Mycoplasma bovis vaccination trial at Wern Farm, Bancyfelin
Background
Over the past 4 to 5 years, the calves and cows at Wern farm have suffered from sporadic bouts of pneumonia resulting in significant losses in terms of lung damage, poor growth rates, calf deaths and decreased production in the dairy cows. Mycoplasma bovis has been isolated from the lungs and nasal passages of calves and appears to be the main of cause of the pneumonia on the farm.
The farm itself has undergone significant changes over the past few years with the introduction of robotic milking, new and improved housing for the dairy cows and a new calf shed for the new-born calves. Despite these changes, the pneumonia in the calves has persisted and has caused ongoing losses on the farm.
With the assistance of Farming Connect, an autogenous vaccination trial was implemented on the farm to help reduce the losses due to Mycoplasma bovis.
An autogenous vaccine is a custom made farm specific vaccine made when a commercial vaccine is not available. These tailored vaccines are specific to the herd/flock and are isolated from the site of an infection.
Mycoplasma bovis
M. bovis is a bacteria that causes serious clinical disease in cattle including pneumonia, arthritis, mastitis, middle ear infections and reproductive disorders. M. bovis belongs to a family of Mycoplasma bacteria, but Mycoplasma bovis is by far the most pathogenic bacteria in the family.
Fig A. Incidents of Mycoplasma bovis diagnosed in cattle with respiratory disease in Great Britain from 2006 to 2017 as a percentage of diagnosable submissions
Over the past few years, there has been a significant increase in the number of pneumonia cases associated with M. bovis submitted to UK laboratories. See fig. A above.
Although the majority of the samples submitted to UK laboratories have been for pneumonia related illness, there have also been samples submitted relating to arthritis and mastitis. See fig B below.
Fig B. Comparison of annual Mycoplasma bovis diagnoses as pneumonia, arthritis and mastitis for the years 2006 to 2017 (VIDA)
Calves are often infected when they drink milk or colostrum from infected cows, but the most infections spread by nose to nose contact with neighbouring animals. Improved ventilation, feeding and housing will help to reduce infection pressure from M. bovis and limit its spread. The risks can also be mitigated by improving passive transfer of immunity to the calves by good colostrum management.
The bacteria lacks a cell wall and as a result it is very difficult to kill using most traditional antibiotics which target the cell wall of the bacteria. It is also a very small bacteria and easily migrates into different parts of the body including the joints, middle ear, brain, mammary gland and lungs. There are a few classes of antibiotics which do work against M. bovis but the bacteria is becoming increasingly resistant to these antibiotics such as the oxytetracyclines. Only the flouroquinolones show any marked effect against M. bovis, but they still fail to completely eliminate the bacteria from the host animal. Flouroquinolones are now classified as Critically Important Antibiotics (CIAs) and their use must be limited to bacteria which can be effectively eliminated or only where other antibiotics fail to work.
Recently in New Zealand, thousands of cows were culled to contain and prevent the spread of this highly contagious disease. Unfortunately, the disease is already widespread in Wales and the United Kingdom and endemic in a large number of dairy herds.
Vaccination trial
As there is no commercially available vaccine for M. bovis, an autogenous vaccine had to be created by isolating the bacteria by taking nasopharyngeal swabs and by direct swabbing of the lungs of calves which had recently died. A special transport medium was used to ensure survival of the bacteria before the swabs reached the laboratory (Mycoplasma Experience). The isolated M. bovis bacteria were then sent to another laboratory (Ridgeway Biologicals Ltd) for attenuation and vaccine production.
Once the vaccine was created and tested on the farm for safety, it was administered to the pregnant dry cows before calving. The colostrum from these cows was given to their calves to provide initial protection. The calves were then vaccinated from two weeks of age when they had a functional immune system. The calves received a booster vaccination 4 weeks later. Colostrum management was monitored and adjustments were made to ensure that all calves received enough antibodies to give them good protection in the first two weeks of life before they were vaccinated. Colostrum transfer was measured using a blood test to measure total serum proteins in the new born calves. Total serum protein is a reliable method to assess passive transfer of immunity.
The calves were monitored for pneumonia and other symptoms of M. bovis and the weight of the calves was also monitored within the first 8 weeks. Calves were checked for nasal discharge, laboured breathing, raised temperature, ear droop and weight change for a period of 8 weeks before vaccination started and then again after vaccination.
The laboratory where the bacteria was isolated is called Mycoplasma Experience. Once isolated and stabilised, the bacteria were sent to Ridgeway Biomedicals for the vaccine production.
References:
- (2018) Mycoplasma bovis investigations in cattle Veterinary Record 183, 256-258.