Rowena M. A. Packer

Do dog owners perceive the clinical signs related to conformational inherited disorders as 'normal' for the breed? A potential constraint to improving canine welfare

Selection for brachycephalic (foreshortened muzzle) phenotypes in dogs is a major risk factor for brachycephalic obstructive airway syndrome (BOAS). Clinical signs include respiratory distress, exercise intolerance, upper respiratory noise and collapse. Efforts to combat BOAS may be constrained by a perception that it is ‘normal’ in brachycephalic dogs. This study aimed to quantify ownerperception of the clinical signs of BOAS as a veterinary problem. A questionnaire-based study was carried out over five months on the owners of dogs referred to the Queen Mother Hospital for Animals (QMHA) for all clinical services, except for Emergency and Critical Care. Owners reported the frequency of respiratory difficulty and characteristics of respiratory noise in their dogs in four scenarios, summarised as an ‘owner-reported breathing’ (ORB) score. Owners then reported whether their dog currently has, or has a history of, ‘breathing problems’. Dogs (n = 285) representing 68 breeds were included, 31 of which were classed as ‘affected’ by BOAS either following diagnostics, or by fitting case criteria based on their ORB score, skull morphology and presence of stenotic nares. The median ORB score given by affected dogs’ owners was 20/40 (range 8–30). Over half (58%) of owners of affected dogs reported that their dog did not have a breathing problem. This marked disparity between owners’ reports of frequent, severe clinical signs and their perceived lack of a ‘breathing problem’ in their dogs is of concern. Without appreciation of the welfare implications of BOAS, affected but undiagnosed dogs may be negatively affected indefinitely through lack of treatment. Furthermore, affected dogs may continue to be selected in breeding programmes, perpetuating this disorder.

Clinical risk factors associated with anti-epileptic drug responsiveness in canine epilepsy.

The nature and occurrence of remission, and conversely, pharmacoresistance following epilepsy treatment is still not fully understood in human or veterinary medicine. As such, predicting which patients will have good or poor treatment outcomes is imprecise, impeding patient management. In the present study, we use a naturally occurring animal model of pharmacoresistant epilepsy to investigate clinical risk factors associated with treatment outcome. Dogs with idiopathic epilepsy, for which no underlying cause was identified, were treated at a canine epilepsy clinic and monitored following discharge from a small animal referral hospital. Clinical data was gained via standardised owner questionnaires and longitudinal follow up data was gained via telephone interview with the dogs’ owners. At follow up, 14% of treated dogs were in seizure-free remission. Dogs that did not achieve remission were more likely to be male, and to have previously experienced cluster seizures. Seizure frequency or the total number of seizures prior to treatment were not significant predictors of pharmacoresistance, demonstrating that seizure density, that is, the temporal pattern of seizure activity, is a more influential predictor of pharmacoresistance. These results are in line with clinical studies of human epilepsy, and experimental rodent models of epilepsy, that patients experiencing episodes of high seizure density (cluster seizures), not just a high seizure frequency pre-treatment, are at an increased risk of drug-refractoriness. These data provide further evidence that the dog could be a useful naturally occurring epilepsy model in the study of pharmacoresistant epilepsy.

Impact of Facial Conformation on Canine Health: Brachycephalic Obstructive Airway Syndrome

The domestic dog may be the most morphologically diverse terrestrial mammalian species known to man; pedigree dogs are artificially selected for extreme aesthetics dictated by formal Breed Standards, and breed-related disorders linked to conformation are ubiquitous and diverse. Brachycephaly–foreshortening of the facial skeleton–is a discrete mutation that has been selected for in many popular dog breeds e.g. the Bulldog, Pug, and French Bulldog. A chronic, debilitating respiratory syndrome, whereby soft tissue blocks the airways, predominantly affects dogs with this conformation, and thus is labelled Brachycephalic Obstructive Airway Syndrome (BOAS). Despite the name of the syndrome, scientific evidence quantitatively linking brachycephaly with BOAS is lacking, but it could aid efforts to select for healthier conformations. Here we show, in (1) an exploratory study of 700 dogs of diverse breeds and conformations, and (2) a confirmatory study of 154 brachycephalic dogs, that BOAS risk increases sharply in a non-linear manner as relative muzzle length shortens. BOAS only occurred in dogs whose muzzles comprised less than half their cranial lengths. Thicker neck girths also increased BOAS risk in both populations: a risk factor for human sleep apnoea and not previously realised in dogs; and obesity was found to further increase BOAS risk. This study provides evidence that breeding for brachycephaly leads to an increased risk of BOAS in dogs, with risk increasing as the morphology becomes more exaggerated. As such, dog breeders and buyers should be aware of this risk when selecting dogs, and breeding organisations should actively discourage exaggeration of this high-risk conformation in breed standards and the show ring.

International Veterinary Epilepsy Task Force's current understanding of idiopathic epilepsy of genetic or suspected genetic origin in purebred dogs.

Canine idiopathic epilepsy is a common neurological disease affecting both purebred and crossbred dogs. Various breed-specific cohort, epidemiological and genetic studies have been conducted to date, which all improved our knowledge and general understanding of canine idiopathic epilepsy, and in particular our knowledge of those breeds studied. However, these studies also frequently revealed differences between the investigated breeds with respect to clinical features, inheritance and prevalence rates. Awareness and observation of breed-specific differences is important for successful management of the dog with epilepsy in everyday clinical practice and furthermore may promote canine epilepsy research. The following manuscript reviews the evidence available for breeds which have been identified as being predisposed to idiopathic epilepsy with a proven or suspected genetic background, and highlights different breed specific clinical features (e.g. age at onset, sex, seizure type), treatment response, prevalence rates and proposed inheritance reported in the literature. In addition, certain breed-specific diseases that may act as potential differentials for idiopathic epilepsy are highlighted.

How Long and Low Can You Go? Effect of Conformation on the Risk of Thoracolumbar Intervertebral Disc Extrusion in Domestic Dogs

Intervertebral disc extrusion (IVDE) is a common neurological disorder in certain dog breeds, resulting in spinal cord compression and injury that can cause pain and neurological deficits. Most disc extrusions are reported in chondrodystrophic breeds (e.g. Dachshunds, Basset Hounds, Pekingese), where selection for ‘long and low’ morphologies is linked with intervertebral discs abnormalities that predispose dogs to IVDE. The aim of this study was to quantify the relationship between relative thoracolumbar vertebral column length and IVDE risk in diverse breeds. A 14 month cross-sectional study of dogs entering a UK small animal referral hospital for diverse disorders including IVDE was carried out. Dogs were measured on breed-defining morphometrics, including back length (BL) and height at the withers (HW). Of 700 dogs recruited from this referral population, measured and clinically examined, 79 were diagnosed with thoracolumbar IVDE following diagnostic imaging ± surgery. The BL:HW ratio was positively associated with IVDE risk, indicating that relatively longer dogs were at increased risk, e.g. the probability of IVDE was 0.30 for Miniature Dachshunds when BL:HW ratio equalled 1.1, compared to 0.68 when BL:HW ratio equalled 1.5. Additionally, both being overweight and skeletally smaller significantly increased IVDE risk. Therefore, selection for longer backs and miniaturisation should be discouraged in high-risk breeds to reduce IVDE risk. In higher risk individuals, maintaining a lean body shape is particularly important to reduce the risk of IVDE. Results are reported as probabilities to aid decision-making regarding breed standards and screening programmes reflecting the degree of risk acceptable to stakeholders.

Inter-observer agreement of canine and feline paroxysmal event semiology and classification by veterinary neurology specialists and non-specialists

BackgroundAdvances in mobile technology mean vets are now commonly presented with videos of paroxysmal events by clients, but the consistency of the interpretation of these videos has not been investigated. The objective of this study was to investigate the level of agreement between vets (both neurology specialists and non-specialists) on the description and classification of videos depicting paroxysmal events, without knowing any results of diagnostic workup. An online questionnaire study was conducted, where participants watched 100 videos of dogs and cats exhibiting paroxysmal events and answered questions regarding: epileptic seizure presence (yes/no), seizure type, consciousness status, and the presence of motor, autonomic and neurobehavioural signs. Agreement statistics (percentage agreement and kappa) calculated for each variable, with prevalence indices calculated to aid their interpretation.ResultsOnly a fair level of agreement (κ = 0.40) was found for epileptic seizure presence. Overall agreement of seizure type was moderate (κ = 0.44), with primary generalised seizures showing the highest level of agreement (κ = 0.60), and focal the lowest (κ =0.31). Fair agreement was found for consciousness status and the presence of autonomic signs (κ = 0.21–0.40), but poor agreement for neurobehavioral signs (κ = 0.16). Agreement for motor signs ranged from poor (κ = ≤ 0.20) to moderate (κ = 0.41–0.60). Differences between specialists and non-specialists were identified.ConclusionsThe relatively low levels of agreement described here highlight the need for further discussions between neurology experts regarding classifying and describing epileptic seizures, and additional training of non-specialists to facilitate accurate diagnosis. There is a need for diagnostic tools (e.g. electroencephalogram) able to differentiate between epileptic and non-epileptic paroxysms.

An exploratory study using a statistical approach as a platform for clinical reasoning in canine epilepsy

Links between deficits identified on neurological examination, age of seizure onset and the presence of structural forebrain disease have often been postulated in dogs presenting with a history of seizures. The purpose of this study was to assess the influence of such factors on the likelihood of structural or functional brain disease, via a thorough history taking process and interictal neurological examination. Four hundred and four dogs with seizures due to intracranial causes were included. Data including age, sex, neuter status, time until diagnosis, age of seizure onset in years, type of seizure, seizure symmetry, seizure severity, interictal neurological deficits, MRI changes and side effects associated with antiepileptic drugs were extracted from medical files. Two hundred and fifty-eight dogs were diagnosed with epilepsy of unknown origin (EUO), 11 with symmetrical structural lesions and 135 with asymmetrical structural lesions. Multinomial analysis demonstrated that dogs that were older at seizure onset were significantly more likely to have an asymmetrical structural lesion than EUO (OR 95% CI: 1.4-1.8). Dogs that had single seizures rather than cluster seizures were less likely to have asymmetrical structural lesions than dogs with EUO (OR 95% CI: 0.2-0.7). Dogs with abnormal neurological examinations were 16.5 times more likely to have asymmetrical structural lesions (OR 95% CI: 8.5-32.1) and 12.5 times more likely to have symmetrical structural lesions (OR 95% CI: 3.0-52.3) than EUO. These findings support the importance of considering interictal neurological deficits and seizure history in clinical reasoning.

Epilepsy beyond seizures: a review of the impact of epilepsy and its comorbidities on health-related quality of life in dogs

Epilepsy is one of the most common chronic neurological conditions in the dog, estimated to affect 0.6 to 0.75 per cent of dogs. Owners of dogs with epilepsy have previously indicated that their dogs quality of life (QoL) is of greatest importance to them above seizure frequency; however, much of the research into canine epilepsy to date has focussed on seizure frequency, and how to reduce it via antiepileptic drug treatment. In people, the impact of epilepsy upon QoL has been widely studied, exploring not only its impact on physical health, but also the psychological health and cognitive capabilities of affected individuals. This paper reviews the existing literature on canine epilepsy, identifies potential threats to QoL, and draws parallels from human epilepsy research. We suggest that canine epilepsy poses threats to both quality and quantity of life, with treatment interventions posing a fine balance of potential benefits and harms to the patient. At present, little is known about the neurobehavioural, emotional and cognitive effects of epilepsy upon affected dogs. Further studies are needed to establish the extent to which unknown QoL-inhibiting comorbidities exist in the dog, in order to avoid their undertreatment, and to objectively quantify the effects of epilepsy on canine QoL.

Impact of facial conformation on canine health: corneal ulceration.

Concern has arisen in recent years that selection for extreme facial morphology in the domestic dog may be leading to an increased frequency of eye disorders. Corneal ulcers are a common and painful eye problem in domestic dogs that can lead to scarring and/or perforation of the cornea, potentially causing blindness. Exaggerated juvenile-like craniofacial conformations and wide eyes have been suspected as risk factors for corneal ulceration. This study aimed to quantify the relationship between corneal ulceration risk and conformational factors including relative eyelid aperture width, brachycephalic (short-muzzled) skull shape, the presence of a nasal fold (wrinkle), and exposed eye-white. A 14 month cross-sectional study of dogs entering a large UK based small animal referral hospital for both corneal ulcers and unrelated disorders was carried out. Dogs were classed as affected if they were diagnosed with a corneal ulcer using fluorescein dye while at the hospital (whether referred for this disorder or not), or if a previous diagnosis of corneal ulcer(s) was documented in the dogs’ histories. Of 700 dogs recruited, measured and clinically examined, 31 were affected by corneal ulcers. Most cases were male (71%), small breed dogs (mean± SE weight: 11.4±1.1 kg), with the most commonly diagnosed breed being the Pug. Dogs with nasal folds were nearly five times more likely to be affected by corneal ulcers than those without, and brachycephalic dogs (craniofacial ratio <0.5) were twenty times more likely to be affected than non-brachycephalic dogs. A 10% increase in relative eyelid aperture width more than tripled the ulcer risk. Exposed eye-white was associated with a nearly three times increased risk. The results demonstrate that artificially selecting for these facial characteristics greatly heightens the risk of corneal ulcers, and such selection should thus be discouraged to improve canine welfare.

Responses to successive anti-epileptic drugs in canine idiopathic epilepsy

Pharmacoresistance to anti-epileptic drugs (AEDs) can be a source of frustration for owners and veterinarians alike in the treatment of canine idiopathic epilepsy (IE), with ongoing seizures having a significant negative impact upon the quality of life of affected dogs and owners (Chang and others 2006, Wessmann and others 2014). Finding an effective AED that reduces seizure frequency to an acceptable level (generally classed as more than 50 per cent reduction in veterinary medicine), or results in remission (seizure-freedom) can be a long process, with several AEDs trialled before optimum treatment is reached (Packer and others 2014). With more AEDs becoming available to veterinary patients, knowing whether (and when) to include further therapies can be challenging for practitioners, when faced with the balance between seizure control and side effect profiles. In human epilepsy, response rates to first-line and further AEDs have been studied in several populations, with the probability of seizure control diminishing progressively with successive AED treatments. Kwan and Brodie (2000) reported response rates (as a proportion of the population) of 47, 13 and 4 per cent for first-line, second-line and third-line drugs, respectively (Kwan and Brodie 2000). Similarly, Mohanraj and Brodie (2006) reported response rates of 50.4, 10.7 and 2.3 per cent, respectively, with just 0.8 per cent responding to any further drugs (Mohanraj and Brodie 2006). If the initial AED fails to control seizures, the prognosis for seizure control may be poor. Failure to respond to the first AED has been demonstrated to predict becoming refractory at two-year follow-up in a study of children with temporal lobe epilepsy (Dlugos and others 2001). In a further study, of those patients unresponsive to the first AED, 76 per cent failed two or more AEDs and 38 per cent failed at least four (Perucca and others 2011). These …