When dealing with issues surrounding aural health, you find a network of closely interlinked factors. Symptoms relating to problems in the ear are, for the majority of cases, very similar hence the requirement for a proper veterinary diagnosis. Improper diagnosis and inadequate treatment will usually result in a painful and very damaging, chronic condition. In others, where symptoms are treated but the underlying issues are not addressed, problems will recur regularly.
Common symptoms of an ear problem can be seen both in the behaviour of the animal and upon inspection of the ear flap (pinna). The animal itself will usually scratch excessively, rub the affected ear(s) along the ground or on furniture and shake its head violently. Quite often, the constant scratching and rubbing leads to loss of hair in the area and broken skin. Occasionally, extreme discomfort and pain can cause animals to become aggressive when bothered. The ears themselves may appear red and swollen, with a dark brown or black malodorous discharge (often musty/yeasty). The inflammation is also often accompanied with thickened patches of scaling skin, excessive wax production and possibly obstruction of the ear canal. In more advanced conditions, hearing loss and balance problems can become apparent.
Some parasites live on the skin and are known as ectoparasites, which include flies, fleas, ticks, lice and mites. While these can all affect the ears to some degree and cause irritation, ear mites are the prominent relevant parasite here. The ear mite, Otodectes cyanotis, causes Otodectic Mange in both dogs and cats, although a much higher proportion of cats are affected (it accountable for around 50% of feline infections) as many are free to roam outdoors. The ear mites are barely visible to the naked eye but may be seen as tiny white spots in the ears. They feed on oil, wax and debris in the ear canal and along with the above symptoms of an ear problem, produce a dark brown crust in the ears, similar to ground coffee. Their saliva and salivary enzymes that digest the skin are the main cause of pruritus (itching). Mites are readily transmitted between infected and non-infected animals by direct contact. Puppies and are usually infected by their mother while suckling and outdoor pets such as cats can catch mites from wild prey animals or fighting with other cats.
While species of mites (Sarcoptes scabei, Cheyletiella) can be found all over the body, Otodectes mites favour the sheltered environment of the ear canal.
Some types of bacteria and fungi (yeast) live naturally on the skin of animals and do not cause harm when present in low numbers. A change in the microclimate of the ear can promote overgrowth of these organisms and lead to establishment of infection and associated symptoms. The changes may be an increase in moisture, excess sebum production and injury among other factors. Bacteria and yeast are opportunistic pathogens and are a secondary factor in many conditions affecting the ear, exacerbating an existing condition.
Bacterial species often involved include Staphylococcus, Pseudomonas and Micrococcus. The bacterial enzymes and toxins further disrupt the ear canal through damage to skin and nerves, causing the animal pain. In addition to the overgrowth of skin dwelling populations, bacteria can also be mechanically transferred from paws or by flies to sores and lesions in the ears. Fungi (or yeasts), namely Malassezia pachydermatis, are frequently responsible for the pungent odour that may develop in the ears. M.pachydermatis is a 'fat-loving' lipophilic organism that lives off of the sebum secreted in the ear canal but is also found on mucous membranes. When present in excess, the digestive enzymes secreted by the yeast irritates the epithelial surface in the ear canal, inciting inflammation and an intensely pruritic reaction.
Inflammation and epithelial damage cause by both organisms encourages further proliferation, as the environment produced favours microbial growth. If left untreated, severe or chronic infections can lead to irreversible damage- the thickening and calcification (hardening) of wax and trapped debris in ear canal, resulting in loss of hearing. Bacteria and yeast can affect any breed or age but some pets are naturally more prone to infections due to the anatomy of their ears or other factors.
These include grass and cereal seeds commonly covered in bristle-like awns and are a common cause of ear problems during spring and summer months. They may at first become tickly so scratching and head shaking will sometimes dislodge them but often they end up migrating downwards, due to the slope of the ear canal. This then becomes a problem as it is difficult for foreign bodies to work their way up naturally. They will often work their way deeper, causing pain and inflammation, encouraging infection. It is far more common in dogs and due to the delicate nature of the ears, anaesthetic is often required for removal.
A significant difference between animal and human allergies is that they manifest within the skin more commonly than the respiratory system. Certain foods, inhaled proteins and contact with allergens in the environment all elicit allergic reactions in the skin which alter the skin's characteristics to those favoured by microbes. The skin becomes flaky and pets scratch to relieve the constant itching sensation caused by inflammatory mediators released under the skin in the allergic reaction.
Hypersensitive reactions to food and fleas are the most common year-round and seasonal causes of allergies, respectively. It has been found that around 80% of dogs with allergies will develop an ear problem at least once.
The anatomy of an animal's ear and the ear canal environment play huge roles in increasing the risk of aural problems. The ear is a delicate structure, usually with a long downward-sloping external auditory canal, then a shorter horizontal section before the ear drum. The tympanic membrane (ear drum) separates the exterior canal from the middle ear and is responsible for transmitting sound waves to the ossicles (three tiny auditory bones) of the middle ear. The ossicles transmit fluid waves and membrane vibrations to the inner ear, which is comprised of two compartments; one for hearing and one for balance.
Some breeds of dogs such as poodles, cocker spaniels, golden retrievers and schnauzers have particularly hairy ears which trap more moisture, ear wax (cerumen) and foreign bodies, encouraging infections to develop. A similar problem arises in breeds with pendant ears, where folded pinnae restrict airflow to the ears retain warmth and moisture, trap debris and create the perfect environment for disease causing organisms. A less obvious problem presents in some breeds prone to a narrowed ear canal, for example, the Chinese Shar-Pei.
The skin itself is part of the innate immune system and forms a physical barrier against the entry pathogens. Any trauma from scratching, rough cleaning or injuries breaks this barrier and effectively leaves the animal with compromised defences.
Hormonal and metabolic disorders, for example hypothyroidism or diabetes, affect the epidermal cell turn over and secretion from sebaceous glands, altering the microenvironment of the ears.
Autoimmune disorders occur when the animal's immune system does not discriminate between 'self' and non-self' antigens. This provokes systemic damage and will affect the ears too, as the immune system attacks the animal's own tissues including skin. An example is Systemic Lupus Erythmatosus, where the hyper-defensive immune system causes nasty lesions and ulcers, alopecia, redness, scaly skin among other uncomfortable symptoms. The skin becomes very unstable, broken and open to infection.
While some of the aforementioned issues can directly cause aural discomfort, it is usually two or more factors acting concurrently that cause commonly recognised conditions like Otitis Externa. That said, effectively diagnosing each individually and targeting it is key for successful treatment and long term management of ear problems.
Predisposing factors that increase the risk of problems developing: often anatomical or breed specific and inherited (stenotic/narrowed canals, excessive hair in ears); constant wetting due to swimming, bathing or high humidity in environment; damage in the ear caused by rough cleaning, scratching, rubbing or fighting. In cats, tumours, polyps an cysts are also common within the ears and contribute to narrowing of the canal and an abnormal environment.
Primary factors directly cause skin related problems to develop in the ear: allergies (environmental, food, Flea Allergic Dermatitis); foreign bodies; hormonal or metabolic diseases; keratinisation disorders; autoimmune disease.
Perpetuating/secondary factors are most often a combination of bacterial and fungal infections at the same time which complicate a condition, making resolution more difficult.
Otitis is the inflammation of the ear canal and may affect one or both ears, depending on the underlying cause. The specific name is relative to the location of inflammation and may be of the external (externa), middle(media) or inner (interna) ear. Inflammation can be triggered in a number of ways but it is essentially an early, non-specific immune response to harmful stimuli and initiates the healing process. The affected area becomes hot, swollen, painful and red due to increased blood flow and influx of fluid and immune defence cells that rapidly accumulate to fight any invaders. After inflammation is set off, sebaceous and ceruminous glands increase secretion of oils and wax in an attempt to protect the canal epithelia and trap potential invading microbes.
Otitis externa is the most common form as the outer ear is in regular contact with potentially damaging organisms and the canal environment is affected by a number of conditions as discussed earlier. Unfortunately, many causes of otitis will result in a progressive condition and when left untreated can spread to the middle ear, even causing perforation of the tympanic membrane. Often, the constant scratching and rubbing will break the delicate skin on the inside of the ear flap, inducing inflammatory responses and secondary infections are common. The majority of otitis externa cases are treatable but in chronic or severe cases, irreversible calcification and narrowing of the auditory canal is a real problem, leading to hearing loss.
Otitis media is often an extension of otitis externa, whereby the tympanic membrane becomes porous or even ruptured, allowing infectious organisms to pass through. Over 50% of animals with chronic otitis externa develop otitis media, while it is seen in around 16% of animals with acute external inflammation. In rare cases, microorgansims present in the oral cavity can ascend to the middle ear via the auditory tube and later spread outwards. Infection of the middle ear can result in deafness and paralysis due to inflammation of the facial nerve on the affected side of the face.
Otitis interna also stems from an infection in the outer ear that has passed through to and spread from the middle ear. The structures of the inner are key for hearing but also balance. Disorientation and loss of balance are symptoms that must never be ignored. Very occasionally with middle and inner ear infections, nausea, vomiting or nervous damage can occur.
A haematoma is a collection of blood, usually clotted, that forms outside the blood vessels. An aural haematoma/othaematoma is found between the skin and cartilage on the ear flap. Head shaking, rubbing and scratching cause the fine vessels between the skin and cartilage to break and a lesion can quickly form. They appear as tense, painful and hot swellings on the inside of the pinna and if close to the tip, can cause erect ears to fold over. Conversely, the swelling can stretch from the base of the inner ear towards the tip (pictured right), holding the ear flap out awkwardly. Haematomas may be incredibly painful but very uncomfortable in the least. Veterinary advice must be sought and the usual outcome would be removal (usually a surgical procedure and sutures under anaesthetic are required) although it is possible to leave them to be absorbed naturally. The problems associated with leaving a haematoma untreated include a long and uncomfortable wait for the dog and possible scarring of the pinna, producing "cauliflower ear" appearance.
Haematomas rarely arise from a one off event and are, as a rule, secondary to an underlying condition that irritates the ears, such as ear mites or an allergic reaction.
Deafness may be temporary or permanent, depending on the cause and whether it is treated appropriately. Temporary deafness is typically a result of a plug forming in the ear, consisting of ear wax and excess hair. Non-permanent hearing loss can also result from foreign objects, ear mite infestation and mild infections, that bring about severe inflammation and narrowing of the canal. In the odd case, an adverse reaction to a drug such as an has been reported to cause temporary deafness in cats. Cats are also more likely to develop aural tumours and polyps that physically obstruct the auditory canals. Some animals, particularly all white blue-eyed cats, are born deaf due to a genetic or anatomical problem, although permanent deafness more commonly observed in senior animals as a natural part of the ageing process. Other causes, such as prolonged exposure to loud noises, drug toxicity, injury or a severe untreated infection can product irreversible damage to the delicate structures of the ear, or mechanical blockage due to calcification.
When an animal is showing any signs of discomfort with their ears, it is most important to get the problem checked as soon as possible. As with any problem, the earlier it is diagnosed, the easier it is to treat.
Vets will use a variety of methods to diagnose ear problems. As the clinical signs are very similar, the use of an otoscope to look deeper in the ear for mites, growth of microorganisms or foreign objects is important. Once infection by a bacteria or fungus is suspected, a swab of the aural exudate (waxy discharge) is examined under a microscope to identify the organism and culturing can be used to work out which treatment it will be most susceptible to. If a middle and/or inner ear infection is suspected, an X-ray of the skull can be performed to investigate the situation. Infections of the middle ear must be resolved in order to prevent frequent reoccurrence and otitis externa.
After diagnosis, thorough cleaning is usually required. It is common for both inspection and cleaning to be done under general anaesthetic (unless only a very mild infection) to eliminate pain and stress for the animal and to ensure they remain still. Generally, broad spectrum lotions can be prescribed for use in the ears, often in combination with a systemic oral or injectible medication for more serious infections. The topical applications have activity against ear mites in addition to microorganisms and some may also have anti-inflammatory properties such as those with corticosteroids. Most ear infections will be manageable using these methods.
When medication is not enough to restore aural health, surgical intervention can be considered to remodel the ear canal. In animals with recurring infections, thickened skin can be removed and the ear canal opened up slightly, to improve air flow and reduce humidity (Lateral Wall Resection). Thick folds of skin harbour microorganisms and would promote recurrence of infection if left in the ear. Removal of this skin also makes application of topical treatments and routine cleaning easier. A procedure called Total Ear Canal Ablation with Lateral Bulla Osteotomy, termed TECA for convenience, may be considered as a last resort. It involves the removal of all of the infection tissues and ear canal, other than the hearing organs in the inner ear. As with any surgery, there are risks associated since the area involved is packed with nerves and other important structures but these will be outlined by the vet. Reduced hearing is unavoidable but the vast majority of owners report a significant improvement in their pet's wellbeing after the operation.
Dealing with the infection itself is only part of the problem. So as to manage the problem long term, any underlying conditions such as an allergy must also be addressed. Additional tests may be required to identify the predisposing factor if they are not already known.
Check your pet's ears regularly for signs of redness, discharge and odour. Any of the symptoms described earlier are indicative of an aural problem and must not be ignored. Fortunately, a high proportion of Otitis externa infections can be treated and so spread to the middle and inner is avoidable if caught early. It is good practice to clean your pets ears at home, between trips to the vet. Your vet will be able to show you to do this safely, with an appropriate product such as CleanAural Fluid for Dogs & Cats. Topical ear products are designed to help clean both infected ears before treatments and for the maintenance of healthy ears. You should pay particular attention to fully dry your pet's ears after they have been swimming and bathing. Keeping a grooming regime will help you to monitor your pet's ears, and asking a professional groomer to clip long haired dogs can be a great asset in the fight against ear problems.
There are a many aspects to aural health but it certainly isn't something to fret over. Simply being an attentive pet owner will ensure that your loved one has the best life possible and there are professionals always willing to give you help and advice.
Friday 27th September 2013
Monday 7th October 2013