- highly contagious mastitis

Recently, there has been renewed focus on a highly contagious bacteria that causes mastitis in dairy cows. Streptococcus agalactiae (or Strep ag for short) is currently active and creating serious problems in herds throughout Australia.

The first indication of Strep ag infection in a herd is either an increase in cell counts (Bulk Milk Cell Counts or Individual Cow Cell Counts) or a rise in the number of clinical cases during lactation.

In cattle, Strep ag has a very restricted “habitat.” It is only found in udder tissue or milk, or on the skin of recently milked teats. In dairies, it can also be found on milkers’ hands or the surfaces of equipment exposed to infected milk.

Spread occurs when infected milk contaminates the teat skin of other cows at milking time. The bug is carried to new quarters by hands or teatcup liners, in splashes or aerosols of milk during stripping, and in cross flow of milk between teatcups.

If post-milking teat disinfection fails, the contaminating Strep ag multiplies on the teat skin and can pass up the teat canal to the udder tissue.

New infections also occur if bacteria-laden droplets of milk penetrate through teat ends during the milking process. This is more likely to happen when there are problems with the milking machine or milking technique (particularly liner slip, rough removal of the cups, or vigorous machine stripping).

Spread of Strep ag may be very rapid.

The key to controlling the bacteria is to stop its spread from cow to cow at milking time.

This involves paying particular attention to hygiene in the dairy, correcting faults with milking machines and milking technique, completely disinfecting teats after milking and improving the health of teat skin. Separating infected cows and milking them as a separate group after the clean cows can also be a useful strategy to reduce the likelihood of spread.

Veterinarians and milking machine technicians in all regions who have completed training with Countdown Downunder are able to help farmers eliminate this problem bacteria from their herds.

Image and caption

The first indication of Strep ag infection in a herd can be an increase in cell counts

Countdown Downunder Farm Guideline or Technote
Guidelines 10 and 11

Keywords
Strep ag, Streptococcus agalactiae  cell counts, infection control

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337