External Parasites 1

Question 1

Fleas

Answer 1

1. Blood sucking
2. Vectors – bubonic plague, intermediate host to Dipylidium caninum
3. Hypersensitivity to flea saliva can cause flea-allergy dermatitis
4. Flea dirt/flea dander – reddish black. Dissolves in water
5. Ctenocephalides felis – dogs and cats

Question 2

Ticks

Answer 2

1. Blood sucking
2. Vectors – bacterial, viral, rickettsial, protozoal diseases – including Lyme’s Disease
3. Tick paralysis – neurotoxin in saliva – Dermacentorandersoni (Rocky Mt. Spotted
   Fever tick)
4. Lifecycle: egg, 6-legged nymph, 8-legged adult
5. Family Ixodidae
6. Family Argasidae

Question 3

Family Ixodidae

Answer 3

a. Hard ticks
b. Rhipicephalussanguines – Brown Dog Tick
c. Dermacentorvariabilis – American Dog tick (also does tick paralysis)

Question 4

Family Argasidae

Answer 4

a. Soft ticks

b. Otobiusmegnini – spinose ear tick

Question 5

Lice

Answer 5

1. Spend entire lifecycle on host
2. Spread by direct contact
3. Eggs = nits – attach to hair shaft
4. Family Anoplura
5. Family Mallophaga

Question 6

mily Anoplura

Answer 6

a. Sucking louse – elongated heads, sucking
mouth parts
b. Linognathussetosus - dog
c. Hematospinusasini – horse
d. Pthirus pubis- – human crab louse – occasionally will see dogs/cats infested

Question 7

Family Mallophaga

Answer 7

a. Biting louse – large rounded head, mandible- like mouth parts
b. Trichodectes canis – dog
c. Felicolasubro strata – cat
d. Daemilineacaprae - goat

Question 8

Family Demodex

Answer 8

mite

a. Non-pathogenic in small numbers
b. Host specific – not transmissable
c. 6-legged larva, 8-legged nymph, adult
d. Live in hair follicles, sebaceous glands
e. Localized demodicosis – patchy alopecia
f. Generalized demodicosis – diffuse alopecia, secondary bacterial infections

Question 9

Family Sarcoptidae

Answer 9

a. Include Sarcoptes sp. And Notoedres sp.
b. Burrow within epidermis, intensely pruritic
c. Canine “scabies” (sarcoptic mange) caused by Sarcoptes scabieivar canis
d. Cats not affected by Sarcoptes, but Notoedrescati can cause notoendric
mange.
e. Hard to diagnose. Use lesions and distribution. Treat based on clinical signs
1) Raised rash, crustiness
2) Irritation, scratching

Question 10

Canine “scabies” (sarcoptic mange) caused by Sarcoptes scabieivar canis

Answer 10

1) Scaling, crusting, self-trauma
2) Ears, lateral elbows, ventral abdomen harbor mites
3) May be transmitted to humans, but
considered to be self-limiting
4) Highly contagious to other dogs. Carrier states may exist.

Question 11

Types of Mites

Answer 11

1. Family Demodex
2. Family Sarcoptidae
3. Family Psoroptidae
4. Cheyletiella sp.
5. Trombicula Mites
   F. Cuterebra flies

Question 12

Family Psoroptidae

Answer 12

Family Psoroptidae
a. Include Psoroptes sp. Chorioptes sp.
Otodectes sp.
b. Mostly cattle, sheep except Otodectes
c. Live on surface of skin, species specific
d. Otodectes cynotis

Question 13

Otodectescynotis

Answer 13

1) Ear mite
2) Causes otitis externa in dogs and cats
3) Not host specific
4) Causes irritation, dark, dry crust in the ear canals

Question 14

Cheyletiella sp.

Answer 14

a. Walking dandruff mite
b. Skin surface
c. Relatively host specific, causes scaling and crusting

Question 15

Trombicula Mites

Answer 15

1. Chiggers
2. Humans, too. Only larva are parasitic, nymphs and adults are free living
3. Larva only attaches for several hours. Causes red rash

Question 16

Cuterebra flies

Answer 16

1. Eggs laid in soil of rodent burrows
2. Infest rabbits, cats, occasionally dogs
3. Larva penetrate host’s skin and live SQ with a fistula to outside
4. Surgically removed