BOVINE TB
What is it?
Bovine tuberculosis Nb TB is a serious disease arising from infection by a bacteria called My cobacterium bovis (M. bovis). Cattle, buffalo and bison are the natural hosts but nearly all warm blooded animals are susceptible to the infection. This complicates the control of bovine TB, particularly when the infection becomes self sustaining in wildlife species.
History
During the 1930s, at least 40 per cent of British cows were infected with bTB. Many were kept near large cities to provide urban dwellers with fresh milk and most were closely confined, in poorly ventilated cowsheds. Many infected cows developed TB in the udders and shed M. bovis in the milk. Because most milk was drunk raw, it was a major cause of TB in humans, with around 2,500 people dying annually from the disease. Routine pasteurisation of cows’ milk and inspections of cattle carcasses at slaughterhouses were introduced. And, by the 1980s, the government had begun a TB testing and slaughter scheme for cattle.
Symptoms in animals
Due to the slow progression of infection and the early age at which cattle are slaughtered, the clinical signs of bTB are now rarely seen in cattle in Britain. Some animals show no evidence of the disease, yet may be found to be so seriously infected during slaughter inspection that their carcasses are condemned. Lesions are common in the lungs, and these cause a hard, dry, short cough, which leads to more frequent coughing and laboured, painful breathing. The animals lose condition and later cough up blood. The udder can also be affected, with hard lumps appearing.
Source
Bovine TB is spread primarily when bacteria are released into the air through coughing and sneezing. This transmission usually happens when animals are in close contact with each other, so crowded conditions play a major factor. Up to 40,000 cattle are slaughtered every year due to bTB. This number has risen by a third since 2007. In the UK, badgers have been blamed for hosting the disease. Since 1975, 30,000 badgers have been destroyed in a failed attempt to curb its spread. Tests revealed that 80 per cent of the slaughtered animals were free of TB.
Symptoms in animals
Due to the slow progression of infection and the early age at which cattle are slaughtered, the clinical signs of bTB are now rarely seen in cattle in Britain. Some animals show no evidence of the disease, yet may be found to be so seriously infected during slaughter inspection that their carcasses are condemned. Lesions are common in the lungs, and these cause a hard, dry, short cough, which leads to more frequent coughing and laboured, painful breathing. The animals lose condition and later cough up blood. The udder can also be affected, with hard lumps appearing.
Source
Bovine TB is spread primarily when bacteria are released into the air through coughing and sneezing. This transmission usually happens when animals are in close contact with each other, so crowded conditions play a major factor. Up to 40,000 cattle are slaughtered every year due to bTB. This number has risen by a third since 2007. In the UK, badgers have been blamed for hosting the disease. Since 1975, 30,000 badgers have been destroyed in a failed attempt to curb its spread. Tests revealed that 80 per cent of the slaughtered animals were free of TB.
Routes of transmission
Bovine TB can be transmitted from affected animals to people, causing a condition very similar to human TB. The risk of exposure is greatest in enclosed areas, as invisible droplets containing TB bacteria may be inhaled. While less than one per cent of all confirmed cases of TB in humans are due of infection with M. bovis, Defra believes that the disease has the potential to be a significant health risk.
Symptoms in people
TB in humans causes the same symptoms whether it is caused by M. bovis or the human pathogen M. tuberculosis Nchest pain, coughing up blood and a prolonged cough. And, in the same way that cattle can spread bTB to humans, a person carrying bTB can infect cattle.
Treatment
A badger vaccine against TB.
The course of treatment for humans with bTB takes 6 to 9 months, with the success rate being more than 95 per cent. In animals, the policy is to control bTB within an affected herd through regular testing and slaughter of any single animal who tests positive until the entire herd tests negative for the disease.A nine year official government study found that when badgers were killed to try to control outbreaks proactive culls, incidence of the disease in cattle actually rose by about 20 per cent because the badgers moved to escape the slaughter, thereby infecting new areas. Proactive culls, which continue year after year, were found to reduce the disease in the cull areas by 23 per cent, but increase it by even more in surrounding areas as infected badgers move in. And unless the culling continues, they eventually return to their old haunts.Other studies suggest that a more effective way of tackling bTB would be to monitor and control cattle movements, given that most cases are caught from other cattle. A badger vaccine against TB is almost ready and could be administered orally, through bait, by 2014.