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Prototheca mastitis in dairy cows: Signs, causes and prevention

June 7, 2023

Prototheca mastitis, caused by a colorless algae called Prototheca, has become an increasing challenge to dairy cattle and farmers. Prototheca can be found throughout the farm environment, entering the teat end in multiple ways, and it can be transmitted from cow to cow through direct contact or poor sanitary protocols. When Prototheca does take hold, it manifests mostly as subclinical cases of mastitis.

Prototheca mastitis can have a significant economic impact on dairy farms, having both direct and indirect costs. With no effective Prototheca mastitis treatments available, preventing it is of utmost importance in mitigating its economic impact on dairy operations.

In this blog, we will delve into the key strategies for identifying and controlling Prototheca mastitis, including diagnostic techniques, prevention measures, and best practices for managing affected animals within the dairy herd.

What does an infection look like?

While most cases are subclinical, subtle changes in milk quality and persistently high somatic cell counts (SCC) can indicate the presence of Prototheca on your operation. Slight changes in milk may be noticed during your pre-milk protocol. Discoloration, watery consistency, flakes or garget would be typical for this pathogen. Chronically infected cows will continue to decrease milk production and increase SCC, sometimes upward of 1 million SCC.

How are cows coming in contact with Prototheca on my farm?

Prototheca are found in wet areas contaminated with decaying plant matter. Common areas include lagoons, manure storage areas, water troughs and runoff areas. These algae can also be found inside the parlor and holding pens. At a certain point, the prevalence of Prototheca in the environment may get so high that Prototheca mastitis can become contagious, passed from cow to cow through direct contact and also through contaminated equipment, infected teat dips, and other fomites.

How do I know for sure that my cows are infected with Prototheca mastitis?

Isolating the potentially infected quarter is the best way to determine which quarter to sample and send for laboratory diagnosis. This can be done with the California Mastitis Test (CMT) or a desktop SCC device. Proper milk sampling techniques ensure accurate samples for identifying mastitis pathogens. DHIA or other regular periodic milk sampling can also be useful in diagnosing Prototheca mastitis. After the infected cow or quarter is identified, milk culturing is the gold standard for diagnosing Prototheca mastitis.

How can I manage currently infected cows?

Because there is no effective treatment for this type of mastitis, the best option is to cull the infected cows immediately. When culling is not an option, infected cows should be isolated into their own string and milked last. Realize that these cows are still a danger to further contaminate the environment when they leave the parlor. They will also continue to decrease in milk production and increase the overall SCC of the herd.

What can I do to prevent infections?

It would be unrealistic to expect to completely eliminate the risk of cows coming into contact with Prototheca, but with proper on-farm protocols and management, we can reduce the risk. Below are three steps that can be taken today to establish your current risk and be proactive in battling the problem.

  • Test milk from the hospital pen and fresh cows Knowing what mastitis-causing organisms you have is key to knowing how to manage the situation. Starting your testing with the fresh cows and the hospital pen will provide valuable information about the presence of Prototheca and other mastitis pathogens. It also will help to evaluate the sanitation protocols that we are initiating, to see their effectiveness.
  • Routinely test cows and make culling decisions — Regular periodic testing allows for informed decisions in real time, helping to prevent further spread. Remember, the best strategy for contagious or untreatable mastitis is to test and cull. When this is not possible, isolating Prototheca-positive cows into a specific pen and allowing for them to be milked last and managed separately from the rest of the herd is a secondary option.
  • Establish and follow milk quality protocols — Training milkers on established milk quality protocols helps reduce the introduction of pathogens during the milking process and reduces the potential spread of pathogens from one cow to the next.

    Steps to reduce the introduction of pathogens
  1. Pre-dip: Use a bactericidal pre-dip to kill any bacteria that may be present on the teats before milking.
  2. Strip: Strip each teat to check for abnormalities in the milk, including signs of Prototheca mastitis such as watery milk, discoloration, flakes or garget.
  3. Wipe: Use a clean towel to wipe each teat thoroughly. Overall cleanliness of the teat and teat end is of utmost importance when dealing with environmental pathogens.
  4. Post-dip: Apply a quality post-dip to each teat immediately after milking is complete to protect the teat from contamination.

If you are interested in more information on designing proper milking procedures, please visit the Alltech On-Farm Support team’s YouTube channel to listen as Jorge Delgado explains the importance of each step in the milking routine.

Prototheca mastitis poses a significant challenge for dairy farmers due to its chronic nature and lack of effective treatments. Identifying and controlling this form of mastitis is crucial to minimize economic losses and maintain the overall health and productivity of the dairy herd.

For additional resources and on-farm support, please reach out to the Alltech On-Farm Support team here.