Mastitis & Strep Uberis

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Willunga Vet Services
37 Main Rd
Willunga
SA 5172

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Phone:
8556 2075
Fax:
8556 2654

Aldinga Vet Services
16 Heathersay Ave
Aldinga Beach
SA 5173

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Phone:
8556 5498

Mastitis

We are seeing a number of spiking cell counts early in the season. We now have access to new type of milk test that is run on a bulk tank sample. It screens for the presence of 12 different mastitis pathogens. It is a highly sensitive test that provides results in about 24 hours. This gives us an idea of the bugs most likely to be contributing to a cell count problem, and then a management plan can be instigated promptly. This test costs around $100. It is a useful tool but as always good mastitis management will always involve:

  • Regular herd testing
  • Good shed hygiene
  • Regular machine checks
  • Regular changing of liners
  • And regular discussions with your vet!

Pfizer (Now called Zoetis) has released its findings from a large Mastitis study conducted in SW Victoria and SA. The study involved collecting large numbers of mastitis samples from affected cows in the 2011-2012 season. They found the most common mastitis pathogen was Strep. Uberis (no surprise there!) at 54%, With Stap. Aureus 15%, E.coli 12% and Strep. Dysgalactiae at 9%. 45% of samples were no growths.

While these findings were no real surprise, its good to get an overview of what’s currently happening and confirmation that what we think is happening, actually is!

Given Strep Uberis is the most common mastitis pathogen, and something we see a lot at this tie of year, we have included an updated summary of this pathogen below.

STREP UBERIS

The bacteria Streptococcus uberis (also known as Strep uberis) is a common cause of mastitis in dairy cattle in many countries around the world. Over the past two decades it has become the leading cause of clinical and subclinical mastitis in Australian and New Zealand dairy herds

Strep uberis is passed in the faeces of cattle and can survive for up to 2 weeks in fresh dung or faecal-contaminated mud or straw. It is regarded as an environmental pathogen’ because cows are likely to develop intramammary infections if their udders are exposed to contaminated material, especially if they have damaged teat skin or open teat ends.

The emergence of Strep uberis as a problem for pasture-based herds follows intensification of the Australian industry, with higher stocking rates increasing cow exposure to environmental bacteria. Typical changes in farm systems that have increased the risk of environmental infection include widespread use of calving and feed pads, stand off areas and heavy traffic around water troughs, gateways and laneways.

Many cows in the herd can become infected if exposed to environmental bacteria at a vulnerable time: especially in the fortnight after drying-off and the weeks either side of calving – or in the hour immediately after milking.

Importantly Strep uberis can also spread from cow-to-cow at milking. Most quarters that become infected have high cell counts (often above 500,000 cells/ mL) that return to a normal cell count within 2-3 weeks but a small percentage of cows remain chronically infected and shed bacteria in their milk. This allows the bacteria to spread from cow-to-cow. So despite its reputation as an environmental pathogen, control of Strep uberis also requires attention to management practices that minimise milk droplet ‘impacts’ during milking, reduce the number of bacteria around the teat end and maintain healthy teats.

It is likely that faecal shedding by cows is needed to maintain Strep uberis in the environment. Strep uberis contamination is common in laneways with medium to high traffic. Paddocks show a high degree of contamination immediately after grazing but minimal contamination before grazing.

 Because cows are likely to be regularly exposed to Strep uberis in the environment, mastitis management should aim to reduce the likelihood of cows becoming infected rather than to eliminate the infection from the herd. The focus of attention here is on having a dry cow strategy and drying-off process that ensures that teat canals are sealed (ie the use of teat seal at dry off); a calving management plan that minimises exposure to contamination; and milking management routines for putting teatcups on clean, dry teats, and minimising exposure of susceptible cows to high traffic areas.

The main opportunity for the treatment and cure of Strep uberis infections that have occurred during lactation is through antibiotic Dry Cow Treatments at drying off. The drug of choice also needs to be discussed with your vet as longer-acting preparations may be benifical.

Treatment of clinical cases during lactation often removes clinical symptoms although it may be difficult to achieve a bacteriological cure in some cases.

A recent review looked at the treatment of clinical and subclinical Strep uberis mastitis during lactation. The treatment duration varied from conventional treatments of 2-3 days to extended treatment periods of up to 8 days for subclinical infections and longer for non-responsive clinical cases. The bacteriological cure rates(ie where no further bug is found) for clinical cases with conventional treatments ranged from 50% to 90%. For untreated clinical cases, the cure rate averaged 19%.

Cure rates are likely to vary with the strain of Strep uberis causing the infection. There are over 600 strains of Strep. Uberis!.

In some circumstances the only way to remove udder infections is to cull persistently infected cows:

those that have had three or more clinical cases in one lactation OR cows that have had cell counts above 250,000 cells/mL in two consecutive lactations despite intervening antibiotic Dry Cow Treatment

Given the relatively low cure rate it is important to remain vigilant for recurrence of clinical cases of Strep uberis. In practical terms, if a treatment regimen appears to be successful on a farm (if no more than 2 clinical cases in 10 require a second course of treatment) it is worth sticking with that protocol. If your protocol is not working then please give us a call.