An effective management plan starts with a strategy to evaluate potential introductions if considering purchasing from outside sources. With M. bovis being widespread, chances of dealing with it are elevated. While no reliable individual method exists for testing youngstock or non-lactating adult animals, questions about the herd history can be asked alongside monitoring of milking cows. No matter the age group of cattle being brought into an operation, the scope of the risk assessment should include the gestating cow at the initial source farm and both the protocols for her as well as the calf once she has freshened. The value would be to learn what control measures have been implemented:
- Have there been clinical signs associated with any of the syndromes that seemingly linger despite treatment?
- Is the bulk tank screened routinely for M. bovis with any positive results followed up by subsampling milking strings to narrow down and ultimately identify cows with mastitis caused by it?
- Are affected cows remaining in the herd segregated and milked last or culled?
- Is colostrum and non-salable milk appropriately pasteurized or are commercial substitutes used?
Furthering the limitations on antibiotic use, there are no effective antibiotics for M. bovis mastitis. With the lack of a positive outcome possible for these animals, it is best to remove them from the herd. Keen attention to clinical cases and use of information from milk testing along with prompt separation of infected animals from healthy cattle, and implementation of either pasteurization or utilization of replacers reduces the likelihood of spread. A review of these practices is the same if M. bovis is suspected within a closed herd.
When M. bovis is thought to be a problem, collaboration with a veterinarian is essential. Confirmation is based on several factors including the application of laboratory procedures, although antimicrobial selection is not based on sensitivity testing. The modified culture methods and slow-growing nature of the organism interfere with conducting the assay. The herd veterinarian’s knowledge can guide the decision based on understanding product label claims, distribution of drugs to sites of infection and modes of action needed to inhibit the pathogen. For pneumonia, inner ear infections and lameness, it is key to detect and intervene early with an appropriate medication to avoid it becoming chronic.
The goal of prevention focuses on good animal husbandry practices including cleanliness of housing and equipment along with adequate ventilation as well as maintaining cohorts of animals intact. Allowing a poor-doer, which may have already been infected over a long period of time in an older pen of cattle, to fall back to a younger group should be avoided. Optimized air quality with the correct flow and proper exchanges reduces aerosol transmission. Drafty conditions should also be avoided to limit the possibility of animals becoming chilled, leading to cold stress. The risk of transfer through fomites can be minimized through a well-maintained environment.
Vaccination may be another consideration with both commercial and autogenous options available. The custom-made vaccine route offers the potential to incorporate the strain variation of a herd as expressed through the genetic makeup of the variable surface proteins. Along with the viral and bacterial diseases typically addressed in protocols, a veterinarian can help fit the implementation of a product for M. bovis into the strategy for bovine respiratory disease (BRD) management. Calves are a focus with the modern approach of raising them at large ranches where multiple sources come in contact. Despite the application with BRD, this approach is not effective for M. bovis mastitis.
The dynamic interaction of animal host, pathogen and environment is influential in the development of disease caused by M. bovis. With special features that give it an innate ability to persist, the deleterious effects of longstanding infection slowly and continually erode the health of infected cattle. Prompt attention and judicious use of antibiotics offer the most potential for treatment success while the risk of exposure to herdmates can be decreased through a combination of prevention strategies in conjunction with removal of disease reservoirs. A well-executed M. bovis control program encompasses an awareness of the distinctive disease characteristics and timely interventions for lasting well-being and productivity.
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