Bovine TB Infection Still Threatens Human Health In The UK

Main Category: Tuberculosis
Also Included In: Respiratory / Asthma;  Infectious Diseases / Bacteria / Viruses;  Veterinary
Article Date: 02 Jan 2009 - 0:00 PDT

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Bovine tuberculosis (TB) still remains a threat to human health in the UK, although the overall risk of infection is considered to be small, reveals research published in the journal Thorax.

The researchers detail three cases of TB infection arising in rural Cornwall, South West England.

Two confirmed cases of bovine TB caused by Mycobacterium bovis arose in a woman and her pet dog. A third case of latent infection occurred in the woman's 12 year old daughter, who had not been vaccinated against TB.

Before diagnosis, the 42 year old woman had felt generally unwell for a month and had had a chesty cough .

She had not drunk unpasteurised milk, recently travelled abroad, or had a compromised immune system-all factors associated with an increased risk of M bovis TB infection in the UK.

But she had worked as a veterinary nurse in the South West of England, and the strain of M bovis she had is a common cause of TB in cattle and badgers in this area.

Her pet dog developed a persistent cough four months later, and was diagnosed with TB. Further analysis revealed that it had been infected with the same strain of M bovis as its owner .

As part of routine procedures, household members were also tested for TB. Only the woman's 12 year old daughter tested positive although she did not have any symptoms.

Like her mother, she had not drunk unpasteurised milk, travelled abroad, or had a compromised immune system.

This particular form of TB infection remains "a serious animal health problem in the UK, despite longstanding statutory surveillance and control measures," say the authors.

But they emphasise that their case reports should not cause undue alarm. Despite the rise in the number of cases of TB infection identified in cattle since the mid 1980s, bovine TB infections account for less than 1% of laboratory confirmed cases of TB in people.

These figures are similar to those in other industrialised countries.

TB infection in animals can be passed on to people through breathing in airborne infectious droplets, drinking unpasteurised milk, or, more rarely, contact with broken skin.

The authors point out that these cases indicate that bovine TB is not a disease of the past, as has been suggested, and that it poses a "low, but ongoing, public health risk."

Doctors, vets, and public health officials need to remain vigilant for signs of this "often forgotten infection," they warn.

"Human and canine pulmonary Mycobacterium bovis infection in the same household: re-emergence of an old zoonotic threat?"
Thorax 2009; 64: 89-91
Click here to view abstract online.

Thorax