Lesson 105 - Management of Pruritic Disease 1

What scales do we use for owners to assess their pets level of pruritus?

1. pruritus visual analogue scale for dogs

2. VAScat

What are the reaction patterns associated with feline alopecia?

1. miliary dermatitis

2. self induced alopecia

3. face, head, and neck pruritus

4. eosinophilic granuloma complex

What are the lesions of eosinophilic dermatoses in cats?

1. plaques

2. linear granulomas

3. indolent ulcers

What causes Malassezia dermatitis?

commensal yeast organism of the skin in dogs and cats called Malassezia pachydermatitis

Which of the following explains why Malassezia dermatitis occurs?

It results from overgrowth of normal skin yeast due to an underlying condition such as allergies or endocrine disease

Which statement best describes individual variation in susceptibility to Malassezia dermatitis among animals?

Some animals can tolerate high numbers of yeast without signs, while others develop hypersensitivity reactions to even small amounts

What animals can have large numbers of Malassezia naturally?

1. some hounds

2. hairless cats

What are the clinical signs of Malassezia dermatitis in dogs?

1. pruritus

2. erythema

3. kerato-sebaceous scale (greasy material)

4. claw fold erythema/swelling with waxy or crusty brown exudate

5. malodorous skin and ears

6. traumatic alopecia

What signs can occur with chronic Malassezia dermatitis in dogs?

lichenification and hyperpigmentation

What concurrent issues can occur with Malassezia dermatitis?

otitis externa

What is the distribution for Malassezia dermatitis in dogs?

1. muzzle, lips

2. folds, neck

3. axilla, ventral abdomen

4. medial hindlimbs, perineum

5. claw folds

6. intertriginous zones favored

What are common underlying diseases associated with Malassezia dermatitis in dogs?

1. allergic skin disease

2. cornification disorders

3. endocrinopathies

4. autoimmune disease

What are the clinical signs of Malassezia dermatitis in cats?

1. pruritus

2. erythema

3. keratosebaceous scale/casts (greasy material)

4. red-brown claw staining

What is the distribution for Malassezia dermatitis in cats?

1. claws and claw folds

2. chin, neck, ventral abdomen

What are the common underlying diseases associated with Malassezia dermatitis in cats?

1. allergic skin disease

2. idiopathic facial dermatitis (Persian and Himalayan)

3. feline acne

4. paraneoplastic alopecia

5. thymoma/non-thymoma-associated exfoliative dermatitis

What diagnostic tool is most commonly used to diagnose Malassezia overgrowth?

cytology

What samples do we take for Malassezia dermatitis?

sample affected area using tape, toothpick, swab, or impression smear

What are the combinations of treatment types for Malassezia dermatitis?

1. topical as sole therapy with daily application

2. topical and systemic therapy

3. maintenance topical therapy every 1-2 weeks

What active ingredients are common for topical Malassezia treatments?

1. chlorhexidine 3-4%

2. miconazole 2%

3. climbazole 0.5%

4. ketoconazole 1%

5. terbinafine

6. nystatin

7. acetic acid 2.5%

8. selenium sulfide 1% shampoo (dogs only)

A dog is diagnosed with Malassezia dermatitis after presenting with pruritus, erythema, and a greasy, malodorous coat. Cytology confirms yeast overgrowth. The owner is hesitant to use antifungal medications and asks for a more natural treatment option.

Which of the following is the most appropriate recommendation?

Apply a topical solution containing acetic acid to help reduce yeast proliferation

Why do we not use selenium sulfide 1% shampoo in cats?

if they were to groom themselves and ingest it, it can be toxic

What systemic therapies are used for Malassezia dermatitis?

1. fluconazole

2. itraconazole

3. ketoconazole (only in dogs)

4. terbinafine

How long do we treat Malassezia dermatitis?

3-4 weeks

What can we do with testing and therapy for animals that have a Malassezia hypersensitivity?

1. Malassezia extracts are included in standard intradermal allergen tests and IgE serology

2. may benefit from the inclusion of Malassezia in their immunotherapy

What causes sarcoptic mange in dogs?

Sarcoptes scabiei var. canis

How is sarcoptic mange transmitted?

direct from infected host or contaminated environment

What does the severity of clinical signs for sarcoptic mange depend on?

severity of type IV hypersensitivity reaction

What contributes to the pathogenesis of sarcoptic mange?

female mites burrow in the superficial layers of the epidermis, laying eggs and scybala

What is the concern with sarcoptic mange?

zoonotic

What are the clinical signs of sarcoptic mange?

1. severe pruritus

2. non-responsive to minimally responsive to corticosteroids

3. papules

4. alopecia

5. scales, excoriations, crust

6. lichenification and hyperpigmentation

7. chronic - lethargy, lymphadenomegaly, inappetence, weight loss

What is the distribution of the lesions for sarcoptic mange?

1. pinnal margins

2. elbows

3. hocks

4. legs

5. ventrum

What is norwegian scabies?

1. severe scabies mite infestation

2. very thick crusting and not pruritic

3. results from severely compromised immune system

How do we diagnose sarcoptic mange?

1. clinical signs and distribution

2. pinnal-pedal reflex

3. superficial skin scrapings

4. therapeutic trial

5. antibody testing not typically performed

How to correctly test for the pinnal-pedal reflex?

must rub the pinnal margin

What is difficult with diagnosing sarcoptic mange?

mites are only found 25-50% of the time so sometimes we have to just try a therapeutic trial

What mite is feline scabies?

Notoedres cati

What is the distribution of Notoedric mange?

ears and head first, then feet and perineum

What is the transmission of notoedric mange like?

1. highly contagious with all cats susceptible

2. zoonotic potential

Which mite is easy to find on superficial scrapings?

notoedres cati

What host has Cheyletiella blakei?

cats

What host has Cheyletiella yasguri?

dogs

What host has Cheyletiella parasitivorax?

cats and rabbits

Where to cheyletiella mites live?

live on skin surface eating the keratin layer and using their mouthparts to suck up tissue fluids

What is the transmission of Cheyletiella like?

1. highly contagious and zoonotic

2. particularly common in regions where flea preventatives not regularly used

What are the clinical signs of cheyletiellosis?

1. multifocal areas of heavy scale/crust on dorsal and lateral trunk

2. miliary dermatitis in cats

3. "walking dandruff"

4. dogs are more likely to have severe pruritus

How do we diagnose cheyletiellosis?

1. clinical signs and dorsal distribution

2. broad superficial skin scrapings

3. acetate tape cytology

4. fecal float of over groomers

5. mites are easy to visualize with minor magnification

What is a non-commensal Demodex species in cats?

Demodex gatoi

What are the clinical signs of demodex gatoi associated with?

1. live in the superficial layers of the skin

2. probably contagious

3. alopecia from overgrooming is most common clinical sign

What diagnostics do we use for demodex gatoi?

1. superficial skin scrapings

2. fecal float

3. therapeutic trial and response to treatment

What drug do we use to treat mites?

1. any isoxazoline

2. ivermectin

3. moxidectin

4. selamectin

5. lime sulfer

6. amitraz

Which animals do we treat for mites?

all in-contact animals

What other treatments do we use for mite infections?

1. manage inflammation, infections, and pruritus

2. secondary infections are common

Mites die-off and can cause a hypersensitivity reaction. What would you treat with?

1. oclacitinib

2. corticosteroids

When treating mites, what do you tell the owner to expect with treatment progression?

inform that the patient will look worse before getting better but the treatment is working

Why do we need to treat the environment also with mites?

1. sarcoptes and notoedres can survive off host at room temp for 2-6 days

2. at low temp and high humidity females can live off host for up to 21 days

3. cheyletiella can survive for 10 days

How do we treat the environment with mites?

1. routine washing of bedding in hot water

2. frequent vacuuming of floors and furniture

3. remove or avoid sources like fox dens

Which diseases cause mild pruritus?

1. autoimmune skin disease

2. endocrinopathy

3. demodicosis

Which diseases cause mild to moderate pruritus?

dermatophytosis

Which diseases cause moderate pruritus?

bacterial infections

Which diseases cause moderate to marked pruritus?

1. demodicosis

2. allergic dermatitis

3. cheyletiella

Which diseases cause marked pruritus?

1. malassezia

2. sarcoptes

3. notoedres

A dog with a history of allergic skin disease develops intense pruritus after minimal exposure to an allergen. The owner asks why such a small amount triggered such a severe reaction.

Which of the following best explains this response?

Allergic reactions are not dose-dependent and can occur with even minimal exposure in sensitized individuals

What causes flea allergy dermatitis?

1. flea bites from Ctenocephalides felis felis

2. Type 1 +/- Type IV hypersensitivity to reactions to allergens found in flea saliva

What is the flea life cycle like?

1. most of it occurs off the host

2. larval stage is most vulnerable to environmental control efforts

3. pupae is the most resistant stage

4. eggs to larvae to pupae to adult

Under ideal conditions, how long is the flea life cycle?

3-4 weeks

What is the distribution for flea allergy dermatitis?

moderate to severe pruritus affecting the caudal half of the body

What are the clinical lesions of flea allergy dermatitis?

1. papules

2. erythema

3. excoriations

4. alopecia

5. scale, crust

6. pyotraumatic dermatitis/erosions

7. lichenification +/- hyperpigmentation

8. can also develop unique non-specific eosinophilic reaction patterns

How do we diagnose flea allergy dermatitis?

1. history and clinical signs

2. presence of flea dirt or fleas

3. excellent response after initiation or adjustment of flea control

4. serologic or intradermal allergy testing

5. absence of fleas does not rule out

What are the treatment objectives for flea allergy dermatitis?

1. provide symptomatic relief using anti-pruritic +/- antimicrobial therapy

2. prevent further flea bites

3. environmental flea treatment

What are the main objectives with flea control with flea allergy dermatitis?

1. choose products that offer rapid speed of kill

Which flea preventative has the fastest kill time of all orals?

nitenpyram (30 min)

Which flea preventative has the fastest kill time of all topicals?

imidacloprid (1-2 hours)

Which flea preventative should we not use on cats?

permethrin

What environmental control can we use for flea allergy dermatitis?

1. vacuum daily

2. set flea traps

3. use of environmental microencapsulated adulticides

4. use of professional exterminators

What hypersensitivities are involved with cutaneous adverse food reaction?

type I, III, IV

What is involved with a food intolerance?

1. no involvement of immune system

2. reactions are dose dependent

3. gradual onset of clinical signs

4. not life-threatening

5. often triggered by histamine-rich foods

What is involved with a food allergy?

1. hypersensitivity reaction to food allergen

2. any amount of exposure will provoke a reaction

3. can be life-threatening

What are common food allergen sources?

1. typically proteins of large molecular size (>10 kD)

2. dog food: beef, chicken, dairy, wheat

3. cat food: beef, dairy, chicken, fish

4. some proteins have cross-reactivity

What is the median age of onset for CAFR?

1. dogs 2.9 years

2. cats 3.9 years

What are the clinical signs of CAFR in dogs?

1. generalized pruritus on feet and ear

2. secondary bacterial and malassezia skin and ear infections

3. concurrent ear disease is common

4. diarrhea > vomiting

5. pruritus

What is the typical distribution for CAFR in dogs?

1. ears

2. feet

3. abdomen

4. perioral

5. perineal

What are the clinical signs of CAFR in cats?

1. concurrent flea allergy dermatitis common

2. concurrent ear disease common

3. vomiting > diarrhea

4. pruritus

What is the typical distribution for CAFR in cats?

1. head/face/neck

2. occasional trunk and limb

3. eosinophilic reaction patterns

What is the appropriate length for a diet trial?

8-12 weeks

What is the only way to diagnose CAFR?

strict elimination diet trial for a period of 8-12 weeks followed a provocation challenge

What are the types of diets used for elimination diet trial?

1. novel protein diets

2. hydrolyzed/amino acid diets

What are the novel protein diets?

1. prescription diets with a novel protein

2. home-cooked diet

What are the pros and cons to prescription diets with a noval protein?

1. pros: readily available, complete/balanced, more options

2. cons: more expensive, cross-reactivity with common proteins isn't fully defined

What are the pros and cons to home-cooked diets for elimination trial?

1. pros: less risk of cross-contamination

2. cons: incomplete/unbalanced, expensive, difficult to maintain

What are hydrolyzed protein diets?

peptide bonds in parent proteins are enzymatically cleaved to reduce cross-linking with allergen specific IgE antibodies on mast cells

What are the pros and cons of hydrolyzed protein diets?

1. pros: more affordable, readily available, complete/balanced, fewer options

2. cons: partially hydrolyzed diet may induce reaction

What are the pros and cons for amino acid based diets?

1. pros: least likely to trigger immune reactions

2. cons: very limited availability, palatability

What is an amino acid based diet?

synthetic amino acids directly integrated into diet

What consists of a positive diagnosis for CAFR?

clinical improvement during elimination trial and flare up with pruritus in the first 14 days of reintroducing old food

What are the treatment options for CAFR?

1. maintain on a novel or hydrolyzed protein diet lifelong

2. perform ingredient challenges to identify which food sources are tolerated

How do you perform ingredient challenges?

introduce something every two weeks and if clinical signs occur resolve them before another challenge

What is a warning to the owners with hydrolyzed diets?

can cause black cat hair to turn red

A 4-year-old dog presents for a routine exam. Skin cytology reveals moderate numbers of Malassezia dermatitis yeast, but the dog has no itching, redness, or lesions. The coat and skin appear normal. What is the most appropriate interpretation?

The dog may normally carry higher numbers of yeast without clinical disease

A dog presents with intense pruritus, especially on the ears, elbows, and abdomen. Physical exam shows erythema, crusting, and hair loss. A skin scraping is performed but no mites are found. Despite this, Sarcoptic mange is still suspected.

What is the most appropriate next step?

Begin treatment for sarcoptic mange based on clinical suspicion

A 6-year-old dog presents with greasy skin, odor, erythema, and pruritus. Cytology shows large numbers of Malassezia yeast. The dog also has a history of chronic allergies. What is the most likely explanation for this condition?

The yeast overgrowth is secondary to an underlying condition such as allergies