great lakes dairy sheep symposium - the Department of Animal ...

1.2.2. Subclinical IMI
It is now well documented that CNS are the most prevalent agents responsible for subclinical
IMI: 80 % of subclinical IMI in dairy sheep are due to CNS (Fig. 2).
Figure 2. Aetiology of dairy sheep subclinical IMI (Bergonier et al. 2003 and 2006)
The increase of SCC depends basically on the gravity of the inflammation / infection and its
persistence. An illustration is shown on the Figure 3: for healthy ewes, the geometric mean of
SCC during all the lactation is about 250,000 cells/ml, while it reaches 800,000 cells/ml for longterm
infected sheep and is 1,400,000 cells/ml for both glands long-term infected sheep.
Figure 3. Annual geometric mean of SCC from 346 ewes according to the level of infection of
the 2 glands: both glands healthy or briefly infected (1+1, 1+2, 2+2), one gland long-term
infected (1+3, 2+3), long-term infected for both glands (3+3)
1600
1400
1200
1000
800
600
400
200
0
6
7
3 3
6
5
79
40
S. aureus
CNS
Streptococci
Streptococcaceae
Corynebacteria
Gram negative
Other
1+1 1+2 1+3 2+2 2+3 3+3