In a female, hybrid breed, 2 months old, rabbit carcass a tumor that affected half of a kidney and the spleen was observed. The first suspicion was a neoplasm, such as a nephroblastoma.

The histopathological study revealed that it was a severe chronic multifocal granulomatous nephritis with the presence of abundant intralesional Encephalitozoon cuniculi.

It is a microsporid, a forced intracellular fungus. The target tissues are the brain and the kidney and it is excreted in the urine. It can affect multiple species of mammals especially if they are immunocompromised, it has even been described in people.

This presentation with conspicuous granulomas is not the most common, non-suppurative interstitial nephritis is usually observed.

Granulomatous lesions in the kidney of a rabbit carcass.


The lesions caused adherences between the spleen and the kidney.


Microscopically the granulomatous lesions were observed (asterisk) in kidney slides (upper half). By means of immunohistochemistry the presene of abundant intralesional Encephalitozoon cuniculi (brown coloures, lower half) were observed.