bactitech
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Which statement is NOT CORRECT when characterizing Trematodes?
a. They infect the intestines, liver, and lungs
b. Mosquitoes are the intermediate host.
c. Eggs are passed with the feces into the water where they hatch.
d. Diagnosis is by fecal analysis for egg or adult forms or blood analysis for schistosomes.
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| mdwannabe
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B......eggs are too big to fit GI of mosquitos
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| bactitech
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Nope - try again.
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| mdwannabe
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oh yeah,...intercalatum is transmitted with mosq...
C...then...they hatch once in the definitive host.
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| bactitech
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Try again - not the answer that my key gave.
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| mdwannabe
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I don't like guessing...this is what I can reason out. May someone else can give it a try with explanation.
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| bactitech
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You know, I haven't had a chance to research this until now. I have a feeling that the "official" answer, which is (A), is wrong. I googled "trematode infection" and got this site:
http://www.emedicine.com/med/topic2301.htm
It characterizes human flukes as coming from blood, liver, lung, or intestine. I would think, from this aspect, that (B) is the correct answer.
Sorry about that. I just slapped the question up and I had quickly circled the answer from the key, which was in the back of the book, and I did it at work at the end of the day (read that "tired") so I was the one that screwed up. My humble apologies. I'll be more careful next time :-).
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| mdwannabe
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Fasciola hepatica...is a Liver fluke
Schistosomas...go to lungs while developing..causing Katayama fever
Echinostome..is intestinal fluke
...So ..A...is wrong.
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| bactitech
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Yeah, I know. I'm truly sorry :-(
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| mdwannabe
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Its OK... I am not shaming you...only supporting your thought. :-)
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| bactitech
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:-) :-)
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| mjl1717
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1 mistake out of 1000 is OK or great!!
Afew thoughts on trematodes although not H. Y. on usmle because they'are rare in the U.S.!!!
1)Schistosome is unique in that it has separate sexes.--can penetrate skin.
2)S.haematobium -bladder CA-----------
3)sometimes 2 intermediate host/key words miracidium and cercariae
4)near snails,crabs, water plants
5)RX all except Fasciola with Praziquantel(Fasiola rxed with Bithionol
mdwannabe you're good if you know the size of the eggs.
bactitech you still got it.
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| mdwannabe
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I made a point, while learning Parasit, to look at everything we studied under microscope. So its easier to recall.
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| bactitech
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When we techs learn parasitology, the biggest thing that is pounded into our heads is to MEASURE the object we are seeing. We have built-in micrometers in our eyepiece and a measurement will rule in or rule out certain parasites, along with other characteristics. This is particularly important when dealing with unknown Entamoebas, and our CAP unknowns usually ALWAYS include an Entamoeba. These can be difficult to identify if four or less nuclei are seen. If one sees over 4 nuclei, and the measurement is okay, it is always Entamoeba coli, which is a commensal. It gets tricky when you have to decide whether you have E. histolytica or not.
Trophs can look different than cysts also. We always have a couple of reference books handy, and if we're not sure, we have multiple techs look at the preparation or slide before calling a positive.
The problem is that we see many many many negatives for every positive we find. Most of the training consists of figuring out what is NOT a parasite. When you first start out you think that there will be one around every "corner." You finally relax when you figure out that they are few and far between.
We scan our concentrated preps under 20X hi-dry and look for anything refractile. If something looks suspicious, we go down to 40X hi-dry. The concentrate is made from the formalin vial of the submitted fecal specimen.
Trichrome smears are always scanned under oil-immersion. These are made from the PVA vial of the submitted fecal specimen. They are dried overnight and stained once a day in a batch, then permanently coverslipped, and read. They are pretty labor intensive.
If there is to be any appreciable delay in testing feces for O&P, the specimen should be submitted in preservative. Your local lab can guide you as to which ones to use. Some labs are going "formalin-free" and using a different kind of preservative (I don't know what it's called). Some use a one-tube preservative, and they perform both the concentrate and Trichrome from that (I believe it's Zn-PVA). We use a two tube, fairly standard method with 10% formalin in one tube, and PVA (poly-vinyl alcohol) in the other. These are given to the patient and then they must put the feces into the tubes, which can be dicey :-(.
Once the stool is in the preservative, it can hold for quite some time before processing.
Remember - the patient should collect stools X 3 but have them space the collection at least 1 and possibly two days between each specimen for optimal collection. DO NOT DO ALL THREE IN ONE DAY. Most insurance won't even pay for all three in one day, and your patient won't appreciate that much. Many parasites, particularly Giardia, will shed only at certain times, and by spacing out the collection, you optimize recovery.
Actually, a Giardia antigen for most patients will give you the fastest result, as that is the most common parasite found in the US UNLESS the patient has a travel history outside the country. Then all bets are off.
I went to a parasit workshop years ago. The one thing I always remembered from it was this: anyone with diarrhea lasting more than one month should always have O&P examinations performed. You can, of course, run other fecal testing at the same time - just make sure you submit the proper specimen. Stool cultures can be submitted - fresh - in a cup without preservative, or in Cary-Blair preservative (optimal). Tests like Rotavirus and Clostridium difficile toxin CANNOT HAVE PRESERVATIVES, so a plain stool specimen must be submitted.
A rectal swab is pretty worthless unless you get a lot of feces on the swab, and then it's usually only good for a culture. It's not the most optimal of specimens.
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| mdwannabe
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thank you! That was an interesting insite! If you'd had to put the most common parasites in US and dzz they cause... what would those be?
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| bactitech
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Giardia is the most common one we see in stools. That's why a Giardia antigen test is the way to go first with people that have no travel history. It's much more sensitive than a visual O&P examination. It's really dependent upon the population you are seeing. If you're working in a big coastal city with a lot of people who've been overseas, all bets are off.
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