A chronic indurative mastitis in sheep, associated with maedi/visna virus infection.

A possible association of a chronic indurative mastitis with mvv (maedi visna virus) infection in sheep was investigated. Sheep of four flocks (group A), in which insufficient lamb growth apparently associated with insufficient milk production and probably related to udder induration, was a serious problem, were clinically examined in mid-lactation. The results were compared with four mvv-free flocks (group B) without such complaints. The incidence of udder induration in group A (n = 263) was about eight times higher than in group B (n = 206): 63.1 versus 8.0%. The clinical picture differed essentially between the groups. In group A the udder abnormalities were of a diffuse and indurative nature, involving both udder halves, while in group B the udder lesions were mainly nodular and often limited to one udder half. Bacteriological examination revealed a difference in infection rate of the udders (6.8% in group A versus 14.1% in group B). A substantial difference was observed in a comparison of the bacteriological infection rate of the clinically abnormal udders (5.4% in group A, versus 47.0% in group B). Serological examination with an indirect ELISA revealed 81% seropositive sheep in group A, versus 0% in group B. Twelve sheep of group A and five of group B, called for reason of mastitis, were selected for pathological examination. The gross and microscopic lesions showed a pronounced difference between both groups. In group A a diffuse interstitial mastitis with slight to moderate fibrosis and a pronounced lymphoid hyperplasia was observed. In group B the mastitis had a nodular character, with a chronic galactophoritis, extensive fibrosis, and in some cases chronic abscesses.(ABSTRACT TRUNCATED AT 250 WORDS)