JPC SYSTEMIC PATHOLOGY
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
- Klossiella sp. are generally nonpathogenic apicomplexa protozoans that inhabit renal epithelial cells of many species
- Rarely reported to cause tubular nephrosis and interstitial nephritis
- Ingestion of sporocyst > sporozoite invasion of intestinal mucosa > spread to
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
TYPICAL CLINICAL FINDINGS:
- Normally absent, but may cause nephrosis and nephritis in immune-compromised animals
TYPICAL GROSS FINDINGS:
- Heavily parasitized kidneys have tiny gray foci on the cortical surface
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Various stages of schizogony can be found in glomerular endothelium and proximal convoluted tubular epithelium (merozoites within schizonts) with micro- and macrogametes, sporonts, and budding and free sporoblasts in the thick limb of Henle’s loop and multinucleated sporocysts in the urine
- Tubular epithelial cell hyperplasia may occur, along with vacuolation of cytoplasm, and regenerative hypertrophy
- Tubules may be obstructed by sporocysts and degenerative cells
- 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
- Each granulated body in the core of a developing sporoblast consists of a membrane-lined nucleated vesicle which contain small spherical sporozoites
- Sexual stages occur as small dense single nuclei (microgametes) or large single vesicular body with a nucleus (macrogametes) in epithelial cytoplasm, which are hypertrophied
- Typical apicomplexan EM findings: crescent shaped merozoites and sporozoites within a parasitophorous vacuole have a polar ring and conoid at the anterior end, and contain rhoptries, micronemes, a Golgi complex anterior to the nucleus, and several mitochondria randomly dispersed in the cytoplasmix matrix
- Protozoa of 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 um); this causes multifocal granulomatous encephalitis and interstitial nephritis
- Toxoplasma gondii: Cysts are small (30-100 um) 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
- Parasites of the genus Klossiella have been reported throughout the world in mice ( 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
- Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits, 4th ed. Ames, IA:Wiley Blackwell; 2016:83, 236.
- Breshears MA, Confer AW. The urinary system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier;2017:672.
- Cianciolo RE, Mohr FC. Urinary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. 6th ed. vol. 2, St. Louis, MO: Elsevier; 2016:443.
- Gardiner CH, Fayer R, Dubey JP. An Atlas of Protozoan Parasites in Animal Tissues. 2nd ed. Washington, DC: Armed Forces Institute of Pathology; 1998:61-62.
- Gathumbi PK, Varma V, Wells CW. Pathological and ultrastructural features of equine Klossiella. The Kenya Veterinarian. 2001; 21:45-8.