Arthropods Flashcards
Arthropod Review: veterinary importance
- they are disease agents
- venom or toxic substances
- IH for protozoans or helminths
- vectors for bacteria, rickettsia, viruses
description of class insecta from phylum arthropoda
segmented body
- head: used for chewing, piercing, lapping, siphoning, sponging
- thorax
- abdomen
arthropod lifecycle
simple (incomplete) metamorphosis
- eggs, larva, pupa, adult
description of Order Acarina, class arachnida, phylum arthropoda
- 2 body regions: head and body
head = gnathosoma/capitulum
body = idiosoma
simple metamorphosis
Order Diptera: true flies (class insecta, phlyum arthropoda)
- 1 pair of wings (second pair vestigial halteres)
- ectoparasites - both permanent and temporary
- disease vectors (viruses, bacteria, rickettsiae)
- IH for protozoans and filarial parasites
- undergo myiasis
facultative myiasis
- normally eggs are deposited in: garbage, feces, rotten carrion
- occasionally eggs are deposited in: contaminated wounds
- larval ID: spiarcular plates “fingerprints” unique to each genus
- early lesions: dermatitis, numerous maggots, pungent odor, inflammation
some diptera (true flies) that undergo facultative myiasis
- blow flies/botle flies: calliphora, phormia, lucilia
- flesh flies: sarcophaga
- house flies, face flies: musca domestica, musca autumnalis
obligatory myiasis
- larvae MUST use animal host to complete life cycle through living tissue, organs, uncontaminated wounds, soft tissue
- larval ID: spiracular plates “fingerprints” unique to each genus
some diptera (true flies) that undergo obligatory myiasis
- cochliomyia hominivorax
- hypoderma spp.
- dermatobia hominis
family culicidae: mosquito
physical description
- most prominent blood sucking dipteran
- larvae (always aquatic, spiracles)
- adults (scales along wing veins & margins, thorax, abdomen)
family culicidae (mosquitoes) have antennae that vary depending on sex:
female = pilose male = plumose
family culicidae (mosquito) lifecycle
eggs = aquatic, semi-aquatic larvae = 1st molt in 5-6 days (3x total), filter feeders pupae = stage lasts 2-3 days, non-feeding adults = lifespan 6-7 days, mate once, females voracious blood feeders
subfamilies of culicidae (mosquitos)
- anopheles sp. (anopheline)
- culicine (aedes sp.)
- culicine (culex sp.)
anophelines (subfamily of culicidae) are different than aedes and culex subfamilies in what ways?
- anopheles lay eggs in singles that float in water while aedes is single on dry surface and culex are on rafts parallel to water surface
- anopheles larva have no air tube and are parallel to water surface while aedes and culex have a short air tube and are angled to water surface
- anopheles pupa have a short air tube, while aedes have have a variable air tube and culex have a long, slender air tube
- anopheles adults have an angled resting position on host while aedes/culex have a parallel resting position on host
palps on anopheline vs. culicine
anopheline:
male palp = length of proboscis, clubbed
female palp = length of proboscis
culcine:
male palp = longer than proposcis, not clubbed
female palp = < 1/2 length of proposcis
anophelines and culicines are v- ectors for what diseases/bacteria?
- anophelines are IH/vector for plasmodium spp.
- culicines are a vector for yellow fever, dengue fever and west nile encephalitis
control for family culicidae
- larvivorous fish (guppies, mosquito fish)
- ‘beneficial’ mosquito larvae
- sticky mustard seeds (stick to larvae when try to eat)
- draining breeding sites
family tabanidae: distribution, annoyance to whom, what it feeds on (order diptera, class insecta)
horse and deer flies
- found where water abundant (most larval aquatic)
- annoyance to livestock
- females are blood feeders (bites numerous times in numerous places)
- males feed on honeydew or nectar
family tabanidae: horse and deer fly differences
- horse fly = tabanus spp.
large sized, gray or black in color, no bands or spots on wings - deer fly = chrysops spp.
medium sized, yellow-brown, black in color, does have bands or spots on wings
family tabanidae: lifecycle
- eggs deposited on vegetation at water edge
- larvae hatch, enter water, sink to mud below
- tabanus larvae: voracious predators feed on frogs, annelids. chrysops larvae: vegetarians.
- both larvae pupate on dry ground along water edge
- adults emerge, mate, feed
family Tabanidae: horse and deer flies control
- difficult
- drain breeding sites
- keep animals away from breeding sites during hottest part of day
- insecticides not extremely useful
Family muscidae: stomoxys calcitrans
taxonomy, distribution, hosts, feeding
- taxonomy: stomoxys calcitrans, family muscidae, order diptera, class insecta, phylum arthropods
- aka “stable fly”
- widely distributed throughout N. America
- hosts: domestic animals & humans - large, dogs, and humans
- males AND females blood feeders, during the day, looks similar to housefly
stomoxys calcitrans: type of vector
- mechanical vector for bacteria, equine infectious anemia, habronema muscae (spirurid nematode of horses), trypanosoma evansi (protozoan of horses)
lifecycle of stomoxys calcitrans, family muscidae
- eggs deposited in organic matter - decaying plant material
- larvae hatch, bury in decaying plant material for 11-30 days
- larvae crawl to dry area, pupate 6-20 days
- adults emerge, ready to fly < 1 hr
family muscidae: stomoxys calcitrans
Control
- residual insecticides (resting places of adults between feedings like walls, fences, etc.)
- remove rotting straw/plant material - removal of breeding sites
Order Anoplura & Mallophaga: lice
term for lice infestation
reasons of veterinary importance
term for lice infestation = pediculosis importance: - irritation to host - severe infestation can cause anemia - social stigma (humans) - disease vectors
description of anoplura and mallophaga
describe host preference and life cycle
- small, wingless
- dorsoventrally flattened
- claw/crablike legs
- permanent ectoparasite
- stenoxenous = very host specific
- simple metamorphosis
lifecycle of lice anoplura and mallophaga
- females produce 1 egg (nit) at a time - cemented to hair shaft or feather. 1 female lays 50 - 100 eggs
- egg (nit) hatches in 1 - 3 weeks - 3 nymphal stages
- adults within 4.5 weeks
host preferences for Order Mallophaga, type of feeding
birds or mammals
- feeding type: chewing/biting lice
host preferences and feeding style for Order Anoplura
mammals only
- feeding type = sucking lice
Order Siphonaptera: fleas!
physical description, name of comb, type of lifestyle
- laterally compressed
- wingless
- ctenidia (combs) = pronotal comb on back, genal comb on mouth
- complex metamorphosis
- irritation, restlessness, anemia, flea allergy dermatitis
is the majority of stages on or off the host?
OFF the host!
flea eggs: description
- laid on host, quickly fall off
- hatch in 2 - 16 days
- > 500 eggs
flea larvae: description
- larval stage lasts 7 - 10 days
- 2 molts; 3 instars
- covered in setae
- found in crevices, rugs
- feed on “frass” aka flea dirt
- susceptible to heat and desiccation
flea pupae: description
- pupal stage completed in 4 days
- adults can emerge in 5 days
- emergence can be prolonged up to 174 days
- adult flea fully developed in 10 - 17 days
- larvae become coated in particles from environment
flea adults - how many times they mate
mate only once!
females store sperm in spermatheca
- begin feeding < 1 hour after colonizing host
different types of fleas: which one is common? which one is rare? which one was responsible for bubonic plague?
common = Ctenocephalides felis
rare = Ctenocephalides canis
bubonic plague = xenopsylla cheopis
order siphonaptera (fleas): diagnosis
look for signs of flea infestation and flea allergy.
look for “frass” aka flea dirt
flea allergy dermatitis
occurs when salivary proteins are introduced by flea
order siphonaptera: flea control
define: integrated flea control
- host-targeted insecticides
- environmental insecticides
- mechanical methods
combination of chemical and mechanical means which target both the animal and its environment
- host-targeted: kill larvae and/or adult fleas
- enviromental insecticides: target areas visited by animals and wildlife, in areas where pet spends most of their time
- mechanical methods: indoors - vacuum and wash bedding. outdoors: remove vegetation, litter, prevent wildlife entry in crawl spaces, etc.
Order Acarina (ticks): general characteristics
- over 800 species
- all stages (male and female) feed on blood
- two families: Ixodidae, Argasidae
- simple metamorphosis - 3 different lifecycles
Order Acarina (ticks) lifecycle
- eggs
- larva = seed tick, 6 legs
- nymph = 6 legs sexually immature
- adult
- entire lifecycle 6 weeks to 3 years
- engorged female deposits eggs on ground
one host tick
goes through 2 molts on host, then drops off to lay eggs
two host tick
during the first year in the spring it goes through 1 molt on first host, falls off in the fall and goes through second molt. then in the spring of the second year it goes on a second host then falls off to lay eggs.
three host tick
during the spring of the first year, it’s on one host then falls off to molt. then the spring of the second year it goes onto a second host and falls off in the fall for its 2nd molt. then in the spring of the third year it goes on a third host but falls off to lay eggs.
veterinary importance to Order Acarina = ticks
what is a severe tick infestation called?
- irritation
- dermatitis
- exsanguination = severe infestations
- intermediate host & vectors for protozoans & rickettsia
- somre are reportable
- tick paralysis
types of transmission by Acarina (ticks)
- transstadial transmission = disease/pathogen acquired during one life stage stays with the tick and can be passed in another
- transovarial transmission = disease/pathogen passed from female to developing offspring
tick paralysis
- ascending, flaccid paralysis due to a neurotoxin in tick saliva.
- disrupts nerve synapses in the spinal cord by blocking neuromuscular junctions
- its reversible
basic body division of acarina (ticks)
- capitulum = head
- mouthparts = toothed hypostome
- basis capituli
- idiosoma (fused cephalothorax and abdomen)
adults & nymphs have 8 legs
larvae have 6 legs
questing
when ticks like the dermacentor variabilis climb to the top of grass and start waving their arms in hopes of attaching to a host
types of hosts
dogs, cats, human
difference between family argasidae and family ixodidae (ticks)
argasidae
- soft tick
- lack scutum
- periodic parasite (feeds quickly, doesn’t engorge, leaves host)
- mate off host
- mouthparts NOT visible (bc on bottom)
Ixodidae
- hard tick
- possess scutum
- permanent parasite (can remain on host for days)
- females engorge
- mouthparts visible
Rhipicephalus sanguineus: common, name, description
family Ixodidae
Order Acarina
"brown dog tick" - three host tick, mainly dogs - throughout US - tick paralysis - disease vector - has an ornate scutum this is the ONLY tick to infest homes!!
Ixodes scapularis: common name, how many hosts, distribution, vector
family Ixodidae, order Acarina
“black legged tick”
- three host tick (birds, small mammals, cattle, sheep, horses)
- southeast to central US along east coast
- disease vector for: Borrelia burgdorfi LYME DISEASE, babesia, anaplasma marginale
ambylomma americanum: common name, how many hosts, distribution, vector
family Ixodidae, order Acarina
- “lone star tick”
- three host tick (rabbits, rodents, deer, cattle, horses, sheep)
- tick paralysis
- Southern US
- disease vector for: RMSF, LYME DISEASE, tularemia
Dermacentor variabilis: common name, how many hosts, distribution, vector
Family Ixodidae, order acarina
“american dog tick”, “wood tick”
- three host tick (rodents, small mammals, dogs are preferred, cow)
- most of US
- tick paralysis
- disease vector: RMSF, anaplasma marginale
which tick is the only genera with a special anal groove that points like an arrow?
Ixodidae
tick control in dogs and cats
manual removal and insecticides/caracides
mites: physical description
- microscopic or barely visible
- pedicels (legs/stalks) used to ID they may have a sucker on the end
- they can be surface dwellers or tunnel through skin
- larva = 6 legs
- adult = 8 legs
- 2 body divisions: head = gnathsoma, body = idiosoma
Otodectes cynotis: common name, host, distribution
Order Acarina
“ear mite”
host: dogs, cats, foxes, raccoons, ferrets
- in external ear canal (surface dwelling)
- short, nonjointed pedicels
females = suckers on some leg pairs
males = suckers on all leg pairs
- permanent parasite
otodectes cynotis: transmission, clinical signs, diagnosis, is it zoonotic?
transmission = direct contact
clinical signs = thick, tarry exudate, host shakes head, scratches ears, bacterial infections
diagnosis - swab external ear canal
NOT zoonotic
demodex canis: common name, host, physical description
order Acarina
"follicle mite of dogs" host: dogs it burrows in hair follicles and adjacent sebaceous glands - alligator/cigar shaped - adults = 8 legs - larvae = 6 legs - permanent parasite
demodectic acariasis: localized vs. generalized
localized
- skin redness
- partial hair loss
- usualy no itching
- commonly on face
Generalized
- more severe
- large patches of alpecia
- secondary bacterial infections
- pyoderma
demodex canis: how its transmitted, diagnosis, is it zoonotic?
transmitted via direct contact, usually mother to offspring
- diagnosis: deep skin scraping, pustule and abscess contents
NOT zoonotic
