Mastitis is an opportunistic disease that can show up on your dairy in many places, even with the best prevention management protocols.
There are thousands of bacteria that can cause mastitis, but there are four well-known pathogens that you’re most likely to see on a dairy: Streptococcus agalactiae (strep), Staphylococcus aureus (staph), Streptococcus dysgalactiae and Escherichia coli.
Knowing exactly which of these pathogens you’re fighting against, and whether or not it requires treatment, can make a big impact on your bottom line. Studies at Cornell University have shown that pathogen-based treatment results in $30 more profit per cow on an annual basis. For a 1,000-cow herd, that adds up to $30,000 in financial upside per year in reduced labor, less antibiotic cost and more milk sold, with the same clinical outcomes as with blanket-based antibiotic treatment.
To decide on a treatment protocol and where prevention measures may need to be strengthened, you must know where the pathogens are coming from and how they are infecting your cows.
Contagious versus environmental pathogens
The first step to successfully preventing and treating mastitis is understanding the disease in all its forms. We can break down mastitis pathogens into two categories: contagious and environmental.
The risk of contagious pathogens has been greatly reduced, thanks to improved milking parlor protocols and well-established dry cow therapy programs. Streptococcus agalactiae and Staphylococcus aureus are the two most common contagious pathogens seen on today’s dairy farms. They primarily live in the cow’s udder and spread from cow to cow, typically during the milking process.
Environmental pathogens are more of a concern in dairy herds today because they are the most opportunistic pathogens, ready to infect cows at any time. Streptococcus dysgalactiae and E. coli are two of the most common environmental pathogens. They can be found in a variety of places on the dairy, such as bedding, manure, water or the milking parlor, if proper hygiene isn’t practiced.
Identifying the microbial category
Digging a little deeper, contagious and environmental mastitis infections can be generally defined through their microbiological group classifications: gram-positive, gram-negative or no-growth.
Gram-positive infections are the type you should focus your antibiotic treatment on. These pathogens typically have a stronger cell wall compared to gram-negative infections, meaning the cow’s immune system isn’t as effective at reducing the growth of these organisms. Gram-positive mastitis infections are most likely to become chronic if left untreated and should be treated with a short-duration antibiotic labeled for gram-positive pathogens.
Many mild to moderate gram-negative mastitis infections will self-cure, and providing an antibiotic treatment will make no difference in the outcome. These pathogens have a weaker cell wall and are more effective at eliciting an immune response from the cow to kill the pathogen. However, it is important to work with your veterinarian to develop protocols that address supportive care for severe gram-negative cases.
A no-growth case means no bacteria can be cultured on the plate and lets us know that the cow has cleared the infection on her own and will not need antibiotics.
On-farm culturing
With the help of your herd veterinarian, an on-farm culturing system can help differentiate between these classifications of mastitis infections, providing results within 24 hours. By keeping records of what cases are causing the most trouble, you can pinpoint what protocols need to be strengthened.
Here is how each of the four well-known mastitis pathogens will show up on a culture plate:
- Streptococcus agalactiae and Staphylococcus aureus (contagious pathogens) will show up as gram-positive. They have characteristic growth patterns that can help identify their presence and can indicate that you should alert your veterinarian.
- Streptococcus dysgalactiae (environmental pathogen) will also show up as gram-positive.
- E. coli (environmental pathogen) will show up as gram-negative. Unless the cow is sick, you don’t need to treat and can wait for the infection to pass.
Knowing the classification of a mastitis case can help you choose which animals to treat, saving you money and improving judicious antibiotic use. By focusing only on gram-positive pathogens, you could potentially cut up to 60% of treatment costs.
If you’re battling chronic mastitis challenges on your farm, further testing with the help of your veterinarian to classify the specific pathogens can help you put more preventive practices in place. For example, Streptococcus dysgalactiae can be prevalent during the fresh period if cows contract the pathogen at the end of the dry period. If you’re seeing an uptick in Streptococcus dysgalactiae in your cultures, you might consider adjusting your dry cow protocols. Or, if you’re seeing more E. coli, you might need to address the cow’s immune response with updated vaccination protocols and evaluate manure and bedding handling.
Mastitis prevention is a team approach
There is not just one singular spot on the dairy that you should look at for mastitis prevention. It is important to remember that preventing mastitis is multifactorial. With the help of your veterinarian, implementing an on-site culturing system can help decipher when antibiotic treatments are necessary and where most cases of mastitis originate on your dairy.
By knowing your top pathogen opponents, you can build the best prevention and treatment protocols to keep mastitis under control.
References omitted but available upon request by sending an email to an editor.
