Sunday, February 12, 2017

Guts & Glory: A Parasite Story--A Parasitology Exhibit Coming to Lincoln, Nebraska, in April!

Greetings Fellow Parasitophiles!

I wanted to share with you, in case you hadn't already heard, that it has just been announced that there will be a new temporary exhibit that focuses on parasitism opening this April. The exhibit is called Guts & Glory: A Parasite Story. It opens on Saturday, April 22nd, 2017.

The exhibit explores the complex relationships that exists between hosts and parasites. It also traces the history of the field of parasitology and is sure to be phenomenal. Here is the Facebook page if you want to keep up to date about the exhibit: Guts & Glory: A Parasite Story

Further details about how long the exhibit will run are to be coming soon, so stay tuned!

Also, be sure to check out the H.W. Manter Laboratory of Parasitology's website here if you haven't already.

I hope that those of you in Lincoln, Nebraska, will take the time to check this out and that those of you from out of town will consider making a road trip this way in April!

Thursday, January 12, 2017

Cochliomyia hominivorax: Getting Screwed by Screwworms

Greetings at long last, fellow Parasitophiles! As you may have noticed, I haven't been able to post lately. I was busy finishing up my degree, graduating, and applying for more jobs than I can count on both hands. Time flies while you're having fun!

Speaking of, I wanted to talk with you about one that is particularly important given its current status. Have you ever heard of Cochliomyia hominivorax? Better known as the New World primary screwworm, this little beastie is capable of causing huge problems. This week, the United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed a case of canine myiasis (a stray dog infested with flies) caused by C. hominivorax near Homestead, Florida.

This is really, really, REALLY bad news.

Image result for cochliomyia hominivorax usda floridaWhy? You ask. Because we aren't talking about a fly that comes to feces or dead things to feast and lay its eggs. We are talking about a fly that prefers instead to dine on living host tissues that provide a nice, warm, plentiful food resource for its young'uns. Additionally, we are not talking about a fly that infests a few smaller mammals and lays an egg or a little clutch of eggs before flying off. No. Not with C. hominivorax. This fly has a wide range of documented hosts, including small mammals, deer, livestock, companion animals like dogs, and even humans. These unlucky hosts are not subject to small numbers of maggots when eggs individual female C. hominivorax can lay up to 500 eggs at a time and during her lifetime, which lasts about 20 days from the time that she hatches from an egg, she may lay as many as 3,000 eggs! If you Google images of this organism, you are sure to find many disturbing pictures of cattle, dogs, humans, and other animals who suffered from these maggots. Particularly disturbing for me is finding photos of oral myiasis...that is, cases where maggots burrowed into the mouths of people. If you liked your lunch today and would rather not meet with it again, I'd advise you not to look that one up! For this post, I avoided such photos this time.

In short: These flies are baby-making machines with wings that need living, warm-blooded hosts to reproduce. This translates to some pretty serious issues for us, but before we go into the impacts that these creatures can have and have had in the past, let us look a little more closely at their biology.

Image result
Cochliomyia hominivorax adult.
These flies, like all flies, are insects belonging in the order Diptera. They are placed within the family Calliphoridae with blow flies, like the shiny, metallic blue and greens that you often find buzzing around dead things. Five species are found within the genus Cochliomyia, including C. hominivorax. The epithet derives from words that loosely translate to "inclined to devour man".

Life Cycle
These flies live about 20 days when the weather is warm and may live a little bit longer in cooler climates. Adult females mate once in their lives before depositing between 250 and 500 eggs on the edges of open wounds or mucous membranes found on unlucky hosts. Three days to a week later, these eggs hatch and form maggot masses that burrow into the flesh of the host where the larvae feed on bodily fluids and living tissues. This causes wounds to enlarge as the screwworms feed, which in turn provides more places for other female flies to deposit their eggs. Left untreated, this infestation can be fatal to the host, which may be your pet cat, dog, or bird, your livestock animals (including cattle, pigs, goats, and sheep), things you hunt like deer or rabbits, or, in rare cases, even that uncle that you feel bad for laughing at when you realize how serious myiasis can be. (Don't worry, I'm sure Uncle Jack will seek medical treatment before it would kill him no matter how macho he tries to appear.)

After several days devouring Fluffy or Uncle Jack, the maggots will drop off of their host and burrow into the soil to pupate. This means that they form a hard shell known as a "pupa" and undergo a complex process before bursting out as adult flies. Do you remember that process from your basic biology courses? That's right! Metamorphosis...just like other insects, like butterflies, undergo to transition from little worms to winged beauties....except in this case beauty is relative (unless you are a male C. hominivorax). Anyway, good job reader!

After adult flies emerge from their pupae, they quickly mate and begin looking for a host with an owie for egg-layin'. These flies are about twice as big as your common housefly and feature three black stripes on their backs along with unmistakably orange eyes. They can travel several miles as adults, but are dispersed much further by their hosts as eggs and larvae.

Image result for cochliomyia hominivorax usda floridaImage result for cochliomyia hominivorax usda florida

Getting Screwed Since the 1920s
We have records going back to the 1920s of government-sponsored public education effort aimed at helping people to identify screwworms. A decade later, we were reporting cases of primary screwworms all across the south in the states and the USDA upped their extension efforts to teach people how to deal with them. In 1933, Emory C. Cushing within the USDA's Bureau of Entomology and Plant Quarantine along with Walter S. Patton from the University of Liverpool in England published a paper describing the New World screwworm as a distinct species from the common blowfly, which many had mistaken as the same fly up until that point. Three years later, Cushing published a follow-up paper with E.W. Laake and H.E. Parish outlining the morphological and biological differences between the primary and secondary screwworms (C. macellaria). These were hugely important papers in the long and drawn-out battle between North America and C. hominivorax.

Photograph of Dr. Edward F. Knipling (seated) and Dr. Raymond C. Bushland<br /><br />
Dr. Edward F. Knipling (seated)
and Dr. Raymond C. Bushland.
The 1940s saw the rise of the Third Reich and the slowing of screwworm research in the U.S. Many of the prominent screwworm scientists of the day were diverted to working with other organisms that troops would  be dealing with in other countries during the second World War. Though domestic screwworm studies slowed, they didn't halt completely. Surveys continued with a disturbing report emerging in 1949 regarding severe infestations occurring in South Dakota on account of infected cattle being shipped into the state. This report by Raymond C. Bushland, the man who developed mass-rearing methods for screwworms by the late 1930s, highlighted the economic impacts of this fly and raised ranchers' concerns about the severity of these flies and how quickly they could be spread.

Edward F. Knipling built on Bushland's work by developing Sterile Insect Technique (SIT). This technique involves mass-rearing flies and then sterilizing them prior to release. Once released, the sterile flies mate with females, who typically only mate once in their lifetime, leaving them unable to reproduce. By the mid-1950s, several labs were experimenting and field testing SIT.

Image result for cochliomyia hominivorax usda florida
Primary screwworm eradication efforts
pushed the flies south little-by-little.
Glossing over a lot of really great stories about studies and struggles, we eventually found success with the implementation of large-scale SIT programs. Florida's eradication efforts led scientists to claim that the state, along with other parts of the Southeast, were screwworm-free by 1959. Seven years, billions of dollars, and a major partnership with Mexico later, the U.S. in whole was declared screwworm free. However, outbreaks continued through the 1970s and
the early 1980s. Since 1984, only isolated, imported cases have popped up, but otherwise North America has been pretty much screwworm-free. The 1990s saw continued efforts to push naturally-occurring screwworm populations south. Eventually, we got them eradicated as far south as Panama. You can read more details about this fascinating story here if you are interested.

Current Concerns
Which brings us up to current events. Over the last few months, we have seen new reports about cases of primary screwworm that have popped up along the Florida keys. Deer have been found to harbor these parasites, which were spreading quickly. With concern that the flies would make the jump to the mainland, eradication strategies were rapidly deployed on the islands. My entomologist friends and I have been tracking these stories in the news hoping to hear that the mainland was safe, but this week our fears were confirmed with the announcement of a stray dog having been found harboring C. hominivorax. The case spurred federal and state agencies to action and they are currently surveying the area to assess the extent of active screwworms in Florida.

For those worried, the stray dog was treated and is doing fine now that he isn't being eaten alive.

Aside from the obvious health concerns for people, wildlife, pets, and livestock, these flies could have catastrophic effects economically. Estimates from the USDA have reported that screwworm eradication has saved the U.S. livestock industry over $900 million dollars per year. Remember that this estimate doesn't include costs to pet-owners, breeders, or wildlife conservation efforts.

Here's to hoping that we can control whatever is already here and prevent future outbreaks, especially as if we see a long, warm spring/summer that would lead to a boom in any existing screwworm populations.

The Moral of the Story
The battle between us and the North American screwworm has been long and hard-fought. Countless man hours and dollars have gone into ensuring our victory over these winged beasties, and yet still they pop up from time to time because one person or another brought in an infected cow or doggy without considering the ramifications (or simply out of ignorance). This reinforces the importance of public outreach and extension efforts. Funding programs to continue educating the public about primary screwworms is both essential and inexpensive relative to the costs of dealing with established screwworm populations on a larger scale as was necessary in the past. Similarly, we need to be supportive of research in the control and prevention of parasitic insects.

Image for the first content page of the item, linking to the full file.
Bumper sticker from 1977.

Thursday, March 10, 2016

Break It Down!: Taphonomic Factors Affecting Parasite Preservation

Greetings Fellow Parasitophiles!

Today, is an exciting day for's the day that I sent my dissertation manuscript off to my supervisory committee for approval before I defend my dissertation here in a few weeks! (Things are getting very, very real!) In celebration of this occasion, I decided to allow myself more writing! (I really am a bit of a nerd sometimes...well, most of the time...and more than a bit...) In trying to decide what to share with all of you, I realized that I had not yet posted about my most recent paper. So, here it is! My first paper of 2016 and the story behind it!

I remember sitting at coffee one Friday, as I do with my advisor for our weekly lab meetings, and discussing some of the various factors that affect the preservation of parasite eggs in archaeological materials. We talked about both the abiotic (non-living) factors, like soil pH and climate, and some of the biotic (living) factors, like the actions of decomposer species. My advisor turned to me and said something along the lines of, "you should write a paper on that sometime".

I found the idea intriguing and thought about it a lot over the next few months. I started working on a manuscript without a clear idea of where I would go with the paper. I thought about how to categorize the major contributing factors that affect the preservation of parasite eggs in both positive and negative ways. I eventually came up with five broad categories of taphonomic (taphonomy is the study of decomposition and preservation) factors that affect parasite eggs existing in archaeological contexts. Those five broad categories were as follows:

[From Morrow et al., 2016]

1) Abiotic Factors--Those non-living things that influence preservation, such as temperature, soil conditions, and the chemical environment in which archaeological materials are found.

2) Contextual Factors--Those reflecting the archaeological context from which we collect parasite data. (i.e. parasite eggs in mummies preserve differently than those in coprolites or latrines)

3) Anthropogenic Factors--Those arising from the interactions humans have with the deposition, manipulations, excavation, transportation, and analyses of archaeological materials.

4) Organismal Factors--Those inherent in the biology of the organisms you are studying, such as the features of an egg that make them more susceptible to degradation or the natural history of a parasite that makes it more likely to be recovered from human feces.

5) Ecological Factors--Those involving the interactions of parasite evidence with other organisms, like decomposers, predators that my ingest parasite eggs, or vectors than can transport the eggs from one fecal deposit to another.

Each of these broad categories could be further subdivided into other categories and can affect the preservation of parasites in both positive and in negative ways. To provide examples of how these factors affect parasite egg preservation, we presented three case studies and discussed these five categories of taphonomic agents for each case.

I won't go into case-by-case detail (you are more than welcome to read the paper if you are interested in that bit), but I will tell you a bit about the three cases. These sites were each near and dear to my heart as they were the first three things that I published about. (One in a special historical journal that hasn't come out yet and two peer-reviewed articles that I talked about in previous posts here and here.)

Case 1: The recovery of intestinal parasites from historic mummies in Vilnius, Lithuania. In the first paper about these parasites, we highlighted a taphonomic issue that only arises with the analysis of mummies.

Case 2: The recovery of intestinal parasites from coprolites recovered from medieval skeletonized burials in Nivelles, Belgium. In the original publication of this material, we discussed an instance of extreme parasitism revealed by the analysis of coprolites from one one of the burials.

Case 3: The lack of parasites recovered during the analysis of embalming jar contents from crypts containing members of the famed Medici family of Florence, Italy. The potential reasoning for the lack of parasite evidence was discussed at great length in the original paper (which is still "in press" after several years). These reasons ranged from taphonomic to cultural in nature and included a discussion of how Medici affluence likely played a role in reducing the risk of parasite infections and in providing the most effective treatments of the time to control for infections had they occurred.

Each of these studies demonstrated a range of taphonomic considerations for the interpretation of archaeoparasitological data. This paper concludes with a discussion of how important it is for researchers to consider taphonomic factors when they discuss their findings. It urges future studies to discuss the five broad categories of taphonomic factors that may have positively or negatively affected the preservation of their parasite eggs.

I have to say that this is probably my favorite paper to have ever published. I love how it turned out. I was happy to have run with a simple suggestion (which my advisor may or may not have expected me to actually follow through with so quickly) and to have created an article that is actually really important for the advancement of the field. I got to work with an undergraduate as a mentor and I got to publish with an international colleague. I feel that this experience has helped me to grow in many ways professionally and I am proud to have such an elegant paper to show for it.

The Moral of the Story
When your advisor gives one of those small comments like, "you should do...." don't brush it off and put it on your list of things to do after you graduate. Take a little time to assess whether or not you could actually gain a lot from working on something might end up with something that is much bigger than you had originally thought it would be! Also, don't let your dissertation be the only thing that you leave with when you graduate. You are much more marketable if you can show that you have the ability to do other things!

Title Shot!

Saturday, February 27, 2016

Sharing Poop and Parasites

I've missed writing to you guys...dissertation and general life has been a little OP lately. (OP = "over powered"'s a slang term used often in the gaming world and I've been married to a gamer for too long to not use it.) I won't waste time saying that this is me starting up regular posts again, the dissertation is still not finished (though I'm getting close!) and I have a pretty busy few months ahead of me. I'm hoping to start back up this summer, after I (FINALLY) graduate, but I'm not making any promises just yet.

Today, I'm writing to you for a different reason. I recently competed in an Elevator Speech Competition hosted by my school. I had a bit of a rough time with delivery, but in the end it wasn't all bad. For this competition, I was given 1 slide (with no moving animations) and three minutes to tell a general audience about my research. For those interested, I've included the slide and a transcript of my speech below. Happy reading!

My Elevator Speech

Poop and parasites; two things that I love despite what other people think. Though not always appropriate dinner conversation, poop provides a wealth of data regarding diet and disease. This is as true for what many of you made earlier today as it was for humans thousands of years ago.

My dissertation focuses on retrieving data from 1,300-year-old paleo-poops known as “coprolites”, like the one in the middle of this slide. By analyzing coprolites, we are able to reconstruct diets and patterns of parasite infections that occurred in pre-history. This allows us to better understand the origins of human-parasite associations that still affect people in the modern world.

The coprolites that I work with come from a cave in Mexico known as “La Cueva de los Muertos Chiquitos”. This cave held hundreds of coprolites that were sealed beneath two adobe floors, making for some of the best-preserved parasite evidence in the world…now that’s the kind of high-quality crap that we archaeoparasitologists dream about!

The diversity of parasites recovered from this site is amazing. Starting at 12 o’clock, we see a Physaloptera egg, which is associated with dogs. Moving clockwise we see a human whipworm egg, then at 4 o’clock we see Toxascaris, another dog parasite that infects humans from time to time. At 6 o’clock are the results of a molecular test used to look for parasites that don’t leave behind eggs. Ignoring the control wells on the top left, every place that you see yellow represents a positive sample for a diarrhea-inducing parasite called Cryptosporidium parvum. Moving along, the egg you see at about 7 o’clock belongs to a tapeworm and the green egg is that of a human pinworm. Finally, the one up there at about 10 o’clock is a fluke egg. Each of these parasites has a distinct life cycle involving different hosts and modes of transmission.

By recovering parasite data, we are able to infer patterns of human behavior, for example, the dog parasites I mentioned tell us that the people using this cave had close associations with dogs and the molecular test at 6 o’clock tells us that lots of people had diarrhea. The pinworm eggs were so prevalent among the coprolites that we know the vast majority of people at this site were infected.
At night, the female pinworm crawls out of the anus to lay her itchy little eggs on the perianal folds, so you know that as soon as the sun set on La Cueva de los Muertos Chiquitos, everyone was either scratching or dealing with diarrhea.  It doesn’t sound like much of a party for them, but it does provide us with lots of information 1,300 years later!

As we continue collecting parasite data from this site, we will gain a picture of the daily lives of people who left no written record, only ancient nuggets of information reflecting what they ate and what was eating them.

Friday, July 3, 2015

Fast Times at the Annual Meeting of the American Society of Parasitologists

Greetings fellow parasitophiliacs! First of all, let me begin how I've begun far to many of my most recent posts by apologizing for my lack of writing lately. As a PhD candidate, I could come up with a million excuses...namely that I'm focusing heavily on my dissertation at the moment...but suffice it to say that I've had good intentions without the available time it takes to write something that you *hopefully* will enjoy reading.

I'll try to keep today's post short and sweet without getting too sentimental. Last weekend I attended my first American Society of Parasitologists meeting. I've been a member of this society for several years, but this was the first time I was able to go to one of the annual meetings.

This meeting was held over the course of four days in Omaha, Nebraska. The meeting consisted of a wonderful mix of student and faculty presentations covering a wide range of parasitological topics. There were a few symposia on topics that included undergraduate education and community outreach with regard to parasitology. These symposia featured several excellent talks by prominent members of the society.

For me, the most fun part of the meeting was the ability to catch up with other parasitologists and to have the chance to meet some of the "big names" for the first time. Like any young professional, I always leave wondering if I made the good impression that I hoped to make or if I said something stupid without realizing it. However, everyone that I met was welcoming and kind, so if I did say something stupid, they were nice enough not to make me feel dumb. It's pretty amazing to be a part of a society that is full of so many people who make you feel like you belong even if they've just met you.

The president of the society described our gathering as being similar to a "family reunion". It certainly felt that way to me, even being a relative new-comer with regard to attending the national meetings. I got to see many familiar faces from the Southwestern Association of Parasitologists (SWAP) and Rocky Mountain Conference of Parasitologists (RMCP) meetings that I've been attending since Dr. Duszynski took me to my first SWAP meeting while I was working on my master's. It's always great catching up and seeing what sorts of things people are working on.

I was also fortunate to meet a number of new people, including fellow students and prominent parasitologists conducting research in all kinds of neat areas. I met the now past-president of the society, Dr. David Lindsay, and got to talk to him about Toxoplasma gondii and other fun coccidia that he has spent his career studying. He introduced me to his student, Richard, who is studying Sarcocystis. He also offered me some of his spit to help with my dissertation...I've never been so excited to have received such an offer! (He is seropositive for T. gondii, so I could really use his spit to help with some of my experimental work.)

I briefly met our new president, Dr. Mark Siddall. Dr. Siddall studies leeches and works at the American Museum of Natural History. We didn't talk long, but we did get to talk a bit about outreach for the society. I can't commit to much, but it would be good to give back to the society in some way. I plan to send him an email later to touch base about how I can help. (I'm thinking I'll pitch the idea of getting ASP on Imgur, which would be pretty cool!) He also talked to me a bit about my dissertation and offered to put me in touch with some ancient DNA people if I have time to add that component into my dissertation work. Additionally, I got to meet one of his students briefly. The student was doing this really great work with microCT scanning of leeches. The animations in his presentation were excellent.

I was able to meet with several people who took the time to speak with me about my dissertation work. First, I met Dr. Charles Faulkner. I have read several of Dr. Faulkner's papers, so it was very exciting to meet him in person. We had a couple of opportunities to chat about the molecular work that I will be embarking upon this August and he was kind enough to give me his thoughts on some of the parasite eggs that I've been finding in my samples. What a great guy!

I also met with Dr. Agustin Jimenez. I've known Agustin for several years and I was happy that he had time to chat with me at ASP. He sat with me for a good while giving his thoughts on some of my photos of parasite eggs from my material and he had lots of insights to share since he had published on material from the same site. He even sent me some supplementary material from his work on the site that I've been looking through since I got back to the station for the summer.

I got to talk with lots of other people, but this post is already starting to look a bit long, so I'll cut it short for now. Overall, this was a great meeting! I enjoyed the food, fun, and familiar faces that filled the venue and it was wonderful to meet so many fellow parasitophiliacs in one place. I look forward to next year's meeting and to doing a little bit of service for such an open and supportive society run by awesome people. :)

The Moral of the Story
If you love what you do, you should seek out societies of like-minded people. Attending these meetings is a great way to enhance your knowledge base of the discipline and to expand your network of colleagues (and friends if you are lucky). These gatherings open the door for collaborative efforts and can be hugely beneficial for troubleshooting your own research. Plus, a hotel full of parasitologists is a pretty fun place to be! Where else can you talk about parasites while eating and not have one person make a comment about how it's not appropriate dinner conversation? (The struggle is real!)

Tuesday, February 10, 2015

Spittin' ELISAs: Using Saliva to Detect Parasitic Infections

Over the weekend I attended a League of Legends tournament with my wonderful husband. Despite anticipating losing a day's worth of work, I wound up hanging out with another fellow parasitophile and then I got an e-mail from my advisor with a paper that I hadn't read yet. So, there I was, reading about detecting Trypanosoma cruzi via ELISA from salivary samples of modern people (well, people from 1995 anyway...). The paper's intro cited one study I was familiar with and FIVE that I wasn't. From that point on, I knew I'd be (eagerly and enthusiastically) reading a lot more over the weekend.

So this is a post for me for you. This is me reminding myself of what I learned and sharing it with you, which I suppose has been the goal of this blog all along.  I guess it just seems more overt at the moment.

Before we jump too far ahead, let's start by talking about what ELISAs are. ELISA stands for "enzyme-linked immunosorbent assay". It's a fancy phrase, but don't let it scare you too much; the concept is fairly straightforward. Essentially, when you are infected with a parasite, the parasite produces antigens that are specific to whichever parasite is infecting you. In response, your body produces antibodies that are specifically designed to deal with the infection of that parasite. ELISAs are tests that are designed to detect either the parasite antigen or the antibody produced in response to said antigen.

Each ELISA kit is parasite-specific to some degree or another. This is really dependent on the parasite. Some kits can detect antigens/antibodies produced by/in response to a particular species, while others can only detect parasites at the genus level, so you may not know exactly which parasite you have. In the medical world, this is sort of "good enough for government work" as you can often treat infections with species belonging to the same genus in the same manner effectively. (If you have a parasite that is susceptible to a the same treatment protocols as a different parasite, it doesn't really matter what you are treating for as long as the treatment works.) As parasite ELISAs are most often used in medical and veterinary settings for rapid diagnosis, the specificity is less of an issue. However, in the case of parasitological research, we have to be careful when we use ELISAs to assess parasitism. We have to pick the kits carefully and be aware of potential cross-reactivatity.

Parasite ELISAs typically work with two types of material: blood and feces. (Wooo-hoo!) As you might imagine, intestinal parasites are typically detected from feces while non-intestinal types of parasites are found via blood serum. The problem with serum is that acquiring it is invasive (and for those of us that study archaeoparasitology, not available for use). Interestingly, your body carries antigens and produces antibodies that wind up in places other than serum...say for example, in your saliva. Really brilliant people in the late 1980s and early 1990s figured out that you could detect a number of pathogens via ELISA testing using patient saliva rather than serum. The Chagas' paper I mentioned earlier cited three studies that found viral infections, two that demonstrated parasitic infections, and one that detected bacterial infections. The two parasitic infections were chronic schistosomiasis (Garcia and colleagues, 1995) and acute toxoplasmosis (Hajeer and colleagues, 1994). Plus the paper on Chagas', of course.

It seems that that literature grows silent on this topic after the 1990s. It doesn't seem that people found evidence that these previous studies were incorrect (as far as I can tell), so I'm wondering if it just fell off of people's radar or if it just became so well-accepted that people stopped writing about it. It's hard to say one way or the other from my limited knowledge of the parasite ELISA literature, but I'm excited to have found something that leads to more. (Before Saturday, only knew about the Hajeer paper, so now I have a little bit more to build off of, which is super exciting for me!)

The Moral of the Story
The point of all this is to tell those of you who, like me, knew/know very little about molecular work and its application to the field of parasitology. Testing saliva from people and animals is a quick, non-invasive way to do preliminary tests for certain types of parasites. It's amazing how far our technology has advanced and it will be interesting to see how these advancements help us to better understand parasitism in the world around us, past, present, and future. I'm hoping to find more parasite studies looking at the application of ELISA testing that utilizes saliva as the detection source, so this is also a request to keep your eyes and ears open and let me know if you know of work being done in the area. (Thanks in advance to those of you that actually do!)

Sunday, February 1, 2015

Sifting Through the Sediments: Parasite Eggs from Night Soil Contexts

While the last thing that most people would want to get in the mail is night soil, I'm one of those people who excitedly awaits for jars of this stuff to arrive. (Because one: Such material is super cool and because two: "most people" are boring.) In my last two posts, I discussed how we look for parasites in the context of mummified tissues and desiccated feces. Today, I'm going to introduce you to another great source of literal pay-dirt for archaeoparasitologists.

Night Soil Sediments from the Past
A nightman's calling card from the 1800s.
For those who haven't been introduced to the phrase "night soil", I'm referring to dirt that has human fecal components. The term originated from the olden days when people would shovel human waste out of cesspools and outhouses during the night and later usually sell the excrement to farmers as a fertilizer. Many of these people employed as "nightmen" or "night soil men" were not allowed to work during the day and made up a portion of the lowest of low classes in most places. This was early human waste management in Europe, Africa, and Asia long before modern standards of disposal.

As you've probably already figured out, there were lots of problems with sanitation in the past. Before modern indoor plumbing, people found a variety of ways to store their steaming piles of...stuff...before nightmen could come and haul it away. Some were indoor chambers for relieving oneself. This included things like chamber pots or water closets (the early ancestor to modern flushing toilets). Others were outdoor pit latrines such as the outhouse, the privy, the dunny, the biffy, or the long-drop.

As excrement, other waste materials, and soil fill these types of features, evidence of parasites is preserved in a stratigraphic way (with the oldest layers at the bottom and the youngest layers at the top). Archaeologist excavate these types of features along with middens (trash heaps), cisterns, and other collections of human waste from sites all over the world. These sediments are collected with provenience information carefully recorded and dates associated with other things recovered from the same layer.

Analyzing Latrine Sediments
Once these sediments make their way to people like me, they are examined using a sequential analysis model (or at least they should be) to gather all of the information that can possibly come from such material. To process this type of material, first we treat sediments with hydrochloric acid to react with any microfossil-binding calcium carbonate that might be present. Next, we use distilled water to screen heavy sediments and separate macrofossils (big pieces of plants, minerals, bones, insect remains, etc.) from microfossils (parasite eggs, starch granules, pollen, etc.) using the swirl technique. The macrofossils are dried and examined via a stereoscopic microscope. The microfossils are examined via light microscopy and exposed to further processing as needed.

SEM of Lycopodium spores.
Depending on the nature of the samples, we may need to use dangerous chemicals like hydrofluoric acid (for dissolving silicates) or zinc bromide (for heavy density flotation). We are very careful when using such things as they can be harmful if precautions aren't taken to protect ourselves. For example, we wear eye protection all the time...especially when we use zinc bromide because it attacks the optic nerve if splashed in your eye and can blind you. We also have lots of special safety protocols when we work with hydrofluoric acid as it can stop your heart if enough gets on your skin and you aren't treated quickly. Rule #1: Never do it alone, just in case. I'll be using this acid later this week for some sediments from Iowa. There will be two other people in the working on mites, and one hanging around in case I have any problems.

We also treat sediments with Lycopodium spore tablets just like we treat coprolites and mummy intestines. By adding a known amount of these spores as markers, we are able to quantify our microfossils and make sense of their presence in our samples. We use a microfossil concentration formula to determine the number of microfossils per unit (weight or volume) of sediment.

Taphonomic Issues
Like other kinds of archaeological materials, we must always consider the state of preservation for our samples. The addition of chemicals to break down excrement is something to be aware of in samples from certain places and time periods. As I learned from a recent set of historic samples from Missouri, the microfossils found in cisterns are fewer in number and much more degraded than those found in privies from the same time period.

We also must consider how often the sediments were exposed to abiotic agents of change, like wind and water. A series of wetting and drying episodes can degrade things as hardy as sporopollenin-laden pine tree pollen grains over time, leaving no evidence of anything that was once there. Biotic agents, like coprophagus (poop-eating) fungi, bacteria, and animals, can also affect what we find in latrine sediments.

From Privies to Parasites
Without going into too much detail about the types of microfossils found in latrine sediments, I thought I'd let all of you parasitophiles see some of the groovy parasite eggs that have been found from these contexts.

Parasite eggs recovered
from cemetery sediments.

Unfertilized  egg of
Ascaris lumbricoides

Molecular techniques have also been used on sediments to search for evidence of parasites that don't leave visible traces of themselves. Enzyme-linked immunosorbent assays (ELISAs) have been applied to samples in order to detect a number of protozoan parasites such as Giardia sp., and Entamoeba histolytica. 

Example ELISA plate.
Yellow wells = positive samples.
The Moral of the Story
Like mummies and coprolites, sifting through latrine sediments elicits reactions of both disgust and amazement from those following your work. The data that can be gathered from such studies are immense in volume and intensity. I have conducted a number of contract archaeology jobs that involved the analysis of latrine sediments, so I can literally call these types of material "pay-dirt" from both a scientific and from an economic standpoint. It is sad that so few researchers understand the importance and potential of examining latrine sediments, but at the same time this allows those of us who do see the value in these studies to work without a lot of interference. As always, these kinds of studies provide the best means of understanding what past people were eating and what exactly were eating them.