Pruritus

• What is the clinical presentation of pruritus?

  Species differences:

  • Scratching, chewing
  • Licking feet (dogs)
  • Feather-plucking (birds).
  • Overgrooming (-self induced alopecia) (cats).
  • Also -> tufts of hair in house, vomiting fur balls, hair in faeces.
  • One of the four feline reaction patterns.
• What are the 4 feline reaction patterns?

  Self-induced alopecia (SIA)

  Face, head and neck pruritus (FHN).

  Miliary dermatitis (MD)

  Eosinophilic granuloma complex (EGC)
• How does self-induced alopecia present?

  Bilaterally symmetrical alopecia in areas that the cat can reach with their tongue.

  • Hair often stubbly
  • Damaged distal tips on trichograms.
  • Often not recognised by the owner (owners think this is haor falling out).
  • +/- tufts of hair in the house, vomiting fur balls, hair in the faeces.
• What are the differential diagnoses for self-induced alopecia?

  Spontaneous loss - may also be symmetrical:

  • Much less common.
  • Hair often easily epilated.
  • Spontaneous hair loss in the cat is very rare
• How does miliary dermatitis (MD) present?

  Papulocrustous lesions, especially on dorsum. Papulo-crustous lesions > often easier to feel than to see, unless there is co-existing alopecia.

  Usually found on the back of the cat but can occur anywhere.

  
• How does face, head and neck pruritus present?

  Tends to occur on the head and neck mostly, will usually be caused by fleas (generally ectoparasites).

  
• How does eosinophilic granuloma complex present?

  Well demarcated, solid, raised, yellow to pink plaques/nodules.

  +/- eroded or ulcerated surface.

  +/- crust.

  Any site but especially caudal thighs (linear), oral cavity.

  Several manifestations.

  
• How do eosinophillic plaques present?

  Raised, flat-topped erythematous plaques.

  Usually ulcerated/eroded and pruritic.

  Usually ventral abdomen/caudal thigh, can appear anywhere.

  Secondary to bacterial infection is common.

  
• How do Indolent ulcers present?

  Erosive/ulcerated lesion on mucocutaneous junction of upper lips.

  Unilateral/bilateral.

  Rarely painful or pruritic.

  Possibly associated with pyoderma and FB reaction to intradermal keratin - caused by licking?

  
• What are the differentials for face, head and neck pruritus?

  D cati

  Otodectes

  Insect bite

  Dermatophytosis

  • Malassezia dermatitis
  • Respiraoty viruses
  • Bacteral pyoderma
  • Pemphigus foliaceus
  • Skin neoplasia (MCT, SCC, cut lymphoma)
  • Drug reactions
  • Idiopathic facial dermatitis (Persians)
  • FOPS (especially Burmese)
• What are the differentials for self-induced alopecia?

  D gatoi

  Dermatophytosis

  • Malassezia dermatitis
  • Feline paraneoplastic alopecia
  • Psychogenic alopecia
  • FLUTD/pain/neuralgia
• What are the differentials for miliary dermatitis?

  Dermatophytosis

  Pyoderma

  Cheyletiella

  Neotrombicula

  Otodectes

  • Pemphigus foliaceus
• What are the differentials for eosinophilic granuloma complex?

  Cow pox

  Mycobacterial infections

  Neoplasia (cut lymphoma, MCT, SCC)

  • Deep bacterial infections
  • Fungal disease
  • Respiratory viruses
  • Insect bite HS
• What are the 3 main groups of causes for pruritus?

  Hypersensitivities (allergies).

  Parasites

  Infection
• What hypersensitivities cause pruritus?

  Environmental atopic dermatitis/ feline atopic skin syndrome

  Food-induced atopic dermatitis/ feline food allergy.

  Parasite-induced hypersensitivities - especially in dogs, cats.

  • Microbial hypersensitivity
  • Contact allergy
  • Drug reaction
• What microbial infections cause pruritus?

  Bacterial pyoderma

  Malassezia dermatitis

  • Dermatophytosis (variably pruritic)
• What parasites cause pruritus?

  Endoparasites (e.g. hook worm in dogs).

  Insects

  Fleas.

  Arachnids

  • Flies
  • Lice
  • Mites
  • Surface
  • Burrowing
  • Demodex (variably pruritic)
• What species does sarcoptic mange affect?

  Dog
• What species does Pyoderma/ Malassezia dermatitis affect?

  More common in the dog than the cat.
• What is the age of onset of Demodicosis?

  Young (<1 year old) and old - immunocompromise.
• What is the age of onset of Ectoparasites?

  Any age
• What is the age of onset of environmental atopic dermatitis?

  6 months old - 3 years.
• What is the age of onset of food induced atopic dermatitis?

  Any age but 30-50% less than a year.
• What is the age of onset of endocrinopathoes?

  Middle-aged to older.
• What is the age of onset of neoplasia?

  Older
• What breeds are affected by demodicosis?

  Staffordshire bull terrier.

  Shar Pei
• What breeds are affected by canine atopic dermatitis?

  Terriers

  Labradors

  French bulldogs.
• What are the differential diagnoses for Pustules?

  Usually:

  • Superficial pyoderma (staphylococcal folliculitis)

  Uncommonly:

  • Demodicosis
  • Dermatophytosis
  • Pemphigus foliaceus

  Rarely:

  • Other sterile pustular disease

  
• What are the differential diagnoses of epidermal collarettes, crusts?

  Usually:

  • Superficial pyoderma

  Occasionally:

  • Pemphigus Foliaceus
• How do you eliminate/confirm ectoparasites?

  Coat brushing/combing - acetate tape strips

  • Eliminate parasites with specific tests, be careful of the sensitivity of the tests, just because you can not find the parasites does not mean that they are not there.
• How do you eliminate/confirm microbial dysbiosis/infection?

  Cytology.

  • Bacterial/ Malassezia dysbiosis/infection - secondary problems but often contributory to clinical signs, so need to keep looking for primary cause.
  • Under take Dermatophyte tests if indicated (especially cats).
• What does the pruritus fully resolving after the elimination of ectoparasites and infection mean?

  Implies non-pruritic underlying cause:

  • E.g. immunosuppressive disease including endocrinopathy (investigate as appropriate).
  • Or ectoparasites, if not previously on good ectoparasite control (continue the ectoparasite control).
• What does pruritus remaining after elimination of ectoparasites and infection mean?

  Implies other pruritus underlying disease - usually atopic dermatitis (environmental or food-induced).
• How do you distinguish between environmental and food-induced atopic dermatitis?

  Exclusion diet trial.
• Exclusion diet trials

  Exclusion diets need to be fed for 8 weeks minimun but the use of prednisolone or oclacitinib (apoquel) can shorten time to diagnosis.

  Treat for initialy 2-3 weeks, then stop to observe the response:

  • Pruritus recurs -> resume prednisolone/oclacitinib -> repeat cycles of treatment/observation to end of the trial.
  • No puritus for 2 weeks -> rechallenge with old diet.
• How do you diagnose feline atopic dermatitis in cats?

  Is a clinical diagnosis only, diagnosis of exclusion.

  Symptomatic control
• You suspect a 2yo french bulldog with generalised pruritus to be suffering from canine atopic dermatitis. You have found no evidence of microbes or ectoparasites on investigation. What is your next step?

  1 Treat this dog, bit not in-contacts, with imidacloprid, and use an environmental flea spray.

  2 Treat this dog and in-contacts with an isoxazoline, and use an environmental flea spray.

  3 Undertake an exclusion diet trial.

  4 Submit samples for IgE serology for environmental allergens.

  2