Of People and Parasites

POST BY: Johnica Morrow

It’s a few minutes after 8:00am and I walk into the lab to start another day of research. I turn on my favorite Pandora radio station, The 90s were great let’s hear it again, and carefully pull the cover off of my research microscope, the aptly named “Beauty”. The slide I was scanning yesterday when my husband arrived to take me home for the day is still sitting exactly as it was left. It is waiting for me to finish documenting the presence of microscopic parasite eggs suspended in glycerin that are on its surface. I turn up the light…not all the way up to avoid blinding myself…and continue my search for the eggs. Look! Another pinworm egg! Few things are as exciting to me these days as running across one of these Enterobius vermicularis eggs. It’s strange to think that I’m seeing evidence of an infection harbored by a human host about 1,300 years ago. This sample, which hails from a collection of desiccated human fecal deposits known as coprolites, is full of these ovoid eggs. Each has one side flattened and the opposite side bowed outwards giving them that distinct pinworm egg appearance. Deposited by one of the Loma San Gabriel, a culture that existed years before Europeans discovered the “New World”, these coprolites have an exciting story to tell. Their story is told not with words, but with microfossils…tiny remains of parasites, starch granules, pollen grains, and other sprinkles of data that leave clues about what people ate and what was eating them.

20907315_10100433075121360_1833572328_oSince starting my Ph.D. program, I have had the privilege of working on everything from sediments out of historic latrines from the American Midwestern to intestinal segments of Lithuanian mummies to the contents of embalming jars labeled with the names of members of the prominent Medici family of Florence. My dissertation project has allowed me to work with 1,300-year-old coprolites excavated from a cave known as La Cueva de los Muertos Chiquitos that is located in the north of present-day Durango, Mexico. These coprolites have been a treasure trove of parasites. We’ve found pinworm eggs as well as fluke eggs, tapeworm eggs, a few whipworm eggs, and lots of nematode (roundworm) eggs. We also do molecular work to test for parasite antigens, substances created by the parasites that your body uses to produce antibodies. By using enzyme-linked immunosorbent assay (ELISA) kits, we can detect parasite-specific antigens to determine what types of parasites people had in the past.  I tested for three different species of parasitic protozoans (single-celled, eukaryotic organisms) that are known to induce diarrhea in humans. My samples were negative for two of these species, but 66/90 of the samples tested positive for the third protozoan known as Cryptosporidium parvum. The prevalence of this parasite among the coprolites from this site is much higher than anything previously reported and gives us new insights about the origins of this parasite on the North American continent.

Over the years, I have also become well-versed in palynology, the recovery of pollen20891491_10100433075839920_1782532704_n.jpgfrom both archaeological and modern materials. Finding pollen in things like coprolites can give researchers an understanding of the depositor’s diet and sometimes can key us into medicinal plant usage. I have also been involved in studies of other organisms that pop up in archaeological materials – mites, flies, beetles, and most recently, pseudoscorpions. Our lab adapted methods usually used to quantify parasite eggs and pollen grains to our studies of microscopic mites found in things like coprolites and mummy intestines. These studies of insect remains from archaeological materials are helping to shape our understanding of the corpocenosis – the community of organisms that contribute to the decomposition of human corpses – that is associated with mummified bodies and other archaeological materials.

I smile as I finish scanning my slide and write down the final counts for my sample. These parasite eggs have revealed to me the centuries-old cryptic tale of their depositors. They have shown me a story of sanitation issues and of overcrowding. A story of lives lived in a society where the majority of people survived with irritating parasitic infections. As of this spring, my rendition of this story became part of the permanent scientific record housed within the University of Nebraska-Lincoln’s Digital Commons. This story can now be shared long after it began in a tiny cave about 1,300 years ago. Their story is part of my story as I embark on the next leg of my journey towards building a career as a pathoecologist.

Johnica Morrow got her Ph.D. in Natural Resource Sciences with a specilization in Applied Ecology from the School of Natural Resources at the University of Nebraska-Lincoln. 

Reference:

Morrow, Johnica J, “Exploring parasitism in antiquity through the analysis of coprolites and quids from La Cueva de los Muertos Chiquitos, Rio Zape, Durango, Mexico” (2016). ETD collection for University of Nebraska – Lincoln. AAI10102325.
http://digitalcommons.unl.edu/dissertations/AAI10102325

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About The Ethogram

The official blog of the UC Davis Animal Behavior Graduate Group.
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