Surgical Management of Ear Diseases in Rabbits

Perioperative complications and outcomes following partial ear canal ablation and lateral bulla osteotomy in pet rabbits: 20 cases (2009-2021)

OBJECTIVE

To investigate the perioperative complications and outcomes of rabbits undergoing partial ear canal ablation and lateral bulla osteotomy for treatment of chronic otitis.

MATERIALS AND METHODS

Surgical logbooks were searched to identify rabbits that underwent partial ear canal ablation and lateral bulla osteotomy between December 2009 and September 2021. Data collected included signalment, history, clinical signs, historical and current medical management, physical examination findings, preoperative diagnostic imaging and aural bacterial culture results, surgical procedure information, duration of hospitalisation, complications and final outcome.

RESULTS

Twenty rabbits with chronic, medically unresponsive otitis underwent 27 partial ear canal ablation and lateral bulla osteotomies. Ten rabbits had pre-existing neurologic deficits and 17 had an ear base abscess at the time of surgery. A total of 13 (65%) rabbits developed at least one complication, either in the perioperative period or between discharge and recheck. Three of these rabbits (15%) underwent revision surgery for persistent or recurrent ear base abscess. Complete resolution of clinical signs ultimately occurred in 12 (60%) rabbits. Three (15%) rabbits showed improved but not completely resolved clinical signs (three facial asymmetry). Five (25%) rabbits died of causes potentially related to chronic otitis and/or partial ear canal ablation and lateral bulla osteotomy; two of these rabbits had undergone revision surgery.

CLINICAL SIGNIFICANCE

Although this study reports a high complication rate (65%), most complications resolved, with 15 (75%) rabbits having a good to excellent final outcome. Since the majority of rabbits in this study had chronic and severe ear disease, further studies are required to determine if surgical intervention earlier in the disease process could result in a lower complication rate.

Injection techniques for auricular nerve blocks in the rabbit cadaver

OBJECTIVE

To describe the landmarks for localization and to determine the methodology and volume of methylene blue dye to adequately stain the auricular nerves in rabbit cadavers.

STUDY DESIGN

Prospective, randomized, cadaveric study.

ANIMALS

A total of 26 rabbit cadavers (Dutch-Belted and New Zealand White breeds).

METHODS

Part I: anatomical dissections were performed to identify the sensory auricular nerves and to establish the ideal injection approach and volume of dye required for nerve staining. Part II: a single injection technique using 0.1 mL kg^-1 dye was evaluated for staining the greater auricular nerve and two techniques (perpendicular and angled needle approaches) using 0.075 mL kg^-1 dye were evaluated for the auriculotemporal nerve. Dye spread was evaluated through cadaveric dissections and nerve staining graded using a 0-2 point scale. Injections were considered successful if the nerve was stained circumferentially. Cadavers were assessed for staining of the mandibular nerve owing to the close proximity to the auriculotemporal nerve. Fisher's exact test and mixed effects logistic regression model were used for statistical analysis.

RESULTS

The greater auricular nerve was stained in 24/27 (88.9%) injections. The auriculotemporal nerve was stained in 7/12 injections (58.3%) with the perpendicular needle approach; staining success increased to 80% (12/15 injections) with the angled needle approach; however, this difference was not statistically significant (p = 0.228). Mandibular nerve staining occurred on seven auriculotemporal injections with no statistically significant difference in the incidence of nerve staining between techniques.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that the auricular nerves in rabbit cadavers can be successfully located and stained using anatomic landmarks and the described injection techniques.

Lop-eared rabbits have more aural and dental problems than erect-eared rabbits: a rescue population study

This research aimed to assess whether rabbits having lop ears, an artificially selected conformation, compromises welfare. We investigated the occurrence of aural and dental pathology in lop-eared compared with erect-eared rabbits. Thirty rabbits (15 lop-eared and 15 erect-eared) from a rabbit-only rescue shelter were examined. An otoscope was used to visualise the ear canals and mouth. Samples were taken from each ear to examine for mites, bacteria and yeast. Medical records were also examined. Lop-eared rabbits showed statistically significantly more frequent ear canal stenosis, higher scores of cerumen and erythema and more frequent potential pain response during ear examination, compared with erect-eared rabbits. We also found statistically significantly more frequent incisor pathology, molar overgrowth, molar sharpness, molar spurs and history of veterinary dental treatment in lop-eared compared with erect-eared rabbits. The effect sizes were often large. Age was not statistically significant between the lop-eared and erect-eared rabbit groups. Thus, lop-eared rabbits were at an increased risk of aural and dental pathology in this study. This brings into debate the ethics of breeding and buying lop-eared rabbits, as they are more likely to suffer conditions that negatively impact welfare, such as pain, and potentially deafness and difficulty eating.

Effects of an enrofloxacin-silver sulfadiazine emulsion in the ears of rabbits with perforated tympanic membranes

OBJECTIVE

To determine whether an enrofloxacin-silver sulfadiazine emulsion (ESS) labeled for treatment of otitis externa in dogs has ototoxic effects in rabbits following myringotomy.

ANIMALS

6 healthy adult New Zealand White rabbits.

PROCEDURES

Rabbits were anesthetized for brainstem auditory-evoked response (BAER) tests on day 0. Myringotomy was performed, and BAER testing was repeated. Saline (0.9% NaCl) solution and ESS were then instilled in the left and right middle ears, respectively, and BAER testing was repeated prior to recovery of rabbits from anesthesia. Application of assigned treatments was continued every 12 hours for 7 days, and rabbits were anesthetized for BAER testing on day 8. Rabbits were euthanized, and samples were collected for histologic (6 ears/treatment) and scanning electron microscopic (1 ear/treatment) examination.

RESULTS

Most hearing thresholds (11/12 ears) were subjectively increased after myringotomy, with BAER measurements ranging from 30 to 85 dB in both ears. All day 8 hearing thresholds exceeded baseline (premyringotomy) values; results ranged from 30 to 85 dB and 80 to > 95 dB (the upper test limit) in saline solution-treated and ESS-treated ears, respectively. All ESS-treated ears had heterophilic otitis externa, epithelial hyperplasia of the external ear canal, various degrees of mucoperiosteal edema, and periosteal new bone formation on histologic examination. Scanning electron microscopy revealed that most outer hair cells in the ESS-treated ear lacked stereocilia or were absent.

CONCLUSIONS AND CLINICAL RELEVANCE

Results supported that ESS has ototoxic effects in the middle ear of rabbits. Further research is needed to confirm these findings. Myringotomized laboratory rabbits may be useful to study ototoxicity of drugs used in human medicine.

The Status of Pet Rabbit Breeding and Online Sales in the UK: A Glimpse into an Otherwise Elusive Industry

Simple Summary

Very little is known about where our pet rabbits come from: Who the breeders are, how good/or bad the conditions are that breeding rabbits are kept in, or whether breeders are being monitored by local authorities. This study aimed to bring to light information on breeding rabbits and breeders in the UK. Several methods of data collection were used combining data from online sales adverts, with a breeder survey and a council freedom of information request. From 3446 online rabbit sale adverts we found 94.5% of adverts were from England and only 1% of breeders were licenced. Out of 33 breeders surveyed, 51.5% provided smaller housing than recommended and housed most rabbits singly, against recommendations, and males were most likely to be housed singly, in too small conditions. However, most provided toys and a diet compliant with recommended guidelines. The most commonly sold/bred rabbits were breeds with flat-faces, which can cause significant health and well-being problems. A freedom of information request sent to 10% of UK councils revealed inconsistency in licensing conditions and confusion about eligibility. Without appropriate guidelines for housing and husbandry and regulation, rabbits within the pet rabbit breeding industry are at risk of compromised welfare.

Abstract

Conditions of pet rabbit breeding colonies and breeder practices are undocumented and very little is known about the pet rabbit sales market. Here, multiple methods were employed to investigate this sector of the UK pet industry. A freedom of information request sent to 10% of councils revealed confusion and inconsistency in licensing conditions. Data from 1-month of online sale adverts (3446) identified 646 self-declared breeders, of which 1.08% were licensed. Further, despite veterinary advice to vaccinate rabbits from five weeks, only 16.7% rabbits were vaccinated and 9.2% of adult rabbits were neutered. Thirty-three breeders completed a questionnaire of which 51.5% provided smaller housing than recommended, the majority housed rabbits singly and bucks were identified as most at risk of compromised welfare. However, most breeders provided enrichment and gave a diet compliant with recommended guidelines. Mini-lops and Netherland dwarfs were the most commonly sold breeds, both of which are brachycephalic, which can compromise their health and wellbeing. From sales data extrapolation, we estimate that 254,804 rabbits are purposefully bred for the UK online pet sales market each year. This data is the first of its kind and highlights welfare concerns within the pet rabbit breeding sector, which is unregulated and difficult to access.