Avian Influenza (AI)
VLA is an International Reference Laboratory for AI and received 137 influenza viruses for confirmatory diagnosis during the year. It was also involved with investigations into the occurrence of a highly pathogenic avian influenza in Chile and infections with H9N2 influenza virus causing severe economic problems in the Middle East and more recently infections of H7N7 in The Netherlands. The Chilean virus was shown to have genetic characteristics whereby an avirulent virus acquired virulence. VLA has also continued to support EU National Laboratories with project co-ordination, development of rapid diagnostic tests, studies on the molecular basis for AI pathogenesis and the development and validation of a rapid genotyping test for all influenza A viruses.

Newcastle Disease (ND)
VLA received over 300 haemagglutinating viral isolates for identification and confirmatory diagnosis of which 176 were avian paramyxoviruses.

Support was provided to the Danish National Laboratory and several laboratories in the Middle East investigating epidemics of ND in commercial and back yard flocks. Using genetic techniques, viruses were separated according to temporal, geographical and host origins. Over 200 pigeon paramyxovirus type1 viruses, derived from the ongoing panzootic, have revealed that the virus most probably originated in the Middle East in the late 1970s.

West Nile Fever (WNF)
WNF virus is a vector borne pathogen with a wide host range and is a potential zoonosis in the UK since recent evidence suggests that the virus is extending into temperate countries. As a precaution, a small team at VLA Weybridge has been established to provide a testing capability for wild birds to complement the enhanced surveillance carried out by our regional laboratories. They have acquired the appropriate tests for virus isolation, virus detection by PCR and serology. As a result, over 300 submissions have been received and tested for WNF by virus isolation and PCR and all to date have proved negative.

Consultancy and expertise on new testing strategies for surveillance and diagnosis in all host groups have been provided to both Defra and the Department of Health and VLA has become a founder member of a newly formed WNF advisory group with the Centre for Applied Microbiology & Research (CAMR), Centre for Ecology & Hydrology (CEH), Oxford and the Animal Health Trust (AHT), Newmarket.

Classical Swine Fever (CSF)
Research at VLA using RT-PCR and ELISA techniques, has shown for the first time that CSF virus exerts control over the innate response and that it prevents the cell from killing itself by apoptosis. Further work is underway to understand the pathways involved and to study strains of differing virulence in an attempt to determine the role of this mechanism in the in-vivo pathogenicity of CSF.

Collaborative studies have continued with:

• Institute of Animal Health
  looking at the effects of CSF infection on vascular endothelial cells - a prime target for infection and thought to be involved in pathogenesis
• Cambridge University
  to undertake microarray analysis and to look at a number of differentially expressed genes that have been identified following infection with CSF virus

This latter project has identified one specific protein which is ‘up-regulated’ in certain uterine cells infected with a related virus, bovine viral diarrhoea (BVD) and has also been implicated in the processes of viral infections for measles, adenovirus and human immunodeficency virus (HIV). Further work is planned to confirm this finding and to identify other genes whose expression is altered following CSF infection.

In response to concerns that the high incidence of porcine dermatitis and nephropathy syndrome (PDNS) may mask CSF infection caused by low-pathogenic strains of the virus, VLA has contributed to a Defra initiative to examine options for active surveillance for CSF in Britain.

Preparation of samples for DNA testing

Bovine leukosis virus (BLV) & equine viral arteritis (EVA)
VLA representatives attended an Office International des Epizooties (OIE) meeting in Sweden in September 2002, to discuss the diagnostic and surveillance implications of BLV strain variation with colleagues from Sweden and Germany. Initial work at VLA has included the evaluation and standardisation of a PCR for BLV and the provision of a replacement for the serological standard.

Over 5,000 sera were tested as part of the EVA Survey of which 2% tested positive. These sera were also tested for Coggins (equine infectious anaemia) and 1.5% were seropositive.

A novel ‘TaqMan®’ assay was developed to complement existing molecular methods for the rapid detection of EVA in semen and clinical samples as part of a joint funded project by the EU and the UK Government.

Rabies
Research into rabies and rabies-related viruses has developed our expertise in molecular-based studies and improved our ability to identify strains of rabies virus within 24 hours of sample receipt.

Examining cell cultures for viral activity

The rabies virus sequence database has been increased through the acquisition of viruses from many countries throughout the world and now forms the largest collection of lyssavirus strains in the world; a vital asset to the global rabies research community.

Nearly 14,000 samples were received at VLA for the Pet Travel Scheme (PETS) and were tested using established rabies serological tests which are expensive, time consuming, require the use of live virus and biological containment facilities. VLA, in collaboration with the OIE Reference Laboratory, AFSSA, Nancy, France and a commercial partner, Synbiotics Europe have successfully developed a rabies antibody ELISA, which was approved for use as a screening tool by the OIE.

Click here for a special profile on rabies research and surveillance.