When I began practicing 16 years ago in Georgia, Staph aureus and Strep ag were two of the most prevalent organisms causing clinical mastitis. By identifying cows with these pathogens, selectively treating them and culling chronic-offenders, they were eliminated from most of our herds. However, an environmental bug has arrived to take their place - Streptococcus uberis.

For years, Strep uberis has been classified as an environmental organism. The pathogen is most commonly found on bovine skin, lips, teats as well as in the environment. I also have isolated this bacteria in the white discharge of a cow infected with metritis. This infectious discharge will drain down onto the cow's tail and then, as she swishes it, be spread to the teat and udder.

If you see a white or cloudy discharge in just-fresh cows, have your veterinarian sample it. I recommend cultures from the uterus and the clitoral fossa. You can help prevent Strep uberis by treating these metritis cases promptly, so they do not become the source of infection. (For more information on treating metritis, see "Metritis" on page 32 of last month's issue of Dairy Herd Management.)

Treatment difficult
The key to stopping Strep uberis from entering the teat and udder is found in utilizing proper teat sanitation and milking procedures. Once the pathogen enters the mammary gland, it becomes quite contagious and can spread from cow to cow via the milking claw. Back flushing and claw sanitation can help eliminate this form of transfer. Identifying problem cows and milking them last also helps prevent the spread.

Little success is seen when treating the Strep uberis-infected udder with antibiotics during the lactation. Prolonged therapy, for periods beyond what is recommended for most antibiotics, has improved the cure rate slightly. However, this is an extra-label use of mastitis products and must be done under the advice and prescription of your veterinarian. Even with this type of therapy, less than 30 percent of clinical Strep uberis cases are cured. As with other contagious forms of mastitis, this can be quite frustrating because these cows often become chronic or repeat cases. The somatic cell count levels of infected cows can increase to more than 1 million, which lowers milk production.

Success in the dry period
Your best bet is to treat the pathogen during the dry period. Culture the pathogen infecting your herd and then match it with the dry tube product that will be most effective. Your laboratory can determine if the pathogen is resistant or sensitive to specific types of antibiotics in different products. Treating in this manner typically clears 50 percent to 60 percent of the cases.

Re-sampling and culturing these cows after they freshen also helps monitor the success of your program. Compare somatic cell counts from the first DHI test of the lactation with the last test of the previous lactation to see improvements.

If your farm is experiencing an increase in somatic cell counts, and if your success in treating clinical cases is decreasing, work with your veterinarian to identify the causative organisms. Culturing your bulk tank on a routine basis and sampling every clinical mastitis case is necessary to find the bacterial organism that is causing the problem. Also, consider culturing cows that have metritis and then develop mastitis.

Strep uberis infections are on the increase and could become a problem in your herd. Identfying infected animals, applying proper milking procedures and administering dry-cow treatments are the best methods to control this form of mastitis.

Jim Brett is a practicing veterinarian in Montezuma, Ga.