A Retrospective Study of Neurological Disease in 118 Rabbits A. Gruber * , A. Pakozdy † , H. Weissenbo ¨ck * , J. Csokai † and F. Ku ¨ nzel † * Institute of Pathology and Forensic Veterinary Medicine, Department of Pathobiology, and † Clinic of Internal Medicine and Infectious Diseases, Clinical Department of Small Animals and Horses, University of Veterinary Medicine, Vienna, Austria Summary A retrospective pathological study of 118 rabbits presenting with neurological disease was conducted. Diagno- ses were categorized on the basis of aetiopathogenesis as inflammatory, vascular, traumatic, metabolic-toxic, neoplastic, degenerative or idiopathic. Central nervous system (CNS) lesions were present in 85 (72.0%) of the rabbits and in most of these cases (70.3%) a causative agent was identified. The majority of animals (n ¼ 78, 66.1%) had disease of an inflammatory nature and 71 of these 78 rabbits had one of two zoonotic in- fectious diseases: encephalitozoonosis (n ¼ 69, 58.5%) and herpes simplex virus (HSV) encephalitis (n ¼ 2). In- fections with zoonotic potential are therefore a major cause of CNS disease in the rabbit. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: encephalitozoonosis; herpes simplex virus encephalitis; neurological disease; rabbit; zoonosis Introduction Neurological disease is not uncommonly recognized in pet rabbits and the major clinical differential diag- noses include encephalitozoonosis, peripheral vestib- ular disorders such as otitis media and otitis interna caused by bacterial infections (primarily Pasteurella multocida), as well as traumatic incidents. The microsporidian parasite Encephalitozoon cuniculi has a wide host range among mammals and commonly infects rabbits (Wasson and Peper, 2000; Mathis et al., 2005). Lesions are primarily located in the kidneys, the central nervous system (CNS) and the eyes, but other organs can also be affected, either separately or in combination. In the CNS, lesions normally do not occur until at least 30 days post-exposure (Percy and Barthold, 1993). Typically, the parasite causes characteristic foci of granulomatous inflammation in the CNS (Harcourt-Brown, 2004). Lymphocytes can be present in the neighbouring leptomeninges, around parenchymal blood vessels, in the neuropil and in the granulomatous foci. Parasites can be found within parasitophorous vacuoles, but free organisms are very difficult to identify in tissue sections stained by haematoxylin and eosin (HE). Lymphoplasmacytic to granulomatous interstitial nephritis is invariably found (Summers et al., 1995). Usually neurological signs are of sudden onset and vestibular in nature, characterized by head tilt, ataxia and paresis (Jass 2004; Ku¨nzel et al., 2008). Infections with E. cuniculi can occur in humans, but are considered opportunistic and are only found in severely immunocompromised people (Mathis et al., 2005). Toxoplasmosis is rarely described in rabbits (Dubey et al., 1992; Sroka et al., 2003) and infections are usu- ally subclinical (Bergmann et al., 1980). In one study of 157 pet rabbits with suspected encephalitozoonosis, only eight animals were seropositive for antibodies against Toxoplasma gondii (Ku¨nzel et al., 2008). Toxo- plasma may induce granulomatous meningoencephali- tis similar to encephalitozoonosis, but foci of necrosis as well as tachyzoites may be found in many organs in- cluding skeletal muscle, spleen, liver, heart, lung and lymph nodes (Dubey et al., 1992; Leland et al., 1992; Gustafsson et al., 1997). The kidneys are usually not af- fected and toxoplasmosis can be differentiated from encephalitozoonosis by serology, tissue morphology and immunohistochemical labelling (Dubey et al., 1992; Leland et al., 1992). Correspondence to: Andrea Gruber (e-mail: andrea.gruber@vu-wien.ac. at). 0021-9975/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcpa.2008.09.009 J. Comp. Path. 2009, Vol. 140, 31e37 Available online at www.sciencedirect.com www.elsevier.com/locate/jcpa