Badgers and Bovine TB

Bovine is a debilitating disease which can affect all mammals, including badgers.

Badger picture: Wikimedia commons

Badger setts and social groups

In the UK, badgers live in social groups that share a territory, which they defend. A social group territory usually contains one or more main setts and a number of less frequently used smaller setts. Territory boundaries are marked by latrines. Badger setts tend to be found in woodland, hedgerows and field margins. Badgers usually forage on grazed pasture and open woodland habitats, with earthworms making up the majority of their diet.

The average life expectancy of a non-captive badger is between three and five years, although badgers kept in captivity can live for much longer. The single largest cause of death in the wild is thought to be as a result of being hit by road traffic.

How many badgers are there in Wales?

Badgers are nocturnal and live underground and so estimating their population can be very difficult. Much of the information we have on the abundance and distribution of badgers in Wales was collected as part of three national badger sett surveys carried out between 1985 and 1987, 1994 and 1997, and 2011 and 2013. The results of the latest survey estimated that there were 7,300 badger social groups in Wales. The results indicate that the number ofn main setts estimated in Wales has remained fairly constant over the three surveys.

A further study estimated social group size by genotyping hair samples collected at 120 main setts across England and Wales. Combining the results from this study and the most recent national badger sett survey, it is estimated that there are approximately 60,000 badgers in Wales.

Badgers are not an endangered species but are protected by UK and European law in order to prevent their persecution.

Bovine tuberculosis in badgers

Bovine TB can affect all mammals, including badgers. There has been evidence of a link between bovine TB in badgers and cattle since the discovery of an infected badger carcass in Gloucestershire in 1971. Other evidence supporting this link includes:

A higher level of bovine TB infection in badgers compared to other wild mammals
High levels of infection in badgers being associated with areas of high levels of infection in cattle herds,
A survey of badgers found dead in Wales in between 2005 and 2006 found that the geographical distribution of molecular types of Mycobacterium bovis (the bacterium that causes bovine TB) found in badgers was similar to those found in cattle
It has been proven experimentally that badgers can transmit bovine TB to cattle.
TB is not a major cause of death in badgers. TB infected badgers can live for several years during which time their ability to infect other animals will vary.

Contact between cattle and badgers

Cattle may pick up infection by coming into close contact with other infected animals. These may be other cattle or wildlife including badgers, or contaminated material like grass, soil and feed. Badgers have been found to visit farm buildings to take food and bedding. They have been recorded defecating and urinating on stored cattle feed and coming into direct contact with housed cattle. Both represent opportunities for the spread of infection.

Direct contact between cattle and badgers in the field is rare, and it is more likely the disease is transmitted in both directions by indirect means through environmental contamination (faeces, urine, sputum and pus).

The organism that causes Bovine TB has been recovered in soil around badger setts and in badger faeces. Cattle are naturally curious animals and may come into contact with infectious material if they are able to investigate these areas. Cattle have also been observed investigating dead badgers.

Contribution to bovine TB in cattle

The lack of a clear understanding of how the disease is transmitted between cattle and badgers poses difficulties in developing new or novel methods to definitely break the transmission routes. The testing and slaughter of infected cattle alone is unlikely to clear-up infection in a herd when re-infection occurs from badgers. This makes control very difficult.

It has proved difficult to eliminate the disease from cattle herds in areas of Wales where infection is also present in badgers. The testing and slaughter of infected cattle alone is unlikely to clear-up infection in a herd when re-infection occurs from badgers. This makes control very difficult and eradication impossible.