Pruritus & feline reaction patterns Flashcards
How dogs express pruritus?
- Scratching with paws
- Rubbing nose, back or sides to carpets, sofas, bushes outside
- Licking (specially paws and groin area)
- Chewing the skin
- Head shaking (ear pruritus and inflammation = skin disease)
How do cats express their
pruritus? (4)
- Scratching with claws (also head and neck
pruritus) - Self induced alopecia
- Miliary dermatitis
- Eosinophilic granuloma complex!
3 main causes for pruritus
1) Parasites
2) Infections - secondary!
3) Hypersensitivity disorders
Working up pruritus, first rule out?
Then do what?
parasites. If pruritus resolves - then the
reason was parasites. If pruritus stays - move to next
step.
Second step; find and treat infections (many diseases
can be pruritic through infection). If pruritus and skin lesions resolve, you’ve got the right diagnosis.
If skin lesions resolve but pruritus stays - follow
third step: allergy diagnostics.
NB ALLERGIES CAN NOT BE DIAGNOSED THROUGH LAB TESTS!
In dermatology, you make your diagnosis by doing steps that rule out different diseases!
Flea allergy dermatitis (FAD)
Needs treatment trial (all animals need flea treatment, but this might already be done at the first step of diagnosing).
Flea allergy dermatitis (FAD) is a common and severe allergic reaction in dogs and cats caused by flea saliva.
Even a single flea bite can trigger intense itching, redness, inflammation, and hair loss, particularly around the lower back, tail base, and hind legs.
Affected pets may excessively scratch, bite, or groom, leading to skin infections and scabbing.
Food allergy diagnosis requires
elimination diet/food trial (with provocation) for diagnosing or ruling out.
Atopic dermatitis diagnosis is made by
is a diagnosis of exclusion! You can diagnose this if all other pruritic diseases are ruled out.
Rare causes of pruritus. (4)
- Drug reaction (ask what drugs have been used on the animal)
- Contact dermatitis (sparsely haired areas)
- Epitheliotropic lymphoma (old animals), pemphigus
foliaceus, zinc responsive dermatitis (nordic breeds - husky, malamute)… - Neuropathies (syringomyelia, Chiari malformation -CKCS) can cause neurogenic pruritus!
Epitheliotropic lymphoma
Old dogs!
Might be pruritic.
Signs: Hypopigmentation, scaling, alopecia, plaques,
nodules, erosions, ulcers, leukoderma, leutrichia.
Mucocutaneous junctions usually, but can be everywhere really.
Needs biopsy for diagnosis.
Parasites that may cause pruritus either directly or indirectly. (7)
- Fleas
- Sarcoptic mange (scabies)/notoedrosis (feline mange/scabies)
- Cheiletiellosis (skin surface mite, “walking dandruff”)
- Otodectosis (ear mites)
- (lice)
- Demodicosis causes pruritus only secondarily. (they live in follicles)
- (Trombiculosis, rare red mite “chigger”)
What parasite can you not rule out without a treatment trial in cats?
And in dogs?
In cats, fleas. Fleas in cats can’t be ruled out by skin/hair samples, because they are vigorous groomers.
In dogs, sarcoptic mange, scabies cannot be ruled out without treating for it. In case of sarcoptosis you only find mites in 50% of the cases so treatment trial is a must.
- Parasites are ruled out.
- Infections have been treated.
- The animal is still pruritic??!
What do you do next?
Allergy diagnostics!
- Fea allergy (usually ruled out at step 1)
- Food allergy (diagnosed through elimination diet + provocation) YOU CAN NOT (LAB)TEST FOR IT!
- Atopic dermatitis (when all other diagnoses are ruled out) MOST COMMON DISEASE!
(If desired, its at this point you can move on to skin or blood tests but these are only for allergen specific therapy.)
Allergen specific immunotherapy can only be used if a specific allergen is identified (1 inj per month long term).
Elimination diet - diet trial is… (5)
- Gold standard to diagnose/rule out food allergy.
- Using a novel protein source (+ preferably also a novel carbohydrate source) OR hydrolyzed dry food. As little new components as possible!
- Diet needs to last at least 6 weeks. If needed then 8-12 weeks.
- If symptoms resolve with diet, it doesn’t mean it is food allergy - you need to provoke with old food to prove a food allergy! If symptoms do not reappear with provocation, then it is not food allergy.
- You should clear all infections in the beginning of the diet (pruritus!). Check at the end of diet!
2-4 weeks of anti-inflammatory for pruritus at beginning of elimination diet in order to resolve signs. But NB you cannot give these when at the point of food provocation.
How is food allergy diagnosed?
Food allergy Is diagnosed by provocation!
Give ALL old proteins at essentially the same time.
Diet trial food options: (3)
- Home cooked diet (new protein source)
- Hydrolyzed dry food (veterinary brand)
- Novel protein (to that specific animal) dry food (these may be called hypoallergenic even though they are not hydrolyzed)
Describe Provocation in the context of elimination diet. (5)
Provocation is short - 2 weeks! And is only done if pruritus resolves with the hydrolyzed diet!
- If the animal itches the same as before - no need for provocation. The issue is not a food allergy.
- If the dog gets pruritus during provocation, then go back to elimination diet and the pruritus should resolve immediately - FOOD ALLERGY.
- If there is no pruritus on provocation - it is not food allergy! Atopic dermatitis!
- If the animal is slightly pruritic before provocation, it gets worse when provoked - poor thing probably has two allergies!
Diff between RC hypo and anallergenic.
The regular hypo is hydrolyzed but not AS hydrolyzed as the peptide chains in anallergenic.
RC says that anallergenic should be used for elimination diet, and hypoallergenic can be used for GI issues as well as identified food allergies that no longer require the “extreme” of anallergenic.
- What protein sources can we choose?
- What can be the pitfalls of the diet?
- Can you use drugs during the diet?
- Do you need to do diet if the animal has
ear pruritus twice a year?
- What protein sources can we choose?
Any novel protein. - What can be the pitfalls of the diet?
Can be difficult to find a novel protein if the animal has been exposed to most everything already. - Can you use drugs during the diet?
Yes, but NOT at provocation. Only unflavored ones too. - Do you need to do diet if the animal has ear pruritus twice a year?
Depends. Not necessarily needed e.g. if the ears are managed with 1 x week cleaning or other.
Atopic dermatitis is the same thing as
Environmental allergy
NB Clinically, atopic dermatitis and food allergy look the same, as food allergy in turn causes atopic dermatitis. This can pose a challenge for diagnosing.
What are the Favrot criteria?
If you have more then 6 of these criteria, then you have a high chance of having an atopic dermatitis case. Sens 58.2, Spec 88.5%.
- age of onset under 3 y
- mostly indoor
- corticosteroid responsive pruritus
- chronic or recurrent yeast infections
- front feet affected
- ear pinnae affected
- non-affected ear margins (cause affected ear margins would make it more likely to be sarcoptes)
- non-affected dorso-lumbar area
What does Atopic dermatitis look like clinically?
- Pruritus (paws, armpits, groin, perianal area,
face, ears) - Recurrent skin infections and otitis
Why does atopic dermatitis happen? (4)
Chronic inflammatory skin disease
IgE antibodies to environmental allergies
Epidermal barrier dysfunction
Genetic predisposition
the most common skin disease in small animals
atopic dermatitis
Eosinophilic granuloma complex (indolent ulcer, eosinophilic plaque, eosinophilic granuloma)
