Characteristics of Streptococcus agalactiae infections

Characteristic Description
Reservoir of infection Infected udders of cows. It can survive on teat skin, milkers’ hands and clothes, floors and equipment for up to three weeks.
Spread Cow to cow at milking; contaminated milk mostly on liners and hands. Spread is very rapid.
Cow susceptibility All lactating cows are susceptible
Clinical signs

 

 Infection can cause high rates of clinical disease, manifesting as hard swollen quarters.

Affected glands may have recurrent acute episodes and eventually become uneven and firm with watery foremilk containing clots. Intermittent clots may be seen, especially at the teat end at the finish of milking

Infected quarters are often subclinical.
Bacterial shedding Very high numbers of bacteria are shed, especially in the early stages of infection when 100 million bacteria per mL of milk may be present.
Cell counts Most, but not all, infected cows have ICCC >500,000 at some stage during infection. ICCC can fluctuate widely from below 200,000 to above 1,000,000 cells/mL
Milk quality

 

 There is a potential for very high numbers of bacteria to be shed in bulk milk, occasionally enough to exceed Total Plate Count (or Bactoscan) thresholds.
Management during outbreaks This infection can be eradicated if all factors contributing to spread are corrected and existing infections are treated or removed.
  • Correct any faults with milking machines and milking technique.
  • Check teat disinfectant mixing and application. It is essential to disinfect teats and improve the health of teat skin.
  • Identify all infected cows, not just clinical cases, for segregation.
  • Use blanket Dry Cow Treatment at drying off.
  • Consider a closed-herd policy. Prevent re-introduction by testing purchased cows and any treated cows before they are allowed to return to the main herd.
 

Image and caption

Use gloves: Strep ag can survive on teat skin, milkers’ hands and clothes, floors and equipment for up to three weeks.

Countdown Downunder Farm Guideline or Technote
Introduction – pages 3-5

Keywords
Strep agalactiae, infection control, management

Word length
290

 

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