Prevention Of African Swine Fever Research Articles

African Swine Fever Virus (ASFV): Biology, Genomics and Genotypes Circulating in Sub-Saharan Africa.

African swine fever (ASF) is a highly infectious and fatal haemorrhagic disease of pigs that is caused by a complex DNA virus of the genus Asfivirus and Asfarviridae African suids family. The disease is among the most devastating pig diseases worldwide including Africa. Although the disease was first reported in the 19th century, it has continued to spread in Africa and other parts of the world. Globally, the rising demand for pork and concomitant increase in transboundary movements of pigs and pork products is likely to increase the risk of transmission and spread of ASF and pose a major challenge to the pig industry. Different genotypes of the ASF virus (ASFV) with varying virulence have been associated with different outbreaks in several countries in sub-Saharan Africa (SSA) and worldwide, and understanding genotype circulation will be important for ASF prevention and control strategies. ASFV genotypes unique to Africa have also been reported in SSA. This review briefly recounts the biology, genomics and genotyping of ASFV and provides an account of the different genotypes circulating in SSA. The review also highlights prevention, control and progress on vaccine development and identifies gaps in knowledge of ASFV genotype circulation in SSA that need to be addressed.

In vitro cytotoxicity and virucidal efficacy of potassium hydrogen peroxymonosulfate compared to quaternary ammonium compound under various concentrations, exposure times and temperatures against African swine fever virus.

Background and Aim:The selection and proper application of disinfectants are crucial to the prevention of many diseases, so disinfectants must be evaluated before being used for the prevention of African swine fever (ASF). Three disinfectant products belonging to the group of potassium hydrogen peroxymonosulfates, product A and product B, and a quaternary ammonium compound called product C, were examined in vitro for host cell cytotoxicity and the efficacy of ASF virus inactivation. The study parameters included various concentrations, exposure times, temperatures, and degrees of cytotoxicity.Materials and Methods:Three disinfectant products were evaluated for cytotoxicity using primary porcine alveolar macrophage (PAM) cells at dilutions from 1:200 to 1:51,200. Disinfectants in concentrations of 1:200, 1:400, and 1:800 were prepared, the pH and the virucidal activity were tested. An equal volume of each dilution was mixed with the ASF virus and incubated at room temperature (20°C) or on ice (4°C) for 1 min, 5 min, or 30 min. Hemadsorption (HAD) or rosette formation was observed using an inverted microscope for 5 days after inoculation, and the virus titer was calculated as HAD50/mL. Each treatment and virus control were tested in triplicate, and the titers were reported as means and standard deviations. The reduction factor was used to measure inactivation.Results:Products A, B, and C at 1:400, 1:800, and 1:25,600 of dilution, respectively, did not show significant cytotoxic effects on PAM cells. Products A and B could inactivate ASF virus at 1:200 dilution within 5 min after exposure at 4°C. However, at 20°C, the exposure time had to be extended to 30 min to inactivate the virus. Product C could inactivate the virus at 1:400 dilution within 5 min under both temperature conditions, whereas at 1:800 dilution, the exposure time had to be extended to 30 min to completely inactivate the virus at 20°C.Conclusion:All disinfectants could inactivate ASF virus in various concentrations, under appropriate exposure times and reaction temperatures, and there was no evidence of host cell cytotoxicity. For the control of ASF in pig farms, the appropriate concentration, ambient temperature, and contact time of these disinfectants should be taken into account.

African swine fever virus MGF505-11R inhibits type I interferon production by negatively regulating the cGAS-STING-mediated signaling pathway

African swine fever (ASF) is an acute, hemorrhagic, and highly contact infectious disease caused by African swine fever virus (ASFV) infecting domestic pigs or wild boars, the mortality rate up to 100 %. Evasion of host innate immunity plays a vital role in the pathogenesis of ASFV. Studies have showed that the MGF505 genes involve in regulating the IFN-I response, but its mechanism of action remains poorly understood. In our present study, ASFV MGF505-11R inhibited IFN-β and ISRE activation induced by cGAS, IRF7, IRF3-5D, STING, IKKε and TBK1 accompanied by decreases of IFN-β, ISG15 and ISG56 mRNA transcription. ASFV MGF505-11R interacted with STING, degrading STING expression by the lysosomal, ubiquitin-proteasome and autophagy pathways. Moreover, ASFV MGF505-11R could inhibit the phosphorylation of TBK1 and IRF3 stimulated by cGAS/STING overexpression. Finally, the truncation mutation analysis indicated that the 1–191 aa and 182–360 aa of ASFV MGF505-11R could inhibit cGAS-STING-mediated activation of IFN-β promoters. In short, these results demonstrated that ASFV MGF505-11R involved in regulating the IFN-I response by negatively regulating the cGAS signaling pathway. In summary, this study preliminarily clarified the molecular mechanism of ASFV MGF505-11R gene antagonizing IFN-I-mediated antiviral, which will helpfully provide new strategies for treatment and prevention of ASF.

Viricidal activity of several disinfectants against African swine fever virus

Prevention of African swine fever, a disease caused by African swine fever virus (ASFV), requires maintenance of high biosecurity standards, which principally relies on disinfection. Finding the perfect disinfectant against ASFV is difficult because of the lack of relevant data. Therefore, we aimed to find the most effective disinfectant and to optimise its concentration as well as contact time to confirm the viricidal effect against ASFV in vitro. We evaluated the viricidal activity of three concentrations each of six common disinfectants against ASFV using immersion disinfection assay (IDA) and spray disinfection assay (SDA); the concentrations of these disinfectants at which complete viral inactivation occurred were almost same as the manufacturer-recommended concentrations, but the exposure times for viral inactivation are different. The following disinfectants (assay: concentration, exposure time) showed complete inactivation: iodine and acid mixed solution (IDA/SDA: 0.5%, 10 min); compound potassium peroxymonosulfate (IDA: 0.25%, 30 min; SDA: 0.25%, 60 min); citric acid (IDA: 0.25%, 60 min; SDA: 0.5%, 60 min); sodium dichloroisocyanurate (IDA: 0.125%, 60 min; SDA: 0.25%, 60 min); and glutaral ang deciquam (IDA/SDA: 0.2%, 60 min); and deciquam (IDA/SDA: 0.5%, 60 min). However, in the presence of organic material contamination, disinfectants did not show a marked inactivation effect. Therefore, disinfection procedures should be performed in two steps: thorough mechanical cleaning followed by application of disinfectant. In conclusion, all the tested disinfectants can inactivate ASFV; these can be used as alternative disinfectants to enhance biosecurity.

Emergence of African Swine Fever in Poland (2014–2021). Successes and Failures in Disease Eradication

African swine fever (ASF) in Poland has been a major concern for pig production for the last seven years. The main constrains in ASF eradication in Poland are due to the high density of wild boar in ASF-affected areas of the country. Other factors, responsible for long-distance ASF spread to new regions of the country, are mainly related to human-mediated activity and lack of awareness of the potential disease threat to pig production. In the case of pig holdings, the only effective measure of ASF prevention is strict implementation of biosecurity rules. Despite many efforts to implement these measures, the disease occurred in a number of voivodeships, poviats and counties of Poland, primarily in eastern Poland; however, starting from 2019, also in the western part of the country. Further recommendations to eradicate ASF in Poland or at least to minimize the economic loss caused by ASF in pig production include effective wild boar population management strategies along with the implementation of strict biosecurity measures. The observations from the last seven years of ASF epizootic in Poland clearly indicate that the disease could not have been effectively controlled in wild boar population and could only be restricted in domestic pig population following severe biosecurity rules. As for ASF spread control in wild boar population, the measures applied in other EU countries include active wild boar carcass search and disposal along with sanitary and reduction hunting. These measures have also been shown non-effective. The only solution for future sustainable pig production in Poland seems to be strict collaboration between pig producers, veterinary inspection, and hunting associations.

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.

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.

A New Method for Detection African Swine Fever Virus: Time-resolved Fluorescence Immunoassay.

African swine fever (ASF) has severely influenced the swine industry of the whole world. Fast and accurate African swine fever virus (ASFV) antigen detection is very important for ASF prevention. This study aims to establish a new detection method for detection ASFV antigen using time-resolved fluorescence immunoassay (TRFIA) in the nose and mouth discharge. A double antibody sandwich TRFIA method was optimized and established. Recombinant P30 recombinant antigen was captured by its antibodies immobilized on 96-well plate, and then banded together with another detection antibodies labeled with Europium(III) (Eu3+) chelates, finally time-resolved analyzer measured the fluorescence intensity. The performance of this TRFIA (sensitivity, specificity and accuracy) was evaluated using the clinical samples and compared with the nucleic acid testing method. The sensitivity of this TRFIA was 0.015 ng/mL (dynamic range 0.24–500 ng/mL) with high specificity. The recovery ranged from 92.00 to 103.62 %, the inter-assay CVs ranged from 5.50 to 11.96 %, and the intra-assay CVs was between 5.20 and 10.53 %. Additionally, the cutoff value was 0.016. TRFIA took only 45 min to generate results, and its detection capability comparable to the nucleic acid detection. This study developed a TRFIA method that could be used for qualitative/quantitative detection of ASFV antigen in pigs nasal discharge, which has high sensitivity, specificity and accuracy. This TRFIA provides a new method for rapidly screening ASFV infection in pigs industry.

The role of Pig production and Market value chain in the occurrence of African Swine Fever in Songwe and Ruvuma regions, Tanzania

Background: In recent years, the pig industry in Tanzania has faced frequent occurrence of outbreaks of African swine fever (ASF). However, there is inadequate information on the pig value chain operation in relation to occurrence of ASF. This study aimed at mapping pig value chain and assess its contribution to the occurrence and spread of ASF in Tanzania.
 Methods: A cross sectional study was carried out in Songwe, Momba, Songea and Mbinga districts of Tanzania. Study districts were purposively selected based on the density of pig population, differences in production systems and history of ASF outbreaks. A total number of 484 pig producers and 28 traders were involved in the study. Random sampling was used to select pig producers. Pig traders were selected using snowball technique. Structured questionnaires were used to collect data on pig management and production practices, veterinary services, pig marketing practices and biosecurity measures using Open Data Kit (ODK) software. Semi structured interviews were conducted with key informants on perceived risk practices that are related to ASF outbreaks, challenges and recommendations on ASF prevention and control measures. Observation method was used to assess structure, facilities and practices within the pig production chain. 
 Results: The main actors in the pig production chain were pig producers, assemblers, wholesalers and retailers. Unknown stock source (30%), poor husbandry practice such as free ranging (5%), poor management of waste products (73%) and poor handling of feed (73%) were risk practices in the production node. Transportation nodes operated under high risk due to frequent movements and pick-ups of ≥ 30 pigs per trip.
 Conclusion: The results demonstrated that different actors operate in the pig production, distribution and marketing chain. Each node operated under low biosecurity measures, and poor infrastructures that are likely to contribute to occurrence of ASF. There is need to improve good husbandry practices, marketing and infrastructures to increase production while ensuring pork safety.

Genotype I African swine fever viruses emerged in domestic pigs in China and caused chronic infection

ABSTRACT The Georgia-07-like genotype II African swine fever virus (ASFV) with high virulence has been prevalent in China since 2018. Here, we report that genotype I ASFVs have now also emerged in China. Two non-haemadsorbing genotype I ASFVs, HeN/ZZ-P1/21 and SD/DY-I/21, were isolated from pig farms in Henan and Shandong province, respectively. Phylogenetic analysis of the whole genome sequences suggested that both isolates share high similarity with NH/P68 and OURT88/3, two genotype I ASFVs isolated in Portugal in the last century. Animal challenge testing revealed that SD/DY-I/21 shows low virulence and efficient transmissibility in pigs, and causes mild onset of infection and chronic disease. SD/DY-I/21 was found to cause necrotic skin lesions and joint swelling. The emergence of genotype I ASFVs will present more problems and challenges for the control and prevention of African swine fever in China.

Development of a Directly Visualized Recombinase Polymerase Amplification-SYBR Green I Method for the Rapid Detection of African Swine Fever Virus.

African swine fever (ASF) is a lethal disease in swine caused by etiologic African swine fever virus (ASFV). The global spread of ASFV has resulted in huge economic losses globally. In the absence of effective vaccines or drugs, pathogen surveillance has been the most important first-line intervention to prevent ASF outbreaks. Among numerous diagnostic methods, recombinase polymerase amplification (RPA)-based detection is capable of producing sensitive and specific results without relying on the use of expensive instruments. However, currently used gene-specific, probe-based RPA for ASFV detection is expensive and time-consuming. To improve the efficiency of ASFV surveillance, a novel directly visualized SYBR Green I-staining RPA (RPAS) method was developed to detect the ASFV genome. SYBR Green I was added to the amplified RPA products for direct visualization by the naked eye. The sensitivity and specificity of this method were confirmed using standard plasmid and inactivated field samples. This method was shown to be highly specific with a detection limit of 103 copies/μl of ASFV in 15 min at 35°C without any cross-reactions with other important porcine viruses selected. In summary, this method enables direct sample visualization with reproducible results for ASFV detection and hence has the potential to be used as a robust tool for ASF prevention and control.

Emergency preparedness and response to African swine fever in the People's Republic of China.

The first recorded outbreak of African swine fever (ASF) was confirmed in the People's Republic of China in early August 2018. By the end of July 2019, there had been 150 outbreaks of ASF in 31 provinces, including 146 in domestic pigs and four in wild boar. The Chinese Government attaches great importance to the prevention and control of ASF. The Chinese animal health authority promptly launched the highest-priority emergency response against this key animal disease; initiated an extensive surveillance network covering all provinces; formulated and promulgated supporting policies, such as compensation for culled animals and financial credit for affected producers; and established a joint coordination body for ASF prevention and control, led by the Ministry of Agriculture and Rural Affairs and involving a further 20 Ministries, including the Departments of Transportation, Customs and Market Supervision. All levels of local government undertook territorial management responsibilities and developed support policies to encourage all stakeholders to take part in ASF prevention and control. Furthermore, the Chinese Government developed a strategy that integrated both the legal and scientific aspects of ASF control, formulating and releasing a comprehensive policy for the whole pork production chain 'from farm to fork'. The plan included daily disease reports from the disease monitoring network, and adopted effective measures, such as blockades and culling, restricting live pig movements and implementing controls on swill feeding, to cut off viral transmission routes to the greatest extent possible.

Inhibition of African Swine Fever Virus Replication by Porcine Type I and Type II Interferons.

Interferons (IFNs) are proteins produced by a variety of cells during the process of virus infection. It can activate the transcription of multiple functional genes in cells, regulate the synergistic effect of multiple signaling pathways, and mediate a variety of biological functions such as antiviral activity and immune regulation. The symptoms of hosts infected with African swine fever virus (ASFV) depend on the combined interaction between viruses and the host. However, it is unclear whether IFNs can be used as an emergency preventive treatment for ASFV. This study focused on the use of recombinant porcine IFNs, produced by Escherichia coli, to inhibit the replication of ASFV. The activity of IFN against ASFV was detected using primary alveolar macrophages at different doses through immunofluorescence assays and quantitative real-time PCR. We found that both 1000 and 100 U/mL doses significantly inhibited the replication of ASFV. Meanwhile, we found that IFNs could significantly trigger the production of a variety of IFN-induced genes (IFIT1, IFITM3, Mx-1, OASL, ISG15, PKR, GBP1, Viperin, BST2, IRF-1, and CXCL10) and MHC molecules, which play key roles in resistance to virus infection. Peripheral blood samples were also obtained from surviving pigs treated with IFNs, and the viral load was determined. Consistent with in vitro tests, low-dose (105 U/kg) recombinant porcine IFNs (PoIFN-α and PoIFN-γ) significantly reduced viral load compared to that with high-dose (106 U/kg) treatment. Our results suggest that recombinant porcine IFNs have high antiviral activity against ASFV, providing a new strategy for the prevention of African swine fever.

Piloting the effectiveness of pig health education in combination with oxfendazole treatment on prevention and/or control of porcine cysticercosis, gastrointestinal parasites, African swine fever and ectoparasites in Angónia District, Mozambique.

A community-based intervention combining health education (HE) and treatment of pigs for control of porcine cysticercosis (PC), gastrointestinal (GI) helminths, African swine fever (ASF) and external parasites was tested involving six villages of resource-poor smallholder pig farmers. Farmers and pigs of six rural villages were randomly allocated into group 1 (HE), which served as controls, and group 2 (HE + OFZ) pigs received a single oral dose of 30mg/kg OFZ. Farmers were trained in pig health, housing and feeding. The proportion of farmers with confined pigs, the adoption rate of the introduced pig pen, the sero-prevalence of PC and ASF, the prevalence and intensity of GI nematodes and the prevalence of ectoparasites were measured at 9, 15 and 24months after initiation and compared to a baseline survey to seek the effectiveness of the interventions. There was no clear effect of the intervention on the sero-prevalence of PC, but analysis of the rate of change in prevalence between the two groups showed significant effect with the rate of change to lower prevalence in the HE + OFZ group compared to the HE group. Although HE managed to improve the farmer's knowledge in the control and prevention of ASF and ectoparasites, there was no significant reduction in the sero-prevalence of ASF and the prevalence of ectoparasites throughout the two-year period. The reported ineffectiveness of the intervention in this study suggested that more research is needed to develop more effective methods for controlling PC, ASF and pig parasites.

Implementation of a Regional Training Program on African Swine Fever As Part of the Cooperative Biological Engagement Program across the Caucasus Region.

A training and outreach program to increase public awareness of African swine fever (ASF) was implemented by Defense Threat Reduction Agency and the Ministries of Agriculture in Armenia, Georgia, Kazakhstan, and Ukraine. The implementing agency was the company SAFOSO (Switzerland). Integration of this regional effort was administered by subject matter experts for each country. The main teaching effort of this project was to develop a comprehensive regional public outreach campaign through a network of expertise and knowledge for the control and prevention of ASF in four neighboring countries that experience similar issues with this disease. Gaps in disease knowledge, legislation, and outbreak preparedness in each country were all addressed. Because ASF is a pathogen with bioterrorism potential and of great veterinary health importance that is responsible for major economic instability, the project team developed public outreach programs to train veterinarians in the partner countries to accurately and rapidly identify ASF activity and report it to international veterinary health agencies. The project implementers facilitated four regional meetings to develop this outreach program, which was later disseminated in each partner country. Partner country participants were trained as trainers to implement the outreach program in their respective countries. In this paper, we describe the development, execution, and evaluation of the ASF training and outreach program that reached more than 13,000 veterinarians, farmers, and hunters in the partner countries. Additionally, more than 120,000 booklets, flyers, leaflets, guidelines, and posters were distributed during the outreach campaign. Pre- and post-ASF knowledge exams were developed. The overall success of the project was demonstrated in that the principles of developing and conducting a public outreach program were established, and these foundational teachings can be applied within a single country or expanded regionally to disseminate disease information across borders; overall, this method can be modified to raise awareness about many other diseases.

Contribution of market value chain to the control of African swine fever in Zambia.

African swine fever (ASF) is a worldwide disease of pigs endemic in most sub-Saharan African countries. Zambia has been experiencing outbreaks of ASF for many years because the disease is endemic in the eastern part of the country, with incursion into the central part of Lusaka Province. The latest outbreaks of ASF in Lusaka occurred in 2013 with substantial pig mortalities, loss in trade, and cost of control measures and compensation of affected farmers. The aims of the study were to identify market value chain-related factors that were associated with ASF outbreaks and assess why these outbreaks are becoming frequent despite control measures being put in place. Using a mixed-method design, participants involved in the value chain were purposively sampled. Some pig farmers were included using a respondent-driven technique. Farmers came from Lusaka, Chilanga, Kafue, and Chongwe districts. Other participants included district veterinary officers, veterinary assistants, police officers, and veterinary staff manning veterinary checkpoints, abattoir and processing plant managers, meat inspectors, market chairpersons, and traders. Semi-structured questionnaires, in-depth interviews, and direct observations were used to collect data to come up with narrations, tables, and flow charts. In assessing the contribution of the value chain in ASF, aspects of ASF screening, market availability and procedures, knowledge on ASF transmission, occurrence of ASF outbreak, and regulation of pig movement were investigated. Despite government ASF control measures being applied, the following were noted: (1) low awareness levels of ASF transmission among pig farmers and traders; (2) only 50% of farmers had their animals screened for ASF before sale; (3) all the markets did not have the pork inspected; (4) laxity in enforcing livestock movement control because of inadequate police and veterinary staff manning checkpoints; (5) lack of enforcement of meat inspection and food safety regulations at pig markets; and (6) inadequate and bureaucratic ASF screening. Improving biosecurity; sensitizing farmers, traders, and all stakeholders in the pig value chain on ASF prevention and control; reinforcement of staff at checkpoints; and regulation of pig markets are some of the ways in which future outbreaks can be prevented.

The African swine fever epidemic in West Africa, 1996-2002

African swine fever (ASF) is a contagious, highly fatal, haemorrhagic viral disease that only affects members of the Suidae family. Currently, no vaccine or treatment exists, so the disease has potentially devastating consequences for the pig industries, availability of affordable protein livelihoods and trade. This study aimed to consolidate historical information generated by working towards the control and eradication of ASF in previously unaffected countries in West Africa during 1996-2002. This descriptive analysis entailed the evaluation and review of archived records and reports of outbreaks, data from veterinary services, veterinary consultants and peer-reviewed publications. Specifically, the analysis focused on establishing the sequence of events in the spread of the disease throughout the region, as well as the possible sources and pathways (mostly human-driven, i.e., movement of pigs and swill feeding). The socio-economic aspects of the epidemic were also assessed. Finally, the prevention and control measures applied were described and evaluated. Major challenges for control that were identified involved lack of capacity to respond to an outbreak of animal disease and the nature of the pig sector in the affected countries. Most of the pigs were produced in low biosecurity subsistence husbandry systems. Actions taken by producers to limit economic losses due to the epidemic (e.g., illegal selling of pigs and infected pork, hiding of outbreaks) increased the risk of spread and frustrated control efforts. The disease has persisted in an endemic state ever since and has negatively affected pig production and marketing in most of these countries. The analysis of this information will allow a better understanding of the disease dynamics in a region infected for the first time, and learning how the prevention and control interventions that were implemented worked or failed. This will help the development of better tailored, sustainable and locally sound interventions. The authors provide a set of recommendations for ASF prevention and control.

Иммунобиологические свойства аттенуированного штамма ФК-135 вируса африканской чумы свиней, выращенного в суспензии клеток костного мозга свиней

For many years, efforts of research scientists have been directed towards obtaining and testing of various attenuated variants of African swine fever (ASF) virus to develop specific methods for ASF prevention. Similar investigations were also carried out in the All-Russian Institute of Veterinary Virology and Microbiology which resulted in obtaining an attenuated ASF virus variant FC-135 through passaging a virulent strain France-32 of serotype 4 (V.A. Burlackov et al., 1979). The above strain grown in a porcine bone marrow (PBM) monolayer cell culture and taken at a 25-fold concentration provided 85 to 100 % protection from infection with a homologous virulent ASF virus. Because of higher manufacturability, performance and cost effectiveness of a suspension culture method as compared to those for a monolayer one, the investigation of antigenic and immunogenic activity of a virus-containing emulsified preparation produced in bioreactors from an ASF virus strain FC-135 grown in a PBM cell suspension was of some interest. The results of the reported research showed that when culturing the attenuated ASF virus strain FC-135 in PBM cell suspension in bioreactors, the highest virus accumulation levels of 7.50 to 8.00 lg HAU 50/cm 3 were observed after 4 day cultivation, and CF-antibody levels of 1:16 to 1:32 were indicated after 5 to 6 day cultivation. The titers of the virus grown in a PBM cell monolayer in mattresses were 0.25 to 0.50 lg HAU 50/cm 3 lower than those as seen in the previous case, although CF-antibody levels as observed within the same period were of 1:16. A concentrated emulsified preparation designed from the strain FC-135 grown in a PBM cell suspension using bioreactors provided protection of gilts against infection with a homologous virulent virus for 4 months (observation period). Also, we showed that the suspension method of the attenuated strain FC-135 culture in PBM cells using automated bioreactors, being more manufacturable, productive and cost-efficient as compared to the monolayer growth in mattresses, when applied under controlled conditions, provided production of homologous virus materials exhibiting high biological activity.

Risk of African swine fever introduction into the European Union through transport-associated routes: returning trucks and waste from international ships and planes

BackgroundThe uncontrolled presence of African swine fever (ASF) in Russian Federation (RF) poses a serious risk to the whole European Union (EU) pig industry. Although trade of pigs and their products is banned since the official notification in June 2007, the potential introduction of ASF virus (ASFV) may occur by other routes, which are very frequent in ASF, and more difficult to control, such as contaminated waste or infected vehicles. This study was intended to estimate the risk of ASFV introduction into the EU through three types of transport routes: returning trucks, waste from international ships and waste from international planes, which will be referred here as transport-associated routes (TAR). Since no detailed and official information was available for these routes, a semi-quantitative model based on the weighted combination of risk factors was developed to estimate the risk of ASFV introduction by TAR. Relative weights for combination of different risk factors as well as validation of the model results were obtained by an expert opinion elicitation.ResultsModel results indicate that the relative risk for ASFV introduction through TAR in most of the EU countries (16) is low, although some countries, specifically Poland and Lithuania, concentrate high levels of risk, the returning trucks route being the analyzed TAR that currently poses the highest risk for ASFV introduction into the EU. The spatial distribution of the risk of ASFV introduction varies importantly between the analyzed introduction routes. Results also highlight the need to increase the awareness and precautions for ASF prevention, particularly ensuring truck disinfection, to minimize the potential risk of entrance into the EU.ConclusionsThis study presents the first assessment of ASF introduction into the EU through TAR. The innovative model developed here could be used in data scarce situations for estimating the relative risk associated to each EU country. This simple methodology provides a rapid and easy to interpret results on risk that may be used for a target and cost-effective allocation of resources to prevent disease introduction.

Approaches to the identification of non-essential genes of African swine fever virus

It is poorly understood why vaccines could not be developed for the control and prevention of African swine fever (ASF) virus infection. The aim of our study was to identify genes non-essential for ASF virus replication because there were indications that certain viral gene products, which apparently parently are non-essential for viral replication, conferred protection from death due to ASF. A cosmid library representing the genome of ASF virus strain France 64 was established and characterized. Then, in order to inactivate viral genes by insertion, the β-galactosidase (β-gal) gene was introduced either randomly or at specific locations of selected cloned DNA fragments. These constructions were tranfected into cells which had been previously infected with a cell-culture-adapted viral strain in order to allow the generation of recombinant progeny virus. Viable recombinant progeny was identified by at least one of the following means: (1) expression of β-gal; (2) detection of β-gal specific DNA by plaque hybridization, and (3) absence of a functional product of the inactivated gene. Presently, we are characteriaing a recombinant virus with an insertionally activated thymidine kinase gene.