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Undergraduate Research Stories at Virginia Tech

Research on parasites plaguing Virginia otters uncovers a mystery

December 2008

By Alyssa Haak, junior English major

Virginia Tech senior honors student Morgan Agnew, of Wyndmoor, Pa., is no greenhorn in undergraduate research. The biology and animal science double major began her undergraduate research career as a sophomore and has been developing her project since. Intending to become a veterinary school student, Agnew chose to do her undergraduate research on parasites in the Virginian otter population.


Morgan Agnew met Flora during an internship at an equine breeding facility in Florida.

While working as a sophomore at the Virginia Tech horse breeding center on the Blacksburg campus, Agnew spoke with the barn's visiting veterinarians. They suggested that she find an opportunity to do undergraduate research while at Virginia Tech and pointed her to veterinary parasitologist Anne Zajac, who is doing otter research. Zajac is associate professor of biomedical sciences and pathobiology in the Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech.

Researchers with Zajac's group hope to document threats to the species and note general differences in the Virginia otter population based on sex, age, and location. Upon speaking with Zajac, Agnew accepted a research position that allowed her a hands-on experience dissecting and analyzing the gastrointestinal tracts and hearts of otters, which are provided to the researchers by the Virginia Department of Game and Inland Fisheries.

Agnew's research encompasses examining the digestive tracts of 70 Virginia otters of all ages and both sexes for signs of parasites. Researching the particular parasites that infect these otters could contribute to an understanding of the health of the Virginia otter population.


Morgan Agnew looks for parasites in a sample from an otter IG system.

After thawing the frozen gastrointestinal (GI) tracts, Agnew removes the contents of the stomach and intestine and preserves them with formalin. Using a dissecting microscope, she then examines the GI contents of each animal in small amounts (about 10 milliliters (ml), which is less than a teaspoon), requiring several hours of work to complete each animal’s sample. "I look for a cell wall that looks like it is its own unit; it looks like a separate organism from the intestinal fluid. It has a distinct cell wall," says Agnew. "For larva that is all you'll see."

Finding and labeling parasite larvae is so difficult that Agnew occasionally must separate the questionable parasite from the 10 ml sample to observe it under a compound microscope. Adult parasites are far easier to identify. Mature parasites have a distinct digestive tract that is revealed under the dissecting scope. Some adults even contain eggs, which helps identify them.


These tapeworm segments were found in a sample from the otter intestine.

Heartworms were the easiest parasite to check for, Agnew says. In addition to the contents of gastrointestinal tracts, she analyzed the contents of the otter hearts. After opening the heart, Agnew looked in each chamber for signs of heartworm. No microscope was needed; heartworms are evident to the naked eye and resemble long hairs intertwined within the heart itself. There was no sign of heartworm infection in any of the otters she examined, Agnew says.


Clinostomum, a type of fluke often found in otters, appear to be less prevalent in Virginia otters than in U.S. West Coast otters.

Because it takes hours to finish one full digestive tract, one 10 ml section at a time, Agnew has also been training and working alongside two more undergraduate researchers. She taught the two new researchers by showing them samples of previously identified parasites. After learning what to look for, the students began examining samples on their own, under Agnew's supervision. When a possible parasite was found, Agnew would double-check the other students' identifications until they were comfortable and knowledgeable enough to continue on their own.

Once the team analyzed all of the GI tracts and hearts, they looked for any patterns and similarities. The comparisons were done based on where the otters were found, sex, and age. No pattern was found based on location, but a notable difference occurred once the team compared the parasite samples based on the ages of the otters. The youngest age group had the highest numbers of Strongyloides – a type of nematode worm, a parasite with a simple lifecycle that can pass through the milk of the mother to her young.

Parasites with simple life cycles, such as Strongyloides, were found in higher numbers than parasites with complex life cycles, such as tapeworms and flukes. This lead the team to believe that there could be a fewer intermediate hosts in Virginia rivers; complex parasite life cycles require a sequence of hosts, such as fish or invertebrates, before the parasite can mature in the final host, in this case the otter. Since complex parasites were found in lower numbers in the otter species, it can be concluded that there may be a problem with the passage of parasites from the first host to the intermediate host or from the intermediate host to the final host, says Agnew.

Agnew and the other researchers in Zajac's group compared their findings with Tennessee and West Coast studies. The West Coast had the most diverse parasite population, followed by Virginia, and then Tennessee. So far, however, nothing else has been determined about the intermediate host mystery, Agnew says.

Upon completion of the research, Agnew hopes that the findings will help Virginia wildlife managers generate a profile of the entire Virginia otter population. Combining the research that Virginia Tech is doing on otter species and the research being done at other universities, the Virginia Fish and Wildlife Information Service should be able to compile age, population distribution, and reproductive data, and determine the overall health of the population. Agnew, who is writing a senior honors thesis on her research, plans to submit her paper for publication in a wildlife journal.

Agnew says the research experience has expanded her future career vision and she hopes to remain involved in research, as well as practice veterinary medicine. "This definitely opened my eyes up to a lot of opportunities in veterinary medicine that isn't just seeing patients," she says.

Agnew's undergraduate research provided great lessons in leadership, presentations, thesis writing, accuracy, and preparation for graduate school. She was selected to present at the Virginia Wildlife Symposium in Richmond, as well as at Virginia Tech for her honors baccalaureate degree.


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