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Dr. Astra Bryant is a professor at the University of Washington who studies neuroscience and parasitology. Growing up in Mountain View, California, Astra was an animal lover and a voracious fiction book reader. While she originally wanted to apply her love of animals into becoming a veterinarian, she ultimately decided to become a research scientist. She studied biology at Bryn Mawr College, a women's liberal arts college in Pennsylvania, and went on to get her PhD in neuroscience from Stanford. She became involved in parasitology during her postdoc at UCLA, and eventually came to the University of Washington to start her own lab, conduct research, and mentor students. When she's not working, she likes to take her 1 year old puppy, Gary, to dog parks, bike around Lake Washington, and paint landscapes.
Astra checks a sample for parasites
Photo courtesy of Astra BryantAstra is a neuroethologist and parasitologist. Neuroethology is a field that lies at the intersection of neuroscience, the study of the nervous system, and ethology, the study of animal behavior. While an ethologist might observe how a male bird's courtship dance impacts his chances of winning a mate and compare one male's dance and reproductive success to another, a neuroethologist would look at what is happening in the nervous system of these birds to identify the underlying mechanisms of the behaviors. Astra's focus isn't on bird behavior, though, it's on parasites. Specifically, the behavior of a species of parasitic soil-dwelling nematodes called Strongyloides stercoralis (strong-gih-LOY-dees stir-core-ALice).
Nematodes are a kind of worm, but they're not the same as earthworms, which is probably what you think of when you see the word "worm". While they may look "worm shaped", they have different anatomy and have been evolving separately for a very long time. A parasitic organism is one that lives on or in another organism for at least part of its life, usually stealing resources like food, water, or even blood from its host. Head lice and tapeworms are examples of parasites. There are also parasitic organisms that rely on other animals to raise their young, like cuckoo birds and some wasps. Strongyloides stercoralis, or S. stercoralis, live in the soil in their larval form. When they find a human host, they enter the human's body and develop into an adult, living out their life in the small intestine. The nematode's eggs and larvae exit the body through feces, and can go back into the soil to infect someone else.
This diagram shows the life cycle of S. stercoralis
Image source: Bryant Lab, University of Washington"I actually realized fairly late - halfway through college. Before, I wanted to be a veterinarian, because I really love animals. But I realized that what I got really excited about what all the things we don't know about how animals work. That curiosity, and the excitement I felt when I did an experiment and was the first person in the world to learn something new, that's how I learned I wanted to be a scientist."
"That I get paid to be curious!"
"There are so many stories I could tell; it's hard to pick one. In grad school, I was trying a set of experiments that just... didn't work. For years! So many times, I convinced myself they were working, but inevitably, they hadn't. I first learned to be optimistic: this time things would work, so I should do the experiment! I also had to learn that science was hard, and many times experiments won't work and it didn't mean I wasn't a good scientist. Eventually, I figured out what was going wrong and changed my experiments. "
Astra and her dog, Gary.
Photo courtesy of Astra BryantParasitic, soil-dwelling nematodes in general affect over a billion people worldwide and can cause a variety of negative health impacts; they can even lead to death. These nematode-related health issues disproportionately impact socioeconomically disadvantaged regions of the world. S. stercoralis, the species Astra studies, "infects at least 610 million people globally, nearly three times as many people as malaria", according to her lab's website. Strongyloidiasis, the condition caused by an infection from S. stercoralis, can cause an itchy skin rash where the nematode entered the body, and mild to severe gastrointestinal issues. Some infections don't cause any symptoms at all. In people with weakened immune systems, strongyloidiasis can be fatal (in fact, it's the only parasitic nematode that can be fatal). When a person's body can't put up a strong immune response, the adult nematodes can create very large numbers of larvae that can eventually make their way to other organs and body systems. When this happens, mortality rates can be as high as 90%.
The soil-dwelling larvae of S. stercoralis can detect human body heat and use that to find their host. Once they turn into adults, they adapt to survive in the much hotter environment of a human's body. Astra and her lab hope to better understand how S. stercoralis senses and responds to temperature, both in its behavior and within its nervous system.
An adult S. stercoralis next to a larva.
Photo credit: CDCIn 2018, Astra and the lab she worked in at the time published a paper that provided the first, detailed evidence for how S. stercoralis respond to heat. The scientific community had known for a while that many parasitic nematodes were attracted to warmth and chemical cues from their hosts, but it hadn't been studied in depth yet.
Through this study, Astra and her team learned that the "infective" larval form of S. stercoralis is strongly attracted to temperatures similar to human body temperature. They are most attracted to this "host temperature" when the ambient temperature is relatively cool, suggesting that someone could at greatest risk of being infected in the early morning or late evening. This is important, because some of the regions where people are impacted most by this nematode experience very high daytime temperatures, so people are more likely to be working outside in the early morning or late evening.
They also identified a gene that is at least partly responsible for this heat seeking behavior. When they selectively mutated this gene, the nematode larvae stopped exhibiting the behavior.
All of these findings are significant because they point researchers in the direction for more effective prevention and treatment of S. stercoralis. Currently, the best course of treatment is to treat the patient with a de-worming medication, but that leaves them susceptible to reinfection and it may be hard to tell they even need treatment if the infection is asymptomatic. Additionally, it may not be a good enough option for immune-compromised people like infants, the elderly, and people taking certain kinds of immune-suppressing medication.
"Cultivate your curiosity and sense of wonder."