Differences in susceptibility to Mannheimia haemolytica-associated mastitis between two breeds of dairy sheep.
We used a Mannheimia haemolytica isolate to study differences in susceptibility to experimental mastitis between two breeds of dairy sheep. The isolate was deposited into the teat duct of Karagouniko (K, n=8) or Frisarta (F, n=8) ewes. The animals were monitored by means of clinical, bacteriological, cytological and pathological methods. K ewes did not develop any systemic or mammary clinical signs, whilst F ewes became ill and developed acute clinical mastitis 12 h later (P<0.001). Bacteria were isolated from 34/48 samples from K ewes and from 46/46 samples from F ewes. Positive California mastitis test (CMT) results were 17/24 samples from K ewes and 23/23 samples from F ewes; leucocytes were seen in Giemsa-stained films. Total pathology score summed over all group K ewes was 41 (maximum possible: 128); Man. haemolytica was isolated from 12/24 tissue samples. Total pathology score summed over all group F ewes was 93; Man. haemolytica was isolated from 24/24 tissue samples. Hyperplastic lymphoid nodules consisting of lymphocytes and plasma cells with germinal activity were characteristically present at the border between teat duct-teat cistern of group K ewes; no such structures were observed in teats of group F ewes. The results identified differences in susceptibility/resistance to a mastitis pathogen among animals of the two breeds. Defence mechanisms of the teat appeared to be inadequate against the invading organisms; as lymphoid nodules have been considered important defensive mechanisms of the ovine teat, their observed lack in Frisarta ewes might have predisposed them to development of mastitis.
Fragkou
Ilectra A
IA
Veterinary Faculty, University of Thessaly, PO Box 199, 43100 Karditsa, Greece.
Skoufos
John
J
Cripps
Peter J
PJ
Kyriazakis
Ilias
I
Papaioannou
Nikos
N
Boscos
Costas M
CM
Tzora
Athina
A
Fthenakis
George C
GC
D000818:Animals; D004198:Disease Susceptibility; D005260:Female; D007774:Lactation; D016978:Mannheimia haemolytica / Q000502:physiology*; D008413:Mastitis / Q000382:microbiology / Q000662:veterinary*; D016871:Pasteurellaceae Infections / Q000382:microbiology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000145:classification* / Q000382:microbiology*; D013045:Species Specificity