Pruritus and Allergy 1

Question 1

The “itch-scratch cycle”.

Answer 1

Mechanical effect of scratching temporarily abolishes sensation of pruritus.
> Pruritus recurs more intense due to damaging effects of self-trauma.

Question 2

What can trigger signs of itch?

Answer 2

Allergy - food allergy, seasonal grasses and plantation, dust, mites, flea etc.
Ectoparasites - fleas, sarcoptes etc., flies, mites.
Contact dermatitis.
Yeast.
Wound healing.

Question 3

How do we assess itch?

Answer 3

Pruritus Visual Analog Scale.
Numerical scales.
With description.
Behaviour and frequency of behaviour.
Licking, rolling, rubbing, pulling hair, nibbling, scratching.
Foot licking / face rubbing may be interpreted as “grooming”.
Head shaking can be manifestation of ear disease or more generalised pruritus.

Question 4

Atopic dermatitis.

Answer 4

In dogs.
Called feline atopic skin syndrome in cats.
Environmental allergens MAY be component.

Question 5

Other allergic skin diseases.

Answer 5

Food allergy.
Flea / insect bite hypersensitivity.
- Culicoides in horses.

Question 6

What is canine atopic dermatitis?

Answer 6

A genetically inherited clinical syndrome that encompasses a diversity of mechanisms and can have a variety of triggers
Multifactorial and complex inflammatory syndrome.
May or may not be associated with a demonstrable allergic response.
Typically associated with antigen-specific IgE antibodies to environmental allergens.
The skin is the main avenue of allergen exposure.

Question 7

1. CAD commonly affected breeds?
2. CAD common age of onset?
3. CAD major sign?
4. Primary lesions of atopic dermatitis.

Answer 7

1. Labradors, labradoodle, golden retriever, staff, GSD, Westie, cocker, FBD.
2. 1-3 yrs. - rare before 6m or after 6y.
3. Pruritus. - Face – muzzle, eyes, ears.
   - Feet.
   - Groin, axilla.
4. Erythema, papules.

Question 8

Other clinical signs of CAD.

Answer 8

Associated with self-trauma and secondary bacterial and Malassezia infections.
- Alopecia, erythema, excoriation, lichenification, hyperpigmentation.
Signs not specific so rule out other conditions that cause pruritus.

Question 9

CAD published diagnostic criteria.

Answer 9

Onset of signs under 3y old.
Dogs that live mostly indoors.
Pruritus is glucocorticoid responsive.
Pruritus is major or only sign.
Front feet and concave aspects of pinnae affected.
Ear margins not affected (Think scabies).
Dorso-lumbar area not affected (more consistent with flea allergy).

Question 10

CAD tx.

Answer 10

Glucocorticoids.
Ciclosporin (Atopica).
Oclacitinib (Apoquel).
Lokivetmab (Cytopoint).
Antihistamines.
Topical - antimicrobial, soothing, glucocorticoids, steroids (Cortavance, Dermanolon), shampoos (Malaseb (antimicrobial), Allermyl (soothing)), essential fatty acids, some over-the-counter w/ limited evidence of efficacy.
Essential fatty acids - supplement and diets.
Over-the-counter – limited evidence of efficacy.

Question 11

Allergen Specific Immunotherapy (ASIT).

Answer 11

Formulated using intradermal allergen testing or allergen serology:
- Ideally following 12m disease - seasonality.
- NOT diagnostic tests.
Protocol:
- SC.
- Sub-lingual (twice daily).
- Intra-lymphatic routes.
- Rush – induction course shortened.
– May reduce time to maximum efficacy.

Question 12

1. Advantages of ASIT.

Answer 12

1. Adverse reactions uncommon.
   - pruritus most common.
   - others = vomiting, urticaria, angioedema, anaphylaxis.
2. Can take up to 12m for full benefit and effective in ~60% dogs.
   - often need concurrent therapies.

Question 13

Cutaneous adverse food reaction.

Answer 13

Food allergy.
Relevance of food-specific IgE and IgG - misunderstood.
DO NOT use serology tests to make diagnosis or to suggest the constituents of a diet trial.

Question 14

Clinical signs of cutaneous adverse food reaction.

Answer 14

Mimic atopic dermatitis.
Pruritus most important sign.
Can be generalised or localised.
May start at any age.
Recurrent infections and otitis externa common manifestations of food allergy.
- As well as atopic dermatitis.

Question 15

Common triggers of food allergy in dogs and cats.

Answer 15

Dogs: beef, dairy, chicken, wheat.
Cats: beef, fish, chicken.

Question 16

Diagnosis of cutaneous adverse food reaction.

Answer 16

Elimination of signs following a restricted protein and carbohydrate diet.
- home cooked – novel.
– good dietary history.
- commercial (dry) selected protein.
– risk of cross contamination.
Hydrolysed diets.
- e.g. Purina HA, Royal Canin Anallergenic.
- Degree of hydrolysis important – not all diets are the same.
Duration of restricted diet is 6-12 weeks.
- Optimum may be 8w in dogs.
Confirmation of the diagnosis.
- rechallenge / provocation with the original diet.
– in its entirety.
– is food the problem?
– clinical signs typically recur within 7 days although can take up to 14 days.

Question 17

Main signs of equine allergy.

Answer 17

Pruritus and/or urticaria.

Question 18

1. When is insect bite hypersensitivity (sweet itch) most prevalent in horses?
2. What is it caused by?
3. What areas of the horse’s body are generally affected?
4. Signs of insect bite hypersensitivity?
5. Age of onset of insect bite hypersensitivity?

Answer 18

1. April to October.
2. Culicoides.
3. Mane, tail, lateral neck, tail to croup, ventral midline.
4. Pruritus - rubbing, biting, stamping, agitation.
   Alopecia, crusting, erosions, lichenification, hyperpigmentation.
5. > 2yo.

Question 19

Other causes of pruritus in horses.

Answer 19

Atopic disease.
Other insect bite hypersensitivities.
Mites - Chorioptes – distal limbs.
Pediculosis.
Oxyuriasis - perineum – pinworm?.
Onchocerciasis - parasite.
Other - e.g. post clipping.
Contact reactions.

Question 20

Therapy and management for Culicoides hypersensitivity?

Answer 20

Avoid.
- manage grazing and housing.
- stable at higher risk periods e.g. dusk and dawn.
Protective fly wear e.g. mask, rug.
Application of licensed permethrin or cypermethrin based emulsion.
Anti-inflammatory therapies:
- Antihistamines and glucocorticoids.
Allergen specific immunotherapy does not appear effective.

Question 21

What other species can be affected by culicoides hypersensitivity?
- % affected.
- signs?
- Time of highest severity?
- parts of body affected?

Answer 21

Sheep.
- 40% ewes may be affected.
- foot stamping, dropping to ground, sternal recumbency.
- September to October.
- Non-wool areas.

Question 22

1. Site of infection in surface pyoderma?
2. Classic manifestations of pyoderma?
3. Clinical signs of surface pyoderma.

Answer 22

1. Interfollicular epidermal layer of the skin.
2. Pyotraumatic dermatitis (hot spots).
   Intertrigo (skin fold dermatitis).
3. Erythema, erosion, serosanguinous to purulent exudate.
   Uncomfortable - pruritus and pain.
   Matted fur.

Question 23

Diagnostics and treatment of pyotraumatic dermatitis.

Answer 23

Cytology of exudate under crust if present.
Clip and clean - may need sedation.
Find the underlying cause e.g. otitis externa, fleas.
Treat topically w/ antimicrobial therapy and oral (+topical) steroids.

Question 24

1. Primary superficial pyoderma site of infection.
2. Clinical signs of superficial pyoderma?

Answer 24

1. Intraepidermal.
2. Pustules - easily disrupted by grooming, scratching or bathing.
   Primary lesions may be transient and secondary lesions may predominate - crust, erosion.
   Peripheral spread produces an annular lesion with a peeling epidermal collarette.
   Lesions and pruritus are antibiotic responsive.
   Disease recurrence if underlying disease not identified and managed.
   e.g. ectoparasites, allergy, endocrinopathies - older.

Question 25

1. Deep pyoderma signs.
2. Diagnostics.

Answer 25

1. Swelling, draining tracts, crusting, ulcerations, often painful.
2. Cytology and culture of draining fluid may not be representative.
   Biopsy for deep material.

Question 26

Pyoderma therapy.

Answer 26

Topical.
- removes crust, scale, exudate.
- reduces number of bacteria.
- promotes drainage of deeper lesions.
- can reduce pain and pruritus.
- usually 2-3 times a week.
- often chlorhexidine based.
- 10 min contact time for shampoos – clip the coat?

Question 27

Pyoderma - culture and susceptibility.

Answer 27

Culture from intact pustule.
- esp. in recurrent cases.
- essential if ABX resistance suspected.
Role of meticillin resistant Staphylococcus pseudintermedius (MRSP).
May be related to coagulase negative Staphylococci - S. schleiferi.

Question 28

Antibacterial agents for pyoderma.

Answer 28

*only if really needed!
Clindamycin - narrow spectrum, bacteriostatic, 5.5-11mg/kg.
Trimethoprim / sulphonamides - broad, bactericidal, 15-30mg/kg.
Clavulanic acid and amoxicillin - broad, bactericidal, 12.5-20mg/kg.
Cefalexin - broad, bactericidal, 15-30mg/kg.

Question 29

1. Pyoderma response to therapy.
2. Important action to take before proceeding to investigations for allergy or endocrinopathies?

Answer 29

1. Superficial - 3-4 week response.
   Pruritus associated with infections may improve completely. - immune response to staphylococci antigens?
2. Treat bacterial infections / microbial overgrowth before committing to investigations for allergy or endocrinopathy.

Question 30

1. Classic equine microbial infection.
   - clinical signs?
   - differentials?

Answer 30

1. Dermatophilosis - Dermatophilus congololensis.
   - Distribution of matted hair, crusts, erosions, fissuring, pain and lameness.
   Zoonotic!
   - Dermatophytosis, bacterial folliculitis (staph).
   - Photosensitisation (white socks and face).

Question 31

Dermatophilosis diagnosis.

Answer 31

smears from underside of crusts.
dermatophilosis.
- if only dry crust, need to soften with saline maceration.
Microscopy shows branching gram+ filamentous bacteria w/ internal compartments w/ “tram-track” appearance.
Culture.

Question 32

Dermatophilosis therapy.

Answer 32

Remove horse from exposure to predisposing factors - excessive moisture, biting insects, abrasive pasture, excessive brushing.
Clip and clean affected area w/ topical antibacterial agents e.g. chlorhexidine.
3-5d penicillin / streptomycin.

Question 33

What dermatological issues can large animals get, reasons?

Answer 33

Staphylococcal infections, dermatophilosis, grazing rough pasture and damaging the skin on the face, introducing bacteria.

Question 34

Malassezia…
1. Type of pathogen.
2. site of residence on the body?
3. Preferred environment of malassezia?

Answer 34

1. Opportunistic yeast pathogen.
2. External ear canal, chin, perioral and interdigital areas.
3. Oily and greasy areas.

Question 35

1. Predisposing factors to malassezia infections.
2. Clinical signs.

Answer 35

1. Alterations in skin microclimate - e.g. sebum production, moisture, otitis externa.
   Allergic and bacterial skin disease.
2. Generalised with ventral distribution or localised to feet, face, skin folds or perianal region.
   Pruritus common and often severe.
   Erythema, scale, hyperpigmentation. greasiness, malodour.

Question 36

Diagnosis of malassezia overgrowth.

Answer 36

Impression smears w/ dry swab or direct slide contact.
Acetate tape strip preparations.
Culture? - not recommended as can be done more cheaply.
Serology not recommended as have yeast naturally anyway.

Question 37

Malassezia infection therapy.

Answer 37

Topical w/ twice weekly bathing w/ shampoo products:
- miconazole - Malaseb.
- chlorhexidine - Malaseb.
- keratolytic effects.
- Selenium sulphide (Human - Head and Shoulders).
Systemic therapy:
- itraconazole – 5mg/kg/day.