Scholarship and Creative Work


Culling vampire bats to stem rabies in Latin America can backfire

Culling vampire bat colonies to stem the transmission of rabies in Latin America does little to slow the spread of the virus and could even have the reverse effect, according to University of Michigan researchers and their colleagues.

Vampire bats transmit rabies virus throughout Latin America, causing thousands of livestock deaths each year, as well as occasional human fatalities. Poison and even explosives have been used since the 1960s in attempts to control vampire bat populations, but those culling efforts have generally failed.

Last year, a team of U-M researchers and their University of Georgia colleagues reported the results of a long-term vampire bat field study in Peru. Now, the same team has combined the field findings with new computer models of rabies transmission and data from infection studies using captive vampire bats to show that culling has minimal effect on containing the virus, and can, in some cases, actually increase its spread by driving infected bats into neighboring colonies.

The findings suggest that geographic coordination of vampire bat control efforts in Latin America—taking into account the interconnectedness of seemingly isolated colonies—might reduce transmission to humans and domestic animals. The team’s new paper, scheduled for online publication in the Proceedings of the National Academy of Sciences on Dec. 2, also establishes that rabies is usually not lethal among vampire bats.

“In the paper last year, we demonstrated that bat colony size wasn’t a predictor of rabies prevalence, which indicated that culling hadn’t reduced transmission,” said U-M population ecologist and epidemiologist Pejman Rohani, senior author of the PNAS paper (the first author is Julie Blackwood, a former postdoctoral research associate in Rohani’s lab who is now at Williams College).

“In the current paper, we do a number of things. First, we fit models that encompass alternative assumptions regarding this system and we identify an important role of movement between colonies. We then use the best-fitting model to examine what happens under culling, especially if the cull is indiscriminate, rather than targeting infected bats specifically. Again, culling is shown to be ineffective, but now the model helps us understand why that is.”

 — Jim Erickson, Michigan News

Extreme black hole is more luminous than astronomers thought possible

For decades, astronomers have puzzled over an odd source of X-ray light in an arm of the Pinwheel Galaxy, just off the handle of the Big Dipper.

The object, like other so-called ultraluminous X-ray sources, is a system made of a star and a black hole that orbit each other. But its brightness and estimated mass haven’t seemed to add up.

Either the system is twice as bright as it should be or it’s much more massive than scientists have surmised. The answer matters, in part, because it could inform theories about how the supermassive black holes at the centers of galaxies came to be.

“This has been a very frustrating field to work in,” said Joel Bregman, professor of astronomy at the University of Michigan. “We’ve been looking for indirect measurements that we thought would tell us something, but you’d get 10 pieces of information and five would be on one side and five on the other. You’d think, ‘This could all be solved if I could just measure the mass directly.'”

Now Bregman is part of an international team that has done that. In findings published in the Nov. 28 issue of Nature, they show that the black hole in the system is a fairly typical one, at least in terms of its mass. It’s a so-called stellar black hole — the kind that forms when a star up to about 200 times the size of the sun collapses at the end of its life. This one, they discovered, is between 20 and 30 times the mass of its companion star.

“As if black holes weren’t extreme enough, this is a really extreme one that is shining as brightly as it possibly can. It’s figured out a way to be more luminous than we thought possible,” Bregman said.

“These findings show that our understanding of black hole accretion is incomplete and needs revision,” said Jifeng Liu, first author of the paper. Liu began working on ultraluminous X-ray sources while he was a doctoral student at U-M and the principal investigator of the observations at the Gemini Observatory in Hawaii. He is now a researcher at the Chinese Academy of Sciences in Beijing.

— Nicole Casal Moore, Michigan News

Michigan’s felony HIV disclosure law criminalizes sickness

Michigan’s felony HIV disclosure law is driven by stigma and fear rather than medical science, according to a new University of Michigan study.

The study investigated the enforcement of Michigan’s disclosure law, which makes it a felony for HIV-positive people to engage in a wide range of sexual behaviors without first telling their partner they are HIV-positive. The law does not distinguish between sexual practices that could transmit the virus and those that pose no risk of transmission.

New medications have transformed HIV from a terminal illness to a chronic, manageable disease. Yet, despite these scientific advances, judges and prosecutors in criminal nondisclosure cases routinely describe HIV as a death sentence and compare not disclosing one’s HIV-positive status to murder. Only four defendants charged under the law were accused of transmitting the virus, according to the study’s author, Trevor Hoppe, a U-M doctoral student in sociology and women’s studies.

Thirty-three states have enacted criminal statutes that require all HIV-positive individuals to disclose their infection before engaging in sexual practices. The vast majority are similar to Michigan’s, in that they do not distinguish between high and low or no risk sexual practices.

Hoppe analyzed 58 trial court cases under Michigan’s felony HIV disclosure law from 1992 to 2010. He found that defendants were convicted for not disclosing even when their alleged sexual conduct did not pose a significant risk of transmission.

“Cases like these illustrate the lack of logic of the law — punish HIV-positive people for being HIV-positive, not because they’re putting anyone else at risk,” he said.

— Jared Wadley, Michigan News

New drug cuts risk of deadly transplant side effect in half

A new class of drugs reduced the risk of patients contracting a serious and often deadly side effect of lifesaving bone marrow transplant treatments, according to a study from researchers at the University of Michigan Comprehensive Cancer Center.

The study, the first to test this treatment in people, combined the drug vorinostat with standard medications given after transplant, resulting in 22 percent of patients developing graft-vs.-host disease compared to 42 percent of patients who typically develop this condition with standard medications alone. Results of the study appear in The Lancet Oncology.

“Graft-vs.-host disease is the most serious complication from transplants that limits our ability to offer it more broadly. Current prevention strategies have remained mostly unchanged over the past 20 years. This study has us cautiously excited that there may be a potential new way to prevent this condition,” says lead study author Dr. Sung Choi, assistant professor of pediatrics at the U-M Medical School.

Vorinostat is currently approved by the U.S. Food and Drug Administration to treat certain types of cancer. But U-M researchers, led by senior study author Dr. Pavan Reddy, found in laboratory studies that the drug had anti-inflammatory effects as well — which they hypothesized could be useful in preventing graft-vs.-host disease, or GVHD, a condition in which the new donor cells begin attacking other cells in the patient’s body.

“We are encouraged by our findings,” Choi says. “Vorinostat combined with standard graft-vs.-host disease prophylaxis after related-donor transplant appears to be safe and associated with lower than expected incidence of acute GVHD.”

— Nicole Fawcett, Comprehensive Cancer Center

U-M Biology students handle previous literatures well

In an article to appear in the January issue of Written Communication, John M. Swales, emeritus professor of Linguistics, shows that “A” papers from Michigan biology students are remarkably adept when it comes to writing about their sources. The papers have been drawn from the Michigan Corpus of Upper-level Student Papers, a large electronic database covering 16 disciplines across the university; the MICUSP papers are restricted to final year undergraduates and graduates in their first three years.

One sign of this sophistication is a well-motivated balance between integral citations (“Brie (2012) claims that the moon is made of cheese”) and parenthetical citations (“The moon may be made of cheese (Brie, 2012))”. Others are the occasional use of strategically placed occurrences of first as well as last names (e.g. “Charles Darwin”) and of direct quotations. These students also use rather more “concept-focused” citations (“Wallace’s hypothesis suggests…”) than expected, as opposed to simpler “person-focused” citations, such as “Wallace suggests…”.

Finally, preliminary studies suggest that U-M biology students are more skilled writers in these respects than those in other disciplines, this being particularly true of students in the evolutionary branch of biology.

— John M. Swales, LSA

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