Posted by Dr. Steve Dudley on June 11 2009 09:58
Mycoplasma bovis is a significant emerging pathogen in cattle. There are several strains of Mycoplasma but the most common species that causes disease in cattle is Mycoplasma bovis. When we refer to Mycoplasma in this article we are referring to Mycoplasma bovis. Mycoplasma is a small organism that commonly causes pneumonia, mastitis, ear infections and/or joint problems in cattle. You may have a problem with Mycoplasma in your calves if you see head tilts, droopy ears, swollen joints, fevers, or pneumonia that does not respond to antibiotic treatment.
Mycoplasma is commonly found in the respiratory and reproductive tracts of healthy cattle. It is contagious and is spread through the air and by nose-to-nose contact. It is also spread orally by nipples, colostrum, waste milk, and buckets. Cattle can carry Mycoplasma for a long time and shed it at times of stress.
Mycoplasma infection is commonly seen as respiratory disease that does not respond to antibiotic treatment protocols. Generally the animals with pneumonia are more bright and alert than we see with bacterial or viral pneumonias. There can also be a thin, clear nasal discharge or crusting around the eyes. Mycoplasma also causes ear infections. Signs of an ear infection include droopy ears, head tilt and ear drainage. Calves may also have fevers and swollen joints that do not improve with antibiotic treatment.
The biggest concern with Mycoplasma, is that once the calves are infected, it is very difficult to treat. This is because Mycoplasma is a very small organism that lacks a cell wall. These characteristics limit our ability to treat it with antibiotics, because many antibiotics kill bacteria by destroying the cell wall. Mycoplasma is often a secondary problem and can cause abscessing that also makes it difficult to treat. Some antibiotics that may have some affect on Mycoplasma include Oxytetracycline and Spectinomyocin.
If you are concerned you have Mycoplasma in your herd, prevention is the best solution. This is because Mycoplasma is so difficult to treat and even when animals recover, they usually have fallen behind the rest of the group. One way to prevent Mycoplasma is to use farm specific vaccines. These farm specific vaccines are very effective at controlling Mycoplasma. The first step is to isolate the Mycoplasma organism from your herd. Mycoplasma may be isolated from ear swabs, joint swabs or lung tissue. There are many different strains of Mycoplasma bovis. This is why sometimes the only symptom on one farm is pneumonia where on the next farm the major problem may be ear infections. This bacteria changes rapidly within the animal. A very useful diagnostic tool is comparing the DNA of Mycoplasma bovis isolates to determine how similar they are. It appears that there is poor cross protection between isolates. The strain comparison allows us to help you choose isolates to make into farm specific vaccines.
The most effective farm specific vaccines contain several strains of Mycoplasma bovis to improve cross protection and vaccine effectiveness. It is also important to implement a strategic vaccination protocol that will prevent Mycoplasma before it occurs in your herd. At least two doses of vaccine need to be given before clinical signs appear. In some instances, three doses of vaccine are required. Other forms of prevention include not pooling colostrum, feeding pasteurized waste milk, bleaching nipples, bottles and buckets between feedings, and decreasing nose-to-nose contact.
Mycoplasma bovis Case Study
This farm had a group of 150, five week old, Holstein calves. The calves were vaccinated for Mycoplasma bovis at one and four weeks old. They were also vaccinated with a 5 way respiratory vaccine at day 7. Currently, they are having an increase number of head tilts, swollen joints, and respiratory disease. The calves are fairly alert and have fevers of 103 degrees. Approximately 10% of the calves are affected.
What is going wrong in this group of calves?
It is easy to get the false hope that if you are vaccinating for Mycoplasma bovis, you will never see that disease on your farm again. In reality, proper vaccination and good protocols can be very good at helping to prevent disease, but they are not 100% effective. There are several reasons Mycoplasma vaccines may not be 100% effective at preventing all clinical disease.
Mycoplasma bovis is an organism that mutates to avoid the body's immune system. This means that if the Mycoplasma vaccine you have been using has previously been effective, and then the Mycoplasma bovis changed, your vaccine may not be as effective on the next group of calves. It is important in this case to re-isolate the Mycoplasma. Diagnostics are performed to isolate the Mycoplasma and then through DNA fingerprinting we can compare the new isolate to the isolates in the vaccine. In this case, the Mycoplasma vaccine was only 60% similar to the Mycoplasma causing disease and therefore it was not capable of preventing all Mycoplasma disease.
Due to the fact that a new isolate has appeared on this farm, it would be advantageous to add this isolate to the farm specific vaccine to increase protection. If this calf farm receives calves from multiple sources, they may have new strains of Mycoplasma on their farm with every group of calves. The best scenario for vaccination in this case would be to minimize disease severity but not necessarily eliminate it. Other areas of transmission need to be addressed as well. One of the best methods of Mycoplasma bovis prevention is to not feed pooled colostrum. If colostrum infected with Mycoplasma is mixed with “clean” colostrum and fed to several calves then all those calves will be infected verses just one if the colostrum were not pooled. Once you see an infected calf in the barn, it is necessary to treat aggressively and isolate if possible. Remember that Mycoplasma can be spread via aerosol and close calf contact.