Pruritus and Allergy 1 Flashcards
The “itch-scratch cycle”.
Mechanical effect of scratching temporarily abolishes sensation of pruritus.
> Pruritus recurs more intense due to damaging effects of self-trauma.
What can trigger signs of itch?
Allergy - food allergy, seasonal grasses and plantation, dust, mites, flea etc.
Ectoparasites - fleas, sarcoptes etc., flies, mites.
Contact dermatitis.
Yeast.
Wound healing.
How do we assess itch?
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.
Atopic dermatitis.
In dogs.
Called feline atopic skin syndrome in cats.
Environmental allergens MAY be component.
Other allergic skin diseases.
Food allergy.
Flea / insect bite hypersensitivity.
- Culicoides in horses.
What is canine atopic dermatitis?
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.
- CAD commonly affected breeds?
- CAD common age of onset?
- CAD major sign?
- Primary lesions of atopic dermatitis.
- Labradors, labradoodle, golden retriever, staff, GSD, Westie, cocker, FBD.
- 1-3 yrs. - rare before 6m or after 6y.
- Pruritus. - Face – muzzle, eyes, ears.
- Feet.
- Groin, axilla. - Erythema, papules.
Other clinical signs of CAD.
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.
CAD published diagnostic criteria.
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).
CAD tx.
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.
Allergen Specific Immunotherapy (ASIT).
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.
- Advantages of ASIT.
- Disadvantages of ASIT.
- Adverse reactions uncommon.
- pruritus most common.
- others = vomiting, urticaria, angioedema, anaphylaxis. - Can take up to 12m for full benefit and effective in ~60% dogs.
- often need concurrent therapies.
Cutaneous adverse food reaction.
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.
Clinical signs of cutaneous adverse food reaction.
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.
Common triggers of food allergy in dogs and cats.
Dogs: beef, dairy, chicken, wheat.
Cats: beef, fish, chicken.
Diagnosis of cutaneous adverse food reaction.
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.
Main signs of equine allergy.
Pruritus and/or urticaria.
- When is insect bite hypersensitivity (sweet itch) most prevalent in horses?
- What is it caused by?
- What areas of the horse’s body are generally affected?
- Signs of insect bite hypersensitivity?
- Age of onset of insect bite hypersensitivity?
- April to October.
- Culicoides.
- Mane, tail, lateral neck, tail to croup, ventral midline.
- Pruritus - rubbing, biting, stamping, agitation.
Alopecia, crusting, erosions, lichenification, hyperpigmentation. - > 2yo.
Other causes of pruritus in horses.
Atopic disease.
Other insect bite hypersensitivities.
Mites - Chorioptes – distal limbs.
Pediculosis.
Oxyuriasis - perineum – pinworm?.
Onchocerciasis - parasite.
Other - e.g. post clipping.
Contact reactions.
Therapy and management for Culicoides hypersensitivity?
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.
What other species can be affected by culicoides hypersensitivity?
- % affected.
- signs?
- Time of highest severity?
- parts of body affected?
Sheep.
- 40% ewes may be affected.
- foot stamping, dropping to ground, sternal recumbency.
- September to October.
- Non-wool areas.
- Site of infection in surface pyoderma?
- Classic manifestations of pyoderma?
- Clinical signs of surface pyoderma.
- Interfollicular epidermal layer of the skin.
- Pyotraumatic dermatitis (hot spots).
Intertrigo (skin fold dermatitis). - Erythema, erosion, serosanguinous to purulent exudate.
Uncomfortable - pruritus and pain.
Matted fur.
Diagnostics and treatment of pyotraumatic dermatitis.
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.
- Primary superficial pyoderma site of infection.
- Clinical signs of superficial pyoderma?
- Intraepidermal.
- 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.
