Is selenium implicated in the badger/cattle/TB problem?

Following on from yesterday’s blog on organic farmer Dick Roper’s experiences of TB, badgers, selenium  and maize I have been investigating  the situation further. I have a friend Elliot Haines who is 5th year medical student at the Peninsula Medical School in Exeter and we have been discussing  tuberculosis (TB). He has found some interesting papers regarding human health, TB and selenium.

For example a paper states that people with TB have lower selenium levels compared to those who don’t have TB – see here. This paper suggests that people with TB (and HIV) who have been given vitamins and selenium show improvements in their health. Another paper also reports an improvement in patient’s health who are suffering from TB when they are prescribed selenium – see here. Selenium levels is clearly playing a role in human health and TB.

Interestingly the Farmer’s Weekly and farming academics have published articles stating that many areas in the UK are selenium deficient and that this is an issue for agriculture and human health. – see here, here  and here.

Below are three maps – they are not at all conclusive but they are worth investigating further ….

TB breakdowns in cattle herds in 2013 (note light blue dots are ‘closed breakdowns i.e. not TB in 2013)

 

This is the British Geological Survey map of selenium levels in the south west – red = lots of selenium, blue = little selenium

Here is the map of maize in the SW in 2010

I really don’t want to get into pseudoscientific analysis and conclusions but this is all very interesting – some high moorland areas of Dartmoor for example have high selenium levels, low maize levels and low TB levels but do have populations of badgers and cattle. The analysis of the maps the maps off Dartmoor is more complex and would be worthy of  detailed analysis.

Questions that I would like answered are:-

Is TB more prevalent in areas where selenium levels are lower?
Is TB more prevalent in areas where maize growing is more prevalent?
In areas where selenium levels are lower, does the growing of maize increase the threat of a TB outbreak?
Would some experimental work  on supplementary feeding of badgers with selenium  reduce the incidence of TB?
It would be interesting to know if all farmers who feed maize to cattle or are in areas of selenium deficient soils supplementary feed their cattle

The science seems to be saying

those (humans) with a selenium deficiency are more prone to TB
those (humans) with TB who are given  selenium make more progress in recovery  than those are aren’t

So maybe we ought to be researching this great deal more. As per my blog of yesterday, along Mr Roper’s experiences, should we be feeding selenium supplements to badgers to see what happens?

None of this is new but sadly we haven’t made enough progress – here are a couple of links to evidence Dr. Helen Fullerton made – the first in 1999 on this topic to a House Of Commons Select Committee – see here and here.

The National Trust has done some brilliant work on badger vaccination against TB on the Killerton Estate – see here. Adding in a ‘selenium element’ via supplementary of feeding of badgers with ‘selenium molasses’ would to me seem logical  – it may show that it is not a factor but imagine the impact  if it was conclusive! It would be cheap to do and be very useful in the overall debate.

So the hypothesis which needs to be tested is:- would supplementary feeding of badgers and cattle with selenium lead to a reduced incidence of TB outbreaks in cattle?

 

 

More on badgers, TB and maize

A few weeks ago I wrote about some research carried out by Exeter University which showed that areas which grew 10ha of maize on their land (as winter fodder for cattle) were 20% more likely to have TB outbreaks in their cattle herds – see here.

Well after publishing the blog I was contacted by Chris Baker who I had been out surveying mosses with in Fingle Woods earlier this year who also has an interest in this topic. Indeed he had written an article in the Guardian about it in 2007. Click here for the link to the article.

In essence the article tells the story of a farmer, Dick Roper,  in the Cotswolds who noticed that after he started growing maize on his farm he started to have TB breakdowns in his herd which he had never had before. He also knew that if you feed cattle with maize you also have to provide supplementary nutrients specifically selenium. He wondered whether the badgers who were also eating the maize had a selenium deficiency too and this in some way this was linked to the transmission of TB on his farm. As a result he started to put out selenium in the fields in small blocks of molasses which the badgers then ate and ….. yes the incidence of TB in his cattle dropped substantially. OK – its all very anecdotal but maybe there is a link between mineral deficiency in badgers and cattle which plays a part in the transmission of TB.

Several things spring to mind, firstly this piece was written 8 years ago, secondly as far as I know DEFRA haven’t followed it up and thirdly if I was a diary farmer and had TB problems I would want to give it a go to see if it made a difference.

Badgers, TB and intensive farming

Last Saturday I wrote a blog about the rise of maize growing in this country including Devon and Dartmoor and the environmental problems associated with it. I also made reference to a Soil Association paper on the subject called  ‘Runaway Maize’ – that document made reference to an anecdotal association between the incidence of TB in cattle and the growing of maize – there was no scientific reference detailing this so I didn’t mention it. However this week the University of Exeter (B Winkler and F Mathews) has published a detailed paper on the topic in a journal of the Royal Society “Environmental risk factors associated with bovine tuberculosis amongst cattle in high risk areas”. You can download the Royal Society paper here and you can read the University’s press office release here.

The paper details a mathematical model which has been produced based on data from over 1300 farms (some where TB was prevalent and some where it was not). The model predicts and I quote from the paper that “The risk of bTB breakdown increased on farms with greater areas of deciduous wood, maize, marsh and rough pasture, and in herds that were larger, fed silage and were dairy units. The risk decreased on farms that had a greater percentage of hedges in boundaries, that grazed cattle on fields that had been cut for silage or hay and had greater numbers of cattle moving off the holding”.

The discussion section states “Broadly, characteristics of higher intensity production, such as larger herd size, maize production, use of silage and reduced hedgerow abundance were linked with elevated infection risk”.

“The dairy industry is currently undergoing particularly marked alterations owing to market and regulatory changes. Average dairy herd sizes rose by 36% from 1990 to 2003 in England. In the same period, the area planted with maize in South West England increased fourfold. Badgers favour maize as a food source: in the south west of England 72% of land owners report badger damage to cereal crops (oats, maize, barley and wheat). Contamination of maize by badger faeces and urine may therefore present a possible route of infection. Maize may also play a role by altering badger population sizes and their nutritional status”.

This is a very important study produced by a highly reputable research unit and published in a world class journal.  In essence the paper says that the way we manage the countryside directly impacts on the incidence of bTB and therefore by changing some of these practices we should be able to reduce outbreaks of TB in cattle.

For every 10ha of maize that is planted the risk of a TB outbreak increases by 20%. In dairy herd of over 150 animals in size they were 50% more likely to suffer a bovine TB outbreaks than herds with 50 cattle or less. The report suggests that by excluding cattle from marshland (by fencing them out) TB outbreaks would be substantially reduced – for every 10ha of marsh on a farm TB outbreaks increase by 70%. On farms with 50km of field boundaries each extra 1km of hedgerow was linked with a 37% reduction in risk.

There is much in here for us all to mull over but there is also a real message of hope. If we are prepared to heed this advice and take action there is a route forward in the battle against bTB. Many of the actions proposed would also lead to a countryside richer in wildlife. If we choose to ignore the findings or are unable to implement them for economic reasons then the incidence of TB in cattle will continue to rise. This approach offers a science based alternative to the current controversial and unproven policies being trialled to reduce TB in some parts of the south west.