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Rachael L. Ticho Zacks comes from a family of attorneys, but she steps to the beat of a different drum. She is graduating from the University of Colorado this December with a bachelor’s degree in ecology and environmental biology.

The choice suits her. Not only is she is graduating Summa cum Laude, but she has also been named Outstanding Graduate of the College of Arts and Sciences. The Columbus, Ohio, native is graduating in 3.5 years.

“I am most impressed, and astounded, to see how much Rachael accomplished in research while maintaining a stellar GPA,” Barbara Demmig-Adams, a professor of ecology and evolutionary biology, wrote as she nominated Zacks to be designated outstanding graduate.

For her honors thesis, Zacks conducted original research on co-infection—being infected with more than one disease—in wild animals, specifically deer mice. In an analysis of the blood samples of 1,500 mice trapped in 44 sites in �Ǹ�Թ� County, Zacks found that mice were relatively rarely infected with both Bartonella vinsonii, a bacterium, and Sin Nombre Virus.

Sin Nombre Virus, a strain of hantavirus, can be transmitted to humans who breathe airborne particles of deer-mice feces or urine. Between 1993 and 2007, the U.S. Centers for Disease Control and Prevention recorded 465 cases of Hantavirus Pulmonary Syndrome.

The syndrome is particularly virulent, killing 34 percent of humans it infects.

In Zacks’ sample, 69 percent of deer mice tested positive for Bartonella vinsonii and negative for the hantavirus. �Ǹ�Թ� 11 percent tested positive for both, and 17 percent tested negative for both. Only 3 percent tested positive for the hantavirus and negative for the bacterium.

Zacks’ results showed that infections of B. vinsonii and SNV are negatively correlated, meaning they tend not to occur simultaneously. The negative correlation might be due to “competitive exclusion,” the principle that two species competing for the same resources can’t coexist if other ecological factors are constant.

Zacks’ thesis notes that further research is necessary to confirm a possible protective immunity of Bartonella vinsonii against Sin Nombre Virus. “However, the promise of co-infection as an important factor in disease ecology is clear; co-infection may serve a possible future predictor of wildlife community health and zoonotic outbreaks,” she writes.

Zoonotic outbreaks of disease are transmitted from wildlife to humans.

The low rates of co-infection among deer mice might stem from a mechanism by which B. vinsonii stimulates the immune system, thereby suppressing SNV infections.

Similarly, the lack of co-infection might help protect human health, Zacks concludes. “If a deer-mouse population has a high prevalence of Bartonella, perhaps there is a decreased risk of SNV infection for the human population.”

After graduation, Zacks hopes to land a fellowship at the Centers for Disease Control and Prevention to study pathogens. “I want to be one of those people in protective suits working with ebolavirus,” she says.

Next year, she plans to apply to graduate school.

In a congratulatory meeting recently with Todd Gleeson, CU dean of the College of Arts and Sciences, Zacks talked about why she loves science and the study of pathogens.

In science generally, “Nobody knows the right answer,” she said. “I always think of it as a game. And I know my job will never be the same. Virus and bacteria evolve so quickly, I’ll never be out of a job.”

Zacks’ research project came about an unanticipated development in the research group of her honors-thesis adviser, Sharon K. Collinge, associate professor of biology and environmental studies. Two members of the laboratory became infected with hantavirus while studying deer-mice populations in �Ǹ�Թ� County, and Collinge suggested that Zacks study data from the mice.

“When I met Rachael, I realized that she had the intellect and the motivation to take this project to a sophisticated level of analysis and interpretation,” Collinge wrote in a letter supporting Zacks’ nomination to be named outstanding graduate for the College of Arts and Sciences.

Zacks has submitted her thesis to a peer-reviewed journal, and Collinge believes it will be published because “it is a novel data set, the analyses are straight-forward, and the results are compelling.”

Zacks herself notes that few scientists study disease in rodents, because they don’t seem to get sick. But, she adds, “you need to understand what’s going on in wild populations because it helps you understand disease in human populations.”