23.11.1: Pruritic ectoparasite disease Flashcards
Aetiopathogenesis of Flea Allergy Dermatitis
- Hypersensitivity (Type I or Type IV) to salivary proteins of the flea
- Leads to self-trauma by pet
True/false: if only one animal in a household is affected, FAD is automatically lower down on the differential diagnoses list.
False
* The house may be infested with fleas but it is possible that only one animal is hypersensitive to flea saliva.
* Therefore, it is perfectly possibly for other pets not to be showing clinical signs.
Clinical signs of FAD in dogs
- Scratching
- Biting skin
- Jumping up suddenly
- Excess licking/overgrooming
- Alopecia
- Skin inflammation ± skin infection
- Crusting
- Lichenification
Which areas of the dog’s body are typically affected in FAD?
- Caudal half of body (tail base, thighs, inguinal area)
- Dorsum
What disease might this pattern make you suspicious of and why?
Flea Allergy Dermatitis
* Caudal half of body (tail base, thighs, inguinal area), dorsum
Which drugs are active against environmental life cycles (larvae, eggs) and adult fleas?
- Imidacloprid
- Selamectin
Which drugs are effective against adult fleas?
- Imidacloprid
- Selamectin
- Dinotefuran
- Permethrin, flumethrin, tetramethrin
- Fipronil
- Pyripole
- Nitenpyram
- Isoxazolines
What are some examples of insect growth regulators (IGRs) effective against flea eggs and larvae?
- Pyriproxifen
- (S)-methoprene
- Lufenuron
Which drugs are effective against adult fleas, but not against eggs or larvae?
- Dinotefuran
- Permethrin, flumethrin, tetramethrin
- Fipronil
- Pyriprole
- Nitenpyram
- Isoxazolines
What flea control measures are there?
- Mechanical removal e.g. flea combing, vacuum cleaning
- Repellants
- Adulticides
- Larvicides
- Ovicides
- Insect growth regulators (these may be juvenile hormone analogues or chitin synthase inhibitors)
How long is the flea life cycle?
3-4 weeks
Can range from 2 weeks - 6 months depending on environmental conditions
Clinical signs of FAD in cats
- Head and neck pruritus
- Miliary dermatitis
- Bilaterally symmetrical alopecia due to overgrooming
- Eosinophilic granuloma complex lesions (eosinophilic plaques, eosinophilic granulomas, indolent ‘rodent’ ulcers)
- i.e. any of the cutaneous reaction patterns of the cat
Indolent ulcers
Diagnosis of FAD
- Demonstration of fleas on the animal + compatible clinical signs (negative finding is unreliable)
- Intradermal and serological testing - limited value
- Response to therapy - best method of diagnosis is by response to thorough flea control trial
Cat with FAD
How long might it take to fully eliminate fleas from the animal and environment?
3 months
1 and 2
Which species should you not give fipronil to?
Rabbits
Which species should you avoid using permethrins in? What is the exception to this?
Cats
Flumethrin is fine
When should you be cautious about using isoxazolines?
If the patient has a history of seizures
a) Advantage (imidacloprid)
b) Advantix (imidacloprid + permethrin)
c) Frontline combo (fipronil + S-methoprene)
d) Simparica (sarolaner)
d) Simparica (sarolaner)
1
2
3
4
1
2
3
4
Trichodectes canis
This is a canine sucking louse
Linognathus setosus
This is a canine chewing louse
Felicola spp.
This is a feline chewing louse
What is the difference between a chewing louse and a biting louse?
They are the same thing
Where does the louse life cycle take place? How long can they survive off a host?
- Whole life cycle on host -> easy to kill!
- Adults survive for only 3 days off the host
- May have nits in bedding -> indirect infestation
True/false: lice are species-specific but contagious within that species.
True
Louse egg a.k.a. nit attached to hair
These have an operculum (lid) that is circled in the image
Clinical signs of lice infestation
- Pruritus, crusting, erythema, scaling, alopecia
- Sometimes asymptomatic
- Heavy infestations can lead to anaemia in puppies and small dog breeds
- Trichodectes can act as intermediate host to the dog tapeworm Dipylidium caninum
- Reaction to bites from Felicola subrostratus can resemble miliary dermatitis
Diagnosis of lice
- Coat combing/ brush
- Hair plucks for eggs
Treatment of lice
- Many flea adulticides effective e.g. imidacloprid, fipronil, selamectin
- Isoxazolines are not licensed but likely effective
- Treat in contacts
- Clean the environment
Sarcoptic mange in a dog
Sarcoptes scabiei var canis
Sarcoptes eggs and faeces
Where are Sarcoptes found - on the surface vs burrowing vs deep?
They burrow in the stratum corneum
Where does the Sarcoptes life cycle take place and how well can they survive off the host?
- Entire life cycle on host
- Can survive off host for limited period 48-72hrs
- Widlife reservoir = foxes
True/false: Sarcoptes is neither contagious nor zoonotic.
False
Sarcoptes is highly contagious and zoonotic‼️
Clinical signs of Sarcoptes
- Severe pruritus - focuses on elbows, hocks, ear pinna, ventral chest
- Erythematous papules with a greyish-yellow exudate
- Lesions spread rapidly covering entire body
- Self-trauma results in severe excoriation, lichenification and patchy alopecia
- Can develop secondary infection and lymphadenopathy
- 80% show pinnal pedal reflex
Diagnosis of Sarcoptes
- Skin scrapings - high risk of false negatives. Need to be deep!
- IgG ELISA serology is available but rarely used; false +ves and -ves and serocoonversion takes 4 weeks
- Therapeutic trial if diseases suspected
Treatment of Sarcoptes
Cheyletiella spp.
Cheyletiella spp.
True/false: Cheyletiella are host-specific and contagious.
False
Cheyletiella are non host-specific and they are very contagious.
They are also zoonotic‼️
Cheyletiella eggs
Where does the Cheyletiella life cycle take place and how long can they survive off the host?
- Life cycle on host
- Can survive for 10+ days off host
Clinical signs of Cheyletiella spp
- Pruritus
- Papular and crusted lesions (miliary dermatitis in cats) esp on dorsum and trunk
- Dry scaling or flaking
- Some affected animals have no signs and can be carriers
Diagnosis of Cheyletiella spp
- Superficial skin scrape
- Microscopy of scale from combing -> in liquid paraffin under coverslip
- Unstained acetate tape strip on skin
- Trichogram for eggs
- Trial treat if suspected - false negatives are common
True/false: some Cheyletiella spp affect rabbits
True
Treatment of Cheyletiella
- Hard - can survive off host
- Treat affected animal and in contacts
- No licensed products but isoxazolines, selamectin and moxidectin effective
- Clean environment and use environmental flea spray
Otodectes
Otodectes infestation is called otoacariasis
Where does the life of Otodectes take place?
- In the ears
- Other areas of the body can be a reservoir
- Life cycle = 21 days
- Can survive off host depending on environmental conditions
Which of the following apply to Otodectes ?
* Host specific
* Contagious
* Zoonotic
Otodectes is contagious!
It is not zoonotic. It is not host-specific.
Clinical signs of Otodectes
- Intense pruritus and head shaking
- Thick dark brown exudate
- Miliary dermatitis in cats
Diagnosis of Otodectes
- Ear swab
- Microscopy
- Otoscopic examinations
Treatment of Otodectes
Neotrombicular autumnalis (harvest mite)
Where does the harvest mite life cycle take place?
Which species can harvest mites affect?
- Dogs
- Cats
- Occasionaly humans
Not host-specific.
Not directly contagious between people or zoonotic but people can be infested from larvae from the ground.
Clinical signs of harvest mites
- Papules
- Crusts
- Pruritus
- Especially seen in interdigital space, pinnae (Henry’s pocket), ventral abdomen
Diagnosis of harvest mites
- Visual ID
- Coat comb/brushing
- Unstained acetate tape strip
- Superficial skin scrape
Treatment of harvest mites
- No licensed products
- Options: fipronil every 2 weeks / selamectin spot-on/ Isoxazolines likely effective
Which of these two parasites is variably pruritic and which is highly pruritic?
Demodex canis
Demodex injai
Demodex injai - highly pruritic (thankfully less common)
Demodex canis - variably pruritic but common
Demodex canis
Demodex injai
Which parasite does this apply to?
Demodex injai
Clinical signs of Demodex cati
- Localised demodicosis is rare can also present as a ceruminous otitis externa
- Pruritus variably - generally absent to mild
- Crusting
- Alopecia
- Mild erythema
- May also see lichenification and hyperpigmentation
Demodex cati
What is this and how will you find it on the animal?
Demodex gatoi
* Superficial skin scrapes from areas inaccessible to tongue - unlike other Demodex which are deep this one lives in the superficial stratum corneum
Clinical signs of Demodex gatoi
- Pruritus
- Generalised overgrooming and self trauma
- Underlying skin may be erythematous (red mange) amd mildly scaly
- Comedomes may be present
Treatment of Demodex cati, Demodex gatoi
- Localised form may be self-limiting
- No licensed products: sarolaner, fluralaner
- Address underlying cause
- For Demodex gatoi treat in-contacts also
A 4 y.o. Boxer presents with dorsal pruritus and scale. What are your top 2 differentials?
a) demodicosis, cheyletiellosis
b) sarcoptic mange, cheyletiellosis
c) flea allergic dermatitis, sarcoptic mange
d) flea allergic dermatitis, cheyletiellosis
e) demodicosis, flea allergic dermatitis
f) demodicosis, sarcoptic mange
d) flea allergic dermatitis, cheyletiellosis
