From UCSC: “Lyme disease researchers seek consensus as number of cases grows”

UC Santa Cruz

UC Santa Cruz

April 24, 2017
Tim Stephens

Several species of ticks in the genus Ixodes transmit the Lyme disease bacteria. (Photo by Catherine Bouchard)

Lizards are a key host for ticks in the western United States. Interestingly, a protein in the blood of western lizards eliminates the Lyme disease bacteria from ticks that feed on them. (Photo by Ervic Aquino, California Department of Public Health)

Scientists have built a large body of knowledge about Lyme disease over the past 40 years, yet controversies remain and the number of cases continues to rise. In the United States, reported cases of Lyme disease, which is transmitted from wild animals to humans by tick bites, have tripled in the past 20 years.

A multitude of interacting factors are driving the increase in Lyme disease cases, but their relative importance remains unclear, according to Marm Kilpatrick, a professor of ecology and evolutionary biology at UC Santa Cruz. Nevertheless, he noted that there are a number of promising strategies for controlling the disease that have not been widely implemented.

Kilpatrick is lead author of a paper published April 24 in Philosophical Transactions of the Royal Society B that examines the complex array of factors influencing the prevalence of Lyme disease and identifies the major gaps in understanding that must be filled to control this important disease.

Areas of agreement

Some of the unresolved issues are highly contentious, so Kilpatrick sought input for the paper from a wide range of Lyme disease researchers and developed a consensus on areas of agreement. “I wanted to address these big disputes. We’ve done so much work, let’s identify what the gaps are and fill them so we can move on,” he said.

A key missing piece in the Lyme disease puzzle is that scientists lack a detailed understanding of what limits populations of the Ixodes ticks that transmit the disease. Deer are the most important hosts for adult ticks, so the ticks are mostly absent from areas with no deer. But efforts to control ticks by reducing deer populations have had mixed results.

“If you eliminate deer completely, you can usually eliminate ticks. But is there a number to which you can reduce the deer population and have an impact on Lyme disease? We don’t have a good answer right now. There have been experiments where the deer population was reduced by 50 percent or more without any measurable decrease in the tick population,” Kilpatrick said.

The Borrelia bacteria that cause Lyme disease are carried by small mammals such as mice and shrews, from which the ticks pick up the infection and transmit it to humans. It may be that in some areas, the most important drivers of tick abundance are the factors that control small mammal populations, including their food supply and predators, Kilpatrick said.

“One group of scientists has argued that the major drivers are not so much deer populations but how we’ve changed the forest ecosystems and small mammal communities,” he said. “Each group’s research focuses on one part of the story, but in working on this paper we found that when they look at all the data together, they tend to agree on many things.”

Multiple strains

Another complicating factor is the existence of multiple strains of the bacteria, which appear to be associated with different small mammal hosts. The strains found in infected humans are often associated with a subset of tick hosts, Kilpatrick said. But the role of each host species, including mice, chipmunks, and squirrels, in sustaining tick populations and infecting them with strains of bacteria that cause disease in humans is still unclear.

“There are many factors causing variation in Lyme disease incidence, and this complexity of factors makes it challenging to make strong predictions about where the hotspots are going to be,” Kilpatrick said.

Pesticides that kill ticks (acaricides) are available and can be effective at reducing the numbers of ticks, but they are only useful on a small scale. In some regions, many infections are thought to be acquired from ticks in suburban backyards, but homeowners are often reluctant to spray pesticides in their yards. Other strategies targeting host animals with acaricides have shown promise in some trials. For example, deer can be lured to feeding stations where they rub against rollers that apply acaricide to their fur, which kills the ticks they carry. Another approach involves putting out treated cotton for mice to take back to their nests where it kills ticks.

A vaccine that was 80 percent effective in protecting people from getting the disease was available for several years, but was withdrawn from the market in 2002 due to lack of interest.

“We have a bunch of tools, but they have been underutilized,” Kilpatrick said. “With ticks, the responsibility for protecting yourself is yours, unlike with mosquitoes where we have mosquito control agencies. It’s an interesting contrast.”

The paper appears in a special issue of Philosophical Transactions of the Royal Society B on the theme of Conservation, biodiversity and infectious disease: scientific evidence and policy implications. Kilpatrick is lead author of another paper in this issue on Conservation of biodiversity as a strategy for improving human health and well-being, in which he examined the evidence linking biodiversity to disease risk and outlined the steps needed to develop biodiversity conservation into a public health control strategy.

See the full article here .

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UCO Lick Shane Telescope
UCO Lick Shane Telescope interior
Shane Telescope at UCO Lick Observatory, UCSC

Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

UC Santa Cruz campus
The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

UCSC is the home base for the Lick Observatory.

Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

Search for extraterrestrial intelligence expands at Lick Observatory
New instrument scans the sky for pulses of infrared light
March 23, 2015
By Hilary Lebow
The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

“Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

“The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

“We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

“This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

“Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

Please help promote STEM in your local schools.


Stem Education Coalition

UCSC is the home base for the Lick Observatory.