Bovine Reproduction. Группа авторов

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Bovine Reproduction - Группа авторов


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Photo depicts an ultrasonogram of testis scored as having mild fibrosis. Photo depicts an ultrasonogram of testis scored as having very severe fibrosis.

      Immunohistochemistry was performed on testis tissues of 10 bulls from the group affected by BRSV. Only one of these bulls had fibrotic lesions in testes. Testis tissue was submitted to a diagnostic laboratory for immunohistochemistry for BVDV and BRSV.

      Fibrotic lesions scored as slight or mild were very common (31.3%) in testes of a group of bulls raised under intensive rearing conditions in western Canada. Only 2.5% had moderate scores and none had severe scores for fibrosis. In the more extensive management in Argentina, in a group not affected by respiratory disease associated with BRSV, fibrotic lesions were also mainly slight or mild, but incidence was higher (48.6%). In that group, 1.9% were scored moderate and 0.95% severe. In the Argentine group affected by BRSV, fibrotic lesion scores were higher and more frequent. Scores for slight to mild, moderate, and severe to very severe were 58.3, 17.1, and 5.7%, respectively.

      Histologically, lesions consisted of masses of fibrous tissue with fine fibrillation, or heavy bundles of wavy tissue seminiferous tubules. Usually there were fewer germinal cells in seminiferous tubules within masses of fibrous tissue. In some tubules, germinal cells and Sertoli cells were missing entirely and hyaline material was present in the lumen. Similar abnormalities were evident in seminiferous tubules adjacent to fibrous tissue masses; however, completely normal tubules were often beside or very close to fibrous tissue masses. Inflammatory cells were consistently absent. Therefore we inferred that neither the insult that caused fibrosis nor proximity of fibrous tissue to seminiferous tubules affected function of adjacent tubules.

Photo depicts cross-section of a bull testis with fibrotic lesions that appeared to radiate from rete testis toward the periphery, suggesting individual tubules were destroyed and replaced by scar tissue. Photo depicts ultrasonogram of a testis with fibrotic lesions radiating from the rete testis toward the periphery.

      The cause of the testicular fibrosis is uncertain. Potential causes are disrupted development of embryonic tubule‐to‐rete connections, an infectious disease process affecting tubule health and development, abnormal testes thermoregulation, and trauma.

      Bacterial and viral infections are common in early post‐weaning period when maternal immunity has waned and animals of multiple origins intermingle [36]. Thus an infectious process, as a cause of fibrotic lesions, would fit the time period when testis lesions appear in young bulls. Although bacterial or viral infections would be expected to cause testicular swelling and pain, perhaps inflammation is mild and not apparent. Infectious agents could cause inflammation of arterioles and capillaries in the testes, leading to local tissue necrosis and formation of foci of fibrosis [10]. Viral infections may also target specific cells within seminiferous tubules, e.g. Sertoli cells or individual germinal cells, resulting in tubule damage and fibrous tissue infiltration [37, 38].

      Two common viral diseases of cattle, bovine herpesvirus (BHV)‐1 and BVDV, have been investigated for their role in male reproductive infections. Both viruses have been isolated from semen [39, 40] and BHV‐1 has been associated with degenerative changes in the seminiferous epithelium, perhaps due to illness and fever [41]; however, there are no reports that associate BHV‐1 or BVDV with lesions in bovine testes.

      The association of a greater prevalence of testis fibrosis with occurrence of a severe outbreak of BRSV respiratory disease in the Group 1 bulls in Argentina, combined with a lesser prevalence of testis lesions in Group 2 (vaccinated against BRSV), suggests that BRSV may be involved in etiology of testis fibrosis. However, immunohistochemistry of testis tissues from 10 bulls that were culled and slaughtered from Group 1 failed to detect BRSV antigen. Failure to find evidence of BRSV antigen may indicate that this virus does not multiply in testis tissue or it might be due to the lack of fibrotic lesions in 9 of 10 of the testes from which samples were submitted and because samples were obtained ~12 months after BRSV incident.

      Viral agents multiply within the testes of several


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