A “Deadly Dozen” animal-borne diseases are likely to spread into new regions around the world as climate change disturbs weather patterns with significant impact on the health of wild animals and consequently on the health of human populations and global economies.
This is the main message of The Deadly Dozen: Wildlife Diseases in the Age of Climate Change, a new report released this week by health experts from the US-based Wildlife Conservation Society (WCS).
The report gives examples of “zoonoses” or animal-borne diseases that are likely to spread as a result of changes in temperature and rainfall. These include: avian flu, Ebola (and its cousin Marburg), cholera, tuberculosis, yellow fever, rift valley fever, Lyme disease, and a range of parasites.
The authors suggest that the best way to protect ourselves against worst possible scenarios is to track how the diseases shift through wildlife populations by establishing a global surveillance network based on a mix of Western science and the knowledge of indigenous people.
The report was presented at the International Union for Conservation of Nature (IUCN) World Conservation Congress in Barcelona, Spain.
The popular perception of “climate change” is images of melting ice caps and dramatic rises in sea levels swamping coastal cities. But what most people are probably less aware of is how rising temperatures and increases in precipitation will affect global distribution of some of the world’s most dangerous pathogens. As WCS president and CEO Dr Steven E Sanderson explained:
“The health of wild animals is tightly linked to the ecosystems in which they live and influenced by the environment surrounding them, and even minor disturbances can have far-reaching consequences on what diseases they might encounter and transmit as climate changes.”
“Monitoring wildlife health will help us predict where those trouble spots will occur and plan how to prepare,” he added.
As well as threatening the health of humans and wildlife, these diseases have already started causing significant economic damage. For example, bird flu and several other livestock diseases that have re-emerged since the mid 90s have caused global losses amounting to an estimated 100 billion dollars, said the report.
One example of a global monitoring scheme is the GAINS program (Global Avian Influenza Network for Surveillance) that was created in 2006 with support from the United States Agency for International Development (USAID). Through GAINS, the WCS leads an international consortium to monitor the progress of avian flu through wild bird populations. This program is now networked with dozens of partners in both public and private sectors to help keep track of avian flu in wild bird movements throughout the world.
WCS is keen to apply the lessons learned from the GAINS program to keep track of other dangerous pathogens.
Vice President and Director of WCS’s Global Health Program, Dr William Karesh, said:
“The monitoring of wildlife health provides us with a sensitive and quantitative means of detecting changes in the environment.”
“Wildlife health monitoring provides a new lens to see what is changing around us and will help governments, agencies, and communities detect and mitigate threats before they become disasters,” he added.
The deadly dozen have been tracked to a certain extent, but there is not enough data to help us work out how they might respond to climate change. So any predictions are likely to be highly speculative.
Ebola hemorrhagic fever virus and its relative, the Marburg fever virus, are deadly to humans, gorillas, and chimps. There is no known cure and evidence suggests that outbreaks are linked to unusual variations in patterns of rain and dry seasons.
Parasites are land and water based and their populations respond to changes in temperature and rainfall such that as these rise they will find more hosts, including humans and animals. Many species are zoonotic, they spread from animals to humans, and only through monitoring species and loads in wildlife and livestock will we be able to spot how they spread among domestic and wild animals and subsequently into human populations.
Lyme disease is spread by a bacteria that gets into humans via the bites of tiny insects called ticks that live on animals like deer and mice. Tick populations are not only sensitive to climate change, but also to human-induced changes in the environment which affect the distribution of tick-carrying animals such as white-tailed deer and white-footed mice.
“We’ve seen Lyme disease work its way up from the US into Canada, and West Nile fever as well,” said Karesh.
“Basically what you have now are fewer frozen nights in this region, and that allows the ticks and mosquitoes that carry these diseases to survive further north,” he explained.
The bacteria that causes cholera incubates in shellfish and is sensitive to rises in water temperature. Changes to distribution of this disease are also caused by water shortage because it causes animals to concentrate at drinking pools making it more likely that cross infections will occur.
Karesh said increasing indigenous knowledge and skills was also important. For example, in the northern Republic of Congo, the hunters used to bring animals they found dead in the forest back into the villages, which could encourage the spread of Ebola, but now they just report them and leave them in situ.
“So they are doing disease surveillance, and there hasn’t been an outbreak of Ebola in this region for several years,” said Karesh in a BBC News report.
“The Deadly Dozen: Wildlife Diseases in the Age of Climate Change.”
Wildlife Conservation Society, 7 October 2008.
Click here for Wildlife Conservation Society.
Source: WCS, BBC.
Written by: Catharine Paddock, PhD.