January 2018

Slide A: Signalment (JPC # 1557420): Guinea pig

HISTORY: Tissue from a clinically normal guinea pig

HISTOPATHOLOGIC DESCRIPTION: Kidney: Multifocally, glomerular capillary endothelial cells contain 5-10 um diameter intracytoplasmic coccidian 1st generation schizonts, each with multiple oval, 2‑3 um eosinophilic merozoites. Within the epithelial cells of proximal convoluted tubules are large cytoplasmic vacuoles (up to 35 um diameter) containing single pale basophilic oval 12‑24 um 2nd generation schizonts, filled with 1‑2 um diameter merozoites. Tubular epithelial cells at the corticomedullary junction and within the medulla are expanded by variably sized, irregularly round 15‑50 um diameter vacuoles which often cause obstruction of the tubular lumen. Within the vacuoles, there are coccidian parasites in various stages of development, including 2‑3 um diameter microgametes, 8‑10 um diameter macrogametes, 15‑20 um diameter sporonts with 1-2 um round sporoblasts budding in a radial pattern from their surface, free mature 4‑6 um diameter sporoblasts, and within tubular lumina are numerous multinucleated 10 um diameter sporocysts. The periglomerular interstitium is multifocally minimally expanded by low numbers of lymphocytes and plasma cells.  

MORPHOLOGIC DIAGNOSIS: Kidney, glomerular endothelium and tubular epithelium: Intracellular schizonts, gametes, sporoblasts and intratubular sporocysts, diffuse, numerous, guinea pig (Cavia porcellus), rodent.

CAUSE: Klossiella cobayae

Slide B: Signalment (JPC # 1624389): Horse

HISTORY: Tissue from a clinically normal horse

MICROSCOPIC DESCRIPTION: Kidney: Within the tubular epithelial cells at the corticomedullary junction and in the medulla are variably sized, irregularly round 12‑75 um diameter vacuoles which greatly enlarge the cells, often occluding the tubular lumen. Within the vacuoles are intracellular coccidian parasites in various stages of development, as previously described. Occasionally, there are second generation schizonts filled with merozoites within epithelial cells of the proximal convoluted tubules. Multifocally, glomerular and interstitial capillaries are dilated and congested, and there are aggregates of sloughed epithelial cells which contain sporonts within tubular lumens. 

HISTOPATHOLOGIC DIAGNOSIS: Kidney, tubular epithelium: Intracellular schizonts, gametes, sporoblasts and intratubular sporocysts, multifocal, numerous, breed not specified, equine.

CAUSE: Klossiella equi

ETIOLOGIC DIAGNOSIS: Renal Klossiellosis 



kidney via capillaries > first schizogony of sporozoites in glomerular capillary endothelial cells > rupture of endothelial cells and release of merozoites > second schizogony occurs in convoluted tubular epithelial cells > in thick limb of loop of Henle, gametogony occurs with formation of microgametes and macrogametes which form sporonts that bud to form sporoblasts, which then divide to form sporocysts filled with sporozoites > sporocysts released in urine








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