Parasitology Flashcards
why do parasites live on the skin
food
habitat
ease of access
what are the cons of parasites living on the skin
- requires access to specific host and location on host
- must be able to avoid defenses and navigate skin/hair/etc
insects
fleas, flies, lice
insect characteristics
- 3 body segments (head, thorax, abdomen)
- 0, 1, 2 pairs of wings
- 6 legs
- antennae, eyes
arachnids
ticks, mites
arachnid characteristics
- 2 body segments (fused head and thorax, abdomen)
- no wings
- 8 legs
incomplete development life cycle
immature stages resemble the mature stages
- lice
- ticks, mites
lice life cycle
egg –> nymph –> adult
tick and mite life cycle
egg –> larva –> nymph –> adult
complete development life cycle
different stages look distinctly differently
- fleas and flies
flea and fly life cycle
egg –> larva –> pupa –> adult
lice characteristics
- obligate ectoparasites
- macroscopic
- HIGHLY host specific
- cause pruritus
- pathogen vector
mites
- sarcoptes
- demodex
- otodectes
- cheyletiella
- notoedres
- chorioptes
- psoroptes
sarcoptes scabiei
- burrowing mite
- superficial
- 4 visible legs, 4 on ventral aspect
- highly contagious
- can be zoonotic
- cause pruritus
sarcoptes scabei host
dogs
pigs
how to diagnose sarcoptes scabei
superficial skin scraping
demodex
- obligate ectoparasite
- live in hair follicles
- host specific
- localized vs generalized
how to diagnose demodex
deep skin scraping
demodex hosts
dogs, mammals
localized demodicosis
circumscribed alopecia, erythema, scaling
- young animals (perinatal)
- spontaneous remission
- NON pruritic
- no treatment
generalized demodicosis
diffuse of patchy generalized alopecia with scaling, crusting, chronic skin changes
- older animals
- genetic component
- secondary pyoderma
- HIGHLY pruritic
- requires treatment
otodectes
ear mites - live on the surface of external ear
- cause otitis externa
- highly pruritic
how to diagnose otodectes
otoscopic exam, ear swab
otodectes host
cats, dogs
cheyletiella
fur mites - walking drandruff
- diagnose with acetate tape, swab, or comb
notoedres
- highly pruritic
- cause chronic infections –> severe lichenification
- affects ears and face
- 4 visible legs, 4 on ventral aspect
how to diagnose notoedres
skin scraping
notoedres host
cats
chorioptes
- non-burrowing mite
- causes mange - excessive crusts, scales, and skin thickening, pruritus
chorioptes host
livestock - sheep especially
psoroptes
- non-burrowing mite
- affects livestock and rabbits
- affects ears of rabbits
most common flea genus
ctenocephalides felis - for both dogs and cats
flea characteristics
- bloodsucking ectoparasites
- jump, do not fly
- host preferred but not specific
- cause flea allergy dermatitis
what stage of fleas are parasitic
adults only
egg, larvae, and pupa live off host
unique characteristics of flea pupae
can survive up to 140 days in cocoon
require host presence to pupate
flea allergy dermatitis
severe pruritus and dermatitis associated with flea infestation
3 major hard tick types
- ixodes
- dermacentor
- rhipicephalus
tick characteristics
- bloodsucking ectoparasites
- cause primary and secondary injury to host
- incomplete development
- females are larger than males with small scutum
festoons
small groove adornments along the back margin of the abdomen
- ixodes do NOT have festoons
secondary injury of ticks to hosts
- exsanguination
- secondary parasitic infection
- dermatoses
- paralysis toxicosis
- pathogen vector
hard and soft ticks
hard: visible head and mouthparts from dorsal view
- use 3 different hosts in life cycle
- feed for days
soft: no visible head and mouth parts from dorsal view
- use 1 host in life cycle
- feed for minutes
dermacentor
common tick in davis
- ornamental
ixodes
Lyme disease vector
- no festoons
rhipicephalus
brown dog tick
- indoor/outdoor ticks
sheep keds
flies that look like ticks
- have piercing mouthparts and feed on blood as adults
ked life cycle
- females lay egg
- larvae develops inside the female (feed from milk gland)
- female births a live prepupa
- prenups immediately pupates after birth
bot flies
cuterebra
- no obligate host; infects hosts that ingest their eggs
- larvae encyst beneath the skin and pupa drops out into environment to pupate
- adults are NON feeding
blow flies
calliphora
- colorful adults
- larvae eat decaying or living flesh
- adults are NON feeding
- cause myiasis
myiasis
fly larvae that infect living hosts, usually on necrotic skin or soiled tissue
- lay eggs on wounds/fleece
- larvae feed on necrotic skin
effects of myiasis
irritation
secondary bacterial infection
septicemia
toxemia
screwworm myiasis
caused by cochliomyia hominiovorax
- infects fresh wounds or bites
- reportable parasite to USDA
biting flies
cause annoyance, hypersensitivity, blood loss, and disease transmission
culicoides hypersensitivity
allergic response to fly bites in HORSES
- immediate and delayed reaction
- highly pruritic
cutaneous habronemiasis
nematode transmitted by flies into open wounds or margins of the eye
- migrates through skin causing excessive granulation + pruritus
“summer sores”
