parasites

successful parasites generally do not _______?
harm their host
what parasitic disease might mozart have died from?
trichinosis
how are parasites classified?
protozoa (single cellular), that exist as cysts (protected form/diagnostic form) in their infective stage and trophozoites (fragile form) in their metabolically active stage. parasites can also exist as multi-celluar helminths, (worms)
is the trophozoite form infective? what is the common route of transmission for protozoa?
no. fecal-oral is the common modes of transmission for protozoa
what are nematodes, platyhelminths, cestodes, and trematodes?
nematodes – round worms, platyhelminths – flat worms, cestodes – tape worms, and trematodes – flukes. these are all considered helminths, or parasitic worms
is there a vaccine for any parasitic infection?
no, the malaria vaccine is probably still 5 yrs away
what are some ways in which helmiths are able to avoid the immune system and cause chronic infections?
complexity of genome, multiple developmental stages, conservation of sequences, use of host-derived cells for sequestration and antigenic variation/masking
what are some symptoms of a parasitic infection?
malnutrition, failure to thrive, mechanical bowel obstruction
what are charcot-leyden crystals? where can they be seen? what is it indicative of? can there be a helminth infection without the presence of charcot-leyden crystals?
by-products of eosinophil breakdown which can be seen in sputum, urine and stool. it is indicative of a helminth infection when the mucous membrane is penetrated and the disease becomes systemic. helminth infections are possible with out appearance of charcot-leyden crystals. (fyi: these can be seen in collagen vascular disease, cancer, allergic diseases and fungal infections)
what is an important consideration in terms of sexual transmission of parasitic infections?
giardia, cryptosporidium, amebiasis can all be transmitted through anal sex – therefore it is important to take a detailed sex hx
what are common forms of giardia transmission beyond sexual contact?
mothers not washing hands after diaper changing and making food, children being exposed to fecal matter at daycare, fecally contaminated fomites, (keyboard, railing, stethoscope, door knobs, long neck ties, cell phones etc)
what is useful test to order in terms of parasitic infection? how should it be explained?
stool O&P, (ova/parasites). pts need to have clear instructions about how to collect the fecal matter (feces should be collected on a newspaper over the toilet bowl), b/c compliance is an issue
if pts have an (often diarrheal) disease hx of long refractory period, travel, lack of response to antibiotics, what should be considered?
parasitic infection
what are some circumstances that probably do not reflect a parasitic infection?
patients in ICU on antibiotics you probably would not assume parasitic, or someone eating at mcdonald’s and starting vomiting and diarrhea within a few hours, probably not parasitic because parasites need time
what is delusory parasitosis?
pts (mostly are women) with psychological mental blocks thinking they have a parasites living on the skin or right under the skin
what do ectoparasites consist of?
mostly scabies and lice
where are most free-living parasites found?
mostly in bodies of water.
what is an example of a free-living parasite infecting the eyes?
acanthamoba castellani can cause acanthamebic keratitis (corneal infection) if contact solution is contaminated by the manufacturer/swimming with contact lenses on/corneal trauma. it is an amoeba
can acanthamoba castellani cause skin ulcers? what are other possible complications? differential diagnoses? tx?
yes, but mostly in HIV pts. scleritis/enucleation are other possible complications. acanthamoba castellani can also appear similar to herpes or fungal keratitis. polihexanide and/or topical hexamidine are common treatments prescribed
what is an example of a mostly fatal infection caused by free-living parasites that can be contracted by swimming in contaminated small lakes/ponds? how does it kill?
naegleria fowleri (trophozoite) which enters the brain through the cribiform plate and causes fatal menigo-encephalitis. it is an amoeba
what is the hygiene hypothesis?
less atopic diseases (lupus, asthma, hay fever, allergies etc), are seen in developed vs developing countries where helminths are still common. this leaves a “niche” for TH2 cells in developed countries for atopic diseases to become more prevalent, and the hypothesis has even been extended to leukemia.
where did parasites come from?
possibly animal domestication
what is toxoplasma gondii?
an AIDS-defining parasite, (the gondii species name comes from giant african rodent), that causes toxoplasmosis.
what are the 3 forms that toxoplasma gondii can take?
oocyst, bradyzoite, tachyzoites
what is the toxoplasma gondii life cycle/transmission?
it exists as an oocyte in cats, (its reservoir) and either active or chronic infections as tachyzoite (crescent shaped), or bradyzoite in other animals that ingest either oocytes from feces or bradyzoite cysts from infected meat. tachyzoites can also be transmitted to the fetus of pregnany women
who are people at risk for becoming infected by toxoplasma gondii?
immunocompromised pts, (HIV/AIDs) and pregnant women. cleaning cat litter is a common mode of transmission
when is toxoplasmosis a problem in pregnant women? when is the risk most serious?
if they do not have an IgG against it, it can be transmitted to the fetus, which is most vulnerable during the 1st trimester
why is there mandatory testing of pregnant women in france/austria for toxoplasmosis?
raw horse meat is a delicacy there
what is the toxo triad for toxoplasmosis? how can this be detected?
chorioretinitis, intracranial calcifications, and hydrocephalus in a developing fetus. ultra sounds can pick up hydrocephaly or intracerbral calcifications
what are some other symptoms of toxoplasmisis?
opisthotonos (congenital rigid arched back), microopthalmia (congenital small eyes), hemorrhagic lesions
what is toxoplasma encephalitis what does it cause? what is common tx?
AIDs defining illness where once CD4 count drops below 100 (due to AIDs), hemmorhage, space occupying lesions, necrosis in the brain and calcifications apparent on MRIs can occur due to a toxoplasma gondii infection. symptoms include focal neurologic defecit/generalized cerebral dysfunction/neuropsychiatric abnormalities. tx is usually trimethoprim sulfamethoxazole, which should help kill toxoplasma.
what do tachzoites in a pt suggest?
they suggest an active infection
can transplant pts/drug needle sharers become infected by toxoplasma gondii?
yes it can be due to a reactivation in the host or it could be new infection from donor
what are recommendations for immune compromised/pregnant pts in avoidance of toxoplasma?
avoidance of raw/undercooked meat, handwashing, washing kitchen surfaces, keeping insects from food
what are recommendations for new pets in avoidance of toxoplasma?
do note feed it raw meat, caution in litter tray removal, disinfection of litter tray w/boiling water, get rid of pet if diarrhea/6 mo old
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