Encephalitozoon cuniculi Levaditi, Nicolau, and Schoen, 1923

(Figure 1-40)

ETYMOLOGY:Encephalito (brain) + zoon (animal) and cuniculi (rabbit).

Schuster (1925) described neuropathology associated with meningoencephalitis in cats infected with Encephalitozoon (syn=Nosema) cuniculi that were apparently normal and healthy. Histopathology performed on a Siamese kitten that had developed spasms, muscle twitching, and depression along with two littermates revealed organisms of Encephalitozoon in the brain, kidney, spleen, lymph node, and in the tunica media of the blood vessels (van Rensburg and du Plessis, 1971). Waller et al. (1983) noted two cats that had low levels of antibody to the spores of Encephalitozoon cuniculi out of a population of 22 cats of which 18 had antibody to Toxoplasma gondii.

The responses to experimental infection with Encephalitozoon cuniculi of 10, 3- to 14-day-old kittens and 3, 2.5-month-old cats that had also been experimen tally infected with FeLV were followed for a period of 3 to 12 weeks (Pang and Shadduck, 1985). Although Encephalitozoon cuniculi was observed in tissue sections of the kidneys of all but one cat, most of these cats showed no signs of infection, All the cats developed a subacute or chronic interstitial nephritis of varying severity with the lesions being markedly more severe in the cats that were also infected with FIV. Meningoencephalitis was observed in 4 of the cats, one of which had received FeLV; however, all lesions were mild. Pneumonia was present in 4 of the cats, 3 of which were those also infected with FeLV. Vascular lesions were seen in none of these cats.


Levaditi C, S Nicolau, R Schoen. 1923. L'agent étiologique de l'encéphalite épizootique du lapin (Encephalitozoon cuniculi). Comptes Rendus Soc. Biol. 89:1157-1162.

Pang VF, Shadduck JA. 1985. Susceptibility of cats, sheep, and swine to a rabbit isolate of Encephalitozoon cuniculi. Am J Vet Res 46:1071-1077.

Schuster J. 1925. Über eine Spontan beim kaninchen auftretende encephalitische Erkrankung. Klinische Wochenschrift 4:550.

van Rensburg IBJ, du Plessis JL. 1971. Nosematosis in a cat: a case report. J S Afr vet med Assoc 42:327-331.

Waller T, Uggla A, Bergquist NR. 1983. Encepahlitozoonosis and toxoplasmosis diagnosed simultaneously by a novel rapid test; the carbon immunoassay. Proc Third InteSymp Assoc Vet Lab Diag pages 171-177.

Figure 1-40.Encephalitozooncuniculi spores in the kidney of an infected rabbit (Histological section stained with Gram’s stain).