So What is Mycoplasma Bovis?
The diagnosis of Mycoplasma bovis is becoming more and more common on dairy farms, it can cause disease in both calves and adult cattle. It is a notoriously difficult bug to treat, and even then vaccination has historically proved difficult.
We have previously relied on autogenous vaccine (those produced in a lab using M. bovis cultured from infected animals), however there is now a vaccine available in North America that is available to import.
So what is Mycoplasma Bovis? They are small bacteria distinguished by their lack of cell wall. M. Bovis produces a biofilm, changing surface proteins and can persist on mucosal surfaces, enabling them to evade the host immune response, therefore causing disease. The organism may be carried asymptomatically and the introduction of subclinical animals into the herd is the primary means that a naïve herd becomes infected. The major route of M. bovis transmission is nose to nose contact and aerosol spread.
Other routes of infection include ingestion via contaminated milk (i.e feeding waste milk to calves) or via contaminated milking/feeding equipment. It can also cause pneumonia and can be seen as a key player in the organisms associated with bovine respiratory disease. Diagnosis of M. Bovis can be difficult due to the low sensitivity and in some cases specificity of the available tests, which can often be complicated by the presence of subclinical infection and intermittent shedding. PCR is the detection method of choice. It proves difficult to treat, its lack of cell wall results in natural resistance to penicillins and cephalosporins and its folic acid independent metabolism results in resistance to TMPS. Whilst other groups of antibiotics do work, the nature of the pathogen, including the ability to create biofilms can reduce a clinical response to treatment. The key to treatment success is early intervention. Reducing incidence of Mycoplasma bovis on farm involves strict biosecurity. Where there is known disease in adult animals, the feeding of waste milk should be avoided at all costs. Milking equipment and milk feeding equipment can aid in the transmission of organisms and therefore disinfection is essential. If feeding whole milk, then this must be pasteurised to reduce the bacterial load of M. bovis.
