Parasitic Skin Diseases of Small animals

Question 1

What are the three types of host parasite relationship?

Answer 1

Parasite = always disease
Parasite = carrier or minimal disease/marked hypersensitivity
Commensal parasite = rarely disease

Question 2

What are some examples of arachnids that are parasitic to dogs?

Answer 2

Demodicosis, Sarcoptic mange, Cheyletiellosis, Trombiculiasis

Question 3

What are some examples of arachnids that are parasitic to cats?

Answer 3

Cheyletiellosis, Trombiculiasis (demodecosis)

Question 4

What are some examples of arachnids that are parasitic to horses?

Answer 4

Trombiculiasis, (demodecosis)

Question 5

What is the main insect hypersensitivity syndrome affecting cats and dogs?

Answer 5

Flea bite hypersensitivity

Question 6

What are the clinical signs of trombiculiasis (harvest mites)?

Answer 6

Can have red skin showing that the animal is mounting a reaction but no scratching so the animal isn’t bothered so don’t treat
Range from asymptomatic to severely pruritic

Question 7

How is trombiculiasis diagnosed?

Answer 7

Strictly seasonal from July to September/October

Small, bright orange mites seen, larvae have 6 legs

Question 8

Where about on the animal are harvest mites found?

Answer 8

Legs/face in horses

Feet/ears on cats and dogs

Question 9

What is the treatment for Trombiculisis?

Answer 9

None licensed but fipronil (Frontline) works

Question 10

What are the different types of Cheyletiella that infect the skin?

Answer 10

Cheyletiella blakei
Cheyletiella yasurgi
Cheyletiella parasitivorax

Question 11

Is cheyletiellosis zoonotic?

Answer 11

Yes will bit people in close physical contact but can’t maintain an infestation in people

Question 12

What are the clinical signs of cheletiellosis?

Answer 12

Scaling (walking dandruff)
Pruritis from mild-severe
Primarily on dorsal trunk
In cats see miliary dermatitis

Question 13

How is cheletiellosis diagnosed?

Answer 13

Look for hook palpebrae of mite, attach eggs to hair shaft, look for them in coat brushing

Question 14

What is the general principles of treatment for cheyletiellosis?

Answer 14

Often difficult requiring >6 weeks of treatment

Treat all in contact rabbits, cats and dogs

Question 15

What products can be used to treat cheyletiellosis?

Answer 15

Non licensed but
For dogs can use amitraz, fipronil, selamectin, moxidectin and selenium sulphate shampoo
For cats can use fipronil, selamectin, moxidectin, ivermectin, selenium suphate shampoo
For rabbits can use ivermectin

Question 16

What is demodecosis?

Answer 16

An inflammatory parasitic skin disease characterised by the presence of larger than normal numbers of demodectic mites

Question 17

What species of demodex are common in the dog?

Answer 17

D. canis, D. injai, short bodied mite

Question 18

What species of demodex are uncommon in the cat?

Answer 18

D. cati (USA), D. gatoi

Question 19

What are the different manifestations of canine demodecosis?

Answer 19

Juvenile onset, localised - spontaneous recovery
Juvenile onset, generalised - inherited predisposition
Adult onset, localised or generalised - > 2 yrs age, suspect underlying immunosuppression

Question 20

What causes juvenile onset demodecosis?

Answer 20

Transient inability to control mite population

Question 21

How do dogs with demodecosis typically present?

Answer 21

For hair loss as not itchy disease

Question 22

What is the treatment for demodecosis?

Answer 22

Minimum of 12 weeks of treatment and monitor by clinical exam and repeat scrapes/plucks
Avoid use of steroids (can develop deep pyoderma)

Question 23

What is the aim of demodecosis treatment?

Answer 23

To reduce the burden to the level at which the body can manage

Question 24

What is the prevalence of sarcoptic mange (scabies) in the different domestic species?

Answer 24

Dogs it is very common
Rare in cats and they are normally immunosuppressed
Notifiable in horses in the UK

Question 25

Define canine scabies

Answer 25

An intensley pruritic transmissible infestation of dogs caused by Sarcoptes scabiei (var. canis)

Question 26

What is the pathogenesis of scabies?

Answer 26

Burrow into epidermis causing a reaction so that exudate forms crusted papules

Question 27

How is scabies diagnosed?

Answer 27

See mites or burrowing tunnel or eggs in skin scrapping

Question 28

What are the mechanisms of ectoparasite hypersensitivity?

Answer 28

IgE-mediated mast cell activation

Delayed cell mediated by basophil hypersensitivity, TH1 macrophage activation or TH2 lymphocyte/eosinophil activation

Question 29

What are the antigens of ectoparasite hypersensitivity?

Answer 29

Saliva, cuticle, excreted metabolites/enzymes/toxins or faeces

Question 30

What is the mechanism of flea allergic dermatitis?

Answer 30

Animals are sensitised to flea salivary antigens resulting in immediate and/or delayed intra-dermal reactions

Question 31

What signalment commonly presents with flea bite hypersensitivity?

Answer 31

Age at onset typically 3-5 years, atopic dogs predisposed?, seasonal or non-seasonal (thought to maintain flea population all year round)

Question 32

How is flea bite hypersensitivity diagnosed?

Answer 32

History and signs
Presence of fleas or flea faeces (wet paper test/coat brushing and look under microscope)
Response to therapy - perform properly
Allergy testing - not as effective as treating and seeing

Question 33

What are the methods of allergy testing for flea bite hypersensitivity?

Answer 33

Intra-dermal testing using whole body extract (cat sens 33%, spec 78%) (dog sens 30-70%, spec 80-90%)
Flea saliva serology (cat accuracy 82%) (dog sens 87%, spec 53%)

Question 34

How is flea bit hypersensitivity managed?

Answer 34

Flea control regimen
Antipruritic/anti-inflammatory medication such as glucocorticoids
Allergen specific immunotherapy but whole flea extract ineffective and salivary antigen rush protocol isn’t available