JPC SYSTEMIC PATHOLOGY

URINARY SYSTEM

January 2024

U-P02

 

 

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

 

HISTORY: Tissue from a clinically normal guinea pig 

 

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

 

MORPHOLOGIC DIAGNOSIS: Kidney, glomerular endothelium and tubular epithelium: Intracytoplasmic 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: Tubular epithelial cells primarily at the corticomedullary junction and in the medulla, and rarely within the cortex, are expanded by variably sized, irregularly round 12‑75 µm diameter vacuoles which greatly enlarge the cells, often occluding the tubular lumen. Within the vacuoles are intracytoplasmic coccidian parasites in various stages of development, including 2-3µm diameter microgametes, 8-10µm diameter macrogametes, 15-20µm diameter sporonts with 1-2µm round sporoblasts budding in a radial pattern from the surface, and free mature 4-6µm diameter sporoblasts. Occasionally, there are 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: Intracytoplasmic schizonts, gametes, sporoblasts and intratubular sporocysts, multifocal, numerous, breed not specified, equine.

 

CAUSE: Klossiella equi

 

ETIOLOGIC DIAGNOSIS: Renal klossiellosis  

 

GENERAL DISCUSSION:  

• Klossiella sp. are generally nonpathogenic apicomplexan protozoans that inhabit renal epithelial cells of many species
• Rarely reported to cause tubular nephrosis and interstitial nephritis 

 

LIFE CYCLE:  

 

TYPICAL CLINICAL FINDINGS:

 

TYPICAL GROSS FINDINGS:  

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:  

• Various stages of schizogony can be found in cytoplasm of glomerular and proximal convoluted tubular epithelium (merozoites within schizonts) 
• Micro- and macrogametes, sporonts, and budding and free sporoblasts in the thick limb of Henle’s loop
• Multinucleated sporocysts in the urine
• Tubular epithelial cell hyperplasia, vacuolation of cytoplasm, and regenerative hypertrophy may occur
• In heavily parasitized kidneys, low to moderate numbers of interstitial lymphocytes, plasma cells, and histiocytes may be present, surrounding foci of necrosis and interstitial fibrosis

 

ULTRASTRUCTURAL FINDINGS:  

 

DIFFERENTIAL DIAGNOSIS:

• Protozoa of renal tubular epithelium:

• Encephalitozoon cuniculi (microsporidian): Organisms are found in the epithelium and lumina of tubules; spores are smaller, ovoid, birefringent, and stain poorly with H&E; have a prominent polar capsule and filament; spores may aggregate but do not encyst (pseudocyst up to 120 µm); this causes multifocal granulomatous encephalitis and interstitial nephritis
• Toxoplasma gondii: Cysts are small (30-100 µm) and spherical
• Haemogregarian sp: May have zoites budding from a sporont/residuum, but also infects erythrocytes and numerous tissues; mostly in reptiles, amphibians, and birds

 

COMPARATIVE PATHOLOGY:  

• Parasites of the genus Klossiella have been reported throughout the world in wild mice; (K. muris); guinea pig (K. cobayae); horse, zebra, jackass, burro, donkey (K. equi); S. American opossum and mouse opossum (K. tejarai); Australian water rat (K. hydromyos); African bats (K. killicki); African muridae (K. mabokensis); snakes (K. boyae); birds; and six different species in Australian marsupials
• Unidentified species have been reported in albino rats, Australian marsupials, and the spiny mouse

 

REFERENCES:

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