Featured Research

from universities, journals, and other organizations

Tick population plummets in absence of lizard hosts

Date:
February 15, 2011
Source:
University of California - Berkeley
Summary:
The Western fence lizard's reputation for helping to reduce the threat of Lyme disease is in jeopardy. A new study found that areas where the lizard had been removed saw a subsequent drop in the population of the ticks that transmit Lyme disease. The decline in tick numbers suggests a decreased risk of human exposure to Lyme disease when the lizard is gone.

The Western fence lizard's reputation for helping to reduce the threat of Lyme disease is in jeopardy. A new study led by researchers at the University of California, Berkeley, found that areas where the lizard had been removed saw a subsequent drop in the population of the ticks that transmit Lyme disease.

"Our expectation going into this study was that removing the lizards would increase the risk of Lyme disease, so we were surprised by these findings," said study lead author Andrea Swei, who conducted the study while she was a Ph.D. student in integrative biology at UC Berkeley. "Our experiment found that the net result of lizard removal was a decrease in the density of infected ticks, and therefore decreased Lyme disease risk to humans."

The study, to be published online on Feb. 15, in the journal Proceedings of The Royal Society B, illustrates the complex role the Western fence lizard (Sceloporus occidentalis) plays in the abundance of disease-spreading ticks.

Lyme disease -- characterized by fever, headache, fatigue and a bullseye rash -- is spread through the bite of ticks infected with spirochete bacteria called Borrelia burgdorferi. In the Western region of the United States, the Western black legged tick (Ixodes pacificus) is the primary vector for Lyme disease bacteria.

In 1998, a pioneering study led by UC Berkeley entomologist Robert Lane found that a protein in the Western fence lizard's blood killed Borrelia bacteria, and as a result, Lyme-infected ticks that feed on the lizard's blood are cleansed of the disease-causing pathogen. Moreover, research has found that up to 90 percent of the juvenile ticks in this species feed on the Western fence lizard, which is prevalent throughout California and neighboring states.

The lizard is thus often credited for the relatively low incidence of Lyme disease in the Western United States. The new UC Berkeley-led study put that assumption to the test experimentally.

"When you have an animal like the Western fence lizard that supports such a huge population of ticks, you can't assume that all those juvenile ticks will go to another host if the lizard population drops," said Lane, UC Berkeley Professor of the Graduate School and co-author of this study.

For their field test, the researchers selected 14 plots, each measuring 10,000 square meters and spread out over two sites in Marin County, Calif. Half the plots were located at China Camp State Park, and the other half were at the Marin Municipal Water District Sky Oaks headquarters. The researchers had already been extensively surveying tick density in those plots over the course of two years, so they had detailed data on tick and vertebrate populations before this experimental field trial.

From March to April 2008, before tick season went into full swing, the researchers captured and removed 447 lizards from six plots -- three at each site -- and left the remaining plots unaltered as controls. The lizards that had been captured were marked before being relocated so the researchers could determine whether any wandered back into their old haunts.

After the lizards were removed, the researchers spent the following month trapping other mammals known to harbor ticks -- particularly woodrats (Neotoma fuscipes) and deer mice (Peromyscus maniculatus) -- to determine whether they bore an uptick in ticks as a result of the lizards' absence. The researchers also checked for differences between control and experimental plots in the abundance of host-seeking ticks by systematically dragging a large white flannel cloth over the ground.

The researchers found that in plots where the lizards had been removed, ticks turned to the female woodrat as their next favorite host. On average, each female woodrat got an extra five ticks for company when the lizards disappeared.

However, the researchers found that 95 percent of the ticks that no longer had lizard blood to feast on failed to latch on to another host.

"One of the goals of our study is to tease apart the role these lizards play in Lyme disease ecology," said Swei, who is now a post-doctoral associate at the Cary Institute of Ecosystem Studies in New York. "It was assumed that these lizards played an important role in reducing Lyme disease risk. Our study shows that it's more complicated than that."

Lane pointed out that this new study only focused on juvenile ticks, so the impact of lizard removal on adult ticks is unclear. "Previous research indicates that adult ticks have lower Lyme disease infection rates because they get their infections cleared after they feed on the lizards during the nymphal stage," he said. "It would be important to find out how removing lizards impacts tick density for both juvenile and adults over the long term."

"In attempting to decrease infectious disease risk, we need to remember the law of unexpected consequences," said Sam Scheiner, program director in the National Science Foundation Division of Environmental Biology, which funded the research through the joint NSF-NIH (National Institutes of Health) Ecology of Infectious Diseases Program. "This study demonstrates the complexity of infectious disease systems."

Other authors on this study are Cheryl Briggs, a professor at UC Santa Barbara's Department of Ecology, Evolution and Marine Biology; and Richard Ostfeld, a senior scientist at the Cary Institute of Ecosystem Studies.


Story Source:

The above story is based on materials provided by University of California - Berkeley. The original article was written by Sarah Yang, Media Relations. Note: Materials may be edited for content and length.


Journal Reference:

  1. Andrea Swei, Richard S. Ostfeld, Robert S. Lane, Cheryl J. Briggs. Impact of the experimental removal of lizards on Lyme disease risk. Proceedings of The Royal Society B, 2011; DOI: 10.1098/rspb.2010.2402

Cite This Page:

University of California - Berkeley. "Tick population plummets in absence of lizard hosts." ScienceDaily. ScienceDaily, 15 February 2011. <www.sciencedaily.com/releases/2011/02/110215191631.htm>.
University of California - Berkeley. (2011, February 15). Tick population plummets in absence of lizard hosts. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2011/02/110215191631.htm
University of California - Berkeley. "Tick population plummets in absence of lizard hosts." ScienceDaily. www.sciencedaily.com/releases/2011/02/110215191631.htm (accessed July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com
Dogs Appear To Become Jealous Of Owners' Attention

Dogs Appear To Become Jealous Of Owners' Attention

Newsy (July 23, 2014) A U.C. San Diego researcher says jealousy isn't just a human trait, and dogs aren't the best at sharing the attention of humans with other dogs. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins