Statutory and Exotic Bacterial Diseases
TB research laboratory in the Stewart Stockman building
The Statutory and Exotic Bacterial Diseases Programme supports Defra in the control of notifiable animal diseases caused by bacteria through surveillance and research projects. Services to the Health Protection Agency and participation with commercial partners in developing animal disease control applications are also carried out.
Bovine Tuberculosis (TB)
TB surveillance activities have included mycobacterial culture and molecular typing of all isolates and although most samples received were from cattle and badgers, there is a growing awareness of the risks of TB in companion animals. This year we have seen a series of positive diagnoses in cats. All new isolates are added to our culture collection, which provides a basis for understanding the population biology of Mycobacterium bovis in GB. It also continues to be a major resource for our OIE Reference Laboratory functions and our molecular epidemiological studies. VLA is a member of VenoMyc, a multi-site European network of institutes with interests in the molecular epidemiology of Mycobacteria.
A new laboratory complex has enabled the bringing together of a multidisciplinary team working on many aspects of TB including epidemiology, vaccine and diagnostic test development, immunology and postgenomics.
During the year, the Regional Laboratories supported the randomised badger culling trial and seven counties badger road traffic accident (RTA) survey, studies of the pathology of tuberculous badgers that will be of particular importance in interpreting the findings of the trial.
As well as producing tuberculin for Defra’s TB national surveillance scheme, VLA has also been involved in several projects designed to improve TB diagnosis in both cattle and badgers. The evaluation of a PCRbased test for detecting M.bovis directly from tissues has provided encouraging results and we are expanding our testing activities using the interferon-assay as Defra looks to use this assay more widely. A similar assay has also been developed for use in badgers, which, along with a trapside antibody test, will be used to underpin a field trial to determine the safety of BCG in wild badgers.
In order to measure how efficacious various vaccines and potentially associated diagnostics are under natural transmission conditions, the natural progression for the research and development programme has been to move from laboratory based studies to field trials. Significant progress has been made in taking these initiatives forward including collaboration with Imperial College, UK, Armauer Hansen Research Institute, Ethiopia, Trinity College, Eire, Swiss Tropical Institute, Switzerland and the International Livestock Research Institute, Kenya in a Wellcome Trust Livestock Initiative, that includes a pilot study of neonatal BCG vaccination in cattle using natural transmission studies.
Collaboration with researchers at the University College Dublin on the experimental vaccination of badgers with the BCG strain of M.bovis has continued. A VLA study has also demonstrated its safety in captive badgers. This has resulted in an Animal Test Certificate being granted to VLA to test its safety in wild badgers, which represents the next step towards obtaining a license for BCG in badgers.
Much of the TB research at VLA is underpinned by post-genomic technologies encompassing comparative genomics, microarray expression technology and population genetics. These studies are being extended through both BBSRC and Defra funded projects to investigate the host-pathogen interaction at the molecular level. Projects with the Centre for Integrative Systems Biology (CISBIC) at Imperial College and the Veterinary Training and Research Initiative (VTRI) incorporating the University of Edinburgh, the Roslin Institute and IAH are on-going.
Significant progress has been made on a joint project with the Environmental Research Group, Oxford, on the predictive modelling and cattle movements. This has been recognised by Defra, who have provided extra funding to extend these models.
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Brucellosis
Brucellosis is an economically important zoonotic disease that remains endemic in many parts of the world. VLA continues to monitor UK livestock for freedom of disease by abortion screening and serological surveillance by testing over one million blood samples. VLA also provided reagents and ELISA plates for a further 200,000 bulk milk sample tests from dairy herds. Tissues from ‘reactor’ animals are also examined in disease containment level 3 facilities.
Confirmatory tests are carried out on suspect cultures from human cases of brucellosis on behalf of the Health Protection Agency. Many of these confirmed isolates are from patients who have travelled abroad and probably consumed unpasteurised milk or milk products.
Brucellosis in marine mammals remains an interest for the team and during this year organisms were isolated from 18 animals mainly washed up on the shores of Great Britain.
The extreme homogeneity of the Brucella organism has precluded the development of molecular techniques with sufficient discriminatory powers. However, a newly developed 21-locus Variable Number of Tandem Repeat (VNTR) typing scheme was used on 2000 field isolates to assess its value as an epidemiological tool and to provide a database for comparison of new isolates. With the use of markers and a range of diversity levels, the assay provided identification at species level and differentiated between local isolates, which has the potential to track Brucella transmission.
Single nucleotide polymorphisms (SNPs) are considered to have huge potential for genotyping and microbial forensics. Extensive sequencing studies on Brucella have not only solved some long standing taxonomic issues and identified new members of the group but also have provided a phylogenetic framework to enable the identification of SNPs for inclusion in diagnostic assays. A single tube multiplex SNP assay has been developed that can rapidly identify an isolate as a member of one of the Brucella species.
Brucella research at VLA is part of an International Consortium that has invested in the development of an ‘ORFeome’ to determine the relationships between the biological and molecular variation in the three main species of Brucella. Five novel antigens with potential for use in ELISA diagnosis have been identified using genome databases and basic bioinformatics methods. A multiplex bead based suspension assay is now under development.
As part of our function as the FAO/WHO Collaborating Centre for Reference and Research on Brucellosis and an OIE Reference Centre, samples are received for culture and identification from around the world. Another function is to ensure the harmonisation of molecular and biotyping methods with other international laboratories and workshops and ring trials have been organised. During the year scientists from Belgium, Turkey, Nigeria, Switzerland, Sicily, Iraq and the United States have visited VLA for training and/or information and technical guidance in routine procedures.
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Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides SC, continues to spread throughout Africa. A trial, attempting to eliminate a new outbreak of CBPP in Namibia with an antibiotic treatment of all cattle in 15 affected herds has been completed and results showed no clinical cases 9 months after treatment and no mycoplasmas in the lungs of selected seropositive animals.
An experimental infection of goats with the pathogen Mycoplasma mycoides subsp. mycoides LC was performed jointly with the IZS Teramo, Italy. Severe lung and joint lesions and associated clinical signs were seen in both intubated and in-contact goats demonstrating the pathogenic potential of this organism, which is widely found in Southern Europe. ELISAs and latex agglutination tests, but not complement fixation tests, detected seroconversion.
A trial, sponsored by Pfizer Animal Health, examining the effects of the antibiotic danofloxacin, on the spread of Mycoplasma capricolum subsp. capripneumoniae, the cause of contagious caprine pleuropneumonia (CCPP) was completed at the Pendik Institute in Turkey. The antibiotic reduced mortality rates in goats naturally affected with CCPP and significantly reduced infection rates in contact animals. This work should help to control outbreaks of CCPP seen for the first time in the Thrace (European) region of Turkey.
There is still little known of the pathogenic mechanisms of mycoplasmas. In the first study of its kind, we have shown that a number of mycoplasmas, including the pathogens Mycoplasma bovis and M.agalactiae, form biofilms which enabled greater resistance to heat and desiccation. The ability to produce biofilms may account for their survival in the environment despite lacking a cell wall.
Anthrax/Contagious Equine
Metritis Organism
(CEMO)/
Glanders
Surveillance for these diseases continues and a recent confirmed case of anthrax underlines the need for continued vigilance.
We have been actively collaborating with the HPA to harmonise diagnostic culture and PCR methodology for Bacillus anthracis. VLA and HPA are continuing to participate in European wide discussions on anthrax therapeutics and detection organised by Anthrax-EuroNet under a EU 6th Framework programme.
