The reporting this week from New Scientist, ProMed and the BBC Midlands website, of a human to human spread of tuberculosis, strain mycobacterium bovis, between 6 young people, one of whom has died, is a timely reminder that bTb, is not confined to cattle, and affects other mammals uncluding human beings.
We have variously reported spillovers not only into the tested 'canaries' - cattle - from the maintenance reservoir of disease in badgers, but into cats, free range pigs and deer. Camelids, such as alpacas are said to be very susceptible as well, but are rarely tested unless for export. Once infected and left to fester, any animal with bTb lesions carrying bacteria capable of onward transmission of the disease is a walking time bomb - to anything that crosses its path.
See some bTb time bombs :
The seriousness with which this disease should be taken, cannot be overstated. And the cavaliar attitude of government towards its eradication is a gross abdication of their responsibilty. After the 'Attested Herd' scheme for cattle in the 1950's, and the pasteurisation of milk, this disease was so nearly eradicated. Almost. This outbreak which spread laterally from one or two indivuduals, is a reminder that bTb kills. Period.
The article on ProMed website, and taken from the New Scientist report [edited]
"Six people who spent a night clubbing near Birmingham, in the English Midlands, in late 2004 have contracted bovine tuberculosis (TB). One man has been identified as the source of the outbreak, and one woman who was infected has died.
This is the 1st time in decades that human-to-human transmission of bovine TB has been documented in the United Kingdom and coincides with a steady increase in the rate of infection in cattle. Nearly one per cent of the British herd is now thought to carry the disease. (And how many badgers? - 28 percent in Monmouthshire - ed)
In the 1930s, around 40 per cent of cattle in the UK were infected with TB, and around 2000 people a year died from the disease, mostly as a result of drinking unpasteurized milk or coming into close contact with the animals. Pasteurization and the introduction of routine TB testing in cattle brought this under control but, in recent years, bovine TB has been on the rise, a trend that some farmers blame on badgers spreading the infection.
Peter Hawkey of the University of Birmingham, who presented findings on the human outbreak last week at the Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco, says that all the evidence suggests it was an isolated incident. "The increase of infections in cattle may increase the opportunity for human infection, but nothing has changed about virulence or transmission from cattle," he says.
(By that we assume he means that cattle are regularly tested, and slaughtered if they show contact with the bacteruium. Milk is pasteurised and so very little opportunity arises in the UK for onward transmission from cattle)
Hawkey says the outbreak was caused by a confluence of rare circumstances and should therefore not cause undue alarm. Some of the people affected had underlying medical conditions such as being HIV positive, or were using anabolic steroids, both of which would make them more susceptible to infection. The average age of the people affected by the outbreak was 32, whereas those who catch the disease from cattle are usually much older.
(bTb can have a long incubation period and contact in early years may not be apparent until late adulthood - although not in this case)
[byline: Michael Reilly and Linda Geddes]- -- ProMED-mail<firstname.lastname@example.org>