A chronic indurative mastitis in sheep,associated with maedi/visna virus infection |
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| Authors: | E J van der Molen U Vecht D J Houwers |
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| Institution: | Central Veterinary Institute , P.O. Box 65, Lelystad, 8200 AB, the Netherlands |
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| Abstract: | Summary 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, culled 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. The lesions were often limited to one udder half Among the necropsied ewes of group A, nine showed lesions characteristic of maedi, whereas in group B no such lesions were observed. The possible causal relation of this chronic indurative mastitis with mvv infection is discussed. |
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