Arthropods Flashcards
1
Q
athropods can affect human health in 4 basic wasy
A
- parasite disease transmission as vectors: mechanical, biological
- bites and envenomations
- tissue invasion
- psychological/psychiatric manifestations = entomophobia, delusion parasitoses
2
Q
arthropods as vectors
A
- Diptera = mosquitoes, flies, midges
- Acarina = ticks and mites
- Hemiptera = triatomid bugs
- Siphonaptera = fleas
- Anoplura = sucking lice
3
Q
arthropods = bites
A
- acarina
- anoplura
- araneae = spiders
- chilopoda = centipedes
- diptera
- heimptera (bedbugs, kissing bugs, triatomid bugs)
- siphonaptera
4
Q
difference between bites and envenomations
A
envenomations = stinging; venomous
bites = non-venomous; inject anticoagulant saliva so they can feed on your blood = body rxn to antigenic components of saliva; not associated with dangerous venomous effects mostly
5
Q
b=venomous arthropods
A
- hymenoptera (ants, bees, hornets, wasps)
- scorpions
- other = caterpillars, spiders, millipedes, blister beetles, etc.
6
Q
tissue invasion arthropods
A
acarina
diptera
pentastomida (tongue worms)
siphonaptera
7
Q
siphonaptera
A
- fleas
- small,wingless, laterally flattened, over 2000 sp
- survive >1 yrs even unfed
8
Q
abnormal or exaggerated fear of arthropods or insects
A
entomophobia
9
Q
people who think they are infested by arthropods regardless of lack of evidence
A
delusion parasitoses
10
Q
flea cycle pyramid
A
- 50% eggs = about 2 weeks to hatch depending on humidity
- 35% larvae = spin cocoons within 5-20 days of hatching from eggs
- 10% pupae = stay in cocoon for many days or weeks prior to emerging when vibrations and body heat alert it that host is near
- 5% fleas = feed from host within few hrs of emerging from cocoon; begin to lay eggs
11
Q
fleas can affect us in 2 major ways:
A
human exoparasites
vectors for infectious diseases
12
Q
human exoparasites
A
red itchy bumps = host rxn to flea saliva = may get infected if scratched
- Pulex iritans (human fleas)
- Ctenocephalides canis/felis (dog/cat fleas)
flea dermatitis = hypersensitive hosts, hives, blisters lasting many days to weeks
most bites localized on feet and ankles
13
Q
flea vectors for infectious diseases
A
Xenopsylla cheopis (rat flea)
plague (bacteria)
typhus (ricketsiae)
dog tapeworm (D. caninum)
14
Q
legs of fleas
A
- unusual adaptation
- protein resilin pads provide energy needed to jump
- jumps can be vertical or horizontal; reach 200 body lengths at 200g acceleration (like flying)
15
Q
do fleas have eyes?
A
usually when they infect diurnal hosts they have well-developed eyes compared to fleas that infect nocturnal animals
16
Q
mouthpartso ffleas
A
adapted to suck blood from host
17
Q
compact body of fleas
A
so they can move swiftly in hairs/feathers of host
18
Q
itch mite
A
Sarcoptes scabiei
- life span = 1-2 months
- severe itch as they burrow through superficial layers of skin
- adult female = burrows and lays eggs; two to three days to develop to develop to larvae and another 2-3 days = nymph => adult female -> mate with males
19
Q
fecal pellets
A
more of an irritant than eggs laid by Sarcoptes scabiei
20
Q
symptoms of Sarcoptes scabiei
A
very severe itchy rash (red lines), blisters
scratching kills mites but may cause bacterial superinfection
NOTE: patient may be asymptomatic for 2-6 wks but after exposure can still spread infection to others
21
Q
T or F. You should avoid direct skin contact with person infected with scabies
A
T! at least after 8 hours after treatment is complete because even treated patient can disseminate infection
22
Q
where can Sarcoptes scabiei be found?
A
mostly skin folds; epidermis (in between pts or interdigital spaces, buttocks, axilla, groin, etc.)
red line = blister formed at end of burrow = where you can usually find a female scabies
23
Q
Norwegian scabies
A
- some hosts such as elderly or diabetics with neurological conditions = don’t feel itch = don’t scratch = 1000s of mites instead of 10 -15
- extremely contagious = high # of mites
- scale, crusted skin = very painful and uncomfortable
24
Q
diagnosis of Scabies
A
microscopy of skin scrapings
preferably at the end of burrows to catch female
25
Cimex sp.
bed bugs
- known since Greece
- feed on blood (warm blooded animals and humans) at night every 5-10 days
- poor eyesight so may use CO2 (that we release) to move along
- *temporary parasite* = because only visit humans when need to feed
- may live up to 18 mos without feeding
- eggs in dark protected places = furniture cracks, behind pictures, wallpapers
- notorious hitchhikers and travel on objects such as clothing, books, bgs, furniture, spreading infestation to new locations
26
larval form of bedbugs
incstars
27
thin when hungry but expand as they feed
bed bugs
28
how many larval stages do bedbugs have?
five
feeding on blood is **required** to develop to next stage
29
T or F. Bed bugs have wings
F! They have wing pads but through evolution lost their wings
30
hunger folds of bed bugs
11
will unfold when feeding = balloons up
but when hungry - flat = slips through crevices
31
unique feeding apparatus of bedbugs
- head fitted with tube-like structure = **rostrum** = folds underneath head and long body when not in use; when in use = unfolds to downward piercing position
- **mandible** = inside rostrum = serrated edges ; cut into host skin
- **maxillae** = behind mandible; once skin breached these search for blood vessels
- **Cibarian pump** = head of bug; initiate sudden gentle suction to have blood flow to bedbug; ensures constant blood flow
- **salivary duct** = anticoag saliva and anesthetic to vessels to ensure bite is painless and host not disturbed
32
how to get rid of bedbugs?
Vacuum your house thoroughly, including cracks and crevices.
Dispose of the vacuum cleaner bag right away (in a sealed plastic bag to contain the bugs)
Wash clothes and other objects in hot water (at least 50°C).
Dry the clothes and other items in a clothes dryer on the high heat setting for 20 minutes.
You can also put pillows and stuffed toys in the dryer (even without washing)
Hire a professional exterminator.
33
clinical manifestations of bedbugs
- little/no rcn to itchy rash/anaphylaxis
- bite marks = may be single but usually multiple and linear = 'breakfast, lunch, and dinner"
- may transmit hep B and Chagas disease (still disputed; so bedbug bites mainly a nuisance than a serious infection)
34
Most common species of bedbugs
Cymex lectularius
35
rustic brownish spots
characteristic of bed bugs infestation
- dont just look for bedbugs; look for these too
36
myiasis
infestation of live humans and vertebrate animals with dipterous larvae which feed o host's dead or living tissue, as well as liquid body substances or ingested food
37
specific myiasis
arthropods behave as obligatory tissue parasites
- life in tissue of hosts = needed for complete cycle
38
semispecific myiasis
eggs or larvae in decaying flesh or vegetable matter/ morbid tissues
- not necessary for cycle; could be replaced by environmental development
39
ACCIDENTAL MYAISIS
eggs accidentally fall in excrements, decaying organic matter or foods
40
nosocomial myiasis
happens more often during neglect in hospitals
41
site of invasion for myasisis
cutaneous
ophthalmic
nasal
aural
- development of larvae in the skin, eyes, nose, ear
42
uncommon forms of myiasis
intestinal
urogenital
lung
43
Dermatopbia hominis
cutaneous myiasis
44
Gasterophilus sp
cutaneous, rarely gastric myiasis
45
Hypoderma bovis
subcutaneous, ocular myiasis
46
Ostrus ovis
nasopharyngeal, ocular myiasis
47
order of lice
Pthiraptera
48
sucking lice suborder
anoplura
49
lice (pthiraptera)
- ectoparasites of mammals and birds
- small, flattened insects that are blood sucking; mouthparts usually retracted iwthing head and modified for piercing and sucking
- segmented body = head, thorax, abdomen, 3 prs of jointed legs, pair of antennae, NEVER wings
- order is divided into suborder = chewing lice = Ischnocera and Amblycera from sucking lice Anoplura
50
where are lice usually found?
preferred host = info on host and site of infestation of host is an important aid to ID
51
species of lice most important to public health
body louse, head louse, and crab louse
52
symptoms of lice
intense irritation
has a role in carrying epidemic typhus, relapsing fever, and trench fever
53
three main soecies of sucking lice
Pediculus humanus (body louse)
Pediculus capitis (head louse)
Pthirus pubis (crab or genital louse)
54
head louse life cycle
gradual metamorphosis; eggs laid on hair shaft
6-7d = young louse hatches
first moult = 2 d after hatching
second mpoult = d after hatching
third moult = 10d after hatching
2 adult louse M & F; F slightly larger; F reproduce
F lays eggs 2d after mating; 4-8 eggs for the next 16d - then dies
55
development of head loiuse
50-300 eggs/female
from egg to adult approx takes 1month
56
the stage that hatches from eggs is the first _________; what does this resemble?
nymph; resembles adult and feeds with them
57
lice nymphs
they resemble adults
molt through three stages and final moult produce sexually mature adults
adults similar except for genital structures
- M has sclerotized gen structures
- F has sclerotized gonopods
58
where is life cycle of lice happening?
entire life cycle spent on host and spread between hosts occurs by lice crawling when hosts come into contact
59
lice as human exoparasites
human pediculosis = papules (small lumps), blisters, skin thickening, and pigmentation
60
Vagabond's disease
human pediculosis
- disease occur in ppl who are street ppl, down and out ppl, and ppl who have bad hygiene habits
61
lice as vectors
louse-borne typhus
= Ricketsjae, Borreliae, Bartonella (trench fever)
= travel over 20 cm/min
62
lice travel speed
over 20cm/min
63
what are the eggs of human head louse referred to
Pediculus capitis = nits
64
body louse Pediculus humanus infects...
clothing of humans esp. those unable to change clothing
65
P. humanus transmits the following:
Rickettsia prowazekii
Bartonella
Borrelia
66
R. prowazekii
louse borne or epidemic typhus
67
Bartonella
bacteria
causes trench fever
68
Bartonella
epidemic relapsing fever
69
T or F. P. capitis transmits pathogens
F!
70
T or F. P. capitis is commonly found infesting school children
T! head louse infests children ... NOT body louse
71
how can process of lice detection be enhanced?
UV lamp
white specs = nits
72
describe nits of head/body louse
- laid singly; 0.8 mm in length and 0.3 mm across
- cap or perculum at one end and attach to host hair by cement secreted by female at time of lay
- head louse lay eggs at base of hair
- body louse lay e ggs in folds of clothing at seams
- eggs hatch between 6-14d if kept at body temp
- 40C eggs will die in couple of days
- maintained at 20C eggs developed but nyph dies in that egg
- exposure to 8C kills it in 7d
- when ready to hatch = nymph pushes off the operculum and forces out of the egg
73
how does the lab report lice?
P.humanis/capitis ; head and body louse bc can't differentiate
74
features of crab louse
- smaller than P. humanis
- body wide and abdomen narrower and short
- head = blunt at tip and small eyes
- mid and hind legs are stout; large claws
- movement slow and deliberate like crabs
- found infesting hairs of armpits, bear, pubic and perianal regions of both sees
- irritation can be intense
75
distribution of crab louse
worldwide like P. humanis but is NOT known to transmit any diseases
76
nits of crab louse
- never found on clothing
- smaller than head/body louse
0 attach to hair of host with larger amt of cement
- nymph hatches from egg after an incubation period of 7-8 d; three nymphal stages than the adult hatch about 13-17d; adult lives for ~month
- rare found on scalp; infants seen with crab louse in scalp = head to head transmission due to close contact instead of sexual contact
- tends to spread among ppl living in bad conditions
77
T or F. Crab louse likes to hand of hair of the host
T
78
prevention of body lice
- spread most commonly by direct contact with an infested person or their clothing
- bathe regularly
- change properly laundered clothes at least once a week
- launder infested clothing at least once a week
- machine wash infested clothing and bedding using the host water (130C) and high heat drying cycle
- clothing and items not washable can be dry-cleaned OR sealed in plastic bag & stored for 2 weeks
- do not share clothing, beds, bedding, and towels used by an infested person
- fumigation or dusting with chemical insecticides sometimes is necessary to control and prevent the spread of body lice for certain diseases
79
prevention of head lice
- historically shaving
- avoid head-to-head contact during play and other activity
- do not share clothing such as hats, scarves ,etc.
- do not share combs, brushes, towels; disinfect combs and brushes used by an infested person by soaking them in hot water (130C) for 5-10mins
- do not lie in beds, couches, pillows, etc that have been in recent contact w infested perosn
- same as body louse = high heat drying cycle and host washing machine settings
80
prevention of pubic louse
- all sexual contacts of infested person should be examined => treay
- sexual contact bw infested persons and their partners should be avoided until al have been examined and treated
- machine wash and dry clothing worn and bedding used by infested person in hot (130C) water; high heat drying OR sealed in plastic bag and stored for 2 weeks
- do not share clothing, etc.
- do not use fumigant sprays or fogs = not necessary to control pubic lice and can be toxic if inhaled or absorbed through skin
- persons with pubic lice should be examinend and treated for other STDs
81
treatment of pediculosis
- improved hygiene and access to regular changes of clean clothes = only treatment needed for body lice
- OTC and prescription meds are available for head and pubic lice infestations
> Pyrethrins
> Permethrin
- use prescribed meds with caution
- head infestations can be dealt with combing with a special fine metal toothed comb paying special attention to hair at back of neck and ears
- no known insecticide removes nits though some may kill them
82
what is a tick?
obligate hematophagous ectoparasite = have to eat a blood meal
arachnid(Acari); not an insect
not an insect; no segmented body, eyes, ears, etc
more closely related to mites and spiders
sense hosts via CO2
cannot jump or burrow into skin
divided into hard ticks (Ixodidae) and soft ticks (Argasidae)
83
soft ticks
- Argasidae
- look a bit like a raisin
- some psinuy outer surface, some leathery outer cuticles
- transmit some diseases
- bed bug- like life cycle = immature life stages and tend to feed at night time
84
hard ticks
- Ixodidae
- scutum = shield-shaped structure on dorsal surface
> in females = less than half of dorsal surface, males = entire dorsal surface
- males only can take a small blood meal
- females = gros quite large
85
unfed vs fully fed female
can be up to 100x size of an unfed female
if full = ready to drop to ground and lay 3000-5000 eggs and then die
86
structure ticks used for feeding
denticles structure like teeth = gluey compound = stick to surface
middle of structure = hollow = used like a straw
87
tick removal procedure
- grasp tick as close to skin as possible
- dont sequeeze; dont grab main mody of tick
- pull off in one steady motion
- examine area for attached mouthparts
- wash area with soap and water
- save tick for surveillance
* there are some tick removal compounds but tweezers better *
88
life cycle of hard ticks
molt between three life cycles
- egg
- larva (6 legs); attach to host; feed; drop off
- nymph (8 legs); attach to different host; drop off
- adult (8 legs, female or male); third host; F feed, mate and feed to repletion and M only take small meals
- ticks can overwinter and live up to 3 yrs
- 3-host and 1-host lifecycle ticks in AB
> 1-host tick = moose tick; can complete entire life cycle on one host
>3-host tick greatly increases a tick's chances of acquiring and transmitting a pathogen
89
T or F. 3-host tick greatly increases a tick's chances of acquiring and transmitting a pathogen
T!
some pathogens can stick with a tick for its entire life cycle, while some have to be re-acquired to be transmittable
90
tick-borne diseases
- ticks = major vector of many human and animal pathogens
- due climate change, arthropod diseases are forecast to increase as vector ticks spread geographically
- bacterial: Lyme disease, Rocky ountain spotted fever, anaplasmosis, etc.
- protozoan: babesiosis
- viral: colorado tick fever virus
- syndrome: tick paralysis Alpha Gal
91
Borrelia burgdorferi sensu stricto
original pathogen and main type found in NA (Lyme Disease)
- B. burgdorferi sensu lato genospecies (eg. B. mayonii) here in NA
intracellular spirochete
interesting genome = 1MB linear chromosome with 15+ mix of linear or circular plasmids
92
how is Lyme disease transmitted?
- B. burgdorgeri is transferred into host via tick saliva
- takes 24 hrs for bacteria to move from saliva to host (so have window of time to remove tick before infection)
- cannot be transmitted transovarially in tick but transstadial transmission does occur
> larval, nymph, or adults must acquire the pathogen during feeding on an infected host
- B. burgdorferi is maintain in an area by reservoir hosts, typically mice here in NA
93
major vector of B. burgdorferi in NA
three-host hard tick = Ixodes scapularis
94
Rocky Mountain Spotted fever
Rickettsia rickettsii
- intracellular cb
- transmitted by Dermacentor sp.
- ticks are vector and reservoir (transovarial transmission)
- lots of vector species in AB but reports of RMSF rare
95
AlphaGal
- (non-primate, vertebrate) red meat allergy caused by immune response to alphagalactose
- Amblyomma americanum bite thought to be major source
> but other ticks also suspected
96
