Ear health and quality of life in pet rabbits of differing ear conformations: A UK survey of owner-reported signalment risk factors and effects on rabbit welfare and behaviour

PLOS ONE RESEARCH ARTICLE Ear health and quality of life in pet rabbits of differing ear conformations: A UK survey of owner-reported signalment risk factors and effects on rabbit welfare and behaviour Benedict D. Chivers ID, Melissa R. D. Keeler, Charlotte C. Burn* Animal Welfare Science and Ethics, Royal Veterinary College, Hertfordshire, United Kingdom a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Chivers BD, Keeler MRD, Burn CC (2023) Ear health and quality of life in pet rabbits of differing ear conformations: A UK survey of ownerreported signalment risk factors and effects on rabbit welfare and behaviour. PLoS ONE 18(7): e0285372. https://doi.org/10.1371/journal. pone.0285372 Editor: Cord M. Brundage, University of WisconsinLa Crosse, UNITED STATES Received: December 12, 2022 Accepted: April 21, 2023 Published: July 19, 2023 Copyright: © 2023 Chivers et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: The data described in this study are only available under a CC-BY-NC license at https://rvc-repository.worktribe.com/ output/1607300/ear-disease-in-pet-rabbits-ownerreported-data-from-a-uk-survey-2021-2022. This restriction is imposed by the Royal Veterinary College’s Social Sciences Research Ethical Review Board. The authors agree to the data being used as part of conference presentations even if the presenter is paid for their presentation. * Abstract The impacts of ear disease on animal welfare and behaviour are little documented. Ear disease may be common in rabbits, but difficult to recognise, and lop-ears have previously been indicated as a risk factor for ear disease. We aimed to better understand the range of ear conditions in pet rabbits, signalment risk factors, and impacts on welfare and behaviour. Through an online questionnaire, we investigated owner-reported signalment, veterinary diagnosis of ear conditions, impaired hearing, and ear pain for UK pet rabbits. Relationships between ear condition measures and ear conformation, quality of life, and behaviour were analysed using logistic regression. Of 551 valid responses, 28.5% of rabbits reportedly had experienced ear conditions; 21.2% diagnosed or mentioned by vets, with otitis and excess cerumen most common. Approximately 25% of lop-eared rabbits had ear conditions indicated by a vet versus 10% of erect-eared rabbits. Lop-eared, half-lop, and older rabbits were most at risk (P<0.050). Rabbits reported as showing ear pain responses had reduced owner-reported quality of life compared with other rabbits (P<0.050). Rabbits with ear problems were less likely to be responsive to relevant sounds, and performed binky behaviour (joy jumps) less frequently, than rabbits without such issues. Understanding prevalence and risk factors for ear conditions is critical to improving welfare standards across this widely owned pet species. The findings suggest that improved recognition and treatment of ear conditions, and avoiding breeding from rabbits with early signs, or a family history, of ear disease are necessary to help combat this animal welfare issue. Introduction Ear conditions could represent considerable animal welfare issues, because they can variously cause pain, hearing impairment, loss of balance, or a combination of these. We aimed to explore the nature and scale of ear conditions as a welfare issue in pet rabbits, via an owner questionnaire. In particular, we were interested in the relative prevalence of different ear conditions in a pet population, effects of ear conformation and other signalment factors on ear disease prevalence, and effects of ear conditions on rabbit welfare and behaviour. PLOS ONE | https://doi.org/10.1371/journal.pone.0285372 July 19, 2023 1 / 24 PLOS ONE Funding: The authors received no specific funding for this work. M.R.D.K included some of this questionnaire in part-fulfilment of her Bachelor of Veterinary Medicine at Royal Veterinary College. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Ear health effects on rabbit welfare and behaviour Prevalence of ear conditions in rabbits Textbooks often describe ear diseases as ‘common’ in rabbits [e.g. 1–3], but prevalence estimates vary. Analysis of the first opinion clinical records of 2506 rabbits in the UK suggested a 1-year period prevalence of approximately 1.0% of rabbits having ‘auditory conditions’, as well as 1.6% having head tilts, which can signify otitis media or interna (middle or inner ear infection, respectively) [4]. Another retrospective study of clinical records of 1152 rabbits visiting a USA teaching hospital over a 20 year period found a lifetime prevalence of 3.5% of rabbits having otitis externa, 1% having otitis media, and 2% having ear mite infestation [5]. However, the true prevalence could be higher, because many ear conditions are difficult to recognise in rabbits [6, 7]. This is because behavioural signs of pain and hearing loss usually manifest as unresponsiveness and reduced activity, which can easily go unnoticed by owners or vets, especially if chronic [7–10], and rabbits may hide pain when humans are present [11]. Moreover, diagnosis of many ear conditions requires expensive, technically complex equipment, such as radiology or CT scanning for otitis media/interna, or brainstem auditory evoked response (BAER) testing for hearing loss, with some of these techniques requiring sedation of rabbits [2, 10, 12]. Nevertheless, some evidence of a higher prevalence comes from post-mortem inspection of 583 farmed adult rabbits reported in 1977, which revealed that 32% had otitis media, even though all the rabbits had appeared healthy on ante-mortem inspection [13]. More recently, retrospective examination of CT scans showed that 22% of 161 rabbits attending a UK university hospital had otitis media [14]. Notably, 61% of those cases had not been presented or referred for ear disease, suggesting that the disease was clinically ‘silent’, previously going undetected by both the owners and the referring veterinary surgeons. Similarly, another retrospective CT scan analysis revealed that 27% of 67 rabbits in the USA, again without clinical signs of ear disease, in fact had middle ear abnormalities [15]. It is worth noting that the opposite also occurred in that study, with 57% of 21 rabbits who did have clinical signs of ear disease showing no evidence of middle ear abnormalities, but perhaps this is not surprising because not all ear diseases affect the middle ear. Effect of ear conformation on risk of ear disease Ear conditions have been reported as especially common in rabbits with ‘lop’ ear (...truncated)