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African swine fever virus: Improved preparedness and control - SE1516

Description
African swine fever is a viral (ASFV) disease of domestic pigs that results in death of almost all infected animals and causes high economic losses in affected countries. Before 2007 the disease was restricted to sub-saharan Africa and Sardinia. Since 2007 disease spread to the Trans Caucasus region and to neighbouring countries including the Russian Federation. From Russia ASF spread to nothern and western areas and was introduced into countries bordering to the West including Belarus, Ukraine and EU countries in the Baltic States and Poland. In 2016 the situation worsened with large numbers of outbreaks in domestic pigs, and in wild boar in the Baltic States. In Poland disease has spread further west and south in the country cuasing more outbreaks in domestic pigs. In 2016 in Europe and Russia 478747 pigs died or were destroyed and 2103 cases in wild boar were reported. The lack of a vaccine, stability of virus in the environment and infected pork, presence of wildlife reservoirs and failure to detect disease early are all contributing factors in disease spread. The main risks of introduction to the UK are illegally imported pork or legal imports following an undetected spread in another disease free country. The stability of the virus means that fomites such as infected clothing or transport vehicles pose a risk. Although introduction of ASFV remains a low risk to the UK the economic costs and welfare issues resulting would be very high. In this project we propose the following objectives in support of DEFRA policy for prevention and control of ASF including earlier lifting of restrictions on premises and control zones. The specific objectives are:
1. To investigate novel diagnostic tests for ASFV to improve early detection and facilitate scale-up of diagnosis in the event of an outbreak. These novel tests will include lateral flow devices for detection of ASFV antigen and antibodies.
2. To investigate the role of fomites in disease transmission. This will include environmental sampling to potentially detect disease on farms and investigation of virus survival in slurry and semi-solid waste.
3. To advance research on development of safe and effective vaccines for ASFV. Use of vaccination could reduce the disease burden in Europe and Africa and thus reduce the risk of ASF introduction to the UK.
Objective
Objective 1. Validation of novel diagnostic methods for rapid detection of ASF virus and antibodies to the virus. The potential for use of newly-available [1] (Ingenasa, Spain) lateral flow devices (LFDs) for rapid detection of ASF virus and antibodies to the virus will be investigated. In preliminary tests we have shown that ASF virus can be detected in less than 10 minutes from blood samples collected from 3 days post-infection of pigs with virulent virus. In this project we plan to further investigate the sensitivity and specificity of these devices using different types of samples (blood, serum, tissue extracts urine or faeces). The sensitivity and specificity of the LFDs will be compared using frozen and fresh samples and with currently used tests including qPCR and ELISA.
We have confirmed in SE1515 that the ZMAC pig macrophage cell line is susceptible to ASFV infection and therefore could replace the need for primary porcine macrophages for virus isolation. In this project we will continue to validate the use of the ZMAC cells for ASF virus isolation in comparison to primary cells. If these cells are confirmed to be equally sensitive to infection as primary cells in diagnostic tests we will negotiate an agreement with the company, Aptimmune, who provided the cells for use in diagnosis.
Completion of objective 1 will depend on obtaining ASFV infected samples from experimental pig infections to be carried out in objective 2 and 3.

Objective 2. Investigation of ASF virus survival in experimental settings and the role of fomites and matrices in virus transmission. Generation of data concerning the likley rates of ASFV inactivation in slurry.
ASF virus is a large DNA virus and is physically very stable persisting over long periods in the environment, on contaminated materials and in pork products. Uncertainties remain regarding the role of environmental contamination in virus transmission and the stability of virus in environmental matrices. The inactivation kinetics for ASFV will be determined initially using a lab-scale inactivation chamber. Collimated UV light will be applied to fomites spiked with known quantites of ASFV. The UV dose (fluence) required to inactivate 90% of ASFV will be calculated and will be used to inform further studies. It is planned that a colimated UV light set up can be used to determine the inactivation rates for ASFV in a variety of matrices. In our previous DEFRA project we investigated the dynamics of ASF virus transmission between pigs in direct and indirect contact [3, 8, 9] . We estimated virus survival in urine, faeces and oral and nasal swabs (Davis et al., 2015). In this project and building on the data generated in the lab-scale UV inactivation experiments,we will investigate the extent of to which infectious ASFV environmental contamination (n pens with ASF virus infected pigs) can be removed/reduced. Thus, the likely stability of the virus in this environment after pigs are removed can be determined using the data generated in this study and can go towards quantitative risk-based control strategies. Determination of the UV inactivation kinetics for ASFV will be used to inform recommendations on the use of this technology to reduce infectious ASFV on fomites and in wastewater.

Objective 3. To advance research leading to development of a safe and effective vaccine for ASFV
Work from the DEFRA project SE1515 has identified a pool of eight ASFV genes that when delivered through a replication-deficient adenovirus prime and MVA boost vaccination regime induces 100% protection against the virulent OURT88/1 strain of ASFV in outbred domestic pigs. In order to progress this to a vaccine that could be used effectively in the field we need to reduce the complexity of the vaccine to a single delivery method and test its ability to protect against strains circulating in Eastern Europe.
Time-Scale and Cost
From: 2017

To: 2020

Cost: £886,017
Contractor / Funded Organisations
IAH - Institute for Animal Health
Keywords
Animals              
Fields of Study
Animal Health