Strep. uberis can often be a mastitis problem on well-managed dairies which are faithfully employing post-milking teat dipping, dry cow antibiotic treatment, good milking hygiene and routine maintenance of their milking equipment as suggested by the National Mastitis Council. These streps are different in many ways from other streps which cause mastitis in dairy cows. Probably the most widely known and recognized of the streps is Strep. agalactiae or "strep ag." This bacteria is consider contagious and easily spreads from cow to cow during milking in the absence of post-milking teat dipping and good milking hygiene. It can easily be controlled in most herds and responds to antibiotic therapy. Another strep is Strep. dysgalactiae. It is not one of the major pathogens and spreads to cows from environmental locations. Strep. uberis is similar to Strep. dysgalactiae in that it most often spreads to cows from an environmental location. It can probably also spread between cows during milking.

As with other causes of mastitis, infections with Strep. uberis can be detected by culturing milk samples. Specific identification is somewhat more difficult as Strep. uberis has a variable reaction on the culture media and biochemical tests. Therefore, results may vary from one laboratory to another depending on their laboratory procedures. Some of these bacteria have capsules while others do not.

Often times cows or even heifers pick up Strep. uberis infections during the non-lactating periods and freshen with mastitis. Actually, the rate of infection is about the same for cows and heifers at calving. These infection primarily occur in the late dry period when the rate of infection may be 5 times greater than during lactation. However, cows in the fourth or greater lactations tend to get more of these infections in later lactation. Actually about 50% of the infections occur in the last 20 days of the dry period and the remaining 50% occur during lactation. Animals that leak milk or have teat end problems seem to be more susceptible to infections. Flies are also thought to be involved in the spread of this bacteria from cow to cow or from the environment to cows.

In the environment, Strep. uberis is associated with manure in the bedding. It is often found in recycled manure. It can also be found in uterine and calving discharges from recently calved cows. Straw bedding is commonly associated with Strep. uberis. Different from the coliforms which are also found in the manure, the Strep. uberis bacterial counts in the bedding do not seem to be related to the numbers of new infections in the cows. Some reports indicated that there may be "carrier" cows which contaminate the environment. From these environmental locations, the bacteria contaminate the teat ends and eventually lead to new infections.

Most of the mastitis caused by Strep. uberis appears as the non-clinical or subclinical mastitis form where the milk is normal in appearance but the somatic cell count is elevated. Nearly as many cases are clinical with abnormal milk and high somatic cell counts. There tends to be more new infections during wet, warmer weather. About 40% of the infections last less than 8 days, however, some last for very long periods. The spontaneous cure rate is almost 50% so many of the infection disappear on their own without treatment. The treatment cure rate has been reported to be about 30% and is variable between herds. The variability of treatment success is because some Strep. uberis has capsules which protect them from the antibiotics so culture and sensitivity testing is no guarantee of success.

Some research reports have shown good results by treating dry cows or closeup heifers with lactating cow, intramammary antibiotic preparations shortly before their anticipated calving dates. This will be an extra-label use of antibiotic and it is very strongly suggested that you consult your herd veterinarian when attempting this type of treatment. Needless to say, there is an increased risk of violative antibiotic residue in the milk so you should be prepared to test for this or have your creamery test your cow before their milk is shipped with the bulk tank milk.

Prevention does not revolve around the usually methods which control the contagious forms of mastitis. Predipping has a positive effect but just how much it helps is not precisely known. Dry treatment with commercial antibiotics is very effective as a treatment for infections which persist throughout the lactation. But dry cow treatment is not too good as a prevention. The lack of preventive effect is due to the fact that most of the dry cow antibiotic is gone at the end of the dry period when most of the new Strep. uberis infections occur. Since most of the infections take place where the teat meet the bedding, frequent bedding changes in the dry cow and closeup pens should be helpful. Avoiding over-crowding in the dry cow pens is also a good step.

Streptococcus uberis is certainly not your usual strep. It attacks from both the environment at the end of the dry period and from infected cows during milking. Often it is resistant to treatment and causes persistent high somatic cell counts without clinical mastitis. And it does all of this in herd which are doing mastitis control right. The best chances for successful prevention is through close attention to cleanliness at the teat end level during the late dry period.

1/2/98