Flea allergic dermatitis

• How common is flea allergic dermatitis?

  Most common skin disease of dogs and cats in the world.

  Fleas are contagious and zoonotic! vectors for tapeworm (Dipylidium caninum) and other diseases.
• Flea allergic dermatitis - pruritic dermatosis

  Pruritus associated with hypersensitivity to salivary proteins of flea (type I +/or Type IV).

  Leads to self-trauma by the pet.
• Flea allergic dermatitis - infestation vs hypersensitivity

  Other pets may be infected but show no clinical signs.

  Client communication is important.

  If you are not hypersensitive then you will not itch, just because other animals in the household are bot itching does not mean its not fleas.
• What are the clinical signs of flea allergic dermatitis in dogs?

  Affected areas - especially:

  • Caudal half of the body (tail base, inguinal area).
  • Dorsum.

  Scratching

  biting skin

  Jumping up suddenly

  Excess licking/over grooming.

  Alopecia

  Skin inflammation +/- skin infection crusting

  Lichenification (top right)
• What are the clinical signs of flea allergic dermatitis in cats?

  Variable presentations including:

  • Head and neck pruritus
  • Miliary dermatitis
  • Self-induced alopecia - due to over grooming
  • Eosinophillic granuloma complex lesions (eosinophillic plaques, eosinophllic granulomas, indolent ulcers).
• Demonstration of fleas/flea faeces

  Flea comb (are big so quite easy to see).

  Vigorous coat brushing - examine debris on moistened paper -> red/brown tinge.

  But

  • False negatives common, particularly in cats.
  • Cats may remove all evidence of fleas from their coat, particularly if flea allergic dermatitis.

  Therefore failure to detect fleas i.e. negative finding is unreliable

  
• Intradermal test

  A test for hypersensitivity, not infestation -> rarely used.

  Inject flea salivary allergen intradermal ly (usually combined tests for other allergens)

  BUT

  • Up to 30% false +ve reactions
  • FAD may involve Type I (immediate) or Type IV (delayed) hypersensitivity. But tests often nor read after 48 hours, so type IV reaction missed.
• What is the pupil window?

  Nothing kills the pupa so need to kill the emergent adults before they bite - environmental control is essential, initially at least.

  May take 3 months + before fleas fully eliminated - ensure your client is aware.
• What is the flea lifecycle?

  Flea lifecycle usually 3-4 weeks but range from 2 weeks to 6 months, depending on environmental conditions.

  Most of the life cycle in environment.
• What are the available flea control measures?

  Mechanical removal (e.g. flea combing, vacuum cleaning).

  Repellants

  Adulticides - both on the pet and in the evironment.

  Larvicides

  Ovicides

  Insect growth regulators

  • Juvenile hormone analogues
  • Chitin synthase inhibitors
• Which animals do you use a fast acting adulticide for?

  Treat all susceptible in contact animals (dogs/cats/rabbits).
• Is environmental treatment necessary for fleas?

  Essential with spot-on adulticides, even if product claims environmental activity against eggs/larvae, due to:

  • More complete coverage of environment.
  • Need to kill emergent adult before feeding.

  NB isoxazilines may be effective alone in uncomplicated cases of flea infestation, due to very rapid speed of kill. But still best to treat environment if possible.
• Your pharmacy stocks 4 products that treat Ectoparasites Infections: advantage (imidacloprid), Advantix, (imidacloprid + permethrin), Frontline Combo (fipronil + S-methoprene), Simparica (sarolaner). Which would you prescribe to an owner with a dog that has fleas but swims in the river daily?

  1 Advantage (imidacloprid)

  2 Advantix (imidacloprid + permethrin)

  3 Frontline Combo (fipronil + S-methoprene)

  4 Simparica (sarolaner)

  4