Ectoparasitic causes of skin disease Flashcards
Why are ectoparasites clinically important?
Directly impacts welfare of host - pruritis, cutaneous myiasis
Predisposition to other diseases e.g., secondary bacterial skin infections, anaemia
Vectors of disease
Clinical signs mimic other disease
Act as pointers to other diseases e.g., immunodeficiency
Give examples of zoonotically important ectoparasites
fleas, Sarcoptes, Cheyletiella
Give examples of ectoparasites commonly found on the skin surface and the effect they cause
Fleas, live, surface mites
usually cause pruritus => alopecia +/- erosions, crust, scale, secondary bacterial infection, chronic changes
Describe the lesion distribution on dogs caused by fleas
caudal/dorsal part of body especially
Describe the lesion distribution on cats caused by fleas
4 cutaneous reaction patterns of cats:
- Head and neck pruritus
- Symmetrical alopecia
- Eosinophilic granuloma complex (EGC)
- Miliary dermatitis
Describe the lesion distribution on rabbits caused by fleas
Ctenocephalides felis/canis (dorsum/rump)
Spilopsyllis cuniculi (pinnae)
Give examples of cattle surface mites and where they cause lesions
Chorioptes bovis (common) - tailhead, lower legs, scrotum, udder
Psoroptes
Give examples of sheep surface mites and where they cause lesions
Psoroptes ovis - sheep scab
Chorioptes bovis - scrotal mange
Give examples of equine surface mites and where they cause lesions
Chorioptes equi (common) – leg/tail mange, esp horses with ‘feathers’
Psoroptes spp – body + ear mange
Neotrombicula sp (harvest mite) – head/legs – late summer/autumn
Give examples of dog/cat surface mites and where they cause lesions
Otodectes (ear mite) – otitis – dark dry otic exudate
Cheyletiella (fur mite) – truncal scale - zoonotic!
Neotrombicula (harvest mite) – esp head/limbs, late summer/autumn
Give examples of rabbit surface mites and where they cause lesions
Cheyletiella (fur mite) – (common) truncal scale +++ - zoonotic!
Leporacus gibbus (fur mite) – often asymptomatic, lesions – brown mite just visible
Psoroptes cuniculi (ear mite) – painful flakey adherent otic crust
Give examples of ectoparasites found below the skin surface and the effect they have
Burrowing/round mites => pruritus, alopecia +/- papules, hyperkeratosis, crust
Demodex => folliculitis, furunculosis
Give examples of burrowing mites found on dogs and the effect they have
Sarcoptes scabiei:
- sarcoptic mange
- Pruritus
- classically crust on pinnal margins/hocks/elbows
- +ve pinnal/pedal reflex
- Zoonotic
Give examples of burrowing mites found on guinea pigs and the effect they have
Trixacarus
- extreme pruritus
- can => seizures/death. - Zoonotic
Give examples of burrowing mites found on birds and the effect they have
Cnemidocoptes (Knemidocoptes):
- ‘scaley beak’
- ‘scaley leg’
What are the clinical signs of folliculitis caused by demodex?
pustules/papules/comedones/follicular casts
alopecia
inflammation/pruritus variable
+/- secondary lesions/ infection
What is furunculosis caused by demodex?
deep pyoderma with weeping sinuses
Describe the features of demodex infection
Most commonly seen in dog, hamster, occasionally cat.
Associated with underlying immunocompromise – most common in young/elderly animals
NOT CONTAGIOUS
NOT ZOONOTIC
Describe the features of tick infestation
Major importance in UK are as vectors of disease
Heavy infestation can => debilitation (rare in UK)
Occasionally => tick granuloma if mouthparts retained
Describe cutaneous myiasis
esp sheep, rabbits
‘Blowfly strike’ – potentially fatal
Blowfly eggs laid at sites of faecal soiling, wounds => larvae (‘maggots’) feed on host tissue
Gives examples of ectoparasites unlikely to be detected on host
midges e.g.,Culicoides spp
Nuisance flies (non-biting and biting)
Dermanyssus gallinae (poultry red mite)
What is the effect of midge infestation?
=> Hypersensitivity - ‘sweet itch’ horse – pruritic lesions along crest of neck, tail base, face
=> Transmit disease (e.g. bluetongue virus of cattle/sheep)
What is the effect of nuisance flies?
=> irritation => behaviour changes => injury/production loss
=> transmit disease e.g. infectious bovine keratoconjunctivitis (’pink eye’), bacteria of summer mastitis
=> skin disease e.g. ventral dermatitis, eosinophilic granulomas (horse)
What is the effect of Dermanyssus gallinae (poultry red mite)?
Lives in environment – only feeds at night
=>irritation/feather loss/ debilitation
Zoonotic!
