Bovine tuberculosis (TB)
Following the FMD epidemic, national skin testing for tuberculosis was resumed in earnest and the State Veterinary Service (SVS) was asked to play ‘catch-up’ and roll two years into one. Above average numbers of TB herd breakdowns were detected and the number of samples submitted for bacterial isolation increased significantly. VLA responded by expanding the number of regional laboratories fitted with specialised culture facilities to cope with the increase and by calling on the resources of the Central Science Laboratory.

©Imperial College London Photo: Neville Miles

Full annotation of the M.bovis genome was completed during the year and VLA commenced microarray production of the genome. Comparative genomics of M.bovis and M.bovis BCG are now being used to identify candidate antigens for improved diagnosis and vaccines. More than 40 antigens have now been defined which may improve the specificity of the interferon gamma (IFN-y) test for cattle. Several of these antigens show particular promise and are now being examined in larger field trials.

VLA also played a key role in the design and implementation of a major intervention trial to assess whether the IFN-y diagnostic test and changes in skin test interpretation can help clear infection from multiple reactor herds more quickly than current practice. Results will be reviewed when 150 herds have been recruited.

Two bioinformaticists have been appointed to the research group to strengthen post genomics research at VLA. Their work has already predicted and validated regions of an antigenic protein that bind to bovine major histocompatibility complex antigens and then interact with T cells.
This information can now be used to reduce the costs of future peptide-based antigen-mining exercises.

The TB research group has also been involved in developing two serological tests for detecting TB in badgers, which are more sensitive than the existing ELISA. One of these tests is a dipstick test that can be performed in the field.

Collaborations are the ‘cornerstone’ of the programme and we have established links with:

• Imperial College London to establish a VLA funded PhD Scholarship to attract high calibre students into veterinary research. An early study is defining the carbohydrate structure of the mycobacterial antigen MPB83.
• The Universities of Leicester and Kent to resolve the 3-dimensional structure of another mycobacterial protein, MPB70.

• The Institute of Animal Health and the Veterinary Services Division, Stormont to undertake both field and laboratory based studies investigating different aspects of TB pathogenesis.

Mycoplasmosis
VLA has been heavily involved in the surveillance and research of mycoplasmas both at home and abroad. Particular progress has been made in vaccine and molecular diagnostics development. A field trial in Hungary confirmed the protective properties of a saponised vaccine for Mycoplasma bovis and this work is being taken forward with a vaccine manufacturer. Field trials in Namibia on T1 vaccine for contagious bovine pleuropneumonia (CBPP), used exclusively in Africa, showed that if the vaccine is given via the respiratory route it can actually cause disease.
This could explain the sporadic outbreaks of CBPP seen in closed vaccinated herds.

Ground breaking work in conjunction with Imperial College London on the application of molecular techniques, resulted in the development of denaturing gradient gel electrophoresis (DGGE) to differentiate most of the important animal mycoplasmas, which may form the basis of a rapid typing system.

Randomly amplified polymorphic DNA (RAPD) techniques have demonstrated major differences in M.mycoides LC ( a cause of severe respiratory disease and contagious agalactia world-wide but exotic to UK), despite previously being thought to be a homogeneous strain.

A new PCR and ELISA were developed to improve the diagnosis of infections caused by M.ovipneumoniae. Isolations of this organism increased significantly in the UK this year, possibly due to closer housing of sheep during the FMD crisis.

Brucellosis
The first confirmation of Brucella abortus infection in cattle in Great Britain for many years, following initial diagnosis by the Scottish Agricultural College (SAC), highlighted the need for continued surveillance for this disease, especially with new breakdowns increasing in Ireland. Data from the current outbreak is being used to validate molecular methods, which could identify infected animals ahead of seroconversion (which can take up to nine months post infection) and to trace the source of the infection.

Developing improved sensitivity tests for Brucella

Brucellosis in pigs exists at a high level of prevalence in several EU countries in wild boar and outdoor-reared herds. Diagnosis, using the classical serological tests is problematic and false positive reactions due to infection with Yersinia enterocolitica O:9 are common. However, the publication of the genome of B.suis has initiated the search for alternative antigens to develop tests with improved sensitivity and specificity.

To strengthen surveillance in this area, all suitable porcine clinical material submitted to Regional Laboratories for B.suis, is screened using bacterial culture and serology to provide an early warning if the disease did enter the national herd. In addition, VLA again contributed to the annual survey of sheep and goats, to provide evidence of freedom from brucellosis in the national flock.

Research collaborations are flourishing in this area and VLA is participating in an EU funded project to clone all genes of Brucella melitensis in order to use DNA arrays to screen for new vaccine determinants and diagnostic antigens. Other collaborations include ring trials with all EU National Reference Laboratories to measure the degree of harmonisation and to compare the analytical sensitivity and specificity of tests and projects with the Veterinary Sciences Division, Northern Ireland and Scranton University, USA.