Navigation Links
Biodiversity does not reduce transmission of disease from animals to humans

More than three quarters of new, emerging or re-emerging human diseases are caused by pathogens from animals, according to the World Health Organization.

But a widely accepted theory of risk reduction for these pathogens one of the most important ideas in disease ecology is likely wrong, according to a new study co-authored by Stanford Woods Institute for the Environment Senior Fellow James Holland Jones and former Woods-affiliated ecologist Dan Salkeld.

The dilution effect theorizes that disease risk for humans decreases as the variety of species in an area increases. For example, it postulates that a tick has a higher chance of infecting a human with Lyme disease if the tick has previously had few animal host options beyond white-footed mice, which are carriers of Lyme disease-causing bacteria.

If many other animal hosts had been available to the tick, the tick's likelihood of being infected and spreading that infection to a human host would go down, according to the theory.

If true, the dilution effect would mean that conservation and public health agendas could be united in a common purpose: to protect biodiversity and guard against disease risk. "However, its importance to the field or the beauty of the idea do not guarantee that it is actually scientifically correct," said Jones, an associate professor of Anthropology.

In the first study to formally assess the dilution effect, Jones, Salkeld and California Department of Public Health researcher Kerry Padgett tested the hypothesis through a meta-analysis of studies that evaluate links between host biodiversity and disease risk for disease agents that infect humans.

The analysis, published in the journal Ecology Letters, allowed the researchers to pool estimates from studies and test for any bias against publishing studies with "negative results" that contradict the dilution effect.

The analysis found "very weak support, at best" for the dilution effect. Instead, the researchers found that the links between biodiversity and disease prevalence are variable and dependent on the disease system, local ecology and probably human social context.

The role of individual host species and their interactions with other hosts, vectors and pathogens are more influential in determining local disease risk, the analysis found.

"Lyme disease biology in the Northeast is obviously going to differ in its ecology from Lyme disease in California," Salkeld said. "In the Northeast, they have longer winters and abundant tick hosts. In California, we have milder weather and lots of Western fence lizards (a favored tick host) that harbor ticks but do not transmit the Lyme disease bacterium."

So, these lizards should be considered unique in any study of disease risk within their habitat. Or, as Salked put it, "All animals are equal, but some animals are more equal than others."

Broadly advocating for the preservation of biodiversity and natural ecosystems to reduce disease risk is "an oversimplification of disease ecology and epidemiology," the study's authors write, adding that more effective control of "zoonotic diseases" (those transmitted from animals to humans) may require more detailed understanding of how pathogens are transmitted.

Specifically, Jones, Salkeld and Padgett recommend that researchers focus more on how disease risk relates to species characteristics and ecological mechanisms. They also urge scientists to report data on both prevalence and density of infection in host animals, and to better establish specific causal links between measures of disease risk (such as infection rates in host animals) and rates of infection in local human populations.

For their meta-analysis, the researchers were able to find only 13 published studies and three unpublished data sets examining relationships between biodiversity and animal-to-human disease risk. This kind of investigation is "still in its infancy," the authors note. "Given the limited data available, conclusions regarding the biodiversity-disease relationship should be regarded with caution."

Still, Jones said, "I am very confident in saying that real progress in this field will come from understanding ecological mechanisms. We need to turn to elucidating these rather than wasting time arguing that simple species richness will always save the day for zoonotic disease risk."


Contact: James Holland Jones
Stanford University

Related biology news :

1. Sri Lankan snake study reveals new species, rich biodiversity in island country
2. BESAFE Conference in Manchester: Working towards a brighter future for biodiversity
3. Data paper describes Antarctic biodiversity data gathered by 90 expeditions since 1956
4. Biodiversity protects against disease, scientists find
5. CU-Boulder amphibian study shows how biodiversity can protect against disease
6. Video study shows which fish clean up coral reefs, showing importance of biodiversity
7. Ancient insects shed light on biodiversity
8. EU BON: Working towards integrated and comprehensive global biodiversity data
9. International biodiversity data symposium to mark the kickoff of the EU BON project
10. Indonesian fishing communities find balance between biodiversity and development
11. Preserving biodiversity can be compatible with intensive agriculture
Post Your Comments:
(Date:10/29/2015)... Mich. , Oct. 29, 2015  Rubicon ... Genomics for U.S. distribution of its DNA library ... kit and Rubicon,s new ThruPLEX Plasma-seq kit. ThruPLEX ... enable the preparation of NGS libraries for liquid ... for diagnostic and prognostic applications in cancer and ...
(Date:10/29/2015)... 2015 NXTD ) ("NXT-ID" ... on the growing mobile commerce market and creator ... a leading marketplace to discover and buy innovative ... wallet on StackSocial for this holiday season.   ... "Company"), a biometric authentication company focused on the ...
(Date:10/27/2015)... NEW YORK , Oct. 27, 2015 ... the major issues of concern for various industry verticals ... This is due to the growing demand for secure ... practices in various ,sectors, such as hacking of bank ... concerns for electronic equipment such as PC,s, laptops, and ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... Therapeutics, Inc. (NASDAQ: HALO ) will be presenting at the ... on Wednesday, December 2 at 9:30 a.m. ET/6:30 a.m. PT . ... a corporate overview. th Annual Oppenheimer Healthcare Conference ... a.m. PT . Jim Mazzola , vice president of ... --> th Annual Oppenheimer Healthcare Conference in ...
(Date:11/24/2015)... 2015  Clintrax Global, Inc., a worldwide provider of clinical research ... announced that the company has set a new quarterly earnings record ... quarter growth posted for Q3 of 2014 to Q3 of 2015. ... Mexico , with the establishment of an Asia-Pacific ... United Kingdom and Mexico ...
(Date:11/24/2015)... New York , November 24, 2015 ... to a recent market research report released by Transparency ... projected to expand at a CAGR of 17.5% during ... "Non-invasive Prenatal Testing Market - Global Industry Analysis, Size, ... estimates the global non-invasive prenatal testing market to reach ...
(Date:11/24/2015)... ... November 24, 2015 , ... InSphero AG, the leading ... culture models, has promoted Melanie Aregger to serve as Chief Operating Officer. ... on the management team and was promoted to Head of InSphero Diagnostics ...
Breaking Biology Technology: