Published on May 1st, 2015 | by Debbie Martin0
Atopic Dermatitis in Cats and Dogs: Recent Advances
Spring is well underway. This is a time of year which pets always enjoy; the extra sunshine allows them to run around, bask in the sun and generally feel good about themselves. But the season also brings with it a number of hazards, not least of which are conditions which affect an animal’s skin.
Of all the skin conditions suffered by cats and dogs, atopic dermatitis is perhaps the most common. While it is more difficult to spot on cats and dogs – since they are covered in fur – it can still provide a source of considerable irritation. As such, it has been the target of a large body of research and some of the results of that research have been encouraging.
In this article, we’ll take a look at Atopic Dermatitis and the veterinary world’s progress in fighting it.
What is atopic dermatitis?
Atopic Dermatitis is a skin condition characterised by the appearance of especially dry and itchy patches on an animal’s skin. While the precise causes of the condition are still unknown, it is thought to be related to dysfunction of the immune system, which causes the skin to over-respond to allergic stimuli like mites and pollen. Usually, this sensitivity is limited to a specific area of the animal’s skin – most frequently the neck, head and back – and this is where the dermatitis will recur. It is, as we have mentioned, more threatening during spring, when mites and pollen are more prevalent.
But what makes the condition ‘atopic’? Simply put, an atopy is a disease to which an animal is predisposed. In most cases, this predisposition stems from genetics; animals who suffer from AD have been shown to be more likely to give birth to animals who suffer similarly. For this reason, pets whose parents are prone to AD should be considered most at risk. Other genetic factors, such as the animal’s breed, also play a role. While any breed of cat or dog can suffer from the condition, there are some which are at greater risk, specifically: retrievers, setters and terriers for dogs.
What causes AD?
Leaving genetic factors to one side, there are a number of environmental factors which have been shown to contribute to an increased propensity toward AD.
One hypothesis holds that exposure to potential allergens early in childhood will help to develop the immune response and so safeguard the animal from the disease in adulthood. Studies have found that animals who live in a rural environment with more frequent exposure to other animals, are less likely to develop these allergic responses. This is also true of animals who are taken for walks in the forest during their formative years. Conversely, animals who are kept in isolation for the first eight months of their lives and given frequent baths, were found to be at increased risk of developing AD. This would seem to support the hypothesis that animals who are exposed to allergens while young are thereby protected.
Another theory holds that problem lies in a breakdown in the skin’s ability to exclude bacteria and other harmful microbes. There is a growing body of evidence that dogs suffering from AD suffer from a breakdown in the lipids and proteins present in the skin – and it is these lipids and proteins that form a sealant between the epithelial cells which constitute the bulk of the skin. As this substance degrades, so too does the ability of the skin to do its job.
How is a diagnosis made?
Diagnosing AD requires that the vet both considers the history of the animal and observes the clinical signs of the disease, as well as eliminating the possibility of other conditions which might share some of AD’s symptoms.
The clinical signs of AD are usually exhibited at dogs between six and thirty-six months old. They will recur seasonally, getting gradually more severe as time goes on. What began as hyperpigmentation can progress into lichenification. The animal will also likely suffer from self-inflicted trauma as a result of scratching at the wound.
Foot allergens can also play a role in the development of AD. For this reason, a pet is often placed onto a diet for around six weeks, which is designed to eliminate possible allergens. The animal can then be re-introduced back onto the original diet, if possible.
In order to establish whether the animal is prone to the condition, a vet will need to be given as thorough a family history of the pet as possible. Unfortunately, this is not always possible,
Serologic testing is often used to check for an animal’s allergies. Other tests can be intradermal (meaning, simply, within the skin) which involve injecting a small amount of the allergen into the animal’s skin and then watching for any discolouration or swelling. Unfortunately, intradermal testing is not conclusive – up to a fifth of dogs who have already been diagnosed with the condition have been shown to test negative to an intradermal test.
What can be done to combat AD?
Unfortunately, AD is notoriously stubborn and will recur seasonally throughout an affected animal’s life. Many treatments are therefore geared toward alleviating the animal’s discomfort, rather than tackling its root causes. Despite its gruesome appearance, the condition is not contagious and so suffering pets need not to be quarantined from one another.
One method of combatting AD is through hyposensitisation therapy. Through this practice, a vet can attempt to reduce an animal’s sensitivity to certain allergens by injecting the animal with small amounts of them. This will reduce itching and in some cases will significantly. However, it will take a long time to do so, with some cats waiting a year before seeing any improvement. It will also be expensive and it may bring about side effects – it may even induce the very symptoms it seeks to alleviate. For these reasons, most vets will only consider it once other options have been exhausted.
Once these options have been explored, the next step normally is to move to medication. Glucocorticoids are available in both oral and topical form and, along with Ciclosporin, have been shown to be effective and with limited side effects. Antihistamines and fatty acid supplements show promise, but the data thus far acquired is not conclusive enough to recommend them.