Badgers, Tuberculosis (TB) and the Danger to Cattle and Humans. Is Culling the Answer? 2
Badgers were first discovered to carry bovine tuberculosis (bTB) in 1971. Since then much research has been undertaken and badgers are now widely considered to represent a significant wildlife ‘reservoir’ of this disease.
Cattle are by far the most susceptible domestic species to the M.bovis bacteria, although farmed deer, boar, bison, buffalo, goats, llamas and alpacas can also be affected.
How does TB spread?
In hotspot areas of cattle TB, the badger population is considered to play a significant role in maintaining the disease and in preventing its eradication. Although other wild mammals carry the disease, badgers have high rates of infection (the number of animals contracting the disease) and high rates of being infectious (where an infected animal then starts spreading the disease).
The ecology and behaviour of badgers means the potential transmission to cattle is high. For example, badgers often forage in pasture, and can spread the disease by cattle sniffing infected faeces and urine. It is considered that these factors make badgers an important link in the cycle of disease. Other routes of disease transmission include direct contact between badgers and cattle and transmission within farm buildings where cattle are housed or feed is stored.
Once a bovine (e.g. a cow) is infected, however, it does not immediately start spreading the disease. TB develops very slowly and it takes time for lesions to grow in the lungs, and these lesions have to open up before cattle start coughing out the bacteria.
What are the symptoms of TB?
TB is primarily a disease of the respiratory system but very few cases are reported in cattle. This is possibly because the symptoms are very similar to other respiratory diseases but also because regular TB testing of dairy herds catches the infection long before it becomes a chronic disease visually affecting the animal.
As lesions are most common in the lungs (called tubercules) a hard, dry, short cough is usually the first symptom, leading to more frequent coughing and laboured breathing. As this continues cattle will lose condition and later cough up blood.
What is the scale of the TB issue in humans?
The Department of Health still views TB as a ‘major public health problem’ and of the 9.2 million new worldwide cases of TB in 2007 (resulting in 1.7 million deaths!) around 7,750 were in the UK.
In the UK and across the world, more than 99 per cent of new cases in humans are caused by M.tuberculosis and not M.bovis. The risk is still there and so TB is a notifiable disease in all farmed animals. TB in humans presents with the same symptoms whether it is caused by M.tuberculosis and not M.bovis.
How do farmers prevent their cattle being infected by TB?
Farmers are required to undertake regular dairy herd surveillance testing for the disease. If cattle test positive they are sent for compulsory slaughter. In 2010 around 25,000 cattle were slaughtered costing the taxpayer tens of millions of pounds. Once a farm has had TB detected in its herd, movement restrictions are placed on that farm. This means animals cannot be moved off the farm (unless straight to slaughter) until the herd passes two further tests, to ensure TB is no longer detected in the herd.
Farmers can often be surprised at the level of badger activity in and around farm buildings, so they also take practical measures to prevent their animals contracting the disease from badgers. Husbandry measures, such as ensuring gates on cattle sheds and feed stores fit well and are shut at night and raising troughs and salt licks.
The financial implication to farmers.
Regular testing and slaughter of animals is a stressful and costly affair. Although farmers receive money for the animals slaughtered, the amount received does not always accurately reflect the true cost of that animal, for example when high value breeding stock contract the disease.
Government figures state that every time a farmer has a breakdown in the herd it will cost an average of £33,000, although this figure can vary greatly between farms. The compensation paid does not cover any consequential losses, for example the loss in milk sales, or the cost of hiring more labour to help with TB testing.
Is culling badgers the right answer?
A poll conducted by the BBC last year found that about two-thirds of the public oppose culling, with majorities in every age group, region and across both genders.
I’m sure the general perception of badgers is a classically beautiful English animal, but before the question of, ‘do you oppose killing badgers to curb cattle tuberculosis’ with a simple yes or no answer, might it be better to enlightened the general public that it’s ultimately costing the taxpayer about £100m per year and resulting in the death of tens of thousands of cattle?
Your views & thoughts?
True, cattle are most susceptible to bTB, because it is a disease of CATTLE.
At least 80% of bTB in cattle is cattle to cattle transmission.Transmission by Badgers to cattle is a still very contentious point, there has been no clear way that it can be done. No scientific study HAS shown that it is possible.
Cattle cannot be infected by just sniffing Badger urine or droppings,that is impossible. The bacterium either has to be taken in as an airborne particle or ingested by it eating it.
Airborne infection is the most prevalent way of infection, which needs continuous contact between the infected and the non infected, whereby millions of bacterium is passed on.
Ingestion is the harder route. It needs many millions more to infect the recipient in this way.
Cattle naturally avoid both urine and faeces of badgers when grazing. By the time they are ready to eat grass that has been urinated on, the bTB bacillus has been destroyed by ultraviolet light from daylight.
If cattle eat anywhere near faeces polluted grass it is because the farm is over stocked with animals and the weaker of the herd are pushed toward the worst grazing areas. That is poor stockmanship.
It is about time people looked at the truth behind the bTB debacle instead of looking for a scapegoat to blame the ills of the industry on.
P.S What happens to culled animals? Many where the bTB lesions are present simply have them removed at the abattoir and are then sent back into the food chain to ofset the cost of the compensation. Something to think on.
Response the Neil,
“Cattle cannot be infected by just sniffing Badger urine or droppings,that is impossible. The bacterium either has to be taken in as an airborne particle or ingested by it eating it.
Airborne infection is the most prevalent way of infection, which needs continuous contact between the infected and the non infected, whereby millions of bacterium is passed on.”
I am not convinced by your thinking on this.
I don’t understand why you think that “sniffing badger urine” could not transfer millions of bacteria from infected badgers.
Surely the taking in of airborn particles is precisely what sniffing is!
Badgers often move around and urinate on pasture, so the “sniffing” could be simply ordinary inhale breaths while eating grass (which is surely virtually a constant normal event among grazing cattle).
It is established that the Bovine TB organism can survive on pasture for months (do a google search for say “M.bovis” pasture months)
If you don’t believe that a grazing cow could take in millions of M. Bovis, then what rate of bacterial particle intake do you assume, per minute say. They are not large beasts you know - these bacteria. If you google on bacterial concentrations you quickly hit some pretty big numbers.
But it seems to me, even if the inhalation rate (per unit time) was - as you seem to suggest - lower than the order of millions, nevertheless cattle graze for quite extended periods of time.
Air is 3 dimensional. That means that - just to get a rough measure of the thing - even as high a number as 0.1 million particles in a single litre of air has them spaced out pretty sparsely (around 2mm apart on average), which, given that bacterial diameters tend to be quoted in micrometers (thousanths of a milimeter), is seems rather sparse to me.