What’s the difference between M. bovis….and M. bovis?
The shorthand for these two diseases of cattle is the same, but they completely different bacteria: Mycobacterium bovis and Mycoplasma bovis.
Every bacteria has a specific name, so that we can identify them better – the “surname” (in this case Mycobacterium and Mycoplasma) and then a “first name” (bovis). To call these two bacteria the same is like saying two men called Paul Brown and Paul Baker are the same (the men might argue that they are very different!). Now, how do these two bacteria compare?
Under the microscope
When examined in the lab, the two bacteria look very different. Mycobacterium bovis is a rod-shaped bacteria with a thick cell wall. This thick cell wall helps it survive being attacked by the body’s white blood cells and prevents many antibiotics from working against it.
Mycoplasma bovis is a lot smaller and doesn’t have a cell wall. Instead it is surrounded by a thin membrane and this makes its shape quite variable. Additionally, many antibiotics will not work against mycoplasma because of this lack of a cell wall. Mycoplasma bovis, like Mycobacterium bovis, is also very good at evading the body’s immune system and both of the M.bovis‘ are capable at causing chronic, sometimes incurable, disease.
Mycobacterium bovis is the bacteria that causes bovine tuberculosis (TB). It’s part of the same family as human TB and leprosy (it’s like if Paul Brown had two brothers, Peter and Steve: same surname, different first names). Signs of bovine TB include ongoing weight loss, weakness, anorexia, fever, swollen lymph nodes and pneumonia. It spreads between animals through inhalation of infected aerosols and can spread to people through drinking unpasteurised milk from infected cows.
Prior to the introduction of pasteurisation, bovine TB was a major cause of disease and death in people. In 1943 it was estimated that 2500 deaths a year in England and Wales were due to bovine tuberculosis and brucellosis (another disease spread in unpasteurised milk). From 1912–1937 over 60,000 deaths attributed to tuberculosis!
Bovine TB is still a significant cause of disease in developing countries as seen in the map below. Those of us travelling overseas should be aware of the risk of catching bovine TB when eating and drinking unpasteurised dairy products. Bovine TB can also enter wildlife populations such as badgers in England, possums in New Zealand and buffalo in Africa. These wildlife reservoirs can then be a source of infection to cattle and people.
In the 1970s, Australia began the bovine brucellosis and tuberculosis eradication campaign (BTEC) which involved testing and culling of infected animals, traceback/forward of farms, and abattoir surveillance. Our country was declared free of bovine TB in 1997.
Mycoplasma bovis also causes disease in cattle across the world. Clinical signs include mastitis, pneumonia and lameness but it is not thought to cause disease in people. Like bovine TB, mycoplasma spreads between cattle through inhalation of aerosols and calves drinking infected milk. Mycoplasma bovis recently made world headlines after it was detected causing serious disease in New Zealand. The disease is present in some Australian dairy herds and is generally spread from farm to farm by purchased cattle. For more information on mycoplasma and how to avoid introducing it to your farm see this post.
So, in summary…
|Can infect cows
|Can readily infect people
|Resistant to many antibiotics
|Evades immune system