Pet Dermatology Discussions

Finding the source of a pet’s skin issues can take time and some serious diagnostic detective skills. Do your veterinary clinics have the right tests and products for treatment?

Whether it’s hair loss, hot spots, or an itchy rash, skin problems are one of the most frequent reasons pet owners make an appointment for veterinary care. Many health issues can go undetected for months, but a problem with a pet’s largest organ – the skin – is something owners can easily spot and then seek treatment to relieve. A dog that’s constantly scratching is obviously miserable and can make the rest of the household miserable, too, lying awake listening to constant digging and scratching all night.

The three layers of skin – the epidermis or outer layer, dermis (middle layer), and subcutis (inner layer) work to regulate body temperature, protect against infectious disease, provide sensory information, and much more, so the health and vitality of a pet is strongly linked to the health of their skin and coat. The challenge for veterinarians is the fact that similar skin issues can have many causes, so finding the source (or sources) can take not only time but some serious diagnostic detective skills.

Take hair loss, for example. Possible causes can be as varied as a bacterial or fungal infection, an endocrine disease such as Cushing’s or hypothyroidism, an autoimmune disorder, or an allergy to food or plants. Where to begin? Factoring in the pet’s medical history, age, breed, environment, and when the skin issue started are the first steps.

Most conditions for pruritis in pets fall into three broad categories of infection, infestation (from parasites), or allergies, so a process of elimination begins. To make diagnosis even more complicated, conditions from more than one category are often present at the same time, and the primary condition may be exacerbated by a secondary infection – a dog with atopic dermatitis has fleas and has developed a secondary bacterial infection, for example. Each issue may build on the discomfort caused by the others.

 

 

Visits and evaluations

At the initial visit, the veterinarian will start the workup by looking for the easiest issues to identify and treat, then continue eliminating possible problems to get to the underlying cause(s), as needed. Failing to eliminate any nonallergic conditions first can interfere with an accurate assessment of the pet’s condition, and potentially skew the results of an allergy workup.

Ruling out parasites on the surface of the skin is often the first step. Going through the coat with a flea comb or taking skin surface tape impressions can reveal any surface-dwelling mites, lice, fleas or “flea dirt.” One of the most common problems associated with a flea infestation is flea allergy dermatitis (FAD) or flea bite hypersensitivity, which happens when a cat or dog’s immune system overreacts to the saliva injected by fleas when they bite. Some pets are so hypersensitive that even a few fleas can cause itching, fur loss and inflammation.

The vet will literally have to dig deeper to find superficial skin parasites like Sarcoptes mites and examine the hair follicles for deep-dwelling parasites such as Demodex canis and Demodex injai mites. The supplies needed for these tests include a #10 blade, glass microscope slides and cover slips, Diff-Quik stain and a Wood’s lamp, which emits long-wave ultraviolet light and causes parasitic, bacterial, or fungal infections to glow a fluorescent green.

Evaluating the pet for an infectious cause of pruritis is the next step. Bacterial or fungal infections can cause skin to appear flaky, crusty, or moist, inflammation and odor may be present. The most common infectious conditions are staphylococcal pyoderma and yeast dermatitis. If ringworm is suspected, the Idexx Ringworm (Dermatophyte) RealPCR panel provides accurate results in 1-3 business days, with a sample provided in a sterile tube or container. Whether the problem is determined to be a fungal or bacterial infection, a variety of treatments are available from oral antibiotics, steroids, medicated shampoos, topical treatments, and fatty acid supplements.

There are several products that contain a combination of both antibacterial and antifungal therapy, along with ingredients that replenish the skin’s barrier function. Be sure you’re familiar with the products you carry with active ingredients like miconazole and chlorhexidine. Many brands carry the same formulations in a variety of products, including shampoos, sprays, mousse, and wipes that give owners a choice of options for less stress, more convenience, and better compliance treating their itchy pets.

As their name suggests, hot spots are most common in the summer, but they can cause misery to dogs any time. Hot spots are painful, sticky, itchy, swollen lesions that are self-induced by a dog repeatedly scratching or licking the same area as a reaction to skin irritation or pain. First and foremost is stopping the dog from continuing to attack and worsen the spot. Treatment may include a combination of using an Elizabethan collar, administering topical or oral steroids, antihistamines to reduce itching, and bandaging the area.

If skin problems persist after parasites or infections have been successfully treated, it’s time for an allergic skin disease workup, which can become time-consuming and expensive. Along with flea bite hypersensitivity, the most common allergies associated with pruritis in pets are food allergies and atopic dermatitis. Much less common is contact dermatitis, when a pet becomes hypersensitive to substances in the environment, such as household or lawn chemicals or some plants.

The best and most accurate way to diagnose a food allergy and identify the cause is with a dietary elimination trial. The pet owner must remove all current food and treats and feed a hypoallergenic diet for 8 to 12 weeks or more. Once the inflammation is controlled, the elimination diet is followed up by a rechallenge with the dog’s previous diet to confirm a food allergy diagnosis.

Atopic dermatitis may be best considered as a syndrome rather than a specific diagnosis. This lifelong condition is generally associated with hypersensitivity to various environmental allergens, which can trigger a skin reaction when the pet is exposed. Testing for atopic dermatitis is generally the last step in diagnosing pruritis and is useful to identify and avoid potential allergic triggers. Treatment options include cyclosporine (Atopica), or immunomodulatory medications like oral oclacitinib (Apoquel), or injectable lokivetmab (Cytopoint) for dogs.

With so many similar symptoms, finding the cause of pruritis can be a diagnostic challenge. By staying on top of the many treatment options and products available, you can make sure your customers are always prepared for one of the most common conditions coming to their clinic.

 

Photo credit: istockphoto.com/RuslanDashinsky

Photo credit: istockphoto.com/Fetrinka