Ask the Vets
When, Why and How of PCR in Mastitis Control Programs
T
he versatility of the Mastitis PCR assay often means there is no cookie-cutter recipe for when, why and how to use it. Even still, many veterinarians incorporate PCR testing into farm-management protocols when they find they need a more convenient, faster, or more sensitive option compared to traditional methods.
Due to test sensitivity, the Mastitis PCR assay has the ability to detect even the smallest amount of DNA from an organism, which gives a broader picture of organisms on a dairy. Dr. Boge said, “While my primary focus is watching for contagious pathogens like M. bovis and Staph aureus, I use PCR to track environmental pathogens over time, which may have an impact on things like calf health.” Additionally, bedding and housing management, as well as parlor procedures are areas that can be evaluated based on environmental pathogens detected by PCR.
United Veterinary Service (UVS), Bear Creek, Wisconsin, has established mastitis management protocols that include a Mastitis PCR assay on several dairy farms. While choosing when, why and how to use PCR instead of culture includes many Results produced by mastitis PCR “PCR is a “hands-off” way to monitor factors for veterinarians, the are sometimes more information UVS team cites PCR’s sensitivity, mastitis pathogens where the producer than most dairy producers and the ability to detect intermittent veterinarians are familiar with, has little or no effort in the process.” shedding of Staph aureus and which is where Ct values come into Dr. Jeremy Boge, Bull Creek Veterinary Service speed as key reasons for when play. “We find the Ct values are very they choose it. helpful in test and cull management decisions,” said the UVS team. “We have established cut-off “Anytime a herd is struggling with milk quality issues, clinical points on each farm that state animals below a designated Ct mastitis or when contagious pathogens are found in the bulk value is an immediate cull, while animals above that threshold tank, the Mastitis PCR assay is a good option,” shared Dr. Eric should be retested. The exact Ct threshold varies by farm Duch, Dr. Cole Anderson and Dr. Valerie Baumgart at UVS. depending on the target species (M Bovis, Staph aureus) and the “Specifically, we like the assays’ ability to detect intermittent farm’s goals.“ shedding of pathogens. Staph aureus can go undetected on culture. We are more likely to find it (Staph aureus) using PCR.” Understanding the advantages of mastitis PCR is important when determining its role in reducing mastitis on dairy Convenience is one of the main reasons Dr. Jeremy Boge, Bull operations. Veterinarians, and producers alike find that the Creek Veterinary Service, Hastings, Michigan, says PCR fits into speed, convenience, and sensitivity of mastitis PCR improves farm protocols. “PCR is a “hands-off way” to monitor mastitis their ability to detect and monitor pathogens that cause pathogens where the producer has little to no effort in the mastitis. Experience shows that better detection methods can process,” said Dr. Boge. “While culture is easy to train on-farm benefit any mastitis control program. Consider the advantages staff to perform, PCR is convenient. If a farm doesn’t have of PCR when trying to improve your mastitis program. employees interested and invested in mastitis, I’ll turn to PCR.” Detecting Mycoplasma bovis quickly is another reason veterinarians turn to PCR. “Compared to traditional myco culture, I appreciate the speed of PCR to identify if that is the pathogen in the herd,” said Dr. Boge. Mycoplasma is an extremely contagious pathogen that affects an entire herd – from milking cows to newborn calves. When this pathogen is detected in a herd, the speed of PCR compared to traditional culture, which can take up to two weeks, is imperative for controlling the spread.
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Michelle Kaufmann CentralStar Customer Solutions Advisor CentralStar Cooperative
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