Intro to parasites Flashcards
What are the 2 types of parasites that infect humans (other than a few inscts)
- Helminths
2. protozoans - single cell
Define definitive host and dead-end host
definitive: contains sexually mature, adult parasite
dead-end: blocks transmissiono
What is a common feature of helminth infections
they suppress the immune system
Where do they multiply with respect to humans:
protozoans
helminths
protozoans: within human
Helminth: outside (lay eggs aoutside and must be re-ingested)
6 parasites prevalent in US (plus one extra in kentucky few decades ago)
- Pinworms (enterobius vermicularis)
- toxoplasma gondii
- Trichomonas
- Pediculus humanus capitus (head lice) -only head-head contact
- Giardia:
- Ameoba: E. histolytica, N. fowleri
- -Nematodes (ascaris, stronglyoides
8 MC worldwide in order from MC -LC
- Big 3 nematodes: roundworm > hookworm > whipworm
- Filarial worms (W. bancrofti–> elephantitis)
- Malaria
- Schistosomes (flukes)
- E. Histolytica
- Trypanosomes
- Leshmaniasis
Intra- vs. Extracellular protozoan pathogenesis (very general)
extra: compete for nutrients
intra: cell and tissue destruction
What is one of the on;y parasite to releas a toxin
E. histolytica
Serological testing is avaialable for what 3 US prevalent parasites
toxoplasma, Trichomonas, Giardia
How is plasmodium falciparum dx?
PCR
Why is dosing an issue with anti-parasitic druigs
bc they target eukaryotic cells
What drug is MC for protozoans, and which is MC for worms/flukes? and MOA
Protoz: metronidazole: converted to active agent only in anaerobes–> DNA damage
worms: Benzamidazoles: interfere with tubulin function
Which proto is resistant to chlorination
Giardia
What disease does E. histolytica cz and pathogenesis
Amoebiasis: dysentery
Naegleria fowleri: disease, habitiat, human host designation
warm fresh water
invades nasal mucosa to cause meningitis
humans are a dead-end host
E. histolytica: habitat, life forms (2), virulence factor and it’s moa
habitiat: human waste
forms: trophozoite and cyst
produces a cytotoxin–> lyse cells –> tissue invasion (thus histoLYTICa)
transmission of E.histolytica, and what hosts is it found in?
fecal-oral (gay dudes)
only host is HUMANS!!
Histo of E. histolytica infx
****Flask-shaped ulcer
What can a chronic E.histolytica infx cause?
IBD
Other than the intestine, where else can E. histolytica infect? Presentation in this location?
liver - cuases “anchovy-paste abscesses”
CP of E. histolytica infx
gradual onset of bloody diarrhea, abd pain, maybe fever
How is E. histolytica infx diagnosed (1 for class, 2 for sketchy)
class: ELISA for antigens in stool
sketchy:
“trophozoite w/ endocytosed RBCs”
Intestinal bx: flask-shaped lesions
Dx of N.fowleri
exam of CSF
E. histolytica tx? (2)
metronidazole
iodoquinol
Iodoquinol MOA
iron chelator
warning signs about swimming in water are warning against what protozoa
n. fowleri
