Examining internal and external factors affecting pathogenic loads and ‘supershedders’

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Jen Owen (view larger image)

More than 60 percent of all human infectious diseases originate in animals, and within the past century, an unprecedented number of diseases have emerged that pose significant risks to wild
and domestic animal and human populations. Many of them originate in wild birds. Jen Owen, an associate professor in the Michigan State University (MSU) Department of Fisheries and Wildlife, is working on a project funded by the National Science Foundation (NSF) to assess variation in the pathogen load in virus-infected birds.

It is an NSF Career grant, one of the most prestigious awards given to early-career faculty members. Unlike many others, these grants require both a research and a teaching component and an integration of the two. Through the project, Owen is looking to better understand why some individuals within a population carry higher pathogen loads than others. She is particularly interested in “supershedders,” the ones in a population that, for unknown reasons, are responsible for most of the pathogen load.

“We’re looking to see if there is a genetic basis for supershedders by using transcriptomics and RNA sequencing,” she said. “We want to see if there are genes that are differently expressed in supershedders than in non-supershedders.”

Owen said there is a significant knowledge gap in disease epidemiology when it comes to understanding the intrinsic and extrinsic factors that determine variation in infectiousness. Knowingmore about the basis for pathogen load variation and why some individuals shed much larger amounts will provide information to develop more realistic epidemiological models that lead to cost-effective, targeted prevention and control strategies, she said.

The project has the following objectives:

  • Use genome-wide technologies to investigate how gene expression affectsvariation in viral shedding using lowpathogenic avian influenza virus and two species of waterfowl — the mallard (Anas platyrhynchos) and the blue-winged teal (A. discors).
  • Test how variation in host body condition — caused by food restriction — affects how a bird responds to West Nile virus, using the American robin (Turdus migratorius) as a focal species.
  • Develop simulation models to demonstrate how environmental factors influence disease outbreaks.
  • Adapt the models to allow non-STEM (science, technology, engineering, mathematics) students in college general science classes to learn about disease dynamics. Through a user-friendly computer interface, students will be able to manipulate environmental stressors associated with climate change and/ or other natural disturbances, and then track disease outcomes that are host- and pathogen-specific.

Through previous research, Owen found that waterfowl infected with avian influenza virus exhibit significant within-species variation in how much virus they produce/shed — i.e., how infectious they became. Furthermore, she and her research team found that, contrary to their predictions, healthy birds shed more disease organisms than unhealthy birds. But they also found that, regardless of environmental conditions, 20 percent of birds within a population shed 80 percent of the virus. These individuals are the supershedders.

“There is clearly something beyond the environment, some intrinsic basis for this pattern,” she said. “It is likely happening in the bird’s gut, where low-pathogenic strains of influenza virus bind to host cells.”

Owen, her students and three colleagues at MSU LearnDAT (Learning Design and Technology) are developing a computer simulation program for non-STEM students. Owen is a faculty member with the MSU Center for Integrative Studies in General Science (CISGS), and she decided to focus on human malaria — a disease she had not previously studied — because there is more data available on malaria, and it is a better fit for the environmental science curriculum in the CISGS program.

“I’m very passionate about teaching nonmajors and getting them to understand the role of science in everyday life and making those connections,” she said. “Disease fascinates students, and once you start talking about infectious diseases like malaria, you quickly get their attention and genuine interest.”

The computer simulation will depict an African village in an area in which malaria is endemic. Students will be able to adjust aspects of the climate such as temperature and rainfall, as well as socioeconomic status in the village. Students will see how changes in climate and levels of poverty affect risk of infection as well as recovery and treatment. She also wants students to be able to understand how the health of the people is linked to the health of the environment.

“We don’t talk about any of these things in isolation because they’re all connected,” she said. “The idea is that this module for human malaria simulation is adapted to be applied to a new environmental organismal biology class some of my colleagues and I will be developing.”

Owen said she hopes to provide non-majors with a yearning to pursue science. In general, she said, their view of the subject is low because of negative experiences and misperceptions. Owen has had previous success in this regard, usually having at least one student every other semester switch from a non-science major to a sciencerelated one. Owen said the key is educating students on how science is relevant in everyday lives, such as pointing out daily examples in the news.

She believes that implementing a computer simulation exercise, such as the one on malaria that illustrates concepts taught throughout the semester, will leave students better equipped to answer relevant and thought-provoking questions and improve the large-class learning experience. The new course she is developing, called “Emerging Infectious Disease and Global Climate Change,” is expected to be offered within the next two years or so. Owen is also in the midst of writing a book about the ecology of infectious diseases in wild birds.

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