Histochemical study of Encephalitozoon cuniculi spores in the kidneys of naturally infected New Zealand rabbits

Abstract

Encephalitozoon cuniculi is an important microsporidian pathogen that is considered an emergent, zoonotic, and opportunistic. It infects both domestic and laboratory rabbits, generating severe chronic interstitial and granulomatous nephritis with fibrosis and granulomatous encephalitis. Encephalitozoonosis is diagnosed in paraffin-embedded sections by examining the spores in the host tissues. The spores are difficult to observe when the samples are stained with hematoxylin and eosin (H&E), particularly when there is an inflammatory reaction and tissue damage. The spores are easily mistaken for other microorganisms, such as fungi (yeasts), protozoa, and bacteria. In our study, we used kidney samples from E. cuniculi-positive rabbits and employed 14 recommended histologic stains for detecting microsporidia spores: alcian blue, calcofluor white, Giemsa, Gram, Grocott, H&E, Luna, Luxol fast blue, Masson trichrome, modified trichrome stain (MTS), periodic acid-Schiff reaction (PAS), Van Gieson, Warthin-Starry (WS), and Ziehl-Neelsen (ZN).We concluded that MTS and Gram stain, detected by light microscopy, and calcofluor white stain, detected by ultraviolet light microscopy, are the best stains for detecting spores of E. cuniculi in paraffin-embedded tissues from infected rabbits. These stains were superior to WS, ZN, Giemsa, and PAS for identifying spores without background "noise" or monochromatic interference. Also, they allow individual spores to be discerned in paraffin-embedded tissues. MTS allows observation of the polar tube, polaroplast, and posterior vacuole, the most distinctive parts of the spore.

Relationship between seropositivity of Encephalitozoon cuniculi and renal biochemical markers in clinically healthy rabbits

“…In our study, after evaluating all tissues mainly kidney, brain, as well as tissues of other parenchymatous organs, such as the liver and the lungs tissue was selected for postmortem diagnosis because parasite spores were detected more frequently in kidney tissue than in any other tissue. According to previous data pertaining to histological studies, an area containing dark red and grey, depressed, irregular pits and subcapsular foci on the surface of the renal cortex is considered indicative of encephalitozoonosis during necropsy (1,(34)(35)(36). In our study, there were no conspicuous findings macroscopically.…”

“…In infected rabbits, clinical symptoms of renal insufficiency such as weight loss, numbness and loss of appetite may be seen, and some rabbits may develop urinary incontinence and become polydipsic and polyuric (36). In our work, no clinical signs were seen throughout the study.…”

“…These changes were observed only in a few interstitial areas. Rodríguez-Tovar et al (36) reported that the inflammatory reaction could have occurred in the cortical regions of the kidney. In our study, inflammatory foci were also observed in the interstitium of kidneys.…”

“…Postmortem diagnosis of E. cuniculi is required for definitive diagnosis. Using this method, the spores can be identified in many chronically infected tissues (1,33,36). Postmortem morphological lesions in the kidneys are characteristic pitted appearance of the shrunken fibrotic kidneys.…”

Effects of Homeopathic Phosphorus on Encephalitozoon cuniculi-Infected Macrophages In-Vitro

“…This pathogen infects rabbits, causing severe and chronic granulomatous interstitial nephritis with fibrosis and granulomatous encephalitis. 1,2 Encephalitozoonosis in humans can cause local infections to spread systemically. The competence of the host's immune response and the fungus species involved are factors that determine the pathogenicity of the disease.…”