Control Of African Swine Fever Research Articles

African swine fever virus vaccine candidate ASFV-G-ΔI177L efficiently protects European and native pig breeds against circulating Vietnamese field strain.

The recent spread of African swine fever (ASF) in the People's Republic of China and neighbouring countries in Asia has had significant economic consequences with an estimated direct cost of $55-$130 billion. This pandemic, originally detected in Republic of Georgia in 2007, has devastated the swine industry in large geographical areas of Southeast Asia with 14 countries reporting ASF outbreaks since the first documented case was confirmed in the city of Shenyang, Liaoning Province, China, on 3 August 2018. In the absence of any available vaccines, the control of ASF relies on the detection and culling of infected animals. The United States Department of Agriculture recently developed a recombinant experimental vaccine candidate, ASFV-G-ΔI177L, by deleting the I177L gene from the genome of the highly virulent pandemic ASFV strain Georgia, which efficaciouly protects pigs from the parental virus. Here, the initial studies were extended demonstrating that ASFV-G-ΔI177L is able to protect pigs against the virulent ASFV isolate currently circulating and producing disease in Vietnam with similar efficacy as reported against the Georgia strain. Comparative studies performed using a large number of pigs of European and Vietnamese origin demonstrated that a minimum protective dose of 102 HAD50 of ASFV-G-ΔI177L equally protects animals of both breeds. In concurrence with those results, the onset of immunity in these animal breed showed appearance of protection in approximately one-third of the animals by the second week post vaccination, with full protection achieved by the fourth week post vaccination. Therefore, results presented here demonstrated that ASFV-G-ΔI177L is able to induce protection against virulent Vietnameese ASFV field strains and is effective in protecting local breeds of pigs as efficiently as previously shown for European cross-bred pigs. To our knowledge, this is the first report showing the efficacy of a Georgia 2007 based vaccine candidate in Asian breed of pigs or challenged with an Asian ASFV strain.

Modelling the role of mortality-based response triggers on the effectiveness of African swine fever control strategies.

African swine fever (ASF) is considered the most impactful transboundary swine disease. In the absence of effective vaccines, control strategies are heavily dependent on mass depopulation and shipment restrictions. Here, we developed a nested multiscale model for the transmission of ASF, combining a spatially explicit network model of animal shipments with a deterministic compartmental model for the dynamics of two ASF strains within 3 km × 3 km pixels in one Brazilian state. The model outcomes are epidemic duration, number of secondary infected farms and pigs, and distance of ASF spread. The model also shows the spatial distribution of ASF epidemics. We analyzed quarantine-based control interventions in the context of mortality trigger thresholds for the deployment of control strategies. The mean epidemic duration of a moderately virulent strain was 11.2 days, assuming the first infection is detected (best-case scenario), and 15.9 days when detection is triggered at 10% mortality. For a highly virulent strain, the epidemic duration was 6.5 days and 13.1 days, respectively. The distance from the source to infected locations and the spatial distribution was not dependent on strain virulence. Under the best-case scenario, we projected an average number of infected farms of 23.77 farms and 18.8 farms for the moderate and highly virulent strains, respectively. At 10% mortality-trigger, the predicted number of infected farms was on average 46.27 farms and 42.96 farms, respectively. We also demonstrated that the establishment of ring quarantine zones regardless of size (i.e. 5km, 15km) was outperformed by backward animal movement tracking. The proposed modelling framework provides an evaluation of ASF epidemic potential, providing a ranking of quarantine-based control strategies that could assist animal health authorities in planning the national preparedness and response plan.

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

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

Identification of one novel epitope targeting p54 protein of African swine fever virus using monoclonal antibody and development of a capable ELISA

African swine fever (ASF) is one of the most lethal viral diseases affecting both domestic pigs and wild boars. The acute infection of the ASF disease in domestic pigs leads to a 100% mortality rate with symptoms including high fever, vascular changes, cyanosis of the skin. Until now, there are no commercial vaccines and antiviral drugs available for ASF control. Therefore, the spread of ASF poses great economic losses to the pig industry and the ecosystems in the affected countries. A rapid and capable method was urgently needed to monitor ASFV-specific antibodies for controlling the spread of ASFV. In this study, we obtained one strain of monoclonal antibody (mAb) against the p54 protein of ASFV, and the target epitope of the mAb was determined to be 175YTHKDLENSL184. The experimental results demonstrated that the monoclonal antibody could successfully recognize the exogenously expressed p54 protein and the chimeric virus constructed in our laboratory. The mAb could be used as a detection tool for the development of ASF vaccine strains. In addition, the ELISA established by using the obtained synthetic epitope peptide as the antigen had high sensitivity, good specificity and showed the great potential for ASF epidemic monitoring and control.

Efficient inactivation of African swine fever virus by a highly complexed iodine

African swine fever (ASF) is a highly lethal contagious disease of swine caused by African swine fever virus (ASFV). Cleaning and disinfection remain one of the most effective tools to prevent the ASFV spread in pig holdings. This study evaluated the inactivation effect of a highly complexed iodine (HPCI) disinfectant against ASFV. A commercially available povidone-iodine (PVP-I) was used as reference for comparison. The results showed that 5% HPCI and 5% PVP-I did not exhibit cytotoxicity in primary porcine alveolar macrophages, and 107.0 and 105.0 TCID50/mL ASFV were completely inactivated by 5% and 0.25% HPCI, respectively, in 5 min via either immersion or spray disinfection. However, 5% PVP-I required at least 15 min to completely inactivate 107.0 TCID50/mL ASFV, whereas 0.25% PVP-I failed to completely inactivate 105.0 TCID50/mL ASFV. This study demonstrated that HPCI could rapidly and efficiently inactivate ASFV, representing an effective disinfectant for ASF control.

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

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

The Context of Application of Biosecurity for Control of African Swine Fever in Smallholder Pig Systems: Current Gaps and Recommendations.

African swine fever (ASF) is a highly fatal disease of pigs. It is a threat to the pig industry as it lowers production and significantly impacts on livelihoods. ASF has no cure and a vaccine against it is yet to be developed. Outbreaks continue to be reported in Africa and Asia, where the setting of the pig value chain (farm, market, and slaughter practices) coupled with the risky behaviors of actors, contribute to persistence of the virus in pig populations. The role of these factors in the epidemiology of the disease is reviewed with a focus on smallholder pig systems in Africa. Biosecurity at the farm level is particularly emphasized, and factors influencing its adoption highlighted. Socio-cultural factors and weaknesses at the disease control policy level are critical and should not be ignored. Gender and equity are important aspects and ought to be considered in discussions to improve the sector. The findings are expected to define priorities for interventions to improve pig productivity (as these regions wait for the vaccine to be developed).

Molecular characterization of African Swine fever viruses in Burkina Faso, Mali, and Senegal 1989-2016: Genetic diversity of ASFV in West Africa.

African swine fever (ASF) has been endemic in sub-Saharan Africa since the 1960s. Following its introduction in Senegal, in 1957, ASF steadily progressed through West Africa, reaching Burkina Faso in 2003, and later Mali in 2016. Despite the heavy burden of disease on pig production, little information is available on the genetic diversity of Africa swine fever virus (ASFV) in Burkina Faso, Mali and Senegal. Here, we used real-time PCR ASFV to detect the ASFV genome in samples collected between 1989 and 2016, in Burkina Faso, Mali and Senegal, and conventional approaches for isolate characterization. The C-terminal end of the p72 protein gene, the full E183L gene and the central variable region (CVR) within the B602L gene in ASFV genome were sequenced and compared to publicly available sequences. ASFV genome was found in 27 samples, 19 from Burkina Faso, three from Mali and five from Senegal. The phylogenetic analyses showed that all viruses belong to genotype I, with the ASFVs from Burkina Faso and Mali grouping with genotype Ia and ASFV serogroup 4, and those from Senegal with genotype Ib and the ASFV serogroup 1. The analysis of the CVR tetrameric tandem repeat sequences (TRS) showed four TRS variants in Burkina Faso, two in Senegal and one in Mali. The three countries did not share any common TRS, and all CVRs of this study differed from previously reported CVRs in West Africa, except for Senegal. Three of the five isolates from Senegal fully matched with the CVR, p72 and p54 sequences from ASFV IC96 collected during the 1996 ASF outbreak in Ivory Coast. This study shows the spread of the same ASFV strains across countries, highlighting the importance of continuous monitoring of ASFV isolates. It also calls for an urgent need to establish a regional plan for the control and eradication of ASF in West Africa.

Rapid and sensitive RPA-Cas12a-fluorescence assay for point-of-care detection of African swine fever virus

African swine fever (ASF) is a serious contagious disease that causes fatal haemorrhagic fever in domestic and wild pigs, with high morbidity. It has caused devastating damage to the swine industry worldwide, necessitating the focus of attention on detection of the ASF pathogen, the African swine fever virus (ASFV). In order to overcome the disadvantages of conventional diagnostic methods (e.g. time-consuming, demanding and unintuitive), quick detection tools with higher sensitivity need to be explored. In this study, based on the conserved p72 gene sequence of ASFV, we combined the Cas12a-based assay with recombinase polymerase amplification (RPA) and a fluorophore-quencher (FQ)-labeled reporter assay for rapid and visible detection. Five crRNAs designed for Cas12a-based assay showed specificity with remarkable fluorescence intensity under visual inspection. Within 20 minutes, with an initial concentration of two copies of DNA, the assay can produce significant differences between experimental and negative groups, indicating the high sensitivity and rapidity of the method. Overall, the developed RPA-Cas12a-fluorescence assay provides a fast and visible tool for point-of-care ASFV detection with high sensitivity and specificity, which can be rapidly performed on-site under isothermal conditions, promising better control and prevention of ASF.

A Semiautomated Luciferase Immunoprecipitation Assay for Rapid and Easy Detection of African Swine Fever Virus Antibody.

African swine fever (ASF) is a highly contagious viral disease of domestic pigs and wild boars. For disease surveillance and control, we developed a rapid and easy luciferase immunoprecipitation assay (MB-LIPS) to detect ASF virus (ASFV) antibody. The MB-LIPS is based on magnetic beads modified with protein A/G and the recombinant fusion protein of ASFV p30 and luciferase, where p30 functioned as the recognition element and luciferase as the signal component. Incubation and washing could be finished automatically on a machine with magnetic rods. Under optimal conditions, the MB-LIPS showed 96.3% agreement to a commercial enzyme-linked immunosorbent assay (ELISA) kit for detecting ASFV antibody in swine sera. Analyzing serial dilutions of a swine serum sample showed that the MP-LIPS assay was 4 times more sensitive than the ELISA kit. The whole run of the MB-LIPS could be completed within 30 min. With its high sensitivity and simple operation, the MB-LIPS platform has great potential to be used for the detection of ASFV antibody and ASF control in small labs and farms.

Research priorities to fill knowledge gaps in wild boar management measures that could improve the control of African swine fever in wild boar populations

The European Commission asked EFSA to provide study designs for the investigation of four research domains (RDs) according to major gaps in knowledge identified by EFSA in a report published in 2019: (RD 1) African swine fever (ASF) epidemiology in wild boar; (RD 2) ASF transmission by vectors; (RD 3) African swine fever virus (ASFV) survival in the environment, and (RD 4) the patterns of seasonality of ASF in wild boar and domestic pigs in the EU. In this Scientific Opinion, the second RD on ASF epidemiology in wild boar is addressed. Twenty‐nine research objectives were proposed by the working group and broader ASF expert networks and 23 of these research objectives met a prespecified inclusion criterion. Fourteen of these 23 research objectives met the predefined threshold for selection and so were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time‐frame study (< 1 year); (5) the novelty of the study; and (6) if it was a priority for risk managers. Finally, after further elimination of three of the proposed research objectives due to overlapping scope of studies published during the development of this opinion, 11 research priorities were elaborated into short research proposals, considering the potential impact on ASF management and the period of one year for the research activities.

African Swine Fever and Its Epidemiological Course in Lithuanian Wild Boar.

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

Estimating the basic reproduction number for the 2019/20 African swine fever epidemics in wild boars in the Republic of Korea

Since the first detection of African swine fever (ASF)-infected wild boar in October 2019, the ASF virus has been circulating among wild boars in the Republic of Korea. The priority for ASF control is to understand the epidemic situation correctly. The basic reproduction number (R0) can be used to describe the contagious disease epidemic situation since it can assess the contagiousness of infectious agents by presenting the average number of new cases generated by an infected case. The current study estimated R0 for the 2019/20 ASF epidemics in wild boars in the Republic of Korea using the reported number of ASF cases and a serial interval of the ASF virus. The estimated mean R0 was 2.10 (range: 0.06 – 10.24) for the 2019/20 ASF epidemics, 2.94 (range: 0.43 – 9.89) for the 2019 ASF epidemics, and 2.00 (range: 0.06 – 11.10) for the 2020 ASF epidemics. In addition, the estimated mean R0 was 3.82 (range: 1.16 – 8.78) in winter, 1.39 (range: 0.16 – 6.30) in spring, 4.82 (range: 0.26 – 17.08) in summer, and 2.21 (range: 0.51 – 5.86) in fall. Even though the Korean government has applied ASF control measures, including hunting or fencing, the ASF epidemic situation in wild boars has intensified. For ASF control in wild boars, tailor-made hunting, wild boar management, or active searching for carcasses are required to reduce the ASF virus. For ASF prevention in domestic pigs, no contact between wild boars and domestic pigs and a biosecurity plan by veterinarians are needed to decrease the risk of ASF virus transmission from wild boars to domestic pigs.

Digital Extension Interactive Voice Response (IVR) mLearning: Lessons Learnt From Uganda Pig Value Chain.

We assessed the effectiveness of Interactive Voice Response (IVR) technology in delivering biosecurity messages for the control of African swine fever (ASF) in Uganda using a randomized controlled trial (RCT) with 408 smallholder pig farmers. Our results show that IVR technology significantly improved knowledge of farmers who had not been exposed to training on biosecurity. Furthermore, it enhanced knowledge for farmers who had received face-to-face (f2f) training in biosecurity. This group of farmers recorded the highest knowledge gain following IVR training compared to farmers who did not receive f2f training. IVR technology was perceived by farmers as a new technology capable of transforming their lives because it is time efficient, has high potential for resource saving and flexibility. IVR also seems to be gender sensitive as it addresses some of the constraints women face in accessing conventional extension services such as time. IVR is an innovative way for delivery of advisory information to pig farmers. The scalability of IVR technology could further be explored and its feasibility assessed for wider use by the extension systems in Uganda and elsewhere.

Research priorities to fill knowledge gaps in the control of African swine fever: possible transmission of African swine fever virus by vectors.

The European Commission requested that EFSA provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: (i) the patterns of seasonality of African Swine Fever (ASF) in wild boar and domestic pigs in the EU; (ii) the epidemiology of ASF in wild boar; (iii) survival of ASF virus (ASFV) in the environment and (iv) transmission of ASFV by vectors. In this Scientific Opinion, the fourth research domain on ASFV transmission by vectors is addressed. Eleven research objectives were proposed by the EFSA working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the 11 research objectives, six were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time‐frame study (< 1 year); (5) the novelty of the study and (6) if it was a priority for risk managers. The prioritised research objectives were: (I) Studies on the potential vector fauna at the pig–wild boar interface and the feeding preference of blood‐feeding potential vectors in ASF‐affected areas; (II) Assessment of the efficacy of insect screens on indoor/outdoor pig holdings to prevent the entry of blood‐sucking vectors (i.e. Stomoxys) in ASF endemic areas; (III) Assess the role of mechanical vectors in the virus transmission in ASF‐affected areas; (IV) Distribution of the potential mechanical transmission vectors in ASF‐affected areas of the EU; (V) ASFV transmission by synanthropic birds; and (VI) Assessment on the presence/absence of the soft tick Ornithodoros erraticus in ASF‐affected areas in Europe. For each of the selected research objectives, a research protocol has been proposed considering the potential impact on ASF management and the period of 1 year for the research activities.

Modelling wild boar management for controlling the spread of ASF in the areas called white zones (zones blanche)

African Swine Fever (ASF) is an infectious lethal disease affecting domestic pigs and wild boar. In the EU the infection perpetuates predominantly in wild boar populations. ASF control comprises wild boar population reduction measures,e.g. pre-emptive culling in delineated zones, called white zones (WZ).TheseWZ areplaced geographically adjacent to an area with ASF circulating in wild boar (ASF positive area).The ideal WZ would be depopulated of wild boar without possibility of recolonization. However, WZ may still harbour live wild boar after its establishment and the functionality of the WZ inherently foresees ASF enteringit. But the spread of the infection is expected tostop within an effective WZ. The concept mustnotmatch legislative zones, likewise infected area, Part I, Part II, etc. In order to compare different approaches to implement a WZ(e.g. targets and speed of population reduction in the WZ, width of the WZ, and distance of the WZ from the ASF-positive area), an individual-based spatially explicit model was adjusted to four historic WZ-like situations in the EU, i.e. Estonia 2014, Latvia 2016, Czech Republic 2017, and France 2018. The model was used to simulate the reported spatio-temporal layout and targeted measures. The stochasticity of the model provided understanding of the general efficiency of these WZ. Alternatives of the local measures were simulated as scenarios to identify caveats of the settings and derive improvements in future applications. The simulation outcome suggests issues to be addressed in implementing future WZ: i) distance between ASF-positive area and the WZ was adequate if adapted to the speed of propagation according to the local wild boar density, and the time horizon of depopulation measures envisaged for the WZ; ii) the width of the WZ was adequately set if everywhere it was preventedthat short infection chains already led out of the zone, iii) the WZ around focal introductions was most efficient if depopulated by culling the maximum of a defined (or fenced) population in shortest time with minimal disturbance, for instance, by trapping, sharp shooting or using silencers.Aspects of density, timing and spatial distribution in relation to the efficiency of WZ layout are explored.

African Swine Fever in wild boar: Assessing interventions in South Korea.

African Swine Fever (ASF) was detected in South Korean pig farms in September 2019. Currently, ASF occurs mostly in wild boar (Sus scrofa). We describe the ASF dynamics in wild boar in South Korea from October 2019 to October 2020 and use case studies to evidence the advantages and limitations of the control measures applied. During 2019, ASF remained confined in fenced areas of three counties. Since January 2020 however, the ASF management policy changed from fencing with limited disturbance to culling (with more disturbance), and ASF spread east and south. Until 31 October 2020, a total of 775 wild boar ASF cases have been confirmed, affecting 9 counties. Interventions for ASF control in wild boar included silent (trapping) and non-silent (shooting) population control, local and large-scale fencing, and carcass destruction. Pre-ASF wild boar densities were closed to 10 per km2 . Biosafety risks arose from the movements of people and vehicles, swill feeding of wild boar, destroying pig herds, handling wild boar during trapping and hunting, and searching for and disposing of carcasses. Despite training efforts, biosafety regulations were sometimes ignored. We observed differences between counties regarding disease control. While interventions apparently succeeded in controlling ASF in one site where geographical features and fast decision making facilitated an early and efficient fencing, and culling was performed silently, biosafety problems and habitat- and management-related delays hindered ASF control in other situations. Given that carcass, destruction faces specific limitations in South Korea, fencing and trapping (under appropriate biosafety conditions) might represent the most effective intervention option.

Development of a Potential Penside Colorimetric LAMP Assay Using Neutral Red for Detection of African Swine Fever Virus.

African swine fever (ASF) has caused huge economic losses to the swine industry worldwide. Since there is no commercial ASF vaccine available, an early diagnosis is extremely important to prevent and control the disease. In this study, ASF virus (ASFV) capsid protein-encoding gene (p72) was selected and used to design primers for establishing a one-step visual loop-mediated isothermal amplification (LAMP) assay with neutral red, a pH-sensitive dye, as the color shift indicator. Neutral red exhibited a sharp contrast of color change from faint orange (negative) to pink (positive) during LAMP for detection of ASFV. The designed primer set targeting highly conserved region of the p72 gene was highly specific to ASFV and showed no cross-reactivity with other swine viruses. The detection limit for the one-step visual LAMP developed was 10 copies/reaction based on the recombinant plasmid containing the p72 gene of ASFV. More importantly, the developed one-step visual LAMP showed high consistency with the results of the real-time polymerase chain reaction (qPCR) method recommended by World Organization for Animal Health (OIE). Furthermore, the results demonstrate that the colorimetric detection with this LAMP assay could be directly applied for the whole blood and serum samples without requiring genome extraction. Based on our results, the developed one-step visual LAMP assay is a promising penside diagnostic tool for development of early and cost-effective ASF monitoring program that would greatly contribute to the prevention and control of ASF.

An outbreak of African swine fever in small-scale pigs, Gauteng, South Africa, July 2020

ObjectivesSince 2012, outbreaks of African swine fever (ASF) in domestic pigs have increased outside of South Africa’s ASF control zone. This study describes the epidemiological investigation and findings of an ASF outbreak in a small-scale pig unit in Gauteng Province and makes recommendations to prevent future outbreaks. MethodsPCR testing and molecular analysis were performed on pig tissue samples. Veterinary services conducted epidemiological investigations, forward and backward tracing, and surveillance. Farm management and biosecurity practices were assessed. Quarantine, culling, carcass disposal, and disinfection were implemented. ResultsASF virus genotype I was detected. A concurrent ASF outbreak in neighbouring Mpumalanga Province was identified as a possible source. Inadequate biosecurity measures probably facilitated viral transmission. Potential mechanisms for the introduction of the ASF virus include swill feeding practices, free roaming of pigs, scavenging, illegal slaughter, and trade of pig products within the community. ConclusionsMolecular typing of the ASF virus linked the outbreak to an ongoing ASF outbreak in Mpumalanga Province. Pig enterprises with poor biosecurity practices may face greater risk of ASF introduction. Small-scale pig keepers should be targeted for ASF awareness and education campaigns. Innovative and cost-effective biosecurity solutions are needed in this resource-poor setting.

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

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.