Parasitic Skin Disease Flashcards
What is the most common cause of pruritis? Is this good?
Ectoparasites
- common
- easy to treat
- always investigate first
Why are ectoparasites important other than pruritic disease?
may be vectors of/contributors to other infectious diseases
Do parasites presence always indicate disease?
No
1. parasite always casues disease
2. some parasites sit on carriers or cause minimal disease BUT parasite may ellicit hypersensitivty
> reaction differs between individuals
3. commensal parasite rarely causes disease
Which parasites ALWAYS cause diseas?
Sarcoptes (mange mites -> scabies)
Which parasites are commensal and always present in the coat?
Demodex
Which species does demodex (arachnids) mainly affect?
Dogs (also cats and horses possible)
Which species does sarcoptes (arachnids) mainly affect?
Dogs only
Which species does cheyletiella (arachnids) mainly affect?
Dogs (also cats possible)
Which species does trombiculiasis (arachnids) mainly affect?
Dogs, cats and horses
Which species can get FAD?
Cats and dogs
Does trombiculiasis always need treatment?
No - only if bothering the dog
When is trombiculiasis season?
Strictly seasonal - autumn!
July -> sept/oct
> regional too
Is trombiluliasis a commensal?
No picked up from environment
Clinical signs of trombiculiasis
- larvae just visable
- may be asymptomatic or severely pruritic
Tx of trombiculiasis?
- none repellant, none licensed
- fipronil
What causes walking dandruff and scale?
Cheyletiella (blakei/yasurgi/parasitivorax)
How may cheyletiella mites be identified?
> hair plucks > coat brushing > tape - palps - eggs attached to hair shaft (nits)
Which animals are affected by cheyletiella?
Cats, dogs, rabbits
Why is cheyletiella a difficult problem?
- survive in environment and on fomites 6 weeks
- zoonotic (will bite people though not establish on them)
Clinical signs of cheyletiella
- walking dandruff
- pruritis may be v. mild or severe
- primarily dorsal trunk
- cats: miliary dermatitis
Tx of cheyletiella?
> suprisingly difficult (> 6 weeks) > none licensed - amitraz (dog) - fipronil (dog and cat) - selamectin (dog and cat) - moxidectin (dog and cat) - ivermectin (cat and rabbit) - selenium sulphide shampoo (dog and cat) > clean environment > treat all in contact dogs, cats, rabbits
What is demodecosis?
- inflammatory parasitic skin disease characterised by ^ no. demodex
Which animals most commonly affected by demodecosis?
- dog (d. canis, d. injai; short-bodied mites live in statum corneum rare)
- uncommon in cat (d. cati, d. gatoi)
- very rare in the horse
Clinical signs of demodecosis?
- prominant hair follicles and comedons
- potential alopecia
- demodex live on hair shaft head down in follicle (cigar shaped)
- not necessarily itchy (no self trauma) but can be
Potential manifestations of canine demidecosis?
> juvenile onset, localised (~4mo) - often recovers spontaneously - inherited from bitch while suckling - cosmetic problem only > juvenile onset, generalised (~4 mo) - inherited predisposition - does not recover spontaneously > adult onset (local or generalised) - true >2yo - suspect underlying immunosuppression eg. glucocorticoids, endocrinopathy, neoplasia (2* infection can -> deep pyoderma)
Tx of demodecosis
- min 12 weeks tx: tell client this!
- monitor by PE and repeat scrapes/plucks
- avoid steroids!!!
Which breeds are commonly affected by demidecosis?
- staffies
- great danes
Which species most commonly affected by sarcoptic mange mites?
- common in dogs
- rarer in cats (usually asociated with affected dog)
- notifiable in horses!!
Which pathogen causes scabies?
Sarcoptes Scaibie
How does sarcoptes behave on the skin?
Buries into epidermis -> crusted papules
how can sarcoptes be found/diagnosed?
With difficulty!!
- skin scrape to find mite, eggs or feaces, will rarely find tunnel (in stratum corneum) full of eggs, baby mites and feaces
- may not easily find it
- only few mites needed for intensely pruritic reaction
Where does FAD cause pruritis?
- Dorsal lumbosacral area
- can be ventral abdo too
> caudal body generally
What mechanisms of FAD hypersesntitivty are possible? What effect may this have on testing?
> multiple - IgE mast cell mediated - delayed cell mediated (basophil hypersense, TH1 macrophage, TH2 lymphocyte/eosinophil) > against various antigens - saliva - cuticle - excreted metabolites/enzymes/toxins - feaces
What is the main allergen associated with FAD?
Saliva
Do fleas usually cause irritation without FAD?
No (some scratching only due to them running around)
Age of onset of FAD?
3-5 years
Predispositions for FAD?
- breed
- atopic derrmatitis
Is FAD seasonal?
May be
- seasonal parasites picked up in summer
- flea infestations in home too!! so may be all year round
Diagnosis and Clinical signs of FAD?
- small crusted papules surrounding bites
- coat brushing: flea feaces
> wet paper towel test
> microscopic analysis
FAD generally diagnosed after disease - need to show no signs with no medications
- challenge test? No longer as spread blood diseases but worked well!
What 2 types of allergy testing is available for FAD?
> intradermal testing (whole body extract)
- immediate and delayed reactions
- low sensitivity, high specificity
- may have false - as diluted saliva
- but may be false + due to environmental challenge
FceR1a based flea saliva specific serology
- better sensitivity and medium specificity (50%)
but doesn’t really change tx and flea control
Management of FAD
- TRY to control or avoid fleas (difficult esp. if going into other peoples houses etc. and even if treated as flea will start feeding within minutes of attaching)
- If cannot be avoided: antipruritic/anti-inflammatory medication (GCs, antihistamines, EFA)
- allergen-specific immunotherapy (whole flea extract ineffective, salivary ag promising but not available!)
