Zygomycotic Lymphadenitis in Slaughtered Feedlot Cattle

Abstract

During the 12 months of 2006, zygomycotic lymphadenitis was diagnosed in 194 of 198 feedlot steers (0.04% of cattle slaughtered during that period) in a California slaughterhouse as part of bovine tuberculosis surveillance. Mesenteric lymph nodes were involved in 190 cases. Affected lymph nodes were enlarged (2 to 42 cm in greatest dimension), firm, and mottled gray-white to yellow with multiple granular or caseocalcareous foci. Histologically, nodal architecture was effaced by necrosis, granulomatous inflammation, and fibrosis. In approximately 20% of the cases, granulomas were mainly restricted to subcapsular sinuses and afferent lymphatic vessels, causing granulomatous lymphangitis. Nonseptate, irregularly branching hyphae with nonparallel walls and bulbous enlargements were common in necrotic areas and within the cytoplasm of multinucleated giant cells. Fungal cultures were performed on 124 affected lymph nodes using 7 media, but no zygomycetes were cultured. Fungal DNA was amplified from 20 lymph nodes. Amplicons from 16 nodes had nearly 100% homology with sequences for Rhizomucor pusillus; 4 amplicons had (> 98%) homology with Absidia corymbifera sequences. Zygomycosis should be considered in the differential diagnosis for granulomatous lymphadenitis in feedlot steers.

Mucormycosis Caused by Unusual Mucormycetes, Non-Rhizopus, -Mucor, and -Lichtheimia Species

“…commonly contaminate air, soil, water, and organic matter, such as garden composting, municipal waste, cultivated mushroom beds, manure, leaf molds, grass, composted wheat straw, citrus waste composting, harvested wheat and sorghum dusts, dust from chicken stalls, guano, poultry droppings, and animal hair (2,24,231,279,302,340,349,356). R. pusillus is a frequent cause of mucormycosis in mammals, leading to abortion and mastitis in cattle, cerebral mucormycosis in cats, and granulomatous lymphadenitis in steers (159,235,274,279,350). Also, R. pusillus has been found in foods such as grains, seeds, nuts, and beans (89,279).…”

Mycotic encephalitis in a grey seal (Halichoerus grypus) pup associated with Rhizomucor pusillus infection

“…In cattle, a third route has been reported, via the gastrointestinal mucosa (Ortega and others 2010). In the absence of pulmonary disease, the most likely route of infection in this seal is the percutaneous route, with the infected digit and minor puncture wounds present being potential portals of entry, although these tissues were not cultured or examined histologically.…”

Diagnostic evaluation and treatment of a Chinese crocodile lizard (Shinisaurus crocodilurus) with seizures

“…The liver had mild to moderate dissecting fibrosis, which may have been caused at least in part by phenobarbital administration (Gaskill and others 2005). The devitalised distal tail was necrotic and the more proximal tail was oedematous and inflamed with intralesional Splendore-Hoeppli reaction, indicative of intralesional bacteria (Ortega and others 2010). The sharply demarcated region of distal necrosis was consistent with infarction and was interpreted as secondary to regional inflammation and infection.…”