A breakthrough in the search for a vaccine for tuberculosis, a disease which kills millions of humans and animals a year, has been made by veterinary scientists trying to eliminate bovine TB in Britain.
The scientists, announcing their find today, discovered after sequencing the entire genome of the organism causing bovine tuberculosis, that humans originally gave animals TB, rather than the other way round as had been supposed.
Glyn Hewinson, leader of the project for the veterinary laboratories agency, part of the Department for Environment, Food and Rural Affairs, said the discovery meant that a vaccine being developed to save cattle from TB would probably work on humans. The human and bovine forms of the disease are 99.9% identical.
There is international alarm at the spread of TB resistant to multiple drugs. The vaccine for human TB is called BCG, but although it is 80% effective in Britain it is useless in some parts of the world because of developing resistance.
Dr Hewinson said the TB types were so close that a bovine vaccine would almost certainly stop both diseases, and even if it did not, it would require only the "tiniest modification to make it effective".
The veterinary laboratories agency, the pathogen genome sequencing unit at the Sanger Institute, Cambridge, and the Institut Pasteur in Paris, are collaborating to produce a vaccine.
The report, published today in the Proceedings of the National Sciences, in the US, says it was always believed that human TB had been caused by bovine TB crossing over to humans when cattle were domesticated 10,000 to 15,000 years ago.
But the gene sequencing shows that the cattle TB genome is smaller than the human form, making it more likely that people gave cattle TB rather than the other way round. Bovine TB can also infect humans but the number of cases has been quite small.
Drug-resistant TB is taking a toll in Asia, South America and southern Africa, and 30m people are expected to die from it in the next 10 years. Many of the large mammals of Africa can also die from the disease.
Another 10 years is expected to pass before a TB vaccine is fully developed. But the genome sequencing means that better testing for TB can be developed enabling early diagnosis and preventative measures to avoid spread of the disease.
Elliott Morely, the minister for animal health, said: "This is a world-class scientific breakthrough which gives us a wide range of new information with which to fight this disease."
The government has been spending £12m a year on wide-ranging research into bovine TB because the disease reached epidemic proportions in western England and is spreading to other parts of the UK. Before the recent outbreak of foot and mouth disease, more than 8,000 cattle were being destroyed each year to keep the TB in check.
The spread of the disease has been blamed by members of the farming industry on badgers, which also get TB and are numerous in the West Country.
A selective badger slaughter policy, to compare infection rates in cattle, continues, clearing all badgers from some areas and none from others. From this it is hoped to prove whether badgers can spread TB, but results will not be clear for another two years.
