Vet's corner: Mycoplasma becoming a more common diagnosis

Ultimately it is often husbandry and nutrition that underlie most clinical outbreaks of disease. However, I have noticed an increasing level and diagnosis of infections and issues around mycoplasma bovis. This is a small bacteria that is quiet unusual as it doesn’t have a cell wall like most bacteria. This means treating it can be difficult. Ultimately, when endemic in a herd, it can also be controlling. While a vaccine is available, it is not licensed in Ireland. Also its effectiveness seems to be very limited from what I have read. Diagnostically, it can also be tricky because testing is not as accurate as one might desire.

Clinically, I have seen a number of conditions caused by mycoplasma:

They often tend to be individual problems with one of the four mentioned. Occasionally, however, we do see a multiple effect, especially with mastitis and polyarthritis in dairy herds. Mycoplasma arthritis cases can be particularly poor at responding to treatment so they can be very frustrating. In some instances we had to cull several infected cases on welfare grounds, and also to reduce spread.

So what do we know about mycoplasma?

We know that it can often be present in the airways of healthy cattle. It is most likely spread through aerosols from the lungs or in the milk. My most recent case in a herd started with mastitis that responded poorly to treatment in some freshly calved cows and then sick calves with pneumonia that weren’t responding well to treatment either. There are some antibiotics more effective than others so talk to your vet once a diagnosis has been made. In our case, both the mastitis and nasal swabs were positive for mycoplasma.

Like most diseases, pneumonia mycoplasma will thrive when immunity is suppressed or housing or husbandry is compromised. It will also be exacerbated by other viruses which cause pneumonia. Like every respiratory disease, it is critical husbandry and housing are addressed as well.

With mycoplasma mastitis, in the cases I have seen it can be quite gritty almost in consistency. When left overnight in a tube, it will often separate into two layers with a pussy layer on top. It is still recommended to get cases cultured. Response to treatment, especially tubes, is very poor in my experience. The best option I have found for these chronic mycoplasma positive cows is culling due to their poor response to treatment and also the potential for shedding and spreading to other cows. Once diagnosed, a control plan should be put in place. Unfortunately, the herds with mastitis often seem to have arthritis also as the disease progresses.

Middle ear infections

Where we are seeing increased cases of middle ear infections in calves, I would advise investigating mycoplasma as a possible cause. These calves will often have ear drop, runny eyes, and purulent discharge from the ears, and can often develop head tilt. There are other causes of this but my cases have been pretty distinctive. Unfortunately, you will also tend to get pneumonia cases in calves or infected joints. It is worth remembering that it can be spread in milk so under no circumstance should cows with mycoplasma-positive milk be fed to calves.

I have also seen mycoplasma arthritis in cows. These are very frustrating cases with really poor response to treatment, often effecting hock, knee or elbow joints. The cows will present with joint swelling and severe lameness. These cases can be often diagnosed by taking a joint tap and sending for culture. Unfortunately, most end up having to be euthanised on humane grounds, especially chronic non-responsive cases.

So as I mentioned previously, cases can be difficult to diagnose because of the poor sensitivity to some tests. Your own vet can decide whether bloods, milk or joint taps are needed to confirm the diagnosis of mycoplasma. This is only a brief overview and there is still a lot we don’t know or understand about mycoplasma.

Read more

Vet's corner: 10 rules to change your mindset around mastitis