Special Issue "African Swine Fever (ASF)"

A special issue of Veterinary Sciences (ISSN 2306-7381).

Deadline for manuscript submissions: 30 November 2020.

Special Issue Editors

Dr. Klaus Robert Depner
Website
Guest Editor
Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald - Insel Riems, Germany
Interests: field epidemiological investigations; high risk period; role of the habitat for ASF persistence in wild boar; disease biology and drivers for endemicity; eradication and control strategies
Dr. Karl Ståhl
Website
Guest Editor
National Veterinary Institute, SVA, SE-751 89 Uppsala, Sweden
Interests: disease dynamics of ASF in different settings including the current European as well as the East African context; disease control; drivers of spread and persistence (including the role of humans); disease modelling
Prof. Dr. Arvo Viltrop
Website
Guest Editor
Institute of Veterinary Medicine and Animal Sciences, Kreutzwaldi 1 Tartu 51006, Estonia
Interests: epidemiology in wild boar and domestic pigs including risk factors for domestic pigs and wild boar; transmission routs in the wild boar domestic pigs interface; causes of the persistence of the infection in the European wild boar populations

Special Issue Information

Dear Colleagues,

Internationally, African swine fever (ASF) is considered as one of the most dangerous animal diseases of pigs. The disease is affecting trade and has a serious socio-economic impact on people's livelihood. No drugs or vaccines are available to fight ASF. The most severe epidemic ever experienced outside of the African continent started in Georgia in 2007, spread throughout the Caucasus and the Russian Federation, eventually reaching the European Union and China. In many countries, the disease has become endemic in domestic pigs and wild boar. In wild boar populations, ASF shows a pattern of habitat bound persistence lacking a tendency of dynamic spatial spread. 

Humans are recognized as the main cause of both long-distance transmission and virus introduction into domestic pig farms. Thus, it has become crucial to include social science when planning prevention-, control-, or eradication-measures. By focusing only on the biological particularities of the disease (for example, the contagiosity, tenacity, and case fatality rate), but ignoring the human aspects, the epidemic will not be controlled.

In this Special Issue, we intend to focus on the ASF field epidemiology in order to explore our understanding of ASF transmission, spread, and contagiosity in domestic pig farms and wild boar populations. We call on researchers to contribute their recent findings, especially focusing on, but not limited to, the following:

  • Epidemiological field investigations
  • Disease control and management
  • Biosecurity
  • Host–pathogen interaction
  • Transmission studies
  • Socio-economic drivers and impacts
  • Modelling
  • ASF epidemiology in the back yard sector

Papers in the form of case reports are also welcome.

Dr. Klaus Robert Depner
Dr. Karl Ståhl
Prof. Dr. Arvo Viltrop
Guest Editors

Manuscript Submission Information

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Published Papers (10 papers)

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Open AccessArticle
Epidemiology of African Swine Fever in Piggeries in the Center, South and South-West of Cameroon
Vet. Sci. 2020, 7(3), 123; https://doi.org/10.3390/vetsci7030123 - 01 Sep 2020
Abstract
African Swine Fever (ASF) is enzootic in Cameroon. A cross-sectional study was conducted in the center, south and south-west regions of Cameroon in order to determine: the knowledge, skills and practices at risk of pig breeders; the prevalence of the disease in piggeries; [...] Read more.
African Swine Fever (ASF) is enzootic in Cameroon. A cross-sectional study was conducted in the center, south and south-west regions of Cameroon in order to determine: the knowledge, skills and practices at risk of pig breeders; the prevalence of the disease in piggeries; the genome of the circulating virus. A total of 684 blood samples were collected in 209 farms for RT-PCR and ELISA analyses at the National Veterinary Laboratory (LANAVET) annex in Yaoundé. Prevalences of 15.2% (95CI: 12.5–17.9%) by ELISA, 23.8% (95CI: 20.6–27.0%) by RT-PCR, and 15.2% (95CI: 12.5–17.9%) by ELISA-PCR, were recorded. Of the farmers surveyed, 90% knew about the ASF and 55.3% have already experienced it. The 47.4% of them would not be able to recognize ASF if it occurred and, according to them, the risk of the disease introduction in farms would be 32% linked to the animal health personnel who work on farms. Molecular characterization revealed that only ASF genotype-I variable 19T-RSs is circulating. ASF is still hovering at a risky rate over the pig sector of Cameroon. The control of ASF needs an epidemiological surveillance, a better involvement of all stakeholders, sensitization of breeders and an effective State support for producers. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessArticle
The African Swine Fever Epidemic in Wild Boar (Sus scrofa) in Lithuania (2014–2018)
Vet. Sci. 2020, 7(1), 15; https://doi.org/10.3390/vetsci7010015 - 30 Jan 2020
Cited by 2
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessArticle
Diversity of Diptera Species in Estonian Pig Farms
Vet. Sci. 2020, 7(1), 13; https://doi.org/10.3390/vetsci7010013 - 23 Jan 2020
Cited by 1
Abstract
In light of the African swine fever outbreaks in Estonian pig farms during the past few years, the question of the vector potential of Diptera in the pig farm environment has risen. However, the arthropod fauna of the pig farm environment is currently [...] Read more.
In light of the African swine fever outbreaks in Estonian pig farms during the past few years, the question of the vector potential of Diptera in the pig farm environment has risen. However, the arthropod fauna of the pig farm environment is currently not well established. Hence, the aim of this study was to clarify the species diversity in pig farms. In total, 22 Diptera species or species groups were found in Estonian pig farms. There were altogether 186,701 individual arthropods collected, from which 96.6% (180,444) belonged to the order of true flies (Insecta: Diptera). The remaining 3.4% were from other insect orders, arachnids, or just damaged and unidentifiable specimens. The activity density and diversity of dipterans differed significantly between 12 sampled farms but not throughout the sampling period. The present study is amongst the few to provide a large-scale overview of pig-farm-associated Diptera in the temperate climate zone. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessArticle
Estimating the Postmortem Interval of Wild Boar Carcasses
Vet. Sci. 2020, 7(1), 6; https://doi.org/10.3390/vetsci7010006 - 05 Jan 2020
Cited by 4
Abstract
Knowledge on the postmortem interval (PMI) of wild boar (Sus scrofa) carcasses is crucial in the event of an outbreak of African swine fever in a wild boar population. Therefore, a thorough understanding of the decomposition process of this species in [...] Read more.
Knowledge on the postmortem interval (PMI) of wild boar (Sus scrofa) carcasses is crucial in the event of an outbreak of African swine fever in a wild boar population. Therefore, a thorough understanding of the decomposition process of this species in different microhabitats is necessary. We describe the decomposition process of carcasses exposed in cages. Trial 1 compared a wild boar and a domestic pig (Sus scrofa domesticus) under similar conditions; Trial 2 was performed with three wild boar piglets in the sunlight, shade, or in a wallow, and Trial 3 with two adult wild boar in the sun or shade. The wild boar decomposed more slowly than the domestic pig, which shows that standards derived from forensic studies on domestic pigs are not directly applicable to wild boar. The carcasses exposed to the sun decomposed faster than those in the shade did, and the decomposition of the carcass in the wallow took longest. To assess the state of decomposition, we adapted an existing total body scoring system originally developed for humans. Based on our studies, we propose a checklist tailored to wild boar carcasses found in the field that includes the most important information for a reliable PMI estimation. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessArticle
Evaluation of the Efficiency of Active and Passive Surveillance in the Detection of African Swine Fever in Wild Boar
Vet. Sci. 2020, 7(1), 5; https://doi.org/10.3390/vetsci7010005 - 30 Dec 2019
Cited by 2
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessArticle
R0 Estimation for the African Swine Fever Epidemics in Wild Boar of Czech Republic and Belgium
Vet. Sci. 2020, 7(1), 2; https://doi.org/10.3390/vetsci7010002 - 27 Dec 2019
Cited by 4
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessArticle
A Long-Term Study of the Biological Properties of ASF Virus Isolates Originating from Various Regions of the Russian Federation in 2013–2018
Vet. Sci. 2019, 6(4), 99; https://doi.org/10.3390/vetsci6040099 - 06 Dec 2019
Cited by 1
Abstract
Biological properties of the African swine fever (ASF) virus isolates originating from various regions of the Russian Federation (2013–2018) were studied in a series of experimental infections. Comparative analysis allowed us to establish the differences in the key characteristics of the infection, such [...] Read more.
Biological properties of the African swine fever (ASF) virus isolates originating from various regions of the Russian Federation (2013–2018) were studied in a series of experimental infections. Comparative analysis allowed us to establish the differences in the key characteristics of the infection, such us the duration of the incubation periods, disease, and the onset of death. The incubation period averaged 4.1 days, varying from 1 to 13 days. An average duration of the disease was 6.3 days and varied from 0 to 18 days. Overall case fatality was 94.5%, and antibodies were detected only in 19.3% of the animals. The biological properties of isolates Odintsovo 02/14 and Lipetsk 12/16 were significantly different from others. For this two, the presence of antibodies to the virus was detected in 71.4% and 75% of animals respectively and mortality levels were of 87.5% and 50%. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Other

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Open AccessCase Report
African Swine Fever in Two Large Commercial Pig Farms in LATVIA—Estimation of the High Risk Period and Virus Spread within the Farm
Vet. Sci. 2020, 7(3), 105; https://doi.org/10.3390/vetsci7030105 - 07 Aug 2020
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessCase Report
African Swine Fever in Mongolia: Course of the Epidemic and Applied Control Measures
Vet. Sci. 2020, 7(1), 24; https://doi.org/10.3390/vetsci7010024 - 17 Feb 2020
Cited by 1
Abstract
African swine fever (ASF) is spreading rapidly in Asia and was confirmed in Mongolia on 10 January 2019. Following the outbreak confirmation, a state emergency committee was established with representation from municipal authorities and other relevant authorities including the General Authority for Veterinary [...] Read more.
African swine fever (ASF) is spreading rapidly in Asia and was confirmed in Mongolia on 10 January 2019. Following the outbreak confirmation, a state emergency committee was established with representation from municipal authorities and other relevant authorities including the General Authority for Veterinary Services, National Emergency Management Agency, General Agency for Specialized Inspection, and the Ministry of Environment and Tourism. The committee provided recommendations and coordinated closely with the State Central Veterinary Laboratory to ensure quick outbreak investigation and response. In addition to outbreak investigations, sampling took place at farms and food premises and suggests a link between the outbreaks and swill feeding practices among backyard pig farmers. Upon government request, the Food and Agriculture Organization of the United Nations (FAO) deployed an expert team to assist in identifying risk factors for the disease spread and provide recommendations as how to improve disease prevention and response. Following the control measures from the involved agencies, the epidemic was successfully controlled and declared over on 11 April 2019. In total, the epidemic affected 83 pig farming households and led to a total of 2862 dead or culled pigs in eleven districts of seven provinces in Mongolia. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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Open AccessFeature PaperCase Report
African Swine Fever in a Bulgarian Backyard Farm—A Case Report
Vet. Sci. 2019, 6(4), 94; https://doi.org/10.3390/vetsci6040094 - 21 Nov 2019
Cited by 4
Abstract
African swine fever (ASF) is one of the most threatening diseases for the pig farming sector worldwide. As an effective vaccine is lacking, strict application of control measures is the only way to fight the disease in both industrial farms and backyard holdings. [...] Read more.
African swine fever (ASF) is one of the most threatening diseases for the pig farming sector worldwide. As an effective vaccine is lacking, strict application of control measures is the only way to fight the disease in both industrial farms and backyard holdings. With generally low biosecurity standards, the latter are at particular risk for disease introduction and offer challenging conditions for disease control. In the following case report, we describe the overall course of an ASF outbreak in a Bulgarian backyard farm and the implemented control measures. Farm facilities and available data have been investigated to estimate the possible source, spread and time point of virus introduction. Contact with contaminated fomites entering the stable via human activities was regarded to be the most likely introduction route. The slow disease spread within the farm contributes to the hypothesis of a moderate contagiosity. As no further ASF outbreaks have been detected in domestic pig farms in the region, it could be demonstrated that successful disease control in small-scale farms can be reached. Thus, the report contributes to a better understanding of ASF in the backyard sector. Full article
(This article belongs to the Special Issue African Swine Fever (ASF))
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