Intestinal and pulmonary mycotic lymphadenitis in cattle.

Among 4877 slaughtered cattle with tuberculosis-like lesions in lymph nodes, 94 cases (1.9 per cent) revealed fungal hyphae on histopathological examination. The survey period was 12 years and most of the affected animals (greater than 77 per cent) were beef cattle. Affected nodes were mesenteric in 84 cases (89.4 per cent), mediastinal and/or bronchial in seven cases (7.4 per cent), and in three cases (3.2 per cent), both mesenteric and mediastinal nodes were affected. The incidence of mycotic lymphadenitis was unrelated to year of study or season. Eighty-two of the cases were re-examined histologically and immunohistochemically. All lesions were granulomatous in nature and, in 26 cases, eosinophilic asteroid bodies (rosette formation) around hyphae were found. In 75 cases, immunofluorescence staining identified the agent as a zygomycete, probably Absidia corymbifera and, in one case, there was a concurrent infection with a Candida species. In seven cases that did not react with the antibodies employed, a diagnosis of zygomycosis was suggested on the basis of hyphal morphology. Hyphae of Aspergillus spp. were not found in any of the lesions. A concurrent fungal and mycobacterial infection (M. avium) was diagnosed in one case. Thus, zygomycetes are the main cause of macroscopically apparent mycotic lymphadenitis, a sporadic disease most probably caused by feeding with mouldy food stuffs.