Otitis media/interna and encephalitozoonosis are the most common causes of head tilt in pet rabbits in the UK: 73 cases (2009‒2020).

BACKGROUND: There are limited studies that identify diseases associated with head tilt in pet rabbits. METHODS: This was an observational, retrospective, single-centre study of rabbits with head tilt presented between 2009 and 2020. Descriptive statistics were performed for all cases, whereas univariate and multivariate analyses were only performed for the 36 cases with a final diagnosis. RESULTS: Seventy-three rabbits met the inclusion criteria. The final diagnoses included Encephalitozoon cuniculi meningoencephalomyelitis (EC) (15/36; 41.7%), otitis media/interna (OMI) (8/36; 22.2%) and concurrent EC and OMI (13/38; 36.1%). Subacute-to-chronic onset was more common in rabbits with OMI than in those with EC (p = 0.018). Previous middle ear surgery (p = 0.046) and a diagnosis of otitis externa (p = 0.004) significantly increased the risk of OMI. Meloxicam was associated with improvement of clinical signs (p = 0.007). Upright ears (p = 0.013), recumbency (p = 0.037) and impaired mentation (p = 0.001) were associated with a higher risk of death/euthanasia. The proportions of residual head tilt (66.7%) and relapse of vestibular signs (42.1%) were high. LIMITATIONS: This was a retrospective study with cases varying in their investigation and conclusive final diagnoses. CONCLUSION: OMI and EC were the most common aetiologies of head tilt in pet rabbits in the UK. Meloxicam might be associated with a favourable outcome in affected rabbits. Paired EC serology and a CT scan of the head should be the baseline investigation for head tilt in rabbits.

Cytological evaluation, culture and genomics to evaluate the microbiome in healthy rabbit external ear canals.

BACKGROUND: Lop-eared rabbits may be predisposed to otitis externa (OE) as a consequence of their ear conformation. Although otoscopy, otic cytological evaluation and culture are valuable tools in dogs and cats, published data on rabbits remain lacking. HYPOTHESIS/OBJECTIVES: This study aimed to assess the utility of otoscopy and cytological results in evaluating healthy rabbit external ear canals (EECs) and to characterise ear cytological and microbiological findings through culture techniques and metagenomic sequencing. ANIMALS: Sixty-three otitis-free client-owned rabbits. MATERIALS AND METHODS: All rabbits underwent otoscopy and ear cytological evaluation. In a subset of 12 rabbits, further bacterial and fungal culture, fungal DNA assessment and metagenomic sequencing were performed. RESULTS: Otic cytological results revealed yeast in 73%, cocci in 42.9% and rods in 28.6% of healthy rabbit EECs. Compared to upright-eared rabbits, lop-eared rabbits had more discharge and more bacteria per oil immersion field. Culture isolated eight different species yet metagenomic sequencing identified 36, belonging to the Bacillota (Firmicutes), Pseudomonadota and Actinomycetota phyla. Staphylococcus were the most commonly observed species with both methods. Ten of 12 rabbits were yeast-positive on cytological evaluation with only three yielding fungal growth identified as Yarrowia (Candida) lipolytica, Eurotium echinulatum and Cystofilobasidium infirmominiatum. CONCLUSIONS AND CLINICAL RELEVANCE: Healthy rabbit EECs lack inflammatory cells yet can host yeast and bacteria, emphasising the need to evaluate cytological results alongside the clinical signs. Lop-ear anatomy may predispose to bacterial overgrowth and OE. Notably, yeasts may be present despite a negative culture.

Ocular biometry in rabbits using computed tomography.

OBJECTIVE: To describe a repeatable method of measuring ocular structures and to establish ocular biometry reference ranges in adult domestic rabbits (Oryctolagus cuniculus) without medical history or imaging findings consistent with ophthalmic disease using a 64-slice multidetector computed tomography scanner. PROCEDURE: In this retrospective and observational anatomic study, 100 eyes from 50 rabbits without medical history or imaging findings consistent with ophthalmic disease who received a head computed tomography scan were selected for measurement of globe length, width, and height using 3D multiplanar reconstruction. Lens width and length, the anteroposterior length of the anterior and vitreous chambers, and attenuation of the lens and vitreous chamber were collected. These parameters were compared against age, sex, weight, body condition, and ear conformation. RESULTS: A reference guide was established, with globe width being the largest dimension (18.03 ± 0.81 mm), followed by height (17.18 ± 0.69 mm) and then length (16.64 ± 0.66 mm). Increased weight was associated with an increase in globe height (p = 2.43 × 10-5 ), length (p = 1.63 × 10-4 ), and width (p = 7.0 × 10-3 ). Increased age was associated with increased lens attenuation (p = 1.28 × 10-7 ) and increased transverse lens width (p = 1.64 × 10-3 ). Inter- and intra-observer agreement was excellent. CONCLUSIONS: CT is a reliable modality for measurement of ocular biometry dimensions in rabbits. These reference values can be applied to aid in identifying diseases that affect the dimensions of the ocular structures in rabbits over 18 months of age.

Computed tomographic features of the normal spleen in rabbits (Oryctolagus cuniculus domesticus).

Computed tomography is commonly utilized for investigation of rabbits, and more recently, for evaluating abdominal pathology. The spleen, however, is an often-overlooked organ, with limited information published. The aims of this retrospective, observational, study were to document the visibility, size, and shape of the normal rabbit spleen and potential correlations with signalment. Institutional imaging archives were reviewed for diagnostic-image-quality abdominal CT studies of rabbits. In 115 cases, the inclusion criteria were met. Pre- and postcontrast CT studies were evaluated by two reviewers for visibility of the spleen. For precontrast CT images, the interrater agreement for identification of the spleen was fair. For postcontrast CT images, interrater agreement was moderate. There were significantly more spleens clearly identified on postcontrast studies compared with precontrast CT. Splenic location, volume, shape, X-ray attenuation, and length were measured, and the splenic-volume-to-body-weight ratio was calculated. The mean splenic volume was 1 mL (range 0.2-3.9 mL), mean length 40 mm (range 20-61 mm), mean attenuation (precontrast CT 80 HU and postcontrast CT 320 HU), and mean splenic volume/body weight ratio was 0.5 mL/kg (range 0.17-1.2 mL/kg). There was a significant relationship between splenic volume and body weight, which was weakly positively correlated. There was no correlation between splenic volume, age, and sex. The most commonly identified splenic shapes were "banana", "tongue", and "elephant trunk". The rabbit spleen can be identified on CT images, but more reliably on postcontrast CT images, which underlines the usefulness of contrast-enhanced CT in this species.

Safety of intravenous iodinated contrast medium injection in rabbits undergoing conscious computed tomography.

Background: Contrast media in CT is widely used in dogs and cats to provide superior tissue delineation and increase the diagnostic capabilities. These contrast-enhanced imaging techniques are gaining popularity in rabbits; published studies reporting the safety of doing so are lacking. Methods: This retrospective observational study aimed to determine the incidence of adverse events following the intravenous administration of iodinated non-ionic contrast medium in 350 rabbits. The medical records of this subset of rabbits admitted between January 2009 and November 2018, that underwent CT examination and received intravenous contrast media, were evaluated. Results: From the 350 rabbits, 342 rabbits were still alive 7 days after the scan. A total of eight rabbits died within 7 days of the scan, seven of which within the first 24 h. All deaths were presumed to be sequelae to the diseases they were being investigated for and not thought to be related to the administration of intravenous contrast medium. Conclusions: The results indicated that the use of intravenous non-iodinated contrast medium was well tolerated and safe in rabbits undergoing conscious CT examination.

In vitro compatibility testing of canine and rabbit blood.

OBJECTIVE: To determine the in vitro compatibility of rabbit and canine blood using both a tube and slide agglutination crossmatch technique and to compare the results obtained from these 2 methods. DESIGN: Prospective observational laboratory study from January to March 2020. SETTING: University veterinary teaching hospital. ANIMALS: Six client-owned rabbits ≥3.5 kg undergoing phlebotomy for a clinical reason. "Pigtail" blood samples from 3 dog erythrocyte antigen (DEA) 1-positive and 3 DEA 1-negative canine packed red blood cell units. INTERVENTIONS: Blood from each rabbit was crossmatched with a single unit of canine blood using both a standard laboratory tube agglutination technique and a simple slide agglutination method with each rabbit/canine unit serving as its own intraassay control. Tube crossmatches were evaluated for agglutination both macro- and microscopically and assessed for hemolysis. Slide crossmatches were assessed for the presence of agglutination both macro- and microscopically.  MEASUREMENTS AND MAIN RESULTS: All crossmatches were incompatible. Varying degrees of agglutination were seen for all crossmatches. Hemolysis was observed with all minor tube crossmatches. Results of both crossmatch techniques were in close agreement.  CONCLUSIONS: The crossmatch results in this present study strongly demonstrate in vitro incompatibility between canine and rabbit blood. Agreement between the 2 techniques in this study indicates that the slide agglutination technique may be quicker, require less blood, and provide reliable results in exclusively assessing the compatibility of canine and rabbit blood. Based on the results of this study, emergency xenotransfusion of canine blood to rabbits cannot be recommended.

Lymphoma with Mott cell differentiation and validation of immunohistochemical lymphoid markers in an African pygmy hedgehog (Atelerix albiventris).

A 2-year-old female intact African pygmy hedgehog was presented for diagnostic investigation of a 2-month reduction in appetite, with weight loss and recent vomiting. Clinical examination revealed a large, firm mass originating from the left cranial abdomen. Ultrasound-guided fine-needle aspirates of the mass, liver, and mesenteric lymph nodes revealed a population of pleomorphic round cells, some of which contained variable numbers of round, clear vacuoles, consistent with a diagnosis of lymphoma with Mott cell differentiation. At postmortem examination, there was marked diffuse splenic enlargement, with infiltration by a soft tissue mass. There were multiple coalescing liver masses, kidney pallor, and mesenteric lymph node enlargements. On histologic examination, the spleen, lymph nodes, and masses in the liver were extensively infiltrated by proliferating lymphoid cells that had plasmacytoid and Mott cell differentiation. Cells with Mott cell morphology had an accumulation of periodic acid-Schiff-positive material in cytoplasmic inclusions and were positive for cytoplasmic nucleic acids when stained with methyl green pyronin. In the population of neoplastic lymphoid cells, a majority of cells expressed the transcription factor Pax5, which drives B-cell differentiation, and a minority expressed transcription factor IRF4/MUM-1, which drives plasma cell differentiation, indicating B-cell lymphoma with plasmacytoid differentiation.

Computed tomographic grading of middle ear disease in domestic rabbits (Oryctolagus cuniculi).

Ear disease, involving the middle and external ear, is commonly reported in pet rabbits, with lop-eared breeds predisposed. CT is the most reliable imaging modality for identifying otitis media (OM) in rabbits. This study aimed to develop a CT-based grading scale to classify the severity of CT changes in rabbits with presumed OM. Three observers independently reviewed CT images of 36 rabbits with OM. For both OM and material within the external ear canal, a grade of I to IV was used, (I=mild, IV=severe disease) and the level of agreement between reviewers was statistically evaluated. The study demonstrated that grades from the three reviewers showed a strong level of interobserver agreement. Comparisons between clinical signs and CT grade were also evaluated. Rabbits with grade IV OM had a high grade of material in the external ear canal. A high proportion of rabbits (83 per cent) underwent CT scanning conscious, demonstrating that diagnostic quality CT images are achievable without the need for anaesthetic intervention, minimising patient risk. This novel CT-based grading scale provides a methodology to correlate grade of disease with clinical signs, ear canal cytology, predisposing factors, treatment options and outcomes for rabbits with ear disease.

The Predictive Validity of Physical Performance Measures in Determining Markers of Preclinical Disability in Community-Dwelling Middle-Aged and Older Adults: A Systematic Review.

Background: Identification of preclinical disability in middle-aged and older adults might allow early identification of and treatment for functional mobility deficits. Purpose: This study aimed to determine which physical performance measures (PPMs) were effective in identifying preclinical disability in individuals at risk for future disability. Data Sources: CINHAL, PubMed, Scopus, and Web of Science databases were searched until September 2017 using key words. Study Selection: Two individuals screened peer-reviewed prospective longitudinal studies that assessed healthy individuals > 45 years old using PPMs at baseline. Eight studies met inclusion criteria. Data Extraction: Two individuals extracted data on participant demographics, PPMs, predictive validity effect size, and disability outcomes. Risk of bias was assessed using the Quality Assessment Tool for Cohort Studies II (Q-Coh II). Data Synthesis: Four constructs were used to guide data synthesis: functional mobility, activities of daily living disability, fall(s), and hospitalization. Multiple sit-to-stands from a chair, standing balance, and gait speed were found to have some merit in identifying preclinical disability across all 4 disability constructs. All studies were scored as good-quality studies using the Q-Coh II. Limitations: The heterogeneity in follow-up times and reporting of risk prediction statistics made it difficult to compare results across studies, PPMs, and constructs. The 4 constructs used as markers of preclinical disability potentially do not fully capture the progression of disability. Conclusions: Physical therapists should consider using PPMs on healthy adult populations to gather baseline data during annual health screens for use in identifying preclinical disability.

Ultrasound and computed tomography of sacculitis and appendicitis in a rabbit.

A 9-month-old neutered male rabbit was referred for lethargy, anorexia, and gastrointestinal stasis. Routine hematology, serum biochemistry, and diagnostic imaging were performed. Computed tomography revealed a wall thickening of the sacculus rotundus and appendix, which was further confirmed on abdominal ultrasound. Full thickness biopsies were collected with histopathology diagnosing a chronic multifocal heterophilic granulomatous sacculitis and appendicitis. The patient was treated medically and at 6 weeks follow-up, clinical signs and intestinal changes had completely regressed. Inflammation of the sacculus rotundus and appendix should be considered as a cause of gastrointestinal stasis in rabbits.