Cattle are twice as likely to catch TB from other cattle than badgers

Cows are twice as likely to catch bovine TB from other cattle as they are from badgers – offering hope for a reduction in culling

  • Researchers spent 15 years studying the genome of bovine tuberculosis
  • The team studied cattle and badgers in Woodchester Park in Gloucestershire
  • They found that inter-species transmission is twice as likely as badger to cattle
  • Instances of badger to cattle TB are ten times greater than cattle to badger TB 

Cattle are twice as likely to catch tuberculosis from other Cattle than they are from badgers according to new study into the make up and spread of the TB virus.

Researchers from the University of Edinburgh studied the genome of bovine tuberculosis in cows and badgers over a 15 year period in Gloucestershire.

The team analysed the entire genetic make-up of the bacteria from 230 badgers and 189 cattle, a process known as whole genome sequencing.

The new data gathered as part of the study will help to properly target treatment and control of the disease, according to Rowland Kao, from the University of Edinburgh.

The team say that if the study turns out to be representative of the country then any future badger culls could be targeted to better combat tuberculosis in cattle but have less of an impact on badgers. 

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 Researchers from the University of Edinburgh studied the genome of bovine tuberculosis in cows and badgers over a 15 year period in Gloucestershire (stock image)

Researchers say that any future culling and control programmes should focus on both cattle and badgers, not just badgers alone. 

‘In terms of policy, the results do not tell us whether killing badgers is more effective than controlling cattle to cattle transmission,’ said Lord John Krebs, Emeritus Professor of Zoology, University of Oxford told the Daily Telegraph.

‘The fact that more infections are transmitted within species than between species suggests that controlling transmission among cattle is a priority in the strategy for eliminating TB.’ 

England’s controversial badger cull was introduced in 2013 and is now being enacted in 40 areas in an attempt to reduce transmission to cattle. 

The Edinburgh team used data from an undisturbed population of badgers in Woodchester Park in Gloucestershire as well as from cattle in nearby farms.

‘This study provides the first direct evidence of transmission between badgers and cattle’, said Professor Kao, lead author.

‘It is an area where tuberculosis is known to occur frequently in both cattle and badgers.’

Bovine TB is an infectious respiratory disease of cattle that is mainly spread through inhaling infectious particles in the air. 

It is caused by the bacterium Mycobacterium bovis, which can also infect and cause disease in other mammals, including humans, deer, goats, pigs, cats and dogs.

‘Current approaches to controlling bovine tuberculosis only discriminate at a very coarse, regional level between areas where badgers are more likely to be involved in infecting cattle from areas where they are not’, said Professor Kao.

‘This work identifies genetic signatures that could guide the interpretation of similar data if collected in other, less-intensively studied areas.

‘This would allow for a more targeted control of tuberculosis in cattle and badgers, aiding efforts to control the disease and reduce the impact on the badger population.’

The team say that if their study turns out to be representative then culling and control should focus on both cattle and badgers, not just badgers alone (stock image)

Dr Kao and his team combined genetic information on the bacteria with details on where the cattle and badgers lived, when they were infected, and whether they could have had contact with one another.

WHAT IS BOVINE TB?

Bovine tuberculosis is a disease of cattle that can also infect badgers, deer, goats, pigs, dogs and cats. 

The disease is caused by the bacteria Mycobacterium bovis. 

This is related to the microbe that causes tuberculosis in humans. 

Bovine tuberculosis is typically transmitted aerially through coughs and sneezes.

It causes fever, coughing, weight loss, pain, diarrhoea and ultimately death.

Badgers are the most significant wildlife reservoir for the bacterium.

In the United Kingdom, most bovine tuberculosis outbreaks occur in the South West and the West Midlands. 

Scientists were then able to estimate how often the two species spread TB. 

They found that badgers play an important role in the maintenance of the disease in this area.

The study suggests that badgers are ten times more likely to give TB to cattle than cattle is to give it to a badger – but it’s most common for members of the same species to pass the disease to another member of its species. 

Farmers say that while the study covers a lot of things, it is also important to address the diseas reservoir in wildlife as well.  

‘For us, there isn’t just one thing that will deal with this disease, it’s a comprehensive approach that involves for both wildlife and cattle control’. Stuart Roberts, Vice President of the National Farmers’ Union told the Daily Telegraph.

‘So far the two areas where we have good evidence from culling, which are the only two that have completed the four year trials, they have shown very comprehensively that culling plays an important role in the control of TB.’

The research has been published in the journal eLife. 

WHAT IS TUBERCULOSIS AND IS IT MAKING A COMEBACK IN BRITAIN?

Tuberculosis (TB) is a bacterial infection spread between people by coughing and sneezing.

The infection usually affects the lungs but the bacteria can cause problems in any part of the body, including the abdomen, glands, bones and the nervous system.

At the beginning of the 19th century, TB killed at least one in seven people in England. But today – thanks to improvements in health, faster diagnoses and effective antibiotics – less than six per cent of those with TB are killed by the disease, with just under 4,672 cases reported in the UK in 2018.

Despite these improvements, in 2010 a report into TB in London and Britain as a whole found that the number of cases in the capital had risen by almost 50 per cent from 1999. 

Professor Alimuddin Zumla of University College London attributed the rise to people living under ‘Victorian’ conditions, with poor housing, inadequate ventilation and overcrowding in certain deprived areas of London.

He also said the increase in TB cases was predominantly among people born outside Britain, but who appear to have been infected in the UK, rather than in their country of origin.

The infection usually affects the lungs but the bacteria can cause problems in any part of the body, including the abdomen, glands, bones and the nervous system

TB infection causes symptoms like fever, coughing, night sweats, weight loss, tiredness and fatigue, a loss of appetite and swellings in the neck.

If the immune system fails to contain TB bacteria the infection can take weeks or months to take hold and produce symptoms, and if it is left untreated it can be fatal. 

TB is most common in less developed countries in sub-saharan and west Africa, southeast Asia, Russia, China and South America.  

Researchers in Wales said that of those infected with this disease in 2017, 55 per cent were born outside the UK. 

Although, 20 per cent had at least one of the following social risk factors: 

  • Being in prison
  • Alcoholism
  • IV drug use
  • Poor housing or homelessness 

Source: NHS   

 

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