A pathological study of bovine alimentary mycosis.

A 10-year study showed that 45 of 692 cattle aged > 6 months had systemic mycosis and, of these, 38 had alimentary mycosis. The percentages of these 38 cattle with lesions in various sites were: rumen (73.7), omasum (71.1), abomasum (34.2), reticulum (21.1), intestine (15.8), omasoabomasal orifice (7.9) and tongue (2.6). Infections in both the forestomachs and abomasum occurred in 31.6 per cent; mucormycosis was found in 94.7 per cent and aspergillosis in 31.6 per cent; 26.3 per cent (10 cattle) had complicated infections with both Mucorales and Aspergillus and eight of these animals had mixed lesions of both mucormycosis and aspergillosis. Macroscopically, focal haemorrhagic necrosis was seen in all 38 cattle. Histologically, thrombosis, coagulative necrosis and hyphae typical of the order Mucorales or of Aspergillus spp. were found. Many of the cattle were also affected by ruminal acidosis-inducing factors (ruminal atony 81.6 per cent, mastitis 63.2 per cent, "downer cow syndrome" 57.9 per cent and parturition 50.0 per cent), which may have predisposed to alimentary mycosis.