More talk about poop, and some results

Posted on December 28, 2011


fecal analysis equipment

While I was in Mariscal Estigarribia I spent some time in the regional hospital for Boqueron learning how they do lab work.  They have limited resources, so they don’t get to use very advanced techniques and often have to come up with creative solutions.

fecal analysis equipment

Equipment for fecal analysis

In particular, I was interested in learning how they do their fecal analyses for parasites.  They use two methods to examine the stool: Lugol’s dye and the Willis method.

Lugol’s dye

Lugols dye

Lugols dye technique

With the Lugol’s dye technique, some of the fecal material is mixed with saline in a centrifuge tube, and then centrifuged so the parasites or their eggs sink to the bottom.  A little bit of the sediment at the bottom of the tube from centrifugation is placed on a glass slide.  A drop of Lugol’s dye is added and the slide is examined at 40x magnification under a microscope.

Willis method

Willis method

Willis method

The Willis method floats parasites or their eggs out of the fecal material.  Some fecal material is placed in a container and a saturated salt solution of is added until there’s a convex miniscus at the top of the container.  The glass slide is placed on top of this meniscus and allowed to sit for 15 minutes.  Then a coverslip is placed over the slide and it is viewed under 40x magnification in the microscope.

I paid one of the biochemists in the lab to do the analysis of my fecal samples.  This was the best way to make sure that the methods and results conformed with local clinical protocols so participants would get treatment with minimal hassle.  We had to haggle a bit about what technique would be used – I wanted to quantify all the parasites or eggs on the entire slide, but the biochemists were used to simply marking the presence or absence of parasites after viewing a limited portion of the slide.

From conversations with the biochemists and lab technicians, the most frequently encountered parasites in the Chaco include: Giardia lamblia  (a protozoan that is responsible for what we call “beaver fever” in Canada), Ancylostoma (a helminth commonly called ‘hookworm’), Ascaris (a helminth), Blastocystis hominis (which we don’t know much about and its pathogenicity is controversial), and Endolimax nana (a generally non-pathogenic amoeba).

The biochemists I talked to emphasized that it was really rare for them to find helminths in fecal samples.  Keep in mind that the patients who have fecal analyses done mostly live in or near the more urban areas with hospital labs (due to the lack of preservative I mentioned in the previous post).  So I wasn’t really sure what I would find in my samples from remote communities.

There were two major results….

*drum roll*

(1) Nobody had helminthiasis.  Not one.

This is pretty surprising, considering the high prevalence of helminths in the Argentinian Chaco and the level of poverty in the study communities.  I have some ideas for why this might be: (1) it could be a methodological problem, or (2) the deworming campaigns in the local elementary schools may have had a big effect.  In my next field season I’m going to do some more sampling and try to confirm this result.

(2) About 65% of participants in both communities had some kind of intestinal parasite.  The most frequently encountered species were Giardia lamblia, Entamoeba coli, and Blastocystis hominis.

All of these parasites are waterborne, which suggests that contaminated water is a big problem in these communities.  I gave a talk in both communities about the preliminary study results before I returned to the U.S. and really stressed this point.  Most people rely on the tajamars (those open water pits I mentioned earlier) for water outside of the rainy season, and they clean this water by filtering it through cloth that has been folded over.  While this does help to remove some parasites, it doesn’t get all of them.

Medication for parasites

Medication for parasites

In cooperation with the Regiones Sanitarias (Health Regions), we provided free treatment to participants who had parasites in their fecal samples.  I delivered the lab results to one of the doctors in the hospital and they would write me a bulk prescription.  Then I would pick up the prescription from the hospital pharmacy and drive it back out to the communities with me.  I heard many stories in the Chaco about people getting blood drawn or some other diagnostic performed and then never hearing from the doctor again; so I tried to make a point of personally informing participants about negative (healthy!) results as well as positive results from the fecal samples.  If we couldn’t find the participant in their home to give the results and medication in person, we left the results and medication at the health post so they could go there at any time and find out.  Unfortunately I had to leave Paraguay before all the fecal analyses were complete, so I set up a network of people in the health regions and at the health posts who could take over the delivery of the results and medications.

More than anything else during my last field season this experience taught me about the challenges of collaborating with local organizations and the major logistic barriers to providing health care in remote communities.  I’ll be doing a second round of fecal sampling during the next field season and I’m hopeful that I’m now savvy enough to avoid some of the major pitfalls.

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