Mycoplasma, not just mastitis

Mycoplasma, not just mastitis

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FLUFFY BUT NOT FRIENDLY: Calves are especially vulnerable to Mycoplasma infections.

FLUFFY BUT NOT FRIENDLY: Calves are especially vulnerable to Mycoplasma infections.

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Mycoplasma is a nasty, complicated bacterial infection that farmers must know about, especially if they buy in new cattle and/or feed their calves waste milk.

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How does a cow vet treat herself when the kids go back to school?

With a fluffy microbe toy of course!

Sounds a bit silly but, in farmer training sessions, I find fluffy toys representing diseases such as Staph aureus or Salmonella are memorable and reinforce my message.

So, when I saw that there was a new Mycoplasma toy (see www.giantmicrobes.com), I couldn't resist.

Mycoplasma is a nasty, complicated bacterial infection that farmers must know about, especially if they buy in new cattle and/or feed their calves waste milk.

Mycoplasma infects both cows and calves and can present in many ways: mastitis in milking cows, joint infections (see photo), respiratory disease and less commonly ear infections (tilted heads), jaw swelling from swollen lymph nodes, and pregnant cows aborting.

There are several strains of Mycoplasma that can cause disease but Mycoplasma bovis is the most common.

Mycoplasma is spread from infected animals through their respiratory secretions and shedding of bacteria in milk and colostrum.

As an example of how the disease can spread consider a cow with subclinical Mycoplasma mastitis entering the milking herd.

Contaminated milk on the teat cup liners or on milkers' hands can infect other cows at milking time.

If the mastitis becomes clinical, unhygienic treatment practices will amplify spread to other animals in the sick/waste milk herd, including freshly-calved cows.

If the waste milk is then fed to calves, they can get joint infections and pneumonia and shed the bacteria in their respiratory secretions and infect other calves in the shed.

Unlike most bacteria, Mycoplasma doesn't have a cell wall (which means most antibiotics won't work against it) and is also very good at disguising itself and evading the body's immune system.

As a result, infected animal will usually be unresponsive to antibiotic treatment and need to be culled.

Testing for Mycoplasma can be done in two ways.

The first is to look for Mycoplasma DNA, generally done on the bulk tank or waste milk using what is called a PCR test, a quick test that can identify if Mycoplasma is present on farm.

The second method, culture, is done on individual animals and is important because it can confirm the cause of clinical disease.

Bacteria are grown (cultured) from infected milk or joint fluid, but since Mycoplasma is fussy and hard to grow, samples need to be sent to special laboratories.

A long-term management plan for Mycoplasma will differ for each farm, but if you suspect Mycoplasma in your calves or cows (i.e. mastitis, joint infections or respiratory disease that does not respond to antibiotics) there are some important actions to take while waiting for confirmation.

Isolate affected calves in a separate shed/air space to minimise the spread via respiratory secretions; always wear gloves and handle sick calves last; wash gumboots and clothes afterwards.

Stop feeding waste milk - feed vat milk instead which is less likely to contain Mycoplasma.

It may be that milk replacer or pasteurised waste milk is an option in the future but feeding vat milk will have the least effect on the calves' diet in the short term.

For the milking herd, hygiene at milking time is paramount; all staff must wear gloves at milking time.

Milk the sick herd last, as a group - this ensures contaminated clusters are cleaned well before milking another cow.

Don't strip the herd looking for clinical mastitis cases until you've reviewed your hygiene practices for the process; Mycoplasma can spread rapidly between cows if this isn't done correctly.

Start collecting milk samples from clinical cases, storing them in the freezer; culturing them for Mycoplasma will help determine how far it has spread in your herd.

Knowing about this disease will help prevent infection in calves and cows, so have a chat with your staff and farming colleagues to help spread awareness - you may want to buy a fluffy Mycoplasma toy yourself!

About the author: Dr Zoe Vogels is a veterinarian at The Vet Group, Timboon.

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