Bovine TB ‘can spread in humans’
Bovine TB can spread from human to human, scientists fear after a cluster of six cases, one fatal, in England.
All had visited the same Birmingham bar or nightclub, yet only one of the young patients had been in contact with infected unpasteurised milk or cattle.
The Health Protection Agency said although rare, the cases emphasised the need for rigorous checks and controls.
Experts told The Lancet that bovine TB was an under-appreciated cause of disease and death in humans.
The HPA investigation was launched after one case was reported in 2004, four in 2005 and one at the beginning of 2006.
DNA fingerprinting showed all six cases were identically linked, most probably by person-to-person spread.
Mycobacterium bovis infection in humans used to be relatively common in the late 19th and early 20th centuries.
During this time, over 50,000 new cases and 2,500 human TB deaths were recorded each year in Britain.
Pasteurisation laws and eradication programmes in cattle helped reduce the toll.
Estimates suggest only 1% of TB cases in the western world are caused by bovine TB – the rest are down to the conventional human TB bug Mycobacterium tuberculosis.
Grace Smith and colleagues from the HPA say there are several factors that could explain how the cluster of infections linked to Birmingham occurred.
Four of the patients had weakened immune systems through either HIV infection, diabetes or misuse of alcohol or steroids, which may have made them more susceptible to the infection.
Also, the environment of clubs and bars is good for spreading airborne bugs – prolonged and repeated contact in a confined space with poor ventilation, noise resulting in shouting and smoke that makes people cough.
The authors warned in The Lancet: "Similar outbreaks of M tuberculosis, and, to a lesser extent, M bovis, are possible unless public health control measures are instituted and maintained."
A Defra spokesman said: "Human to human spread of M bovis is extremely unusual.
"A low occupational risk of M bovis infection remains for farmers, veterinarians, abattoir workers and other people who may come into contact with infected animals or their carcases, or for those who regularly consume unpasteurised cows milk."
Charles O Thoen, of the College of Veterinary Medicine at Iowa State University in the US, said M bovis infections in humans was most likely to be a problem in places where HIV infection is widespread, such as sub-Saharan Africa.
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