Hooo-Hooo Volume 10, Nr 2 - Page 9

Vet Diagnostix Mycotic Rumenitis in a Blesbuck Dr Rick Last – BVSc; M.Med.Vet (Pathology) Specialist Veterinary Pathologist Vetdiagnostix – Veterinary Pathology Services We were presented with a carcass of an adult female Blesbuck which had died acutely on a game farm in the Natal Midlands. The most striking feature of the post mortem was a severe acute infarctive rumenitis with multifocal to coalescent areas of red to black discoloured rumen wall affecting primarily the ventral sac of the rumen, reticulum and omasum (See Figure 1). There was an associated severe fibrinopurulent peritonitis with large mats of fibrin with omental adhesions on the rumen surface. These fungi involved are opportunists and usually include the zygomycetes of the Order Mucorales, genera; Mucor, Rhizopus and Absida and Order Entomophorales, genera; Basidiobolus and Conidiobolus. These fungi cannot be distinguished in histological sections. These saprophytic moulds are associated with decaying material, water, soil and substrate high in carbohydrate. They are opportunistic invaders with predisposing factors in domestic ruminants including antibiotic therapy, rumenal acidosis, reflux of acidic abomasal content and erosive viral diseases (MCF, IBR, BVD, EHD). Occurrence in a free range Blesbuck on veld would most likely be associated with some nutritional or environmental factor/s that have induced rumen stasis with rumen wall irritation and secondary invasion by these saprophytic fungi. In the days prior to this animal being discovered, a cold front with heavy rain had occurred. Figure 1 The gross appearance of the rumen pathology is typical of that expected with mycotic rumenitis which is essentially a blood vessel associated condition due to invasion of blood vessels by the fungal hyphae resulting in vascular thrombosis and ischemic necrosis. Histopathological examination of the rumen wall confirmed a mycotic rumenitis in this animal. Mycotic rumenitis is a severe condition that is often fatal due to the extensive forestomach wall infarction and tissue necrosis with associated endotoxaemia. The inflammation extends to the peritoneum, causing hemorrhagic and fibrinous peritonitis that mats the omentum to the rumen, as noted in this instance. In fatal cases, most of the ventral sac as well as the reticulum, omasum and/or abomasum are involved, as was observed in this particular case. 2016 MAY 9