A proof of concept study to assess the potential of PCR testing to detect natural Mycobacterium bovis infection in South American camelids.

BACKGROUND: Cases of Mycobacterium bovis infection South American camelids have been increasing in Great Britain. Current antemortem immunological tests have some limitations. Cases at post mortem examination frequently show extensive pathology. The feasibility of detecting Mycobacterium bovis DNA in clinical samples was investigated. FINDINGS: A sensitive extraction methodology was developed and used on nasal swabs and faeces taken post-mortem to assess the potential for a PCR test to detect Mycobacterium bovis in clinical samples. The gross pathology of the studied South American camelids was scored and a significantly greater proportion of South American camelids with more severe pathology were positive in both the nasal swab and faecal PCR tests. A combination of the nasal swab and faecal PCR tests detected 63.9% of all the South American camelids with pathology that were tested. CONCLUSIONS: The results suggest that antemortem diagnosis of Mycobacterium bovis in South American camelids may be possible using a PCR test on clinical samples, however more work is required to determine sensitivity and specificity, and the practicalities of applying the test in the field.

Mycobacterium bovis infection in domestic pigs in Great Britain.

Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), infects a wide range of wild and domestic mammals. Despite a control programme spanning decades, M. bovis infection levels in cattle in Great Britain (GB) have continued to rise over recent years. As the incidence of infection in cattle and wildlife may be linked to that in swine, data relating to infection of pigs identified at slaughter were examined in this study. Between 2007 and 2011, almost all M. bovis-infected pigs originated from farms in the South-West and West-Midland regions of England. The data suggest that pigs raised outdoors or on holdings with poor biosecurity may be more vulnerable to infection with M. bovis. In the majority of cases, the same strains of M. bovis were found in pigs and cattle, despite that fact that direct contact between these species was rarely observed. Genotyping and geographical mapping data indicated that some strains found in pigs may correlate better with those present in badgers, rather than cattle. In consequence, it is proposed that pigs may represent a useful sentinel for M. bovis infection in wildlife in GB. Given the potential implications of this infection for the pig industry, and for the on-going effort to control bovine TB, the importance of understanding the epidemiology and pathogenesis of M. bovis infection, as well as monitoring its prevalence, in pigs should not be underestimated.

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 cat's 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.

Significant rising antibody titres to influenza A are associated with an acute reduction in milk yield in cattle.

Sporadic cases of an acute fall in milk production, "milk drop", were investigated in a Holstein Friesian dairy herd in Devon. The investigation was a case control study with two controls per case. Paired blood samples demonstrated that rising antibody titres to human influenza A/England/333/80 (H1N1) and human influenza A/Eng/427/88 (H3N2) were associated with an acute fall in milk production. Rising titres to bovine respiratory syncytial virus (BRSV), bovine virus diarrhoea virus (BVD), infectious bovine rhinotracheitis (IBR) and parainfluenza virus 3 (PI3) were not associated with an acute fall in milk production. Cases with rises in antibody to influenza A had significantly higher respiratory scores and rectal temperatures than their controls. The mean loss of milk production for the cases with rises in antibody to influenza A compared to their controls was 159.9L. This study provides further evidence that influenza A persists in cattle and causes clinical disease.