Wednesday, September 24, 2008

PVA Yo Momma!

General Pre-Post Disclosure:
Adam and I understand that the bulk of people reading this blog are not scientists. While the purpose of my portion of the trip is primarily to take samples for my thesis research, the heavy/dry science side of the trip is not the primary focus of this blog. The experience of traveling to Congo is by far the more exciting topic for the average reader, but in the spirit of accuracy, posts like this one are somewhat necessary too!

Preservation of poop is just as important as preservation of accuracy of what doing field science is all about! Feel free, of course, to skim, but note my helpful dandy links too!

I’ve worked in a genetics lab (loved it) and I’ve been in the field collecting poop before -- for paternity/DNA analysis -- but I’ll admit, I’ve never done primarily parasite work and I’m a bit out of my element.

Of course, it’s not like it’s easy to figure out yourself. And now that my IRB proposal is 90% done, I have to decide on a firm choice for my field faecal collection protocol. Once you submit your IRB, you can’t really change it without resubmitting it for re-approval.

My previous experience has involved storing faeces in silica beads or ethanol, so after pouring over the protocol supplied to me by the very experienced primate parasitologist I met at IPS in August, I discovered that a) silica/ethanol wasn’t going to cut it and b) I needed to start over with my thinking process.

There’s nothing quite like being humbled back to your scientific roots, but it’s all part of the process.

I mean, I thought silica was complex! It comes in all these different meshes and what-not. Silly me.

So I’ve been researching the process of formalin-preservation, as well as its complement, PVA (polyvinyl alcohol). Science is very much about repetition. Buffered formalin is preferable for the preservation of helminths, while PVA is the top choice for the preservation of protozoa. Ergo when you take samples, you take two samples and put each in a separate tube. Same poop, different preservation technique.

Seems simple enough, right? You’d think you can just buy some Falcon tubes and some chemicals and be on your merry way!?


Seems that most fecal collection materials are sold almost exclusively in kits. Kits! Sounds easy! Right?


The kits do seem inordinately expensive though not unreasonably so (all lab materials are, in my experience, inexplicably expensive). But the PVA seems to come in several mixes -- varying viscosities, contents, etc. I’ll admit that I had to send off an email to ask what kind of PVA I was aiming for!

It’s sort of nice to get pre-buffered formalin, though. At first, I wondered whether there would be a huge difference depending on whether I buffered it with milli-Q water versus standard DeIonized/Distilled water. Or how I’d get any of that out in Aketi!?

Until email reply, I leave myself just a few hours less until I need to have everything together.

I am also triple-dipping on my samples and buying some Whatman FTA cards and doing onsite smears to catch any potential bloodborne pathogens and give DNA information to any other researchers who might need it, as some have already expressed interest in having access to my samples for DNA analysis.

And just to reassure any worried advisors/readers reading this post, most of the milling in thought of protocol has been happening for several months now, but since I am down to the end, I must actually make a decision and go with it, hence the post now. Hehe.

It might be nice, not being up at 4:15am, Thomas-Aquinas-ing all my research choices.

And right now, I have only 10 days left.


Congogirl said...

Actually I think this discussion is very interesting, since I know a teeny bit about collecting samples, and the discussion of appropriate supplies is ESSENTIAL. And I know about IRBs, AND Congo! What do you know about regulations surrounding the export/import and property rights (including intellectual) related to your research? This might be an email question...

Laura Darby said...

Do you mean getting samples out of the country? Or people stealing my research ideas off the blog?

I do have a pretty extensive log of visitors to the blog, so I'd be able to prove pretty solidly if someone DID try to steal my ideas --

With regard to export of samples, it's still a work in progress -- thankfully one I don't have to worry about for several months yet. Hehe.