Derm 4 - parasites

Question 1

most common flea in both the dog and the cat

Answer 1

Ctenocephalides felis

Question 2

Ctenocephalides felis life cycle

Answer 2

o Eggs, larva, pupa and adult
o The adult flea is an obligate parasite – spends all its time on the pet and are only in the environment after
being dislodged
o Eggs easily fall off the host into the environment, hatch into larvae, move away from the light and down
(into carpeted areas), pupate (spin a cocoon and then wait for carbon dioxide and heat in the form of an
unsuspecting host – preferable dog or cat

Question 3

what is the florida triangle for fleas?

Answer 3

starts at the thoracolumbar junction and fans out to the lateral flank/ischial area

Question 4

are fleas always easy to find?

Answer 4

It is very difficult to find fleas on some patients, especially those suffering from flea bite hypersensitivity.

Question 5

classic flea locations

Answer 5

Fleas are classically found behind the ears and at the lumbar region

Question 6

if you suspect fleas, it would be good to do what:

Answer 6

A parasiticide response trial is almost always recommended, even in strictly indoor pets.

Question 7

flea treatment, general - who/ what do we treat?

Answer 7

o All pets in the household should be treated
o Consider environmental treatment in the case of patients (owners or pets) with flea bite hypersensitivity

Question 8

Sarcoptes scabei - how contagious? to who?
- where they live?
- hallmark of disease

Answer 8

 highly contagious; zoonosis (but the absence of pruritus of other pets or people does not rule it out)
 life cycle in entirely on the host (eggs, larva, nymph and adult
 extremely pruritic (hypersensitivity reaction) – hallmark of this disease

Question 9

Sarcoptes scabei
- site predilection
- Dx

Answer 9

 site predilection: pinnal margins, elbows, ventrum, hocks
 diagnosis – superficial skin scraping

Question 10

Otodectes cynotis - what are these? affect who? symptoms? Tx? Otic discharge?

Answer 10

 Ear mite of dogs and cats
 Contagious to both cats and dogs
 3-week life cycle
 Intense pruritus – hypersensitivity reaction and so I recommend steroid
containing ear drops
 Classical appearing coffee ground appearance to otic discharge

Question 11

Cheyletiella - what type are there for dog, car, rabbit
- where they live
- physical characteristics
- repro / life cycle
- contagiousness?
- Tx plan?
- Dx

Answer 11

C. yasguri (dog), C. blakei (cat), C. parasitovorax (rabbit)
 Aka “walking dandruff” – commonly affects dorsal lumbar area and top of the tail
 Surface dwelling mites, quite large with prominent hooks on the mouth parts
 Entire life cycle on the host
 Eggs cemented onto hair shafts (like lice)
 Contagious and a zoonosis. Treat all pets in the home
 Diagnosed by superficial skin scrapings or tape prep

Question 12

how can we tell a chayletiella egg vs a louse egg?

Answer 12

Eggs are attached by fine strands, are much smaller than louse eggs and are not operculated

Question 13

lice
- host specificity?
- where they live
- transmission
- symptoms of infestation
- life cycle
- eggs > what they look like, where?

Answer 13

 host specific
 spend entire life on host
 transmission through contact with animals or fomites (e.g. brushes)
 mild to moderate pruritus associated with patchy alopecia, scales and crusts
 life cycle 17-21 days
 nits (operculated eggs) are deposited on the hairs (more firmly attached and larger than cheyletella)

Question 14

Demodex canis
- transmission
- what each life cycle looks like?

Answer 14

(“cigar with legs”)
 mite is transferred from the bitch to the neonate within the first 3 days of life and are kept in relatively small numbers by cell mediated immunity
 nymph has shorter body and 4 pair of stubby legs
 larva has a shorter body and 3 pair of legs
 eggs look like “pregnant banana”

Question 15

character of the immunodeficiency leading to canine demodecosis

Answer 15

The immunodeficiency leading to Demodicosis may be a D. canis specific T-cell function issue (numbers are normal)

Question 16

many lesions associated with demodecosis in dogs

Answer 16

◦ Papulopustular dermatitis
◦ Moth eaten coat appearance/ alopecic macules to patches
◦ Erythematous dermatitis (“red mange”)
◦ Hyperpigmented patches/ comedones, ”blue skin”
◦ Scaling dermatosis
◦ Pododemodicosis

Question 17

Demodex injai
- what it looks like, who is affected
- symptoms
- predisposing causes?
- secondary issues?

Answer 17

 Long bodied demodex mite of the dog
 Dogs older than 2 years and terrier breeds appear to be overrepresented, though the parasite has been identified in other breeds as well (such as the
Dachshund and Lhasa Apso)
 These patients present with a seborrheic dermatitis on the dorso-lumbar area
 Excessive glucocorticoid therapy and hypothyroidism have been reported as
predisposing causes
 Secondary bacterial folliculitis and Malassezia dermatitis may be seen.

Question 18

short bodied demodex of the dog - what is this?

Answer 18

 Surface dweller
 About 50% the length of D. canis
> most likely a morphological variant of D. canis

Question 19

Demodex gatoi
- host, body shape
- symptoms
- transmission
- common locations

Answer 19

 Short bodied demodex mite of cats
 pruritic skin disease in usually young, short-haired cats with alopecia (broken hair), erythema, scaling, excoriations and crusting,
 contagious between cats (unlike most demodex)
 head, neck and elbows and/or flanks, and the ventrum and rear legs are common locations
 Hyperpigmentation can occur, and the disease may be symmetrical
 History may also be suggestive, given the possibility of contagion between cats with this mite
 There may be also an association with allergic skin disease (steroid treatment?).
 Recovery of this parasite seems to be regional. In our practice in Toronto, we have only found it 5 times.

Question 20

Demodex cati
- anatomic locations, symptoms
- morphology
- how common
- disease associations
- breed predispositions

Answer 20

 most commonly found at the head and neck of cats and can be a cause of ceruminous otitis externa
 morphology similar to D. canis
 The ova are more oval compared to the “pregnant banana” appearance of D. canis
 Localized feline demodicosis is a rare disease that most often affects the periocular region, head, neck and eyelids and presents as a variably pruritic, patchy alopecia, scaling and crusting
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 Localized lesions can self-heal, especially if you can find and resolve an underlying cause
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 Generalized demodicosis in the cat is usually associated with an important underlying disease such as diabetes, hyperadrenocorticism, FIV or FeLV.
 Infestation by Demodex cati was identified at lesional sites of multicentric squamous cell carcinoma in situ (SCC in situ).
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 Siamese and Burmese cats may be predisposed

Question 21

DDx for demodex cati

Answer 21

 Differential diagnosis includes dermatophytosis (which can occur simultaneously), bacterial pyoderma, allergic skin disease and, in fact, all causes of feline seborrhea and crusting in cats.

Question 22

localized demodicosis - how and when to treat?

Answer 22

• Systemic antiparasitic therapy is not appropriate in cases of localized demodicosis. There is no evidence
  that failure to treat localized cases results in generalized ones and, in fact, this treatment may fail to identify the patients that become generalized and should not be used for breeding
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  “Treatment” for these pets can begin immediately and should include:
  o deworming for parasites
  o nutritional evaluation and making sure that the dog leads a “stress free” life
  o Benzoyl peroxide containing products are often recommended by dermatologists as they are said
  to aid “follicular flushing” - the owner should be advised that manipulation of the lesion could increase hair loss of hairs that were “thinking of leaving anyway”. It is also useful to note that Benzoyl peroxide can bleach fabrics and that a shampoo with a Benzoyl peroxide product can be drying and so should be followed by a conditioner.

Question 23

generalized demodicosis - what is it?

Answer 23

• definition: >5 affected regions (especially if there are multiple life stages found on skin scraping), or if there is >50% of a single region involved, or if the pet has pododemodicosis

Question 24

generalized demodicosis treatment
- what is our treatment approach and timeline?
- how do we monitor progress?
- what drugs can we use?

Answer 24

• treat these patients aggressively
• Once systemic treatment is started it is important to treat for an appropriate period – 2 months past negative scraping – this could be 3-7 months (in some cases of adult onset demodicosis, negative scrapings will not be attained).
• therapy should be monitored by recording and repeatedly scraping affected areas every 4 weeks
• Record life stages and numbers of parasites to get an idea of progress
• If one form of treatment doesn’t work, try a different one
• There are some patients that are “control versus cure”.
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• Isoxazoline Family (Afoxolaner, Fluralaner, Sarolaner, Lotilaner) > Treatment of Choice
• amitraz
• Avermectins (ivermectin, doramectin)
• Milbemycins (milbemycin oxime, moxidectin)
• Lime sulfur dips for feline

Question 25

only product that is licensed for the treatment of demodicosis?
adverse effects?

Answer 25

Amitraz (also α2-adrenergic agonist
- potential side effects for the patient and operator are concerning. Treatment should only be performed in a well- ventilated area by veterinary personnel wearing protective clothing and dogs should remain in the veterinary hospital until they are dry and should not become wet between rinses. Adverse effects such as respiratory problems have been observed in humans.

Question 26

Avermectins (ivermectin, doramectin) for generalized demodicosis
- should never be combined with what?
- dangers

Answer 26

• NEVER treat a dog concurrently with ketoconazole and ivermectin at doses used for demodicosis.
• danger of toxicosis in some dogs > start at a trial dose

Question 27

Lime sulfur dips - use for demodicosis
- safety? use?
- warn owners about what?

Answer 27

(2% - weekly X 4-6 weeks) are quite useful in the treatment of feline demodicosis
- very safe, and is often used as a parasiticide response trial to rule out Demodex gatoi in the pruritic cat (most affected cats will improve after 3 treatments)
- Treat all in contact cats when ruling out Demodex gatoi, and don’t forget to warn the owners that lime sulfur can discolor jewelry (and white cats can turn yellow). Warn them about the odor associated with treatment. Be sure to have the cat wear an e-collar until it’s dry as it can lead to emesis when wet.

Question 28

Concomitant therapy during demodicosis treatment?
- why we may do this? what conditions are commonly concurrent?

Answer 28

• Follicular demodicosis is often associated with bacterial furunculosis. Treatment with antibiotics is appropriate until the infection is under control
• Twice weekly benzoyl peroxide (BPO) shampoo therapy in patients treated with avermectins or milbemycin is very helpful. Be sure to always follow with a conditioner.
• Vitamin E has been recommended (200 IU, 5 times daily) as an adjunctive treatment.