On today's episode of Twin Trees Vet Talk, we welcome our very special guest, Dr. Vincent Defalque. Dr. Defalque is a Board Certified Veterinary Dermatologist in Vancouver, BC (Canada). We discuss the causes of itch (pruritus) in dogs and cats, as well as what owners can expect with regards to diagnostic testing and management of itchy skin conditions resulting from problems like parasites (fleas, mites), food allergies, and environmental allergies (also called atopic dermatitis or atopy).
We hope you enjoy this episode! Please leave your questions and comments below!
About Dr. Vincent Defalque, DVACD:
Following graduation from the University of Liege (Belgium), Dr. Defalque completed an internship at Vet’Agro Sup (France), then a dermatology residency at Michigan State University. He became a board certified veterinary dermatologist in 2006. Dr. Defalque is a Past-President of the Canadian Academy of Veterinary Dermatology, and currently serves as the Canadian representative at the World Association for Veterinary Dermatology. Dr. Defalque works at North West Veterinary Dermatology Services in Vancouver, BC and St. Albert, AB. His special interests include the diagnosis and management of ear diseases in dogs and cats as well as feline dermatology.
[TEASER]:The three main causes of itch: 1) parasitic infestations such as fleas, mange or ear mites. The second one is food allergies and the third one is environmental allergies. It is not possible to reliably diagnose food allergies with skin testing, a blood test or direct-to-consumer hair and saliva test. There is no cure for atopic dermatitis. They do not outgrow this disease. This is something that we need to manage for the rest of their lives. Immunotherapy is the only treatment that may alter the course of this disease. Everybody be aware that this is something that can be passed on to the puppies or kittens. [Music]
[Dr. Lopez]: Today we have a very special guest, Dr Vincent Defalque. He is a board-certified Veterinary Dermatologist at Northwest Veterinary Dermatology Services in Vancouver, British Columbia. We get so many questions about all of these different skin conditions, and you are the best person to help us answer them. What would make a pet very itchy and what should owners expect as far as trying to get to the bottom of that and ongoing management of an itchy skin condition?
[Dr. Defalque]: So itch, or pruritus as we call it in scientific language, it's a self-protective mechanism. It's an unpleasant sensation that provokes scratching, biting, pulling the fur, nibbling, rubbing, but also excessive licking or over-grooming in cats. And it is by far the most common reason for consultation in my field of Veterinary Dermatology.
[Dr. Lopez]: There are a fair number of dogs that get brought into the emergency room because they they are so itchy that they're actually perceived by the owners to be in distress.
[Dr. Defalque]: It is not a specific symptom, and it is associated with a wide variety of causes. Therefore a thorough step-by-step workup is required it is important to have a consistent plan, and to not "put the cart before the horse." There is also no single therapy that is effective in every case; there is no magic bullet.
[Dr. Lopez]: Let's talk about some of the different causes for a dog or a cat to be itchy.
[Dr. Defalque]: So there are three main causes of itch in dogs and cats. The first one is parasitic infestation, such as fleas, mange or ear mites; the second one is food allergies and the third one is environmental allergies.
[Dr. Lopez]: So in the consultation, one of the goals would be to try to figure out why the pet is itching, so your veterinarian or dermatologist is going to want to run some basic tests to give them an idea of why the pet is itching. What could they expect as part of a routine diagnostic workup for something like itching?
[Dr. Defalque]: So the first steps of a Dermatology consultation are: first take a thorough history because there are a lot of important clues in the history such as a seasonality, dermatological signs and non-dermatological signs. The second step is a thorough physical and dermatological examination. The third step is to obtain in-house samples- and examples of that are ear and skin cytology to look for secondary infections with bacteria and yeast, but also microscopy to look for parasites. Even if parasites are not found, we might treat for parasites anyway just to rule that out; it's not always easy to find the parasites0 they are microscopic for the most part.
[Dr. Lopez]: Just in case you haven't heard the word cytology basically that means looking at the cells under the microscope. So your veterinarian might take a swab from the waxy brownish debris or pus in the ears, or from lesions on the skin, and roll those on a slide look at them under the microscope to look for things like bacteria, yeast and other abnormalities. If they see a lot of bacteria they might want to get a culture so that they know what kind of bacteria it is and what antibiotics it is susceptible to. Antimicrobial resistance is becoming so common now that even if we see something looks like a staph infection we're not really sure what antibiotic is going to work this day in age.
[Dr. Defalque]: In dogs and cats with year-round itch, and especially in pets with chronic vomiting and diarrhea a very important initial intervention is a strict eight-week Elimination Diet Trial, because unfortunately it is not possible to reliably diagnose food allergies with skin testing or blood tests or direct to consumer hair and saliva tests.
[Dr. Lopez ]:That's so interesting because there are so many tests on the market where people think they can get a blood test for chicken allergies. And so it sounds like those tests aren't actually very reliable.
[Dr. Defalque]:So we do not recommend these tests. The only reliable test is a strict Elimination Diet trial.
[Dr. Lopez]: That is really important to know. What are the most common food allergies that you see in dogs and cats?
[Dr. Defalque]: The food allergens in dogs and cats are different from what they are in people. And in dogs the most common food allergens are beef, dairy products, chicken wheat, and lamb, and in cats they are beef, fish and chicken.
[Dr. Lopez]: Wow that's so interesting. Just to confirm, these blood tests and saliva tests are not useful in diagnosing food allergies. You need a restrictive elimination trial where you're removing certain ingredients to see if that positively impacts their skin.
[Dr. Defalque]:That's right
[Dr. Lopez]: That's so interesting. Cool. Okay, so then once you've ruled out parasites and food allergies, what would the next step be?
[Dr. Defalque]: So once parasites and food allergies are ruled out, then a diagnosis of environmental allergies is made. And the disease that we're talking about here is called Atopic dermatitis, which is way more common than food allergies. So it is defined as a genetically heritable inflammatory and pruritic [itchy] allergic skin disease with characteristic clinical features and associated most commonly with antibodies to environmental allergens.
[Dr. Lopez ]: So compared to something like food allergies, how common is atopic dermatitis, which people also call atopy?
[Dr. Defalque]: So in my estimation there are one million atopic dogs in Canada; this is based on a population of 7.7 million dogs and the fact that 10 to 15 percent of them are atopic.
[Dr. Lopez]: Wow so 10 to 15 percent of dogs have this problem. Again circling back to testing- how is atopic dermatitis diagnosed?
[Dr. Defalque]: So it is a diagnosis of exclusion. So as I have mentioned the step-by-step approach- after we've ruled out parasites or treated for parasites, and after we've had a failed food trial, then we make a diagnosis of atopic dermatitis. So the diagnosis is not made based on skin testing or a blood test- these allergy tests are used to prevent disease flare ups by implementation of allergen-specific immunotherapy, like allergy shots or allergy drops. But that's the only point of these tests- it's only if the owners are interested to pursue immunotherapy.
[Dr. Lopez]: Wow blood tests for environmental and food allergies those are really more useful in helping to develop immunotherapy. Can you talk a little bit more about how immunotherapy works?
[Dr. Defalque]: So it's important to know that unfortunately there is no cure for atopic dermatitis. Atopic dermatitis will typically develop in the first few years of life- in dogs typically between six months and three years of age. They do not outgrow this disease. This is something that we need to manage for the rest of their lives.
[Dr. Lopez]: That's really important to know.
[Dr. Defalque]: In terms of treatment they are actually two ways to treat atopic dermatitis. The first type of treatment is called symptomatic therapy, so we're just purely treating the symptom, which is the itch. For this, unfortunately, antihistamines do not work in dogs and cats, so we're relying on veterinary-labelled medications such as steroids ( or prednisone for example), another medication is cyclosporine the brand name is Atopica), another medication that can be used is oclacitinib (the brand name is Apoquel) and lastly we do have an injection in dogs that is a solution of monoclonal antibodies the ingredients is called Lokivetmab (the brand name is Cytopoint) and that provides itch relief for several weeks at a time. Again, we're just treating the symptoms here. It doesn't address the primary underlying cause, which is the atopic dermatitis. If we want to treat more specifically for atopic dermatitis, then we would be looking at a second type of treatment called immunotherapy. Immunotherapy is the only treatment that may alter the course of this disease and that truly addresses the underlying problem. By giving what the patient is allergic to in a small amount on a regular basis, we build some kind of tolerance over time.
[Dr. Lopez]: Wow.
[Dr. Defalque]: So immunotherapy is a very valuable treatment option because it is a more proactive and holistic treatment. Holistic because it's not a drug; it's a solution of what the patients are allergic to based on allergy tests. And so we common allergens in dogs and cats would be things like house dust mites, tree pollens, grass pollens, wheat pollens and molds. It is also proactive because we are actually treating the allergy and try to make them less allergic over time.
[Dr. Lopez]: It's almost like that movie- what is it? The Princess Bride! Where he ingests small amounts of the poison and ultimately develops a tolerance, and then they switch the poison?
[Dr. Defalque]: Yeah immunotherapy is a lot like that.
[Dr. Lopez]: You're basically giving them very small amounts of the thing that they're allergic to you, and it's like a custom solution based on their allergy profile. Some of the things that you said I think are really important take-home points. #1) Atopic dermatitis is a lifelong condition, so a lot of people get really frustrated that every year they have to go to their vet when it flares up, when the grasses are pollinating and the trees are pollinating. And they think that their vet might be doing some something wrong when actually their expectations might not be in line with the reality of the disease, which is that it's a lifelong problem. The other thing too is all of the itching and scratching can basically traumatize the skin barrier and lead to infections, and so a lot of these patients need antibiotics to help clear up the infections. Because of this, as time goes on, we can have a higher risk of seeing antimicrobial resistance or basically superbugs that are resistant to antibiotics, especially if owners aren't following the instructions on the bottle. If you miss doses or you stop antibiotics early, then bacteria are a lot more likely to develop resistance. So that's the first thing- lifelong condition, lifelong management. Along with that, this is a very genetic condition. So if you have a very itchy dog who at the age of one or two is already spending a lot of time at the vet for itchy skin, please don't breed that dog. Because there is a very high likelihood that you'll be passing on another lifelong medical condition to the puppies or kittens. And in the interest of breeding pets that are as healthy as possible for their new owners, their new families, it's just not fair. It is expensive and uncomfortable. So just to everybody be aware that this is something that can be passed on.
[Dr. Defalque]: That's correct and that's also the reason why we're seeing pretty much the same breeds every day in our practice. French Bulldogs, English Bulldogs, Shepherds, Terriers.
[Dr. Lopez]: Is there like a genetic test that can be done?
[Dr. Defalque]: Unfortunately it seems to be multifactorial and multiple genes may be affected. So there isn't really a test to detect the disease. Again it's more of a clinical diagnosis by exclusion of other causes of itch.
[Dr. Lopez]: Well that is very helpful.
[Dr. Defalque]: So for more information, I recommend to take a look at the Canadian Academy of Veterinary Dermatologists "Empathy for Itch" Pet Parent page.
[Dr. Lopez]: So on each of the different dermatological conditions they can find more information straight from the source- board certified veterinary dermatologists. These are the experts. You can spend a fortune at the pet store and on Amazon on all of these different topical solutions and remedies. Some of those can cause more harm than good if you don't know exactly what you're dealing with, and some of them might just be a complete waste of money. There's a whole spectrum of how severe these problems are, so if you're on the more severe end of the spectrum, it might be very helpful to bring in a dermatologist to help make sure that you're on the right track
Why does my pet itch? (Summary courtesy of Dr. Defalque)
Itch (or pruritus in scientific language), is a self-protective mechanism. It is an unpleasant sensation that provokes scratching, biting, pulling fur, nibbling, rubbing, but also excessive licking or overgrooming in cats.
It is by far the most common symptom and reason for consultation in my field of Veterinary Dermatology. It is not a specific symptom and it is associated with a wide variety of causes!
Therefore a thorough step by step work-up is required. It is important to have a consistent plan, and to not put the cart before the horse.
There is no single therapy that is effective in every case. There is no magic bullet!
The three main causes of itch are parasitic infestations (such as fleas, mange or ear mites), food allergies and environmental allergies.
The first steps of a dermatology consultation with are:
- Taking a thorough history
- Physical and dermatological examinations
- In-house samples such as cytology to look for secondary infections with bacteria and yeast, and microscopy to look for parasites.
Even if parasites are not found, we might treat for parasites anyway.
In dogs and cats with year-round itch, and especially in pets with chronic vomiting and diarrhea, a very important initial intervention is a strict 8 week elimination diet trial.
It is not possible to reliably diagnose food allergies with skin testing, a blood test, or a direct-to-consumer hair/saliva test.
In dogs, the most common food allergens are beef, dairy products, chicken, wheat, and lamb. In cats, these are beef, fish, and chicken.
The disease we are talking about here is called atopic dermatitis, which is way more common than food allergies. It is defined as a genetically heritable inflammatory and pruritic allergic skin disease with characteristic clinical features, and associated most commonly with antibodies to environmental allergens.
In my estimation, there are ONE MILLION atopic dogs in Canada. This is based on a population of 7.7 million dogs and the fact that 10 to 15% of them are atopic.
This diagnosis of atopic dermatitis is NOT made based on skin testing or a blood test.
Allergy tests are used to prevent disease flares by implementation of allergen-specific immunotherapy (allergy shots or allergy drops).
For more information, I recommend to take a look at the Canadian Academy of Veterinary Dermatology Empathy for Itch pet parent page: