Parasites I Flashcards
sarcoptes scabei: disease, transmission, parts of body affected, diagnosis
causes scabies
transmission by direct contact with an infected person or by contact with infected clothing or bedding. also transmitted from one part of the body to the next by scratching
diagnosis: scrape affected skin and check for adult or eggs
prefers skin folds (btw digits, where limbs join trunk, etc)
sarcoptes scabei: lifecycle
burrows in skin. 3-4 days later lays eggs. then, larva is released and excavates new burrows and matures (3-4 days). can live 1-2 mo. on the body
crusted scabies
severe scabies of the immunocompromised
people develop thick crusts of skin that contain large numbers of scabies mites and eggs.
highly infectious
may not be as itchy as people with regular scabies
What is the mechanism of disease in scabies infection? How is scabies treated?
acute inflammatory response to infestation and delayed type hypersensitivity reaction.
treatment: wash with soap and warm water. topical treatment with insect repellent. or, benzene hexachloride (as long as pt isn’t pregnant)/lindane or malathion be careful- this can be toxic to people on high doses or in cases of long-term use.
hair follicle mite Demodex folliculorum
lives in hair follicles and sebaceous glands
usually commensal
wash with soap and water.
associated with improper make up removal
chiggers: what, how does disease work (vague), on what do they feed, how treat? How prevent? dangers?
mite larvae that induce a painful inflammatory response, esp. in those who have been previously exposed.
feed on tissue juices (not blood)
treat with rubbing alcohol, lontions with benzocain/lindane to releive itching and pain. Permethrin can be applied to clothing to prevent infection in those working in the field. can also be a vector for transmission of scrub typhus.
Body louse: life cycle, hosts, treatment, detection
life cycle exists exclusively on human host- lice die in 1-2 days without host.
detect by looking for nits, aka louse eggs. can be seen on hair with naked eye or using Wood’s light UV lamp (nits fluoresce).
Louse die when/if host gets a fever (very temp sensitive). Also, soap and water and Lindane are used for treatment. also treat infected clothing (heat, lindane)
Phthirius pubis: disease, transmission
pubic louse
transmitted by person-person contact or contact with infested clothing
fly larvae: transmission, treatment
adult fly traps a mosquito mid-flight and lays eggs on the abdomen. when mosquito takes a blood meal, the warmth of the skin stimulates larval hatching and burrowing. mature 6-7 wks, then exit the skin.
hard to remove since chitinous hooks can cause skin tearing and pain. may be removed surgically or by blocking spiracles (breathing tubes)protruding from the skin with fat. larvae can’t breath, so they take themselves out of the skin.
cordylobia anthropophaga aka tumbu fly
presentation, transmission, treatment
non-resolving “mosquito bites”
larvae mature rapidly. fly lays eggs on damp clothes (can be dangerous with baby diapers). Do NOT confuse tumbur fly withb helmiths. tumbu fly can be teated only with physical debridement.
cimex pemipterus aka bedbugs
what do they eat? special features, complications?
large
hematophagous
can persist monthes without feeding
OTCs usually fine be careful of other ninfections- can be transmitted by bedbugs!
Talk about the adult flea: what makes it a good parasite and why is is it important?
notorious for yersinia pestis transmission. flea bites a rat and picks up the bacteria; bacteria multiplies in the gut and blocks the flea gut; flea bites human to try to feed- human gets sick!
durable and resiliant: can persist months w/o food; can survive freezing for a year without problems. don’t fly but can jump very long distances (30X their body length). they are blood-sucking parasites.
can also carry mites
what causes the major arthropod-borne helminth infections? what are some characteristics of that type of worm? Reproductive features? How long can they live in the body?
nematodes, aka roundworms non-segmented worms complete digestive tract- mouth and anus reproduction: sexual- separate males and females (females are bigger than males) lifespans range from 1 yr to decades
dracunculus medinensis aka guinea worm: how do you acquire the infection/lifecycle
- drink water contaminated with infected copepods (water fleas), esp. standing water
- larvae are released from the copepod in the stomach
- larvae penetrate the stomach wall
- larvae develop to maturity in the body cavity or tissues
- live subcutaneously and cause a skin blister/ulcer prior to releasing its larvae into fresh water to infect a copepod
What do we know about prevention and treatment for dracunculus medinensis?
treatment: none, though antibiotics can be used to treat secondary bacterial infection that may result if a worm breaks and causes extra inflammation
prevention: copepods and people are the only reservoirs- so elim should be possible. drinking water can be boiled or filtered or treated chemically. obstacles are cultural and economic
