Featured Research

from universities, journals, and other organizations

Declines in large wildlife lead to increases in disease risk

Date:
April 29, 2014
Source:
University of California - Santa Barbara
Summary:
In the Middle Ages, fleas carried by rats were responsible for spreading the Black Plague. Today in East Africa, they remain important vectors of plague and many other diseases, including Bartonellosis, a potentially dangerous human pathogen. The researchers concluded that the "spike in disease risk results from explosions in the number of rodents that benefit from the removal of the larger animals."

A plains zebra (Equus quagga) in front of the Kenya Long-Term Exclosure experiment.
Credit: Duncan Kimuyu

In the Middle Ages, fleas carried by rats were responsible for spreading the Black Plague. Today in East Africa, they remain important vectors of plague and many other diseases, including Bartonellosis, a potentially dangerous human pathogen.

Research by Hillary Young, assistant professor in UC Santa Barbara's Department of Ecology, Evolution and Marine Biology, directly links large wildlife decline to an increased risk of human disease via changes in rodent populations. The findings appear today in the Proceedings of the National Academy of Sciences Early Online Edition.

With an East African savanna ecosystem as their research site, Young and her colleagues examined the relationship between the loss of large wildlife -- defaunation -- and the risk of human disease. In this case, they analyzed Bartonellosis, a group of bacterial pathogens which can cause endocarditis, spleen and liver damage and memory loss.

"We were able to demonstrate that declines in large wildlife can cause an increase in the risk for diseases that are spread between animals and humans," said Young. "This spike in disease risk results from explosions in the number of rodents that benefit from the removal of the larger animals."

The researchers discovered this effect by using powerful electric fences to experimentally exclude large species like elephants, giraffe and zebra from study plots in Kenya. Inside these plots, rodents doubled in number. More rodents meant more fleas, and genetic screens of these fleas revealed that they carried significantly numbers of disease-causing pathogens.

The study was concentrated in an area where rodent-borne disease is common and sometimes fatal. According to Young, these rodent outbreaks and associated increases in disease risk may be exacerbating health problems in parts of Africa where diminishing wildlife populations are rife.

"This same effect, however, can occur almost anywhere there are large wildlife declines," Young said. "This phenomena that we call rodentation -- the proliferation of rodents triggered by large wildlife loss -- has been observed in sites around the world."

Downturns in wildlife numbers can cause rodent increases in a variety of ways, including by providing more access to food and better shelter. "The result is that we expect that the loss of large animals may lead to a general increase in human risk of rodent borne disease in a wide range of landscapes," Young said.

"In this study, we show the causal relationship between disturbance and disease is alarmingly straightforward," she added. "We knock out the large members of ecosystems, and the small species, which generally interact more closely with humans, dramatically increase in number, ultimately brewing up more disease among their ranks.

The study provides ecosystem managers with yet another reason to protect large and at-risk wildlife species. "Elephants are an irreplaceable part of our global biodiversity portfolio," Young said, "but they also appear to be circuitously protecting us from disease."


Story Source:

The above story is based on materials provided by University of California - Santa Barbara. The original article was written by Julie Cohen. Note: Materials may be edited for content and length.


Journal Reference:

  1. H. S. Young, R. Dirzo, K. M. Helgen, D. J. McCauley, S. A. Billeter, M. Y. Kosoy, L. M. Osikowicz, D. J. Salkeld, T. P. Young, K. Dittmar. Declines in large wildlife increase landscape-level prevalence of rodent-borne disease in Africa. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1404958111

Cite This Page:

University of California - Santa Barbara. "Declines in large wildlife lead to increases in disease risk." ScienceDaily. ScienceDaily, 29 April 2014. <www.sciencedaily.com/releases/2014/04/140429142201.htm>.
University of California - Santa Barbara. (2014, April 29). Declines in large wildlife lead to increases in disease risk. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2014/04/140429142201.htm
University of California - Santa Barbara. "Declines in large wildlife lead to increases in disease risk." ScienceDaily. www.sciencedaily.com/releases/2014/04/140429142201.htm (accessed July 31, 2014).

Share This




More Plants & Animals News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. 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