Flea allergic dermatitis Flashcards
FAD
= flea allergy dermatitis
FBH
= flea bite hypersensitivity
Pruritic dermatosis
- pruritus associated with hypersensitivity to salivary proteins of flea
- Type 1 +/- Type IV
- leads to self trauma by pet
True or false: FAD is the most common skin dz of dogs and cats in the world
- True
Why are fleas bad?
- Fleas are contagious and zoonotic
- Vectors for tapeworm (Dipylidium caninum) and other diseases
Clinical signs of FAD in the dog
- Affected areas - especially caudal half of the body (tail base, thighs, inguinal area) & dorsum
- Scratching
- Biting skin
- Jumping up suddenly
- Excess licking/over grooming
- Alopecia
- Skin inflammation +/- skin infection
- Crusting
- Lichenification
Clinical signs of FAD in cat
Variable presentations including:
- Head & neck pruritus
- Miliary dermatitis
- Self-induced alopecia
- Eosinophilic granuloma complex lesions
(i.e. the feline cutaneous reaction patterns)
- rule out fleas early on when see any of these presentations
Diagnosis
- Demonstration of fleas/flea faeces
- Intradermal and serological testing
- Response to therapy
Demonstration of fleas/flea faeces
- Flea comb
- Vigorous coat brushing – examine debris on moistened paper -> red/brown tinge
- But: false negatives common, cats may remove all evidence of fleas from their coat, particularly if flea allergic
- Therefore failure to detect fleas, i.e. negative finding, is unreliable
Intradermal and serological testing
Both only test for hypersensitivity, not infestation -> rarely used
Intradermal test:
- Inject flea salivary allergen intradermally
- But up to 30% false +ve reactions, FAD may involve Type I (immediate) or Type IV (delayed) hypersensitivity. But tests often not read after 48 hours, so Type IV reaction missed -> false -ve
In vitro/serological test:
- Measures antigen-specific IgE (Type I reaction) but not delayed (Type IV) reaction
– Negative result of limited value
Response to therapy
- Best method of diagnosis
- Diagnosis is confirmed by response to thorough flea control trial
Flea control
- Flea life cycle usually 3-4 weeks but range 2 weeks - 6 months, depending on environmental conditions
- Most of life cycle in environment
- ‘Pupal window
nothing kills the pupa so need to kill emergent adults before they bite – environmental control essential, initially at least - May take 3 months+ before fleas fully eliminated
Available flea control measures
- Mechanical removal* (eg, flea combing, vacuum cleaning)
- Repellants
- Adulticides*
- Larvicides
- Ovicides
- Insect growth regulators*
– Juvenile hormone analogues
– Chitin synthase inhibitors
Action of drugs for flea control
- *Imadacloprid (POM-V and OTC): larvicidal/ovicidal + adulticide
- *Selamectin (POM-V only): larvicidal/ovicidal + adulticide
- Dinotefuran: adulticide
- Permethrin, flumethrin, tetramethrin: adulticide
- *Fipronil (OTC & POM-V): adulticide
- Pyriprole: adulticide
- Nitenpyram: adulticide
- *Isoxazolines (oral) (POM-V only): adulticide
- Pyriproxifen: IGR
- (S)-methoprene: IGR
- Lufenuron: IGR
When necessary treat with
Fast-acting adulticide – used as per datasheet
Which animals?
- Treat all susceptible in-contacts (dogs/cats/rabbits)
Which product?
- Products to optimise compliance
- Products to suit patient’s lifestyle – e.g. systemic treatments if swim or bathed regularly
- NB concern re environmental impact of non-systemic spot-ons (e.g. fipronil, imidacloprid)
- Beware toxicity to patient! e.g. Fipronil and rabbits, Cats and permethrins (except flumethrin), Isoxazolines if history of seizures
- Consider toxicity to owner – spot-ons?
