Parasitic diseases

Question 1

List the 4 main arachnid ectoparasites of small animals

Answer 1

• demodecosis
• sarcoptic mange (scabies)
• cheyletiellosis
• trombiculariasis

Question 2

Outline trombiculariasis:
name
signs
Tx

Answer 2

• (Neo) Trombicula autumnalis
• SIGNS: Larvae just visible, strictly seasonal (July-Sept-Oct), Asymptomatic –> severe pruritis
• Tx (NL) - fipronil

Question 3

Describe the appearance of a dog with Cheyletiella

Answer 3

thin, greasy, oily, white flecks, alopecia,

• EGG attaches to hair shaft
• CS - scaling (walking dandruff), pruritus (mild >severe), primarily dorsal trunk, miliary dermatitis (Cats)

Question 4

Which species can Cheyletiella affect? 3

Answer 4

cats, dogs, rabbits

Question 5

Which Cheyletiella species infect the skin? 3

Answer 5

• C. blakei
• C. yasurgi
• C.parasitovorax

Question 6

T/F: Cheyletiellosis is zoonotic

Answer 6

True

Question 7

Tx - Cheyletiellosis

Answer 7

> 6 weeks usually, often difficult

• in contact dogs, cats and rabbits
• NL but can use amitraz, fripronil, selamectin, moxidectin, ivermectin, selenium sulphide shampoo,

Question 8

Define Demodecosis

Answer 8

an inflammatory parasitic skin disease characterised by the presence of larger than normal numbers of demodectic mites (as normally a commensal)

Question 9

List the demodex species in dogs, cats and horses

Answer 9

DOG - D.canis, (D. injai, short-bodied mite)
CAT - v rare, (D.cati, D.gatoi)
HORSE - v rare.

Question 10

T/F: demodecosis is zoonotic

Answer 10

True

Question 11

CS - demodecosis

Answer 11

• prominent hair follicles

- alopecia

Question 12

What are the 3 main manifestations of canine demodecosis

Answer 12

1. juvenile onset (up to 6 months), localised - often recovers spontaneously
2. juvenile onset, generalised - inherited predisposition, Great Danes and SBTs
3. adult onset, generalised or localised, usually > 2 years old, suspect underlying immunosuppression (drugs - GCs, endocrinopathy, neoplasia)

Question 13

Tx - canine demodecosis (generalised cases)

Answer 13

• expect minimum 12 weeks tx
• minotr (CS and repeat scrapes/plucks)
• AVOID steroids
• manage client expectations

Question 14

What species are affected by sarcoptic mange?

Answer 14

DOGS - common
CATS - rare, usually immunosuppressed and exposed
HORSES - very rare, UK notifiable

Question 15

Define canine scabies

Answer 15

An intensely pruritic transmissible infestation of dogs caused by Sarcoptes scabei (var. canis?)

Question 16

What are the 3 commonest CS of FAD?

Answer 16

• hair loss
• inflammation
• self-trauma

Question 17

What are the main mechanisms of ectoparasite hypersensitivity?

Answer 17

• IgE mediated (MC activation)

- Delayed cell mediated: basophil hypersensitivity, TH1 (macrophages), TH2 (lymphocyte/eosinophil)

Question 18

What antigens may be responsible for ectoparasite hypersensitivity?

Answer 18

• saliva *
• cuticule
• excreted metabolites/enzymes/toxins
• faeces

Question 19

T/F: flea infestation in non-FAD animals is unlikely to cause skin lesions

Answer 19

True

Question 20

What animals develop flea bite hypersensitivity?

Answer 20

• age usually 3-5 years
• breed predisposition?
• AD dogs predisposed?
• seasonal or non-seasonal (especially house cats)

Question 21

Dx - flea bite hypersensitivity

Answer 21

• Hx and signs
• presence of fleas or flea faeces
• response to therapy
• allergy testing

Question 22

How can you allergy test for flea bite hypersensitivyt?

Answer 22

• Intradermal testing (by whole body extract) causing immediate and delayed reactions. N.b. proportion of salivary gland in this is minimal therefore possible diluted response.
• Serology (saliva-specific)

Question 23

How can flea bite hypersensitivity be managed?

Answer 23

• flea control regimen * (think of all possible sources)
• Antipruritic/anti-inflammatory medications (GCs, anti-histamines, EFA)
• Allergen-specific immunotherapy (whole flea extract is ineffective, salivary antigen rush protocol promising but is unavailable)