Genetically modified pigs: Emerging animal models for hereditary hearing loss.

Hereditary hearing loss (HHL), a genetic disorder that impairs auditory function, significantly affects quality of life and incurs substantial economic losses for society. To investigate the underlying causes of HHL and evaluate therapeutic outcomes, appropriate animal models are necessary. Pigs have been extensively used as valuable large animal models in biomedical research. In this review, we highlight the advantages of pig models in terms of ear anatomy, inner ear morphology, and electrophysiological characteristics, as well as recent advancements in the development of distinct genetically modified porcine models of hearing loss. Additionally, we discuss the prospects, challenges, and recommendations regarding the use pig models in HHL research. Overall, this review provides insights and perspectives for future studies on HHL using porcine models.

Early onset adult deafness in the Rhodesian Ridgeback dog is associated with an in-frame deletion in the EPS8L2 gene.

Domestic dogs exhibit diverse types of both congenital and non-congenital hearing losses. Rhodesian Ridgebacks can suffer from a progressive hearing loss in the early stage of their life, a condition known as early onset adult deafness (EOAD), where they lose their hearing ability within 1-2 years after birth. In order to investigate the genetic basis of this hereditary hearing disorder, we performed a genome-wide association study (GWAS) by using a sample of 23 affected and 162 control Rhodesian Ridgebacks. We identified a genomic region on canine chromosome 18 (CFA18) that is strongly associated with EOAD, and our subsequent targeted Sanger sequencing analysis identified a 12-bp inframe deletion in EPS8L2 (CFA18:25,868,739-25,868,751 in the UMICH_Zoey_3.1/canFam5 reference genome build). Additional genotyping confirmed a strong association between the 12-bp deletion and EOAD, where all affected dogs were homozygous for the deletion, while none of the control dogs was a deletion homozygote. A segregation pattern of this deletion in a 2-generation nuclear family indicated an autosomal recessive mode of inheritance. Since EPS8L2 plays a critical role in the maintenance and integrity of the inner ear hair cells in humans and other mammals, the inframe deletion found in this study represents a strong candidate causal mutation for EOAD in Rhodesian Ridgebacks. Genetic and clinical similarities between childhood deafness in humans and EOAD in Rhodesian Ridgebacks emphasizes the potential value of this dog breed in translational research in hereditary hearing disorders.

Are dogs with congenital hearing and/or vision impairments so different from sensory normal dogs? A survey of demographics, morphology, health, behaviour, communication, and activities.

The births of domestic dogs with pigment deletion and associated congenital hearing and/or vision impairments are increasing, as a result of mutations of certain genes expressing popular coat colour patterns (Merle, piebald, Irish spotting). The future of these dogs is often pessimistic (early euthanasia or placement in rescues/fosters, lack of interactions and activities for adults). These pessimistic scenarios result from popular assumptions predicting that dogs with congenital hearing/vision impairments exhibit severe Merle-related health troubles (cardiac, skeletal, neurological), impairment-related behavioural troubles (aggressiveness, anxiety), and poor capacities to communicate, to be trained, and to be engaged in leisure or work activities. However, there is no direct scientific testing, and hence no evidence or refutation, of these assumptions. We therefore addressed an online questionnaire to owners of 223 congenitally sensory impaired (23 vision impaired, 63 hearing impaired, 137 hearing and vision impaired) and 217 sensory normal dogs from various countries. The sensory normal cohort was matched in age, lifetime with owner, breed and sex with the sensory impaired cohort, and was used as a baseline. The questionnaire assessed demographics, morphology, sensory impairments, health and behavioural troubles, activities, and dog-owner communication. Most hearing and/or vision impaired dogs exhibited abnormal pigment deletion in their coat and irises. Vision impaired dogs additionally exhibited ophthalmic abnormalities typically related to Merle. The results are opposed to all above-listed assumptions, except for neurological troubles, which were more frequently reported in sensory impaired dogs. However, we suggest that this finding could be partially accounted for by a lack of diagnosis of breed-related drug sensitivity and impairment-related compulsive behaviours. Results about communication and activities are particularly optimistic. The need for future studies of numerous dogs from various breeds tested for Merle, piebald and medical-drug-resistance genes, and the beneficial effects that present and future research may have on the future of sensory impaired dogs, are discussed.

Evaluation of nephrotoxicity and ototoxicity of aminosidine (paromomycin)-allopurinol combination in dogs with leishmaniosis due to Leishmania infantum: A randomized, blinded, controlled study.

Canine leishmaniosis due to Leishmania infantum is a widespread zoonotic disease. Although aminosidine can be an effective treatment, current therapeutic recommendations do not advocate its use, mainly due to concerns regarding the potential nephrotoxicity and ototoxicity of this drug. The aim of this randomized, blinded, controlled study was to evaluate the nephrotoxicity and ototoxicity of aminosidine-allopurinol combination and compare it with that of meglumine antimonate-allopurinol combination in non-azotemic dogs with leishmaniosis. Forty dogs with leishmaniosis were randomly assigned to be treated with either aminosidine at 15 mg/kg, subcutaneously, once daily for 28 days (group A) or with meglumine antimonate at 100 mg/kg, subcutaneously, once daily for 28 days (group B). In addition to either drug, dogs in both groups were administered allopurinol at 10 mg/kg per os twice daily for 2 months. Kidney function was evaluated through measurement of serum creatinine, urea nitrogen, inorganic phosphorus, and cystatin-c concentrations and complete urinalysis, including protein-to-creatinine ratio, at baseline and after 14, 28, and 60 days from the beginning of the treatment. At the same time points, vestibular and auditory functions were evaluated through neurological examination and brainstem auditory evoked response (BAER) recordings of wave I, wave V, inter-wave I-V latencies, and minimum hearing thresholds. None of the dogs developed clinicopathological evidence of kidney disease during the study. Serum creatinine concentration increased >0.3 mg/dl over baseline in 2 dogs in group A and in 5 dogs in group B. Parameters of kidney function were not significantly different or were improved compared to baseline and the only difference between the two groups was the lower concentration of serum creatinine in group A. None of the dogs developed peripheral vestibular syndrome or hearing impairment. At the end of the study, parameters of auditory function were not significantly different or were improved compared to baseline and there were no differences between the two groups. The results of this study show that the nephrotoxicity and ototoxicity of aminosidine, when administered to non-azotemic dogs with leishmaniosis at 15 mg/kg subcutaneously once daily for 28 days along with allopurinol, is minimal and does not differ from that of meglumine antimonate.

Impacts of broadband sound on silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carp hearing thresholds determined using auditory evoked potential audiometry.

Invasive silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carp, collectively referred to as bigheaded carps, threaten aquatic ecosystems of the Upper Midwestern USA. Due to the extensive ecological impacts associated with these species, prevention of their further range expansion is the aim for fisheries management. Recent behavioral studies indicate bigheaded carps are deterred by acoustic barriers and exhibit negative phonotaxis in response to anthropogenic sound sources (≥ 150 dB re 1 µPa). However, the impact of long-term exposure to these sounds on the hearing capabilities of bigheaded carps has not been well documented. In this study, the auditory evoked potential (AEP) technique was used to determine auditory thresholds among bigheaded carps before and after exposure to high intensity (155.7 ± 4.7 dB re 1 µPa SPLrms; - 8.0 ± 4.7 dB re 1 ms-2 PALrms; mean ± SD) broadband sound. Fish were exposed to sound for 30 min or 24 h and AEP measurements were taken at three time points: immediately after exposure, 48 h, or 96 h later. Results indicate that silver and bighead carp experience temporary threshold shifts (TTSs) in frequency detection following sound exposure with the magnitude and length of TTS correlated with exposure duration. The findings from this study will be used to increase the long-term efficacy of acoustical deterrent measures aimed at preventing further range expansion of bigheaded carps.

Ecology of fish hearing.

Underwater sound is directional and can convey important information about the surrounding environment or the animal emitting the sound. Therefore, sound is a major sensory channel for fishes and plays a key role in many life-history strategies. The effect of anthropogenic noise on aquatic life, which may be causing homogenisation or fragmentation of biologically important signals underwater is of growing concern. In this review we discuss the role sound plays in the ecology of fishes, basic anatomical and physiological adaptations for sound reception and production, the effects of anthropogenic noise and how fishes may be coping to changes in their environment, to put the ecology of fish hearing into the context of the modern underwater soundscape.

Deafness and vestibular dysfunction in a Doberman Pinscher puppy associated with a mutation in the PTPRQ gene.

BACKGROUND: A congenital syndrome of hearing loss and vestibular dysfunction affects Doberman Pinschers. Its inheritance pattern is suspected to be autosomal recessive and it potentially represents a spontaneous animal model of an autosomal recessive syndromic hearing loss. HYPOTHESIS/OBJECTIVES: The objectives of this study were to use whole genome sequencing (WGS) to identify deleterious genetic variants in candidate genes associated with the syndrome and to study the prevalence of candidate variants among a population of unaffected Doberman Pinschers. ANIMALS: One affected Doberman Pinscher and 202 unaffected Doberman Pinschers. METHODS: WGS of the affected dog with filtering of variants against a database of 154 unaffected dogs of diverse breeds was performed. Confirmation of candidate variants was achieved by Sanger sequencing followed by genotyping of the control population of unaffected Doberman Pinschers. RESULTS: WGS and variant filtering identified an alteration in a gene associated with both deafness and vestibular disease in humans: protein tyrosine phosphatase, receptor type Q (PTPRQ). There was a homozygous A insertion at CFA15: 22 989 894, causing a frameshift mutation in exon 39 of the gene. This insertion is predicted to cause a protein truncation with a premature stop codon occurring after position 2054 of the protein sequence that causes 279 C-terminal amino acids to be eliminated. Prevalence of the variant was 1.5% in a cohort of 202 unaffected Doberman Pinschers; all unaffected Doberman Pinschers were heterozygous or heterozygous for the reference allele. CONCLUSION AND CLINICAL IMPORTANCE: We report the identification of a genetic alteration on the PTPRQ gene that is associated with congenital hearing and vestibular disorder in a young Doberman Pinscher dog.

Brainstem auditory evoked responses in 37 dogs with otitis media before and after topical therapy.

OBJECTIVES: The objective of this study was to determine whether intra-aural administration of aqueous solutions of marbofloxacin, gentamicin, tobramycin and ticarcillin (used off-licence) was associated with changes in hearing as measured by brainstem auditory evoked responses. MATERIALS AND METHODS: Dogs diagnosed with otitis media (n=37) underwent brainstem auditory evoked response testing and then were treated for their ear disease. First, the external ear canal and middle ear were flushed with sterile saline followed by EDTA tris with 0·15% chlorhexidine. Then, a combination of aqueous antibiotic mixed with an aqueous solution of EDTA tris was instilled into the middle ear. Follow-up examinations were undertaken for each dog, and treatment was continued until there were no detected infectious organisms or inflammatory infiltrate. Brainstem auditory evoked response testing was repeated after resolution of the infection and discontinuation of therapy. RESULTS: Brainstem auditory evoked responses in dogs treated with aqueous solutions of marbofloxacin or gentamicin remained unchanged or improved after therapy of otitis media but were impaired in dogs treated with ticarcillin or tobramycin. CLINICAL SIGNIFICANCE: If off-licence use of topical antibiotics is deemed necessary in cases of otitis media, aqueous solutions of marbofloxacin and gentamicin appear to be less ototoxic than aqueous solutions of ticarcillin or tobramycin.

Distortion product otoacoustic emissions in young adult and geriatric cats.

Recordings of distortion product otoacoustic emissions (DPOAEs) were taken from 15 geriatric cats (mean age ± standard deviation, SD, 13.6 ± 2.7 years; range 10.2-19.4 years) and 12 young adult control cats (mean ± SD 4.6 ± 0.5 years; range 3.4-5 years) to identify frequency-specific age-related changes in cochlear responses. Recordings were performed for primary frequencies from 2 to 12 kHz in 2 kHz increments. Cats were considered to be geriatric > 11.9 ± 1.9 years of age. Brainstem auditory evoked response (BAER) recordings were also made for subjective comparison with DPOAE responses. No differences in DPOAE response amplitudes were observed at any tested frequency in geriatric cats compared to control cats, reflecting an apparent absence of loss of cochlear outer hair cells along the length of the cochlea. No linear regression relationships were found for DPOAE response amplitude versus age in geriatric cats, despite the progressive nature of age-related hearing loss in other species. The absence of reductions in response at any of the tested frequencies in cats within the age span where cats are considered to be geriatric indicates that age-related hearing loss, if it does develop in cats, begins later in the life span of cats than in dogs or human beings.

AUDITORY EVOKED POTENTIALS AND BEHAVIORAL CONSIDERATIONS WITH HEARING LOSS IN SMALL CETACEANS: APPLICATION AS A STANDARD DIAGNOSTIC TEST IN HEALTH ASSESSMENT.

The primary sense in odontocetes is hearing and a large portion of the odontocete brain is devoted to the auditory processing of echolocation signals. Hearing deficits in odontocetes potentially compromise the ability to forage, navigate, socialize, and evade predators. This presents a challenge to survival and reproduction in wild odontocetes and can affect the general welfare of odontocetes under human care. Currently, little empirical information on how odontocete behavior is affected by hearing loss exists. This study investigated hearing deficits in several species of stranded dolphins and age-related hearing deficits in dolphins kept under human care through auditory evoked potential (AEP) testing and evaluated whether individual behavior correlated with hearing impairment. Behavioral questionnaires for participating animals were completed by individuals with extensive knowledge of the animals' history and behavior. A chi-square analysis determined whether animals with hearing impairment demonstrated behaviors that differed significantly from those considered normal. All tested individuals under human care over 35 years of age had some degree of hearing loss, as did a large percentage of previously stranded animals. Individuals with hearing loss exhibited a range of behavioral changes, including delays in learning new behaviors, accepting novel enrichment, and habituating to new environments. Some individuals with profound hearing loss also displayed a change in vocalization rate in various situations. Findings within previously stranded animals suggest AEP studies should be conducted in all stranded individuals entering rehabilitation. It is further recommended that dolphins living under human care undergo hearing tests as part of their normal health assessments, with emphasis on aging individuals and animals that exhibit delayed learning, respond poorly to audible cues, or show atypical vocalization behavior.

Distortion product otoacoustic emissions in geriatric dogs.

Recordings of distortion product otoacoustic emissions (DPOAE) were taken from 28 geriatric dogs aged 12.2 ± 2.2 years and 15 control dogs aged 5.9 ± 3.0 years (mean ± standard deviation) to demonstrate frequency-specific changes in cochlear responses. Recordings were performed for primary frequencies of 2-12 kHz in 2 kHz increments. Brainstem auditory evoked response (BAER) recordings were also made from geriatric dogs for comparison with DPOAE responses. Significant decreases in DPOAE response amplitudes were observed at frequencies of 6-12 kHz in geriatric dogs compared to control dogs, reflecting loss of cochlear outer hair cells along the length of the cochlea. Significant decreases in response amplitudes were not seen at frequencies of 2 or 4 kHz. Decreases in BAER response amplitudes subjectively paralleled the depressed DPOAE amplitudes. No significant linear regression relationships were found for DPOAE response amplitude vs. age despite the progressive nature of age-related hearing loss. The reductions in response at all frequencies starting at the age where dogs are considered geriatric indicate that age-related hearing loss begins earlier in the life span. DPOAE recordings provide a means to assess cochlear function across different portions of the auditory spectrum for assessing hearing loss associated with aging, and potentially for losses from other causes of decreased auditory function.

High prevalence of vaterite in sagittal otoliths causes hearing impairment in farmed fish.

The rapid growth of aquaculture raises questions about the welfare status of mass-produced species. Sagittal otoliths are primary hearing structures in the inner ear of all teleost (bony) fishes and are normally composed of aragonite, though abnormal vaterite replacement is sometimes seen in the wild. We provide the first widespread evaluation of the prevalence of vaterite in otoliths, showing that farmed fish have levels of vaterite replacement over 10 times higher than wild fish, regardless of species. We confirm this observation with extensive sampling of wild and farmed Atlantic salmon in Norway, the world's largest producer, and verify that vateritic otoliths are common in farmed salmon worldwide. Using a mechanistic model of otolith oscillation in response to sound, we demonstrate that average levels of vaterite replacement result in a 28-50% loss of otolith functionality across most of a salmonid's known hearing range and throughout its life cycle. The underlying cause(s) of vaterite formation remain unknown, but the prevalence of hearing impairment in farmed fish has important implications for animal welfare, the survival of escapees and their effects on wild populations, and the efficacy of restocking programs based on captive-bred fish.

Endogenous retrovirus insertion in the KIT oncogene determines white and white spotting in domestic cats.

The Dominant White locus (W) in the domestic cat demonstrates pleiotropic effects exhibiting complete penetrance for absence of coat pigmentation and incomplete penetrance for deafness and iris hypopigmentation. We performed linkage analysis using a pedigree segregating White to identify KIT (Chr. B1) as the feline W locus. Segregation and sequence analysis of the KIT gene in two pedigrees (P1 and P2) revealed the remarkable retrotransposition and evolution of a feline endogenous retrovirus (FERV1) as responsible for two distinct phenotypes of the W locus, Dominant White, and white spotting. A full-length (7125 bp) FERV1 element is associated with white spotting, whereas a FERV1 long terminal repeat (LTR) is associated with all Dominant White individuals. For purposes of statistical analysis, the alternatives of wild-type sequence, FERV1 element, and LTR-only define a triallelic marker. Taking into account pedigree relationships, deafness is genetically linked and associated with this marker; estimated P values for association are in the range of 0.007 to 0.10. The retrotransposition interrupts a DNAase I hypersensitive site in KIT intron 1 that is highly conserved across mammals and was previously demonstrated to regulate temporal and tissue-specific expression of KIT in murine hematopoietic and melanocytic cells. A large-population genetic survey of cats (n = 270), representing 30 cat breeds, supports our findings and demonstrates statistical significance of the FERV1 LTR and full-length element with Dominant White/blue iris (P < 0.0001) and white spotting (P < 0.0001), respectively.

Brainstem auditory evoked responses in an equine patient population. Part II: foals.

BACKGROUND: Reports of the use of brainstem auditory evoked response (BAER) as a diagnostic modality in foals have been limited. HYPOTHESIS/OBJECTIVES: To describe BAER findings and associated causes of hearing loss in foals. ANIMALS: Study group 18 foals (15 neonatal, 3 nonneonatal), control group (5 neonatal foals). METHODS: Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Clinical data were extracted from the medical records. Foals were grouped under disease categories. Descriptive statistics were performed. RESULTS: Ten neonatal foals had complete absence of BAER bilaterally and 5 had findings within reference range. Abnormalities were associated with common neonatal disorders such as sepsis, neonatal encephalopathy, neonatal isoerythrolysis, and prematurity. BAER loss also was observed in foals with specific coat color patterns such as completely or mostly white with blue irides or lavender with pale yellow irides. An American Miniature foal with marked facial deformation also lacked BAER bilaterally. One nonneonatal foal with an intracranial abscess had no detectable BAER peaks bilaterally, and 2 older foals, 1 with presumed equine protozoal myeloencephalitis and the other with progressive scoliosis and ataxia, had BAER within normal limits. CONCLUSIONS AND CLINICAL IMPORTANCE: In neonatal foals, BAER deficits commonly are complete and bilateral, and associated with common neonatal disorders and certain coat and eye color patterns. Sepsis, hypoxia, bilirubin toxicity, and prematurity should be investigated as potential causes of auditory loss in neonatal foals.

Brainstem auditory evoked responses in an equine patient population: part I--adult horses.

BACKGROUND: Brainstem auditory evoked response has been an underused diagnostic modality in horses as evidenced by few reports on the subject. HYPOTHESIS/OBJECTIVES: To describe BAER findings, common clinical signs, and causes of hearing loss in adult horses. ANIMALS: Study group, 76 horses; control group, 8 horses. METHODS: Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Horses were grouped under disease categories. Descriptive statistics and a posthoc Bonferroni test were performed. RESULTS: Fifty-seven of 76 horses had BAER deficits. There was no breed or sex predisposition, with the exception of American Paint horses diagnosed with congenital sensorineural deafness. Eighty-six percent (n = 49/57) of the horses were younger than 16 years of age. The most common causes of BAER abnormalities were temporohyoid osteoarthropathy (THO, n = 20/20; abnormalities/total), congenital sensorineural deafness in Paint horses (17/17), multifocal brain disease (13/16), and otitis media/interna (4/4). Auditory loss was bilateral and unilateral in 74% (n = 42/57) and 26% (n = 15/57) of the horses, respectively. The most common causes of bilateral auditory loss were sensorineural deafness, THO, and multifocal brain disease whereas THO and otitis were the most common causes of unilateral deficits. CONCLUSIONS AND CLINICAL IMPORTANCE: Auditory deficits should be investigated in horses with altered behavior, THO, multifocal brain disease, otitis, and in horses with certain coat and eye color patterns. BAER testing is an objective and noninvasive diagnostic modality to assess auditory function in horses.

Brainstem auditory evoked potential testing in Dalmatian dogs in Brazil / Potencial evocado auditivo de tronco encefálico em cães da raça Dálmata no Brasil

The brain stem auditory-evoked potential (BAEP) is an electrophysiologic test that detects and records the electrical activity in the auditory system from cochlea to midbrain, generated after an acoustic stimulus applied to the external ear. The aim of this study is to obtain normative data for BAEP in Dalmatian dogs in order to apply this to the evaluation of deafness and other neurologic disorders. BAEP were recorded from 30 Dalmatian dogs for a normative Brazilian study. Mean latencies for waves I, III, and V were 1.14 (±0.09), 2.62 (±0.10), and 3.46 (±0.14) ms, respectively. Mean inter-peak latencies for I-III, III-V, and I-V intervals were 1.48 (±0.17), 0.84 (±0.12), and 2.31 (±0.18) ms, respectively. Unilateral abnormalities were found in 16.7% of animals and bilateral deafness was seen in one dog. The normative data obtained in this paper is compatible with other published data. As far as we know this is the first report of deafness occurrence in Dalmatian dogs in Brazil...

O potencial evocado auditivo de tronco encefálico (BAEP) é um teste eletrodiagnóstico que detecta e registra a atividade elétrica do sistema auditivo desde a cóclea até o tronco encefálico, gerada após a emissão de um estímulo acústico na orelha externa. O objetivo deste estudo é obter dados normativos para o BAEP em cães da raça Dálmata para usá-lo para detecção de surdez e de outras alterações neurológicas. BAEP foi obtido de 30 cães da raça Dálmata para um estudo normativo no Brasil. As latências médias para as ondas I, III e V foram 1,14ms (±0,09); 2,62ms (±0,10) e 3,46ms (±0,14), respectivamente. A média das latências dos intervalos I-III, III-V e I-V foi 1,48ms (±0,17); 0,84ms (±0,12) e 2,31ms (±0,18), respectivamente. Alteração unilateral foi observada em 16,7% dos animais, e surdez bilateral foi observada em um cão. Os dados normativos obtidos neste trabalho são compatíveis com outros dados já publicados. Segundo a revisão realizada, este é o primeiro relato da ocorrência de surdez em cães da raça Dálmata no Brasil...

Use of a hearing loss grading system and an owner-based hearing questionnaire to assess hearing loss in pet dogs with chronic otitis externa or otitis media.

BACKGROUND: Hearing loss is important when assessing the suitability of dogs with otitis externa/media for medical or surgical therapy. HYPOTHESIS/OBJECTIVES: To assess an owner-completed questionnaire as an indicator of hearing loss and a canine hearing loss scoring system in chronic canine otitis. ANIMALS: One hundred hospital population dogs referred for chronic otitis investigation. METHODS: Owners completed a questionnaire to assess their dog's response to common household noises. The presence of otitis externa or media was determined and brainstem auditory-evoked response measurements were performed on each dog. The minimal hearing threshold (MHT) in decibels normal hearing level (dB NHL) was recorded and categorized according to the human World Health Organization grading system into five grades from 0 to 4 with cut-off values of ≤25 dB NHL, 26-40 dB NHL, 41-60 dB NHL, 60-80 dB NHL and ≥81 dB NHL. RESULTS: The questionnaire correctly determined normal hearing in grade 0 cases, but did not reliably detect unilateral or grade 1 bilateral hearing loss. For dogs with bilateral hearing loss ≥ grade 2, questionnaire sensitivity was 83% [24 of 29, 95% confidence interval, (CI) 64-94%] and specificity was 94% (67 of 71, 95% CI 86-98%). Higher grades of hearing loss were significantly associated with the presence of otitis media (P < 0.01). CONCLUSIONS AND CLINICAL IMPORTANCE: The questionnaire may be a useful in-practice screening tool in chronic canine otitis for moderate to severe bilateral hearing deficits (MHT ≥41 dB NHL). The hearing loss grading system may help clinicians make therapeutic decisions. Chronic otitis media may be associated with higher grades of hearing loss.

Canine hearing loss management.

Dog owners and handlers are naturally concerned when suspicion of hearing loss arises for their dogs. Questions frequently asked of the veterinarian center on warning signs of canine hearing loss and what can be done for the dog if hearing loss is confirmed. This article addresses warning signs of canine hearing loss, communication training and safety awareness issues, and the feasibility of hearing aid amplification for dogs.

Electrodiagnostic evaluation of auditory function in the dog.

Given the high incidence of deafness within several breeds of dogs, accurate hearing screening and assessment is essential. In addition to brainstem auditory evoked response (BAER) testing, 2 other electrophysiologic tests are now being examined as audiologic tools for use in veterinary medicine: otoacoustic emissions and the auditory steady state response (ASSR). To improve BAER testing of animals and ensure an accurate interpretation of test findings from one test site to another, the establishment of and adherence to clear protocols is essential. The ASSR holds promise as an objective test for rapid testing of multiple frequencies in both ears simultaneously.