Parasitic Skin Disease

Question 1

What is the most common cause of pruritis? Is this good?

Answer 1

Ectoparasites

• common
• easy to treat
• always investigate first

Question 2

Why are ectoparasites important other than pruritic disease?

Answer 2

may be vectors of/contributors to other infectious diseases

Question 3

Do parasites presence always indicate disease?

Answer 3

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

Question 4

Which parasites ALWAYS cause diseas?

Answer 4

Sarcoptes (mange mites -> scabies)

Question 5

Which parasites are commensal and always present in the coat?

Answer 5

Demodex

Question 6

Which species does demodex (arachnids) mainly affect?

Answer 6

Dogs (also cats and horses possible)

Question 7

Which species does sarcoptes (arachnids) mainly affect?

Answer 7

Dogs only

Question 8

Which species does cheyletiella (arachnids) mainly affect?

Answer 8

Dogs (also cats possible)

Question 9

Which species does trombiculiasis (arachnids) mainly affect?

Answer 9

Dogs, cats and horses

Question 10

Which species can get FAD?

Answer 10

Cats and dogs

Question 11

Does trombiculiasis always need treatment?

Answer 11

No - only if bothering the dog

Question 12

When is trombiculiasis season?

Answer 12

Strictly seasonal - autumn!
July -> sept/oct
> regional too

Question 13

Is trombiluliasis a commensal?

Answer 13

No picked up from environment

Question 14

Clinical signs of trombiculiasis

Answer 14

• larvae just visable

- may be asymptomatic or severely pruritic

Question 15

Tx of trombiculiasis?

Answer 15

• none repellant, none licensed

- fipronil

Question 16

What causes walking dandruff and scale?

Answer 16

Cheyletiella (blakei/yasurgi/parasitivorax)

Question 17

How may cheyletiella mites be identified?

Answer 17

> hair plucks
> coat brushing
> tape 
- palps
- eggs attached to hair shaft (nits)

Question 18

Which animals are affected by cheyletiella?

Answer 18

Cats, dogs, rabbits

Question 19

Why is cheyletiella a difficult problem?

Answer 19

• survive in environment and on fomites 6 weeks

- zoonotic (will bite people though not establish on them)

Question 20

Clinical signs of cheyletiella

Answer 20

• walking dandruff
• pruritis may be v. mild or severe
• primarily dorsal trunk
• cats: miliary dermatitis

Question 21

Tx of cheyletiella?

Answer 21

> 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

Question 22

What is demodecosis?

Answer 22

• inflammatory parasitic skin disease characterised by ^ no. demodex

Question 23

Which animals most commonly affected by demodecosis?

Answer 23

• 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

Question 24

Clinical signs of demodecosis?

Answer 24

• 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

Question 25

Potential manifestations of canine demidecosis?

Answer 25

``` > 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) ```

Question 26

Tx of demodecosis

Answer 26

- min 12 weeks tx: tell client this! - monitor by PE and repeat scrapes/plucks - avoid steroids!!!

Question 27

Which breeds are commonly affected by demidecosis?

Answer 27

- staffies | - great danes

Question 28

Which species most commonly affected by sarcoptic mange mites?

Answer 28

- common in dogs - rarer in cats (usually asociated with affected dog) - notifiable in horses!!

Question 29

Which pathogen causes scabies?

Answer 29

Sarcoptes Scaibie

Question 30

How does sarcoptes behave on the skin?

Answer 30

Buries into epidermis -> crusted papules

Question 31

how can sarcoptes be found/diagnosed?

Answer 31

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

Question 32

Where does FAD cause pruritis?

Answer 32

- Dorsal lumbosacral area - can be ventral abdo too > caudal body generally

Question 33

What mechanisms of FAD hypersesntitivty are possible? What effect may this have on testing?

Answer 33

``` > 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 ```

Question 34

What is the main allergen associated with FAD?

Answer 34

Saliva

Question 35

Do fleas usually cause irritation without FAD?

Answer 35

No (some scratching only due to them running around)

Question 36

Age of onset of FAD?

Answer 36

3-5 years

Question 37

Predispositions for FAD?

Answer 37

- breed | - atopic derrmatitis

Question 38

Is FAD seasonal?

Answer 38

May be - seasonal parasites picked up in summer - flea infestations in home too!! so may be all year round

Question 39

Diagnosis and Clinical signs of FAD?

Answer 39

- 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!

Question 40

What 2 types of allergy testing is available for FAD?

Answer 40

> 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*

Question 41

Management of FAD

Answer 41

- 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!)