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Everything Dairy Farmers Need to Know About Strep. uberis 

If you’re farming in a pasture-based dairy system, you’re already dealing with Streptococcus uberis (Strep. uberis). It’s one of the most important mastitis pathogens in countries with predominantly grazing systems, such as New Zealand, Ireland, and parts of the UK. Data from Mastatest indicates that it causes as many as 24% of clinical cases in NZ(1), and 16% in the UK(2). For these farms, Strep. uberis can quietly impact production, profitability, and workload.

Understanding how this pathogen behaves and what actually controls it, is one of the most valuable steps you can take to reduce mastitis. 

What is Strep. uberis? 

Streptococcus uberis is an environmental gram positive bacterium that lives almost everywhere a cow lives. Unlike contagious pathogens that spread from cow-to-cow primarily during milking, Strep. uberis thrives in pasture, soil, and muck, especially when it’s wet and muddy. It is commonly found on teat skin and udders. 

Because it is so widespread, it is not something you can eliminate. The focus instead needs to be on control - managing the level of exposure to reduce the infection pressure on cows. 

Why Strep. uberis is such a big issue in pasture-based systems 

Pasture-based dairy systems create ideal conditions for Strep. uberis. Cows spend most of their time outdoors, often in environments where moisture, mud, and manure are unavoidable. During wetter periods, laneways and paddocks can quickly become heavily contaminated, increasing the bacterial load on teats. 

Calving adds another layer of risk. In many grazing systems, calving takes place outdoors, often in variable weather. At the same time, cows are immunologically vulnerable, and udders are frequently exposed to contaminated environments.  The result is conditions that are perfectly suited to this pathogen. 

When is the Strep. uberis risk highest?

Although Strep. uberis is present year-round, infection risk is not evenly distributed. The dry period is one of the most critical windows, particularly shortly after dry-off when the teat canal has not fully sealed. This is when many infections are established, even if they are not detected until later. 

The calving period is another high-risk time. Cows are under physiological stress, immune function is reduced, and they may be lying in wet or contaminated areas. 

Early lactation follows closely behind, and this is when many clinical cases become visible. 

But it is important to remember that any time Mother Nature throws us some wet weather, this creates the ideal conditions for Strep. uberis growth in the environment. That means more bacteria which significantly increases exposure risks for the herd. 

How Strep. uberis infection develops 

The infection process is relatively straightforward. Bacteria from the environment contaminate the teat surface and enter through the teat canal. Once inside the udder, they establish infection and trigger inflammation which then shows up as the signs (high SCC count) and symptoms (redness, swelling, changes in the milk) of mastitis. 

What Strep. uberis looks like on farm 

Strep. uberis can present as either clinical or subclinical mastitis. Clinical cases of mastitis are often quickly detected by identifying changes in the milk – whether that is clots, flakes, or watery milk – and swelling in the affected quarter. Subclinical infections are more subtle, typically appearing as elevated somatic cell counts. 

One of the biggest challenges with mastitis at farm level is that you cannot reliably tell which bacteria is causing the infection just by looking at the cow or the milk. Strep. uberis can look very similar to other common pathogens, including E. coli, Staph. species  or other Strep. species. Assumptions often lead to broad or unnecessary antibiotic use, or in some cases, the wrong treatment choice altogether. 

This is where on-farm diagnostics are becoming increasingly important. Tools such as Mastatest allow farmers and vets to identify the actual causative bacteria and determine which antibiotics are likely to be effective. This moves mastitis management away from guesswork and toward evidence-based decision making. 

In practical terms, this means better treatment outcomes, fewer repeat cases, more responsible use of antibiotics, reduced discarded milk volumes, and greater profits. 

Treatment realities for Strep. uberis

One of the more encouraging aspects of Strep. uberis is that it is generally responsive to common penicillin-based antibiotics, with good cure rates when treatment is timely. Early detection is critical, as delays reduce the likelihood of a successful outcome. 

However, treatment alone is not enough. If environmental pressure remains high, new infections will continue to occur, and some cows may experience repeat cases. Your Mastatest reporting features can quickly pin-point whether you have an issue with repeat cases, so you can work on a bespoke plan for those animals and for solving environmental issues around the farm. 

There is also increasing awareness of antimicrobial resistance, which reinforces the importance of targeted and responsible antibiotic use—something that is much easier to achieve when treatment decisions are supported by diagnostic information. 

What actually works for prevention of Strep. Uberis? 

Effective control of Strep. uberis is fundamentally about managing the cow’s environment. Clean, dry conditions reduce the number of bacteria on the teat and therefore reduce the likelihood of infection. Even incremental improvements in areas such as laneways, paddock selection, and drainage can have a measurable impact. 

Calving management is another key factor. Cleaner calving areas, reduced stocking pressure, and prompt milking after calving all help lower the risk during this vulnerable period. 

Attention to the dry period is equally important. Many infections begin at this time, so protecting the teat canal is essential. Internal teat sealants and selective dry cow therapy are widely used tools that can significantly reduce new infections when applied correctly. Your herd SCC data and Mastatest data from the past season can guide you and your veterinarian to make optimal selective dry-off decisions. 

Good milking practice plays a critical role too. The teat end is the cows’ first line of defence to any bacteria, so keeping them in good condition is crucial. Good teat preparation reduces contamination before milking. Post-milking teat disinfection helps protect the teat canal while it is still open, and maintains good teat skin condition. Regular teat scoring, to check for excessive damage, means you can act early to manage teat condition issues.  Finally, monitoring and early detection underpin successful control. Regular somatic cell count monitoring, combined with diagnostic testing, allows for more precise and effective mastitis management. 

New tools and evolving approaches for managing Strep. uberis

There is growing interest in additional tools such as vaccination and rapid on-farm diagnostics.  

Vaccines targeting Strep uberis have shown promise in reducing both the number and severity of cases, particularly when combined with strong environmental management. 

At the same time, diagnostic tools such as Mastatest are helping farmers move toward more precise treatment strategies. By identifying the causative pathogen and its likely response to antibiotics, farmers can reduce unnecessary treatments while improving cure rates—an increasingly important balance in modern dairy farming. 

The key takeaways: 

• Strep. uberis is  primarily an environmental disease problem. Focusing on treatment without addressing the underlying conditions will always limit progress. 

• Without testing, it is very difficult to know what you are dealing with. Not knowing what bacteria are present can undermine even the best management practices. 

• Farmers who achieve the best results combine strong environmental control, good milking practice and informed treatment decisions. They reduce exposure, improve calving and dry period management, and use diagnostic tools to guide their response. The result is fewer mastitis cases, lower reliance on antibiotics, and better overall herd performance. 

References: 

1.AgriHealth Technical Bulletin MS 10.3: New Trends from Analysis of NZ Mastitis Milk Samples 

2. Saila S, Bork O. Proceedings of the British Mastitis Conference (2024) Sixways, Worcester, p 72 - 73