The approach to pruritus Flashcards
What is pruritus?
Unpleasant sensation that elicits the desire or reflex to scratch
How does pruritus manifest in dogs?
*Scratching
*Rubbing (along furniture)
*Chewing
*Licking: often not perceived as pruritus by owners
*Rolling
*Temperament changes
How does pruritus manifest in cats?
*Scratching
*Chewing
*Licking
*May be secretive and not noticed by owners
What are common differentials of pruritus?
*Hypersensitivity reactions (allergic skin disease + parasite hypersensitivity)
*Microbial infections
Less common differentials =
-Epitheliotrophic lymphoma
-Pemphigus foliaceus
-demodicosis
-dermatophytosis
What are the different parasitic infestations?
*Sarcoptic mange
*Cheyletiellosis
*Pediculosis (lice)
*Trombiculiasis (Harvest mites)
*Flea infestation
*Notoedric mange
*Hookworm dermatitis
How would you differentiate the different diseases?
*History
*Dermatological examination
*Diagnostic tests
Where does atopic dermtaitis affect?
Muzzle
Eyes
Ears
Paws
Ventral aspect
Where does sarcoptic mange affect?
Ear margins
Ventral aspect
Where does cheyletiellosis + pediculosis affect?
Dorsum
Where does pemphigus foliaceus affect?
Nose
Eyes
Ears
Whole body
Where does Epitheliotropic lymphoma affect?
Muzzle
Whole body
Why are cytology tests important?
-very important to rule out secondary microbial overgrowth or infection (indicated in most cases)
*Direct/indirect impression smear
*Acetate tape impression (stained)
How would you identify parasitic disease?
*Coat brushing and wet paper test
*Acetate tape impression (unstained)
*Skin scraping
*Hair plucks and trichography
When would you use skin biopsy?
to rule out less common differentials for pruritus; Pemphigus foliaceus, Epitheliotropic Lymphoma
What cats are more at risk of fleas?
*Outdoor cats
*Multi-cat household
What is flea allergy commonly seen with in dogs?
Canine Atopic Dermatitis
What are the primary and secondary lesions caused by fleas?
Primary lesions
*Pruritus
*Papules
*Erythema
Secondary lesions
*Crusted excoriations
*Alopecia
*+/- bacterial pyoderma
signs
What is the typical distribution of fleas?
Caudodorsum (+ventral abdomen in dogs)
What diagnostic tests can be taken to identify fleas?
*Direct observation
*Wet paper test
*Coat brushings: direct microscopy may reveal coiled faeces
*Serology/intradermal allergy testing: limited usefulness
*Treatment trial
What is the most common flea in the UK?
Ctenocephalides felis
How are fleas transmitted?
*Direct zoonosis
*Bartonella henselae
*Dipylidium caninum
What and where are the primary + secondary lesions of sarcoptic mange?
Primary lesions
*Pruritus - severe
*Papules
*Erythema
Secondary lesions
*Excoriation
*Alopecia
*Crusts
*Pyoderma signs
Distribution =
*Pinnal margins, elbows, hocks
*Becomes more generalised with time
What are diagnostic tests for sarcoptic mange?
*Pinnal-pedal reflex: often present but unreliable
*Superficial skin scrapes: high specificity (100%) & low sensitivity (50%)
*IgG serology: variable sensitivity and susceptibility, cross reaction with
house-dust mites!
*Treatment trial: often chosen above others as most reliable
What is the main sarcoptes found in dogs?
Sarcoptes scabei var canis
What is the feline form of sarcoptic mange?
Notoedres cati
Where do female sarcoptes lay their eggs?
Tunnel into stratum corneum
What is a common treatment for sarcoptic mange?
*Common topical and oral treatments are effective
*Anti-pruritic therapy often needed to control severe pruritus
What is the distribution of harvest mites (Trombicula)?
Henry’s pocket - pinnae
Ventrum - nipples
Between footpads
What are common treatments for harvest mites?
*Larval forms temporarily parasitise animals to feed then return to environment
*Avoidance is best policy as killing following feeding fails to address irritation
*Fipronil spray for the legs (not licenced)
*Isoxazolines?
*Prednisolone as before to control pruritus and inflammation
What is the ear mite?
Otodectes Cynotis
What is the distribution of the ear mite?
Usually in the ear
But can leave canal and affect head/tail
What is the treatment of otodectes?
Spot-on /oral therapies
+Topical
What diagnostic tests can be done for otodectes?
*Direct observation of mites using otoscope (photophobic)
*Unstained ear wax examination (mount in liquid paraffin)
What are the most common species of cheyletiellosis?
Cheyletiella yasguri
C. blakei
C. parasitivorax
What is the distribution of cheyletiella?
Dorsal trunk
Rarely head
What diagnostic tests can be done for cheyletiella?
*Coat brushings: walking dandruff
*Superficial skin scraping from scaly areas
*Faecal flotation may be used in cats where excessive grooming present
What is the treatment for cheyletiella?
*No licenced therapy
*Fipronil spray or spot-on selamectin
effective
What are common chewing lice?
Felicola subrostratus
Trichodectes canis
What is a common sucking louse?
Linognathus setosus
What is the normal distribution of lice? (Pediculosis)
Dorsum
How can you diagnose lice?
Coat brushings - lice seen under microscope + eggs
What animals are affected by epitheliotropic lymphoma?
*Disease of older animals (very rarely seen in
young animals)
*Lesions before pruritus
What is the distribution of epitheliotropic lymphoma?
Anywhere on body
Often mucocutaneous junction
How is Epitheliotropic lymphoma diagnosed?
*Skin biopsy & histopathology
What is the primary lesion of demodex?
Alopecia
What are clinical features of demodex gatoi?
*Contagious (unlike all other forms of demodicosis)
*Pruritus often seen (but not in all animals)
*Self-induced alopecia ± excoriation (anywhere)
How is demodex diagnosed?
*Surface dwelling mites so skin scrapes have very poor sensitivity
*Tape impression more useful
*Faecal floatation has been used successfully
What is the treatment of demodex gatoi?
*Selamectin/sarolaner spot-on combo (Stronghold Plus)
*Fluralaner (Bravecto)
*Lime sulphur dip (weekly until 2 negative samples)
*Treat in contact cats and investigate potential immunosuppressive disease
What species are predisposed to demodex injai?
Terriers - Border, Welsh, Norfolk, WHWT
