'The outbreak of TB begs the question: in what circumstances - if any - might culling of a human population be considered?'

Culling is now the only answer' are words we are unlikely to hear from ministers when referring to the recent outbreak of tuberculosis in Leicester. But some may ask, 'why not?'

If culling is a solution to the foot and mouth outbreak, why not use the same draconian methods in cases of deadly disease which affect humans?

TB is not some fairly harmless infection like the common cold - it has a reputation as one of the nastiest of human afflictions. In the early 19th century, a third of all deaths in the UK were TBrelated. In 1930s Britain, 40 per cent of those volunteering for TB testing were still found to be infected. That observation led, despite the country being at war, to mass x-ray screening in October 1943.

At this distance we may wonder why the situation was still so bad by the 1940s. A TB vaccine had already been available for many years. The famous BCG - Bacille Calmette-Guérin - had been developed in 1922 by doctors Calmette and Guérin, producing immunity to the human disease by vaccinating with attenuated bovine TB.Alas, the breakthrough was soon followed by a health scare in 1930, when more than 70 children died in Lübeck, Germany, after being given the vaccine. The cause remains a mystery, but it soon led to a new BCG vaccine.

Of course, consumption wasn't all bad: TB did see off two of the appalling Brontë sisters, saving the world from yet more of their turgid literary excrescences - not to mention doing to Doc Holliday what the Clanton gang failed to achieve at the OK Corral.

TB also led indirectly to the birth of the giant Swiss pharmaceutical industry after the creation of hundreds of TB sanatoria in the Alps which provided a captive market for medicines of all kinds. It also eventually led to huge sales of lino as a floor covering: one of its major selling points was that saliva could be easily and hygienically wiped off it.

And inevitably the medical profession benefited financially too, via the many state-funded sanatoria which sprang up all over Britain during the early decades of the 20th century - despite mortality rates being exactly the same for those who stayed at home. But at least something was seen to be done.

Sadly for doctors'wallets, the physicians' armory was enhanced for a second time in 1950 when, in addition to the shield of vaccination, the sword of streptomycin, developed in the US in 1945, was first used to cure TB. But today new strains of TB are emerging which are resistant to these wonder drugs.

Of course, no one is seriously suggesting that culling - of, say, the entire population within 3km of Leicester - is a serious response to TB. But the outbreak of such a life-threatening disease does beg the question, in what circumstances - if any - might culling of a human population be considered?

The idea has been covered extensively in films and literature.Heartless governments have been regularly portrayed as only too willing to 'nuke the bugs' - and their own citizens with them. Curiously, in real life there seem to be few examples of state-sponsored culling.

One of the few recorded cases took place in Switzerland in 1348 at the height of the Black Death.

Ten Jews admitted under torture that they were responsible for spreading the contagion. Their execution was followed by rather more informal 'culling' of many thousands more Jews across France and Germany until Pope Clement demanded a halt.

But murdering people of a different culture in a climate of fear and ignorance is quite a different proposition from deciding to kill one's own kith and kin.Historically, quarantine seems to have been the more common method. For example, isolating lepers in colonies rather than execution and incineration, is a time-honoured practice, though had our ancestors been less ignorant of the means by which disease is transmitted, they might have been less kind.

Nature is full of nasty surprises, and viruses mutate continuously;

there is every possibility that in the near future a lethal killer bug will emerge.How would the government, or indeed each of us, have reacted had HIV been transmitted by sneezing, or been as contagious as influenza?

Can there ever be ethical grounds for culling humans?

Logically the answer must be yes.

In principle, public authorities would be justified in culling if those infected with a lethal disease could not be isolated and the number expected to die as a result of not culling were greater than those to be culled.Whether any western government would ever have the courage to take such a drastic step remains questionable.

Meanwhile, would anyone care to speculate on whether such a contingency plan exists somewhere in the vaults at the Department of Health?