Article By: Linden Reid
One thing that remains true, and that will always remain true, is that parasitologists deal with blood and guts. The nature of the beast is that we deal with animals that live inside and off of other animals. The organisms we study and dearly love can't live without that blood and those guts from the animals that live around us. So my first lesson in parasitology was that that was something that needed to be accepted - and quickly.
The other thing that not many people think about when considering parasites and their studiers is that it deals with a lot of poop. A lot of it. there are parasites that come out alive in poop, there are parasites that lay eggs in poop, and there are parasites that you can only contract by ingesting infective stages from poop. And for the first few minutes, the thought of that churns the stomach a little. But then, it's gone, and you move on. Because there are parasites to be found.
And that's what it really comes down to. Parasitologists study one of the most intricate, frustrating, beautiful, and understudied groups of animals on the planet. There are parasites that mate for life, parasites that can cloak themselves against host immune systems, and even parasites that can zombify their hosts. And we love them for all of those things and more.
So without further ado, I've wanted to walk through a day in the life of a parasitologist from the point of view of a trainee - myself. It is worth mentioning that not all parasitologists study the same hosts - not by a long shot. They study the parasites of everything; insects, trees, fish, birds, cats, people, even other parasites. I've chosen a mammal parasitologist, Dr. Scott Gardener, from the University of Nebraska-Lincoln, for this particular example, because he is one of the most highly esteemed, highly published parasitologists in practice right now. And only partially because he was willing to let me shadow him on a day off and take excessive pictures.
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Before I begin, it's worth mentioning that there are blood, guts, and poop in this presentation. I told you that's what parasitology was all about.
The day begins early with Sherman Live traps. They're small, aluminum or steel traps that contain a lever that when stepped on will trigger the door to snap shut, trapping the animal inside. The traps are usually baited with oats or instant oatmeal, but the latter tends to turn into a cleaning problem if there happens to be rain. We let these traps sit overnight - usually they're set in the afternoon or evening, and collected early in the morning the next day.
The next morning, as early as possible, we troop out to retrieve our traps. They're set in lines, on this particular day of twenty each, with ten paces in between each trap. The start and finish of the lines are marked with colored flags so it's easy to see where the traps are laid, especially when you're trapping in brush. We always check which traps have animals in them, and number and label those specifically. On a great day in Nebraska, you'll get animals in about 10% of your traps - but that's not always the case. On this particular day, we set out around 150 traps, and got 9 animals.
When we're back in the lab, we press down the levers on the traps, and upend the animals into plastic bags. We have to be careful of this process, because many of the animals that we trap have the potential to carry Hantavirus, among other things. We also want to catch any ectoparasites that are hanging onto the skin and fur of the animals that we trapped. Once we have them in the bag, a chemical (and several can be used) is injected into the bag, and the animal is euthanized from the fumes. This process takes less than five minutes, and is the least stressful process for the animal possible. When the animal is dead, we have a specimen to begin processing.
The first thing to be done is measurements. Without host data, the parasites are nearly useless to the parasitologist, and in parasitology, the host is as important as the parasite itself. Four common measurements are taken for the animals that we trapped ( all of our animals were white-footed mice, Peromyscus leucopus) - the length of a hind foot, the length of the ear, the length of the animal from the tip of the nose to the base of the tail, and the length of the tail. After that, the animal is weighed and blood smears are taken to look for any blood parasites that might be present. The bag that contained the animal is emptied and preserved to be searched through later for ectoparasites. The mammal is given a unique number, and this number is associated with the host and all its parasites for the data that's collected.
At this point, the animal is ready to be examined for endoparasites living inside the body. Once a single incision down the length of the body is made, samples are taken from the spleen, liver, kidneys, and sometimes several other organs for preservation in liquid nitrogen to use for genetic work. The intestines, stomach, cecum (a digestive organ used for absorption of fluids), liver, and often lungs are set aside to be checked for parasites. The animal is then either saved whole for use in a mammalogy study, or skinned for depositing in a museum. If the animal is skinned, the skull is often removed for skeletonization, along with the rest of the skeleton if the museum or researcher does not have one in the official collection for research reference.
Now we look through the organs that we removed for parasites. Each one is isolated separately and carefully cut open, as the parasites inside are often very fragile. If we find parasites, which we did today, we set them aside in saline and preserve them differently depending on which kind of parasite we've found. We found plenty of nematodes (round worms) today, which are relaxed in glacial acetic acid, and then preserved in 70% ethanol.
Once we have everything properly preserved, we can work on the most rewarding part of the process - identifying what we've found. The nematodes that we found today haven't been identified yet, but in the past few days we've found Trichuris peromysci, Syphacia peromysci, both nematodes, Catenotaenia peromysci, a cestode (tapeworm), and Cuterebra castrator, a bot fly larvae, all in the same host species as we caught today (Peromyscus leucopus). We also found several bot fly larvae today that were identified as Cuterebra castrator.
Once we're done processing animals and all of our specimens are identified and properly deposited into museums (though sometimes the identification and depositing comes later), we get to go home for the day with a few more lessons in parasitology and usually a new lesson in life.
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Sometimes it's something as simple as remembering to never, ever forget to bring sunscreen with you whenever you're outside, and sometimes it can be something as significant as truly understanding what it means to have another life in your hands.
Parasites are pretty great. To those who study them, they're more than pretty great. There are parts to studying parasitology that are dirty, exhausting, and sad. But there are even more parts to parasitology that are beautiful, mind-boggling, and important, many of which have spawned some of the greatest ideas in biology in hundreds of years. And that is why we study them.
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I'd like to give a special thanks to Cedar Point Biological Station, and especially Jon Garbisch for allowing me to take photographs of this Field Parasitology class. This class is offered every summer our at Cedar Point, just outside of Ogallala, Nebraska. It's a worthwhile class, not only for those interested in parasitology, but for those interested in the more general sciences as well.
I would also like to thank the Harold W. Manter Laboratory of Parasitology and Dr. Scott Gardner for providing their expertise and equipment for this article. I cannot thank you enough for the help you've given.
Visit and support Cedar Point Biological Station here:
and visit and support the Manter Lab here:
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