We’ve all seen the statistic – a case of clinical mastitis in the first 30 days of lactation can result in an economic loss of $444. We talk about all the ways to prevent mastitis but what do we really know about the bugs that actually cause mastitis to begin with? What impact do they truly have on the cow? Are the measures we take actually effective?
One of the most persistent and damaging culprits behind mastitis is Staphylococcus aureus (Staph. aureus). This pathogen has been a major mastitis causing pathogen in U.S. dairy herds and across the world. While infection with this bug can cause severe outward (clinical) signs of mastitis, such as gangrene, it more commonly leads to infection with little to no visible signs (subclinical), and nothing more than an elevated Somatic Cell Count (SCC). But don’t let the lack of clinical signs fool you, Staph. aureus is still causing immense damage to the udder of the infected cow.
Infection and spread
Once Staph. aureus penetrates the udder, typically through the teat end, it has the ability to wall itself off in tiny abscesses throughout the udder, protecting it from the body’s immune system and antimicrobial therapies. As the immune system attempts to fight this pathogen, the natural inflammatory response causes damage to cells responsible for milk production. These infections easily become chronic, and occasionally the bacteria escape the infected area, shed in the milk, and go on to contaminate the environment (such as the milking parlor) where they can then infect another cow in the herd.
Treatment success
The success rate for treatment with antimicrobial therapy is relatively low compared to responses of other mastitis causing pathogens. Most commonly, management strategies include identifying and removing infected cows from the herd. Pre- and post- milking hygiene are crucial to reducing the spread in the herd. Biosecurity measures such as screening purchased cows should also be a top priority to avoid an outbreak of Staph. aureus.
Keys to control
Monthly testing of bulk tank samples for Staph. aureus can be a great way to monitor the herd overall. The increased sensitivity of PCR reduces the risk of missing low-level infections, even in larger herds. When Staph. aureus is detected, individual cow testing will be necessary to address the problem. Identification and treatment, or removing infected animals is the best way to avoid widespread outbreaks.
The decision about which cows to test individually is often herd-specific. While some choose to test the entire herd at one time for rapid response, others take a more gradual approach only testing certain high-risk groups (such as fresh cows) or limiting based on SCC. Any of these options can be successful if combined with proper management strategies for positive cows. The most important piece to remember when dealing with Staph. aureus is that it never truly goes away, there is no finish line. Proactive monitoring, even when everything seems to be going well, is the key to success.
Author: Michelle Kaufmann, CentralStar Customer Solutions Advisor