Hello!
I have to store for a long term (a few weeks or months) Schistosoma haematobium eggs from urine samples. They are meant to be used for morphology but also for molecular typing. Where I am I only have access to ethanol. Although it is ok for storing them for DNA extraction, will the ethanol distort the eggs too much for morphological recognition in the future? I have experience with STHs eggs in stools stored in ethanol for months and still ok morphologically, but I am not experienced with Schistosome eggs. I am not sure whether to store only the eggs after centrifugation/sedimentation or the entire urine sample (that I still have). Many thanks for your help;)!
Dear Corrado Minetti,
In my opinion, fixation of eggs in ethanol are good for both purpose, i.e. molecular and morphological studies. Yes, aiming that ethanol do not be diluted due to the presence of urine in your samples, fix only the sediment obtained after centrifugation or sedimentation.
Have a good luck in your studies!
Hudson
Dear,
First, it is important to know why you want to preserve the morphology of eggs of S. haematobium, since, whether the aim is only to identify the egg in urine samples, the use of ethanol as a fixative may be feasible. In general, it is possible to use 70-90% ethyl alcohol as an alternative fixative of feces presenting schistosome eggs, although in this case, the morphology of the Schistosoma mansoni egg may undergo some variations, which do not prevent their identification. Anyway, I suggest that the method of fixation is standardized before you start your study.
Best regards,
Vitor
Corrado,
Fixation in high percentages of ethanol is good for molecular work, but leaves many artifacts that would be less favorable for morphological work, even at the light microscope level. For morphology and ultrastructure work with electron microscopy, ethanol is not at all satisfactory. The best general fixative is probably glutaraldehyde, but this is similar toxicologically to formalin (i.e., aqueous formaldehyde solution). A great method for preserving helminth eggs for both molecular and morphological or ultrastructural work without toxic chemicals is through cryotechniques, involving rapid freezind followed by freeze substitution. We have used this recently in our studies of the eggs of the cestode, Gyrocotyle urna, whose eggs are very similar to those of Schistosoma and other trematodes. I have linked below a very recent abstract and Powerpoint presentation below.
Best wishes for success in your work.
Bruce
Data Conn with Levron et al 2015 CRYOTECHNIQUES REVEAL NOVEL ULTR...
Conference Paper Cryotechniques reveal novel ultrastructural features of embr...
Having eosin and ethanol together can preserve schistosomias eggs as long as you want and can be checked when ever you have the chance to look at the sample
For keeping the original morphology of Schistosoma haematobium eggs, it is best to use simple household-bleach. Just add some drops (about 0.1 ml) 1%v/v Sodium-Hypochlorite solution (household-bleach) to 20 ml of urine. That should do the trick! The advantage is that bleach is usually easy to come by. The problem is that your sample becomes useless for molecular analysis. Why not divide your sample into two portions? One that you treat with bleach, one that you treat with Ethanol?
I will add a reference article for your convenience!
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