The pruritic animal Flashcards
What are the signs of pruritus?
Scratching, chewing
Licking feet (dogs)
Stamping (horses)
Overgrooming (=‘self-induced alopecia’) (cats)
barbering (small furries)
What is the difference between primary and secondary pruritus?
Primary pruritus = itching that has no identifiable underlying cause
Secondary pruritus = itching that is a result of another medical condition e.g., skin disease
What are the causes of pruritus?
Hypersensitivities
Parasites
Microbial infections
Others e.g., contact irritant reactions, auto-immunity, neoplasia
Give examples of hypersensitivities causing pruritus
Environmental and food induced atopic dermatitis
Parasite-induced hypersensitivities:
- esp large animals,
- fleas in dogs and cats
- scabies in dogs
- Demodex gatoi in cats
Microbial hypersensitivity (esp Malassezia)
Contact allergy and allergic drug reactions
Give examples of parasitic causes of pruritus
Endoparasites e.g. hookworm in dogs and Onchocerca and Oxyuris in horses
Insects: fleas, flies and lice
Mites and ticks
Give examples of microbial infections the cause pruritus
Bacterial pyoderma, Malassezia and occasionally dermatophytosis
Give an example of an auto-immune disease that causes pruritus
pemphigus foliaceus
What is pemphigus foliaceus
a rare autoimmune skin disease that causes painful blisters and sores
Give examples of neoplasia that causes pruritus
mast cell tumour and epitheliotropic lymphoma
What tests can be done to rule out parasitic causes of pruritus?
Coat brushing/combing
Trichogram
Skin scrape
Acetate tape strips
What tests can be done to rule out microbial infections as a cause of pruritus?
Cytology for bacterial/malassezia infection
Dermatophyte tests if indicated
Describe what the outcome of treating a pruritic animal for a microbial infection can tell us about the underlying problem?
If pruritus resolves fully: consider non-pruritic underlying causes, e.g. immunosuppressive disease
If pruritus remains**: consider pruritic underlying causes, esp allergies
If parasites, microbial infection and fly-bite associated pruritus have been ruled out, what is the next step?
Perform an elimination diet trial to test for food-induced pruritus
If food is unhelpful in controlling the disease. A clinical diagnosis of environmental atopic dermatitis is made by exclusion
Describe how an elimination food trial is performed to test for food-induced pruritus
Novel protein or hydrolysed protein used in cats and dogs for 6-8 weeks
Limited forage diets are used in horses (may not suit work/energy needs) and difficult to find best foods in horses e.g. alfalfa, oat or timothy hay. Food allergy is rare in this species
Challenge with the old foods to validate the results
If a clinical diagnosis of environmental atopic dermatitis is made by exclusion, what are the next steps?
Treat the pruritus
Modify animals response to allergens using allergen-specific immunotherapy (ASIT)
How is pruritis caused by environmental atopic dermatitis treated?
Anti-pruritic and/or anti-inflammatory drugs
Prophylactic treatments to control secondary infections (esp. dogs)
Describe how an animals response to allergens can be modified using allergen-specific immunotherapy (ASIT)
Test for allergen-specific IgE through blood or ELISA testing
If appropriate results use immunotherapy.
