SA External Parasites

Question 1

Life cycle of flea:

Answer 1

1. Eggs, larvae and pupae in the environment
2. Adults emerg from pupae anytime b/w 10 days - 6 months (stimuli = pressure, heat)
3. Adults jump onto permanent host
4. Mating -> produced ~24-36 hours after adult’s first bloodmeal

Question 2

Flea Allergy Dermatitis (FAD): where are lesions on dogs versus cats?

Answer 2

Dogs: dorsal lumbosacral are (rump) and tailhead

Cats: neck, lower back; sometimes generalized along the dorsum

Question 3

Flea Allergy Dermatitis (FAD): common dermatologic reaction pattern from flea bites in cats?

Answer 3

Miliary Dermatitis

Question 4

What condition can fleas cause, especially in young animals?

Answer 4

Anemia

Question 5

What drug class is only an insecticide (only used on fleas, doesn’t work on ticks)?

Fleas and lice = insects
Ticks and mites = arachnids (like spiders, scorpions)

Answer 5

Neonicotioids (imidacloprid – e.g., Advantage)

For mites: fipronil (phenylpyrazole) & imidacloprid (neonicotioid) are only used to aid in control/tx -> do not resolve

Question 6

Environmental control measures for fleas?

Answer 6

• repeated, thorough vacuuming (removes flea stages & flea dirt- stimulates fleas in pupae to emerge) for up to a month!
• wash bedding in cold water, dry in high heat
• treat outdoor areas

Question 7

Echidnophaga gallinacea - what type of flea is it?

Answer 7

Poultry stick tight flea - primarily a bird pest that can also parasitize dogs & cats. Adult femals attach semi-permanently

Question 8

Xenopsylla cheopis - What type of flea is it?

Answer 8

Rodent flea - important b/c of plaque transmission in endemic areas (western states)

Question 9

How to differentiate biting from sucking lice?

Answer 9

Sucking: small, narrower head
Biting: wider head

Question 10

Difference in transmission and pathogenic stage b/w fleas vs. lice?

Answer 10

Transmission
- Fleas: environmental
- Lice: direct contact

Pathogenic Stage
- Fleas: adult life stage
- Lice: all life stages

Treating animal for lice will completley eliminate since they do NOT survive in the environment!

Question 11

Life stages of lice?

Answer 11

egg -> nymph -> adult

No pupa stage!

Question 12

How do dogs/cats get infected by Cuterebra spp. // rodent bot flies?

Answer 12

Host = rabbits / rodents -> adult cuterebra lay eggs in brush / near entrances of burrows; along trails. Dogs/cats pick up these larvae here => larave develop in SQ cyst!

Question 13

What mite is a common cause of dermatitis in dogs? Where do lesions typically start at? Why is it pruritic?

Answer 13

Sarcoptes scabiei
- lesions start @ pinnae, lateral hocks and elbows
- pruritic b/c animal has hypersensitivity rxn to the feces of the mite

APPROVED tx: selamectin, moxidectin/imidacloprid - NO LARGE ANIMAL DOSE OF IVERMECTIN!

Question 14

A deep skin scraping where capillary bleeding is produced is needed for what mite?

Answer 14

Sarcoptes scabiei - are burrowing mites!

skin biopsy or histopathology may also be needed for dx

Question 15

How does the ear mite Otodectes cynotis cause dermatitis?

Answer 15

• hyperplasia & hyperkeratosis of ear canal epithelium, + hyperplasia of sebaeceous glands w/ dark exudate

Question 16

What mite is this? Why are they nicknamed “walking dandruff”?

Large palpal claws

Answer 16

Cheyletiella spp.
- are large (0.5mm), surface mites -> only need to collect the dandruff for diagnosis

Question 17

Insect vs Arachnid?

Answer 17

Insect: 3 major body segments (head, thorax, abdomen) – fleas & lice -> imidacloprid!

Arachnid: 2 major body segments (fused head + thorax, abdomen) – ticks & mites ->

Question 18

What protozoa is zoonotic and causes dermatitis? How is it transmitted?

Answer 18

Leishmania spp.
- transmission = bite of infected sand fly
- dogs = chronic carriers

Question 19

Two forms of Leishmania?

Answer 19