@andy_1robertsonBovine TB biosecurity videos
In 2011 FERA (now APHA) created a series of videos on bovine TB and farm biosecurity.
They are available on the TBhub website, on a playlist on the Defra Youtube channel and can also be found below. There are five videos covering:
- Introduction –badger behaviour and TB infection in badgers.
- Identifying badger activity – badger setts, runs and latrines.
- Biosecurity at pasture – measures to reduce interactions between badgers and cattle at pasture.
- Biosecurity in farm buildings (part 1) – measures to reduce badger access to farm buildings and yards.
- Biosecurity in farm buildings (part 2) – measures to reduce badger access to farm buildings and yards.
The videos contain a wealth of useful information, especially the biosecurity at pasture and in farm building videos (videos 3-5), which feature several practical examples and interviews with farmers who have used measures on their farms. The effectiveness of measures at reducing badger activity in yards and buildings is largely based on a paper by Judge et al. (2011) and many of the measures are also outlined in a series of factsheets on the TB hub.
As these videos are now a few years old, there are a couple of areas which need updating based on research published in recent years (ie after the videos were created).
Video 1 – Introduction
Video 1 – corrections /updates
At 3:15 the video states…….
“Local badger population densities vary considerably throughout the country, from 20 adults per km2 in the Southwest to less than 1 adult per km2 in less favourable areas. The last national survey of the badger population in 1997 estimated that it was around 325,000. There is the perception that in some areas the badger population has increased dramatically since then, but there is no evidence currently available to support this.”
A national badger survey carried out from 2011-2013 (Judge et al. 2014; Judge et al. 2017) estimated that average badger densities in the south west were around 6 badgers per km. In particularly high density areas badger densities can be 20 per km2, as quoted in the video, but this is more the upper value, rather than the average across the whole south west region.
This more recent study estimates that the population is 424,000 for England and 61,000 for Wales (Judge et al. 2017). It is important to remember that this was conducted in 2011-2013, which was prior to the roll out of culling across England. These population estimates use modern genetic based methods (which makes it difficult to compare the numbers to previous studies), but as the authors state “our results are consistent with a marked increase in the badger population of England and Wales since the 1980s”. Comparisons of main sett numbers (comparing 2011-13 to the 1985-88 surveys) also suggest a large increase in the badger population, with a 103% increase in England, but no change in Wales (Judge et al. 2014).
Video 2 – Identifying badger activity
Video 2 – corrections / updates
At 1:10 the video states…
“The relationship between badgers, cattle and bovine TB is extremely complex. Badgers undoubtedly become infected with bovine TB and can pass it on, but what proportion of cattle herd breakdowns are caused by badgers is unknown.”
It is true that there is a lot of uncertainty over the proportion of breakdowns which are caused by badgers (as opposed to by infected cattle). A study published after this video has estimated the contribution of badgers to TB breakdowns using data from the RBCT (Donnelly & Nouvellet 2013). This study found the following:
- Badgers to cattle transmission is estimated to cause 6% (1-25%) of cattle breakdowns
- Further cattle to cattle transmission means that TB from badgers is then transmitted further, so that the overall contribution to cattle breakdowns is 52% (9-100%).
There is a lot of uncertainty around these numbers (hence the wide ranges in the brackets), for more details about this study see the fact sheet and post on this website.
At 4:02 the video states……
“In high density areas there are usually 3 to 6 setts per territory, but in lower density areas there can be up to 40.”
I think this statement must have been a slight mistake, of course there will not be almost 10 times the number of setts in low density areas. Although the density of badger groups (main setts) varies among land types in the UK (higher in the SW and lower in the N/E), numbers of setts per main sett (ie setts per group) recorded in the national sett survey are actually similar in high density and low density areas (Judge et al. 2014).
Video 3 – Biosecurity at pasture
Video 3 – corrections / updates
At 2: 30 the video states….
“While contact with faeces, urine and other excretions from infectious badgers are a real risk of disease transmission the M. bovis bacteria may only remain infectious on pasture for a few days to a few weeks depending on the weather. Therefore, it is highly unlikely that any faeces taken up during the silaging process will still be infectious by the time it is fed to cattle.”
Several different experimental studies have investigated the survival times of M. bovis in different environments, which are summarised in several fact sheets on this website.
Although it is true that risk from silage are probably lower than other sources, longer term survival of M. bovis in silage cannot be ruled out (at least based on the limited available science on the subject). See the survival of M bovis in feed water and soil fact sheet.
Video 4 & 5 Biosecurity in farm buildings (no updates required)
If you are interested in free biosecurity advice contact the TB advisory service at http://www.tbas.org.uk/
