T. R. Crawshaw

Bacillus Calmette-Guérin vaccination reduces the severity and progression of tuberculosis in badgers

Control of bovine tuberculosis (TB) in cattle has proven particularly challenging where reservoirs of infection exist in wildlife populations. In Britain and Ireland, control is hampered by a reservoir of infection in Eurasian badgers (Meles meles). Badger culling has positive and negative effects on bovine TB in cattle and is difficult, costly and controversial. Here we show that Bacillus Calmette-Guérin (BCG) vaccination of captive badgers reduced the progression, severity and excretion of Mycobacterium bovis infection after experimental challenge. In a clinical field study, BCG vaccination of free-living badgers reduced the incidence of positive serological test results by 73.8 per cent. In common with other species, BCG did not appear to prevent infection of badgers subjected to experimental challenge, but did significantly reduce the overall disease burden. BCG vaccination of badgers could comprise an important component of a comprehensive programme of measures to control bovine TB in cattle.

Mycobacterium microti: More Diverse than Previously Thought

ABSTRACT Mycobacterium microti is a member of the Mycobacterium tuberculosis complex of bacteria. This species was originally identified as a pathogen of small rodents and shrews and was associated with limited diversity and a much reduced spoligotype pattern. More recently, specific deletions of chromosomal DNA have been shown to define this group of organisms, which can be identified by the absence of chromosomal region RD1mic. We describe here the molecular characteristics of 141 strains of the Mycobacterium tuberculosis complex isolated in Great Britain over a 14-year period. All strains have characteristic loss of some spoligotype spacers and characteristic alleles at the ETR-E and ETR-F variable-number tandem-repeat (VNTR) loci, and a sample of these strains was deleted for regions RD7, RD9, and RD1mic but intact for regions RD4 and RD12. We therefore identified these strains as M. microti and show that they have much more diverse spoligotype patterns and VNTR types than previously thought. The most common source of these strains was domestic cats, and we show that the molecular types of M. microti are geographically localized in the same way that molecular types of Mycobacterium bovis are geographically localized in cattle in the United Kingdom. We describe the pathology of M. microti infection in cats and suggest that the feline disease is a spillover from a disease maintained in an unknown wild mammal, probably field voles. The location of the cats with M. microti infection suggests that they do not overlap geographically with the strains of Mycobacterium bovis in Great Britain.

Validation of the BrockTB Stat-Pak Assay for Detection of Tuberculosis in Eurasian Badgers (Meles meles) and Influence of Disease Severity on Diagnostic Accuracy

ABSTRACT A lateral-flow immunoassay (BrockTB Stat-Pak) for detecting tuberculosis in Eurasian badgers was 49% sensitive and 93% specific against culture for M. bovis (n = 1,464) at necropsy. However, the sensitivity was significantly higher (66 to 78%) in animals with more severe tuberculosis, indicating that the BrockTB Stat-Pak may be useful for the detection of badgers with the greatest risk of transmitting disease.

Mycobacterial disease in cats in Great Britain: I. Culture results, geographical distribution and clinical presentation of 339 cases

This study investigated 339 cases of feline mycobacterial disease from cats with cutaneous lesions or masses found at exploratory laparotomy. Tissue samples were submitted to the Veterinary Laboratories Agency for mycobacterial culture over a 4-year period to December 2008. The study assessed which species of culturable mycobacteria were involved, where the cats lived, and their clinical presentation (physical findings, serum biochemistry, radiography, feline leukaemia virus and feline immunodeficiency virus status). Mycobacterium microti was cultured from 19%, Mycobacterium bovis 15%, Mycobacterium avium 7%, non-M avium non-tuberculous mycobacteria 6%, with no growth in 53% of samples. M microti, M bovis and M avium were found in almost mutually exclusive clusters within Great Britain (GB) (ie, M bovis in South-West England/Wales/Welsh Border, M avium in eastern England and M microti south of London and in South-West Scotland). While differences were seen in the clinical presentation and distribution of lesions caused by the different infections, these were not sufficiently different to be diagnostic. Cats commonly presented with single or multiple cutaneous lesions (74%), which were sometimes ulcerated or discharging, located most frequently on the head (54%). Lymph nodes were usually involved (47%); typically the submandibular nodes. Systemic or pulmonary signs were rarely seen (10–16%). When a cat is suspected of having mycobacteriosis, accurate identification of the species involved helps to determine appropriate action. Our findings show that knowing the cats geographic location can be helpful, while the nature of the clinical presentation is less useful. Most cases of feline mycobacterial disease in GB are cutaneous.

Outbreak of tuberculosis caused by Mycobacterium bovis in golden Guernsey goats in Great Britain.

An outbreak of caprine tuberculosis caused by Mycobacterium bovis was disclosed in June 2008, affecting goats of the golden Guernsey breed kept on 10 separate smallholdings in south-west Wales and the west of England. Following the initial diagnosis at postmortem examination, 30 goats that reacted positively to the single intradermal comparative cervical tuberculin (SICCT) test, together with five in-contact animals, were euthanased and subjected to postmortem examination and mycobacterial culture. Spoligotyping and variable number tandem repeat analysis of isolates showed that they were all of the same genotype, endemic to south-west Wales. Retrospective movement tracings identified a goat herd in south-west Wales, by then completely dispersed, as the probable common source of infection. There was a perfect correlation between the SICCT test and culture results in all slaughtered goats. Grossly visible tubercular lesions were observed at postmortem examination in all but one reactor.

Comparison of a standard and a detailed postmortem protocol for detecting Mycobacterium bovis in badgers

A standard postmortem protocol, consisting of gross pathology, culture for mycobacteria and limited selective histopathology, was used in the randomised badger culling trial in Great Britain to detect Mycobacterium bovis infection. This standard protocol was compared with a more detailed protocol in which more tissues were examined grossly, more tissues were cultured, more culture slopes were seeded, the culture period was extended and tissues were examined routinely by histopathology. The standard protocol was more sensitive in badgers with gross visible lesions than in badgers with no gross visible lesions. When applied to the study population of badgers, the overall sensitivity of the standard protocol relative to the more detailed protocol was estimated to be 54·6 per cent (95 per cent confidence interval 44·9 to 69·8 per cent). Badgers with tuberculosis (tb) detected by the standard protocol had a mean of 7·6 tissues with microscopic lesions suspicious of tb. The additional badgers detected by the detailed protocol had a mean of 4·4 tissues with microscopic lesions suspicious of tb.

TB in goats caused by Mycobacterium bovis

SIR, — We would like to report a severe outbreak of tuberculosis (tb) caused by Mycobacterium bovis in golden Guernsey goats. Reports of caprine tb have been very rare in the uk since the introduction of a mandatory tb testing and slaughter scheme for cattle herds in the 1950s. However, the extent

Protection of Eurasian badgers (Meles meles) from tuberculosis after intra-muscular vaccination with different doses of BCG

Mycobacterium bovis infection is widespread in Eurasian badger (Meles meles) populations in Great Britain and the Republic of Ireland where they act as a wildlife reservoir of infection for cattle. Removal of infected badgers can significantly reduce the incidence of bovine tuberculosis (TB) in local cattle herds. However, control measures based on culling of native wildlife are contentious and may even be detrimental to disease control. Vaccinating badgers with bacillus Calmette-Guerin (BCG) has been shown to be efficacious against experimentally induced TB of badgers when administered subcutaneously and orally. Vaccination may be an alternative or complementary strategy to other disease control measures. As the subcutaneous route is impractical for vaccinating wild badgers and an oral vaccine bait formulation is currently unavailable, we evaluated the intramuscular (IM) route of BCG administration. It has been demonstrated that the IM route is safe in badgers. IM administration has the practical advantage of being relatively easy to perform on trapped wild badgers without recourse to chemical immobilisation. We report the evaluation of the efficacy of IM administration of BCG Danish strain 1331 at two different doses: the dose prescribed for adult humans (2-8×10(5)colony forming units) and a 10-fold higher dose. Vaccination generated a dose-dependent cell-mediated immune response characterised by the production of interferon-γ (IFNγ) and protection against endobronchial challenge with virulent M. bovis. Protection, expressed in terms of a significant reduction in the severity of disease, the number of tissues containing acid-fast bacilli, and reduced bacterial excretion was statistically significant with the higher dose only.

Mycobacterial disease in a population of 339 cats in Great Britain: II. Histopathology of 225 cases, and treatment and outcome of 184 cases

This study investigated 339 cases of feline mycobacterial infection, with histopathology findings from 225 cases, and treatment and outcome information from 184 cases. Tissue samples from cats with cutaneous lesions or suspicious masses at exploratory laparotomy were submitted to the Veterinary Laboratories Agency for mycobacterial culture over a 4-year period to December 2008. The study reviewed the files for information about histopathology, treatment and outcome, and blindly reviewed histopathological changes (including staining for acid-fast bacteria [AFB]) in a sub-set of 45 cases. When a cat is suspected of having a mycobacterial infection, accurate identification of the species involved helps to determine possible treatment options and prognosis. The study confirmed that histopathology and the presence of AFB are useful tools in the recognition of mycobacterial infection. Unfortunately, they did little to help determine the species of mycobacteria involved. The study identified a group of cats that were negative for AFB at the primary laboratory, but from which mycobacteria could be cultured; commonly Mycobacterium bovis or Mycobacterium microti. The study also identified a group of cats which where culture negative, despite typical signs of mycobacterial infection and positive AFB staining. Many cases responded favourably to treatment (56% of the cases where information was available), and many cats gained complete remission (42%). However, relapses were common (64%) and often followed by pulmonary and/or systemic spread that may have resulted from treatment with short courses of single drugs. This study shows that the diagnosis and treatment of feline mycobacteriosis is complex and challenging.

Use of serological techniques for diagnosis of Mycobacterium bovis infection in a llama herd

Mycobacterium bovis is increasingly being identified in domestic species other than cattle in Great Britain ([Defra 2008][1]). Amendments to the legislation first introduced in 2006 and later incorporated into the current Tuberculosis (TB) Order ([Anon 2007][2]) resulted in the obligation to notify