Bovine tuberculosis (TB)

At the start of the year the effects of the Foot and Mouth Disease epidemic were still being felt as increased skin testing of the national herd identified more cases which required confirmatory diagnosis by culture. A large backlog of samples accumulated but VLA showed its flexibility by increasing the number of Regional Laboratories able to perform this specialised service. A new data recording system was also developed to track the samples through each stage of processing and the backlog of culture samples was cleared by the end of the year. The Weybridge TB culture unit has now become a designated OIE reference laboratory.

During the year, Defra launched a TB control strategy development initiative and VLA was asked to advise on vaccination, pre-movement testing, confirmation rates in reactor cattle and the probability of herds suffering a confirmed new TB incident. In addition, a range of laboratory support services was also provided including database development, the management of questionnaires, the provision of post mortem examinations to support field trials and epidemiological surveys and the continuing production of Tuberculin (the basic constituent of the skin test used in the national control programme).

Our research has made major advances in genomics and post-genomics (where the genome sequence of Mycobacterium bovis was published) and ELISA and interferon-g (IFN-g) tests for badgers and cattle were developed further. Molecular epidemiological projects covered interactive internet-based mapping development, variable number tandem repeats (VNTR) typing developed for routine use and the population structure of M.bovis in GB was defined. Good progress was also made on the pathogenesis of TB and vaccine development. (see Selected Papers list for further information).

Collaborations continue to be a major source of strength and impetus for the programme and we have established links with:

The Wellcome Trust Sanger Institute and Institut Pasteur

• sequencing of the genome of M.bovis and the genomes of BCG and M.microti.

The Bacterial Microarray Group at St George’s Hospital

• producing TB-complex genome DNA microarrays.

Imperial College, London and Armauer Hansen Research Institute, Ethiopia

• assessment of diagnostic tests developed at VLA and the molecular epidemiology of M.bovis being elucidated in Ethiopia, potential stepping stones along the way to vaccine candidate evaluation.

AgResearch, New Zealand and National Institute for Medical Research (NIMR)

• identification of a vaccination regime that improves the efficacy of BCG in cattle.

Institute of Animal Health and the Veterinary Sciences Division Stormont

• tripartite pathogenesis studies to provide an insight into the chronology and character of immunological and pathological responses following natural and experimental infection.

Brucellosis

Two incidents of brucellosis were confirmed in Great Britain during the year. The first, introduced by an imported animal, was successfully detected by post-import screening. Recent advances in molecular typing methods for Brucella, including IS711 profiling and VNTR typing, were applied to isolates from this breakdown and conclusively demonstrated homology with strains isolated from the Irish herd of origin. As a result of this incident, VLA’s risk assessment for Brucella importation was updated to reflect the increased incidence in Northern Ireland and will form the basis of a Defra review of the current national brucellosis control programme.

These outbreaks reinforce the importance of national surveillance for brucellosis and the key role VLA plays in supporting Defra to keep this zoonotic disease out of the country, particularly through abortion investigations, post import testing, national serology and quality assurance of national milk testing. VLA also continues to support the HPA by providing a diagnostic service for suspect human isolates.

Taking a milk sample from bulk tank for further analysis

Research has focused on developing a model of Brucella infection in pigs to provide material for assessing the stability of VNTR profiles during infection. Comparative in silico analysis of Brucella genomes is also progressing to identify areas associated with host specificities and differences in DNA patterns which could form the basis for improved diagnostic techniques. Samples from marine mammals, especially from around the Cornish coast, continue to be examined and the molecular phylogeny of these isolates will be presented as evidence to support a re-classification of the Brucella genus.

As an OIE and WHO Reference Laboratory for Brucellosis, VLA continues to receive isolates from laboratories throughout the world for confirmation of Brucella and also through a network of collaborations with laboratories in Tanzania, Greece, Ireland, Kosovo, Sri Lanka, Macedonia and Dubai.

Mycoplasmosis

Research into mycoplasmas was reviewed by Defra and the development of a Mycoplasma bovis vaccine at VLA and the subsequent demonstration of the vaccine’s efficacy and protective effect in challenge trials was considered to be an outstanding achievement.

A new denaturing gradient gel electrophoresis (DGGE) method for the identification of Mycoplasma species was developed in collaboration with Imperial College, London. This technique has undergone extensive testing and validation and will now be used as the first approach when identifying a Mycoplasma species. A PCR test for detecting M.conjunctivae has also been validated this year.

Samples have been tested for Mycoplasmas from a range of animal species, including cattle, sheep, goats, pigs, a variety of poultry and a grey seal. M.bovis and M.ovipneumoniae continued to be isolated in high numbers from pneumonic calves and sheep respectively. Using a range of molecular typing tools, isolates of M.bovis have been divided into two distinct groups possibly relating to their history of origin. Fortunately, no exotic Mycoplasmas have been detected though a number of suspicious cases were investigated. However, M.capricolum subsp. capripneumoniae, the cause of contagious caprine pleuropneumonia (CCPP), was identified at VLA for the first time for over 80 years in samples received from Turkey. Collaborative work with the Pendik Institute, Istanbul aims to determine the source of these outbreaks.

Commercial work included preparations for marketing a rapid diagnostic test for contagious bovine pleuropneumonia (CBPP), assessing the in vitro sensitivity of CBPP strains from Africa to antibiotics and performing minimum inhibitory concentration (MIC) tests on Mycoplasma species isolated within the EU.

Collaborations form an important part of the programme and links have been established with:

Namibian Government

• antibiotic trials for CBPP.

Istituto Zooprofilaticco Sperimentale, Teramo

• experimental infections of CCPP.

Istituto Zooprofilaticco Sperimentale, Palermo

• vaccine trials against contagious agalactia.

VLA continues to provide a diagnostic service for anthrax diagnosis and to strengthen our expertise in this area, Defra has supported a test development project with the aims of introducing PCR detection and VNTR typing.

VLA is an OIE Reference Laboratory for Contagious Equine Metrits (CEM) and provides a diagnostic service for this notifiable disease. During 2003, samples were received from continuation of the tracings exercise that followed the identification of a CEM culture-positive warmblood stallion in the previous year. One in-contact mare was found to be infected.