Global bullfrog trade spreads deadly amphibian fungus worldwide

The global trade in bullfrogs, which are farmed as a food source in South America and elsewhere, is spreading a deadly fungus that is contributing to the decline of amphibians worldwide, according to a U-M biologist and his colleagues.

Amphibian populations are declining worldwide at an alarming rate, and the spread of the deadly chytrid fungus is believed to be a contributing factor. The fungus infects the skin of frogs, toads and salamanders.

In a study to be published in an upcoming edition of the journal Molecular Ecology, U-M evolutionary biologist Timothy James and his colleagues examine the role of bullfrog farming in spreading the chytrid fungus between the forests and frog farms of Brazil and then to the United States and Japan.

The researchers collected and analyzed bullfrogs sold at Asian food shops in seven U.S. cities and found that 41 percent of the frogs were infected with chytrid fungus, which is harmless to humans. Frogs in these shops are imported live primarily from farms in Taiwan, Brazil and Ecuador and sold as food for their legs.

James and his colleagues also analyzed bullfrogs from frog farms in Brazil and several native frog species from Brazil’s Atlantic Forest, one of the most amphibian-rich regions in the world. Their DNA sequencing studies identified the various strains of the chytrid fungus, Batrachochytrium dendrobatidis or Bd for short, present in the frogs.

The data suggest that the Bd-Brazil chytrid strain probably originated in Brazil among native frogs, rather than being introduced to the country by imported bullfrogs. The Bd-Brazil strain likely spread from infected native frogs to a Brazilian bullfrog farm and from there to other locations in bullfrogs shipped globally.

Additional U-M authors are Maria Lee, Serena Zhao and Catherine Wangen.

— Jim Erickson, News Service

Preschool children at risk for stress after seeing domestic violence and another traumatic event

Preschool children exposed to domestic violence and additional traumatic events are at increased risk for developing traumatic stress disorder, a new U-M study shows.

Researchers sampled 120 children between ages 4-6 who were exposed to domestic violence in the past two years. About 38 percent of the kids were faced with additional traumatic events, such as sexual assaults by family members, physical assaults or life-threatening illnesses.

Those children had higher rates of post-traumatic stress disorder than the other children who were exposed to domestic violence.

The research involved children who lived in low-income households (less than $7,500 annually), where domestic violence incidents happen more often than in families with other economic backgrounds. Through flyers and brochures, women in a Midwest state were recruited and they chose where interviews would be conducted, such as a shelter or a home, if the woman was not living with an abusive partner.

Respondents answered questions about the frequency of being abused within the last year and what their child’s behavior was after being exposed to domestic violence and any other potentially traumatic events.

Of the 120 children, the research indicated that 74 (or 62 percent) never experienced an additional traumatic event beyond exposure to domestic violence. The remaining 46 children experienced at least one additional traumatic event, resulting in behavior problems such as becoming anxious, depressed or more aggressive.

These results, as well as other studies on multiple trauma exposure, indicate the challenges for children adapting to their situations that could affect their school performance and social development.

Graham-Bermann collaborated on the study, published this month in the Journal of Traumatic Stress, with U-M graduate Lana Castor; Laura Miller, a doctoral candidate in the clinical science program; and Kathryn Howell, a postdoctoral fellow in the Department of Psychiatry.

— Jared  Wadley, News Service

Bacteria in tap water can be traced to the water treatment process

Most of the bacteria that remain in drinking water when it gets to the tap can be traced to filters used in the water treatment process, rather than to the aquifers or rivers where it originated, U-M researchers discovered.

Their study — a unique, broad-based look at Ann Arbor’s water supply from source to tap — could open the door to more sustainable water treatment processes that use fewer chemicals and, as a result, produce lower levels of byproducts that may pose health risks. Eventually, the work could enable engineers to control the types of microbes in drinking water to improve human health like “live and active cultures” in yogurt, the researchers say.

The research, led by Lutgarde Raskin, a professor of civil and environmental engineering, is published online in Environmental Science & Technology and will appear in a forthcoming print edition. Over six months, the researchers sampled water at 20 points along its path from groundwater and Barton Pond sources to residents’ faucets and several more places in the water treatment plant. They harvested bacteria from each sample and sequenced their DNA.

Most previous drinking water studies have focused more narrowly on disease-causing pathogens, Pinto said. But bacteria such as Legionella, Salmonella, and E. coli don’t exist in isolation. Their fate is influenced by the microbial community around them.

The study found that the “activated carbon filters” commonly used to remove suspended particles play a significant role in determining which bacteria are most prevalent in treated drinking water.

— Nicole Casal Moore, News Service

Why retire later? U-M experts show how to encourage longer careers

What if every U.S. worker got an automatic 10 percent pay raise at age 55? According to a new U-M study, most people would work quite a bit longer to enjoy the extra income before they retired.

By eliminating social security payroll taxes starting when workers are 55-years old, the study shows that take-home pay would jump by 10.6 percent and they would work 1.5 years longer on average, paying more income taxes and helping to reduce the Federal deficit.

“People are living longer, healthier lives, and so far have opted to take most of that extra time as additional retirement rather than work,” says U-M economist John Laitner, who conducted the analysis with U-M economist Dan Silverman. “We are proposing a way of responding to this situation through targeted tax-rate changes that would reward older workers for staying on the job and also benefit the economy as a whole.”

Both Laitner and Silverman are affiliated with the U-M Retirement Research Center, based at the U-M Institute for Social Research (ISR). Their analysis appears in the August issue of The Journal of Public Economics.

Using data from the ISR Health and Retirement Study and from the Consumer Expenditure Survey conducted by the U.S. Bureau of Labor Statistics, Laitner and Silverman explore how tax cuts targeted at older workers would affect the likelihood of working longer and the size of the federal deficit.

“Our idea is to lower the taxes on an individual precisely at the time of life when people are making decisions about whether to work longer or retire,” Silverman says.

— Diane Swanbrow, News Service

Could a cancer drug potentially prevent learning disabilities in some kids?

A drug originally developed to stop cancerous tumors may hold the potential to prevent abnormal brain cell growth and learning disabilities in some children, if they can be diagnosed early enough, a new animal study suggests.

The surprising finding sets the stage for more research on how anti-tumor medication might be used to protect the developing brains of young children with the genetic disease neurofibromatosis 1 — and other diseases affecting the same cellular signaling pathway.

The findings, made in mice, are reported in the journal Cell by scientists at the Medical School and their colleagues. The results also are important to understanding the stem cells that become different brain cells.

Neurofibromatosis 1, or NF1, affects one in every 3,000 children, and causes benign tumors to grow throughout the body, large head size and other issues. Many children with NF1 also struggle with learning to read, write, do math and behave well.

The new paper’s senior author, Yuan Zhu, cautions that the particular drug in the trial may not be appropriate to give to children who have been diagnosed with NF1. But other MEK inhibitors are being developed against cancer.

“The important thing is that we have shown that by treating during this brief window of time early in life, when neural stem cells in a developing brain still have time to ‘decide’ what kind of cell to become, we can cause a lasting effect on neural development,” he says. Zhu is an associate professor of internal medicine, in the Division of Molecular Medicine and Genetics, and in the Department of Cell & Developmental Biology, at the Medical School.

In addition to Zhu, the research team includes U-M postdoctoral research fellow and former Zhu graduate student Yuan Wang, Ph.D.; Edward Kim, B.S.; former postdoctoral research fellow Xiaojing Wang, Ph.D.; and colleagues from other institutions Bennett G. Novitch, Kazuaki Yoshikawa and Long-Sheng Chang.

— Kara Gavin, UMHS Public Relations