, the two tools with the strongest motivational effect for taking part in passive surveillance were: (1) higher monetary incentives as compensation for the hunters' work, and (2) the reduction of the negative consequences by limiting the hunters' duties to solely reporting found dead wild boar. In conclusion, participatory methods can be used as a highly suitable tool for the evaluation of acceptance of measures and surveillance systems. Potentially, the results can help to improve control and passive surveillance in Estonia, as well as functioning as an example for other countries battling or awaiting ASF., (Copyright © 2020 Elsevier B.V. All rights reserved.)

African swine fever (ASF) was first detected in the Estonian wild boar population in September 2014, while the first domestic pig farm was affected in July 2015. In the present study, we aimed to analyse, retrospectively, the epidemiology of the disease in all 26 outbreaks in domestic pig herds that occurred in Estonia during the period 2015-2017. Formal interviews were conducted to estimate the high-risk period for every farm, and to identify the possible origin of the ASF virus and the mode of virus introduction. Furthermore, the clinical manifestation of the disease as well as the course of the disease within the farm were investigated. Survival analysis was used to calculate herd incidence and to estimate outbreak risk. A hierarchical Bayesian space-time model was used to analyse the associations between outbreaks and ASF occurrence in wild boar. The spatial and temporal distribution of outbreaks was analysed to characterise the ASF epidemic in the Estonian domestic pig population from 2015 to 2017. The estimated high-risk period varied from seven to 20 days with a median of 11 days. On most of the affected farms, the first clinical signs were mild and not specific to ASF despite the high virulence of the circulating virus. Morbidity and mortality were often limited to a single pen or unit of the farm. The highest mortality (29.7%) was seen on backyard farms with 1-10 pigs and the lowest (0.7%) on large commercial farms (>1000 pigs). The spread of the virus within affected farms has been slow and the contagiousness of the virus has been relatively low. Farms of all sizes and types have been at risk, including large commercial farms operating at a high biosecurity level. In none of the affected farms could the specific route of introduction be verified. However, the findings suggested that virus introduction occurred via indirect transmission routes due to insufficient biosecurity. The total herd incidence of outbreaks was similar across all three years, being 2.4% in 2015 and 2016, and 2.0% in 2017. All outbreaks occurred from June to September, during the warmest period of the year. The results suggest that the increase in ASF cases in local wild boar populations is the main risk factor leading to the infection of farms; 88% of outbreaks occurred in areas where ASF virus was detected in wild boar prior to the outbreak, within a radius of 15 km from the outbreak farm., (Copyright © 2018 Elsevier B.V. All rights reserved.)

African swine fever (ASF) in wild boar populations is difficult to control. In affected areas, samples from all wild boar shot and found dead are investigated. The use of laboratory tests allows estimating the duration of the infection in affected animals. The study aimed to test the hypothesis that the stage of the epidemic in different areas of Estonia can be assessed on the basis of prevalence estimates. ASF surveillance data of Estonian wild boar were used to estimate prevalences and compare them between the East and West of Estonia. The temporal trend of the estimated prevalence of ASF virus positive animals and of the estimated seroprevalence of wild boar showing antibodies against ASFV was analyzed. Due to the potential influence of population density on the course of ASF in wild boar, also population density data (number of wild boar/km 2 ) were used to investigate the relationship with laboratory test results. In areas, where the epidemic had already lasted for a long time, a small number of new cases emerged recently. The prevalence of samples that were only seropositive was significantly higher in these regions as compared to areas, where the epidemic is in full progress. The observed course of the disease could be the beginning of an ASF endemicity in this region. However, the results may also indicate that ASF has started to subside in the areas that were first affected in Estonia.

African swine fever (ASF) in wild boar emerged in Estonia for the first time in September 2014. The first affected region was located in the South of Estonia close to the border with Latvia. It was considered to be epidemiologically connected to the outbreaks in the North of Latvia. About two weeks later, cases were detected in the North of Estonia, close to the Russian border. In the present study, we aimed to investigate the epidemiological courses of the disease in the South and in the North of Estonia. Potential associations between risk factors and the laboratory test results for ASF were examined. A hierarchical Bayesian space-time model was used to analyze the temporal trend of the ASF seroprevalence in the two areas. Young wild boar were statistically significant more likely to be ASF-positive by both, serology and virus detection, than older animals. A statistically significant difference between the two areas in the temporal course of the seroprevalence was found. While the seroprevalence clearly increased in the South, it remained relatively constant in the North. These findings led to the hypothesis that ASF might have been introduced earlier into the North of Estonia then into the South of the country.