Microscopic and Ultrastructural Renal Pathology of Oosporein-Induced Toxicosis in Broiler Chicks

Kidneys from broiler chicks receiving 300 micrograms of oosporein K salt per gram of feed continuously from 0 to 21 days of age were examined by light and electron microscopy. Chicks that died at 3 days had nephrosis of initial proximal tubular segments with an early pyogranulomatous interstitial response. Macula densa cells had cytoplasmic accumulations of periodic-acid-Schiff-positive granules. Kidneys from chicks surviving 21 days had hypercellular or atrophic glomeruli and hyperplastic dilated proximal tubules. Centrilobular distal tubules were dilated and filled with hyaline basophilic casts. Interstitial fibrosis was prominent in cortical and medullary zones. These findings indicate that oral oosporein is a severe nephrotoxin which can cause visceral urate deposition and severe nephrosis of initial proximal tubular segments. The histopathology of this mycotoxicosis was compared with those of infectious-bronchitis-induced nephrosis and avian urolithiasis syndrome.