Wildlife gives early warning of 'deadly dozen' diseases spread by climate change

Lewis Smith, Environment Reporter in Barcelona

Scientists have nicknamed them the “deadly dozen”: 12 diseases, lethal to humans and wildlife, that are increasing their geographical range.

Ebola, cholera, plague and sleeping sickness were among those identified yesterday by veterinary scientists from the Wildlife Conservation Society (WCS) as spreading across the planet because of climate change. The scientists said that wildlife could give an early warning of the approach of diseases and save millions of people.  Researchers called for wildlife monitoring systems to be set up around the globe to watch for signs of disease among animals before it spreads and kills people. Monitoring networks have already been introduced in parts of the world and have proved successful in saving lives.

William Karesh, of the WCS, told the International Union for the Conservation of Nature (IUCN) conference in Barcelona that there was increasing concern about the impact that climate change would have on the spread of disease. Changes in rainfall patterns and temperatures were known to have an effect, though the reason was not always clear, he said at the launch of the report, The Deadly Dozen. By watching for the arrival of diseases in the animal population it should be possible to take measures to protect both people and local economies. “What we are calling for today is a comprehensive approach to disease globally. Our long-term vision is a comprehensive monitoring network to watch the health of wildlife across the globe,” Dr Karesh said.

Among the trials that have already proved the success of the idea is a network of hunters and other locals who use the forests of the Republic of Congo. By reporting on sightings of gorillas and chimpanzees that have died from outbreaks of Ebola they have prevented any human outbreaks of the deadly disease in northern parts of the country for three years.  Until the hunters were recruited for the project, they brought back dead animals to their villages, hastening the spread of Ebola among people. Similar projects have been established in South America, where data is just starting to be gathered on the impact of climate change on diseases such as yellow fever. Vaccination programmes are now carried out in areas where outbreaks are observed in primates.

Animals are regarded by scientists as a valuable indicator of climate change because they can rarely adapt rapidly enough for change to pass unnoticed. Changes in the diseases they suffer or the pattern of disease outbreak can often be the result of climate change. The means by which climate change influences the spread of diseases includes warmer weather, which helps the pathogens or their carriers to live longer; changes in livestock management, such as water availability, bringing them into more frequent contact with wild animals; and altered rainfall patterns that make it easier for pathogens to survive and spread.

The dozen diseases include cholera, which survives better in warmer conditions, lyme disease and babesiosis, which are carried by ticks, and avian flu, which can spread when climate change disrupts migration patterns of wild birds.

Malaria, which is expected to spread because of climate change, was excluded from the deadly dozen list because the version that affects people cannot be caught by animals, despite being carried by mosquitoes. Kristina Smith, of the WCS, joined the call for a wider network of monitors. She said: “We are starting to see trends where disease is affected by the climate. We have a flashing warning sign. Wildlife can be our early warning system.”

The coming contagion

Avian influenza An increase in stormy weather can disrupt flights and force infected wild birds into new areas - and into greater contact with domestic birds

Babesiosis A tick-borne disease that is increasingly a problem for humans. Climate change is thought to have aided a tick boom among lions and buffalo in East Africa

Cholera Warmer water suits the pathogen perfectly. Global warming will cause widespread outbreaks

Ebola Has been linked to variations in rainfall patterns. It kills gorillas, chimpanzees and people

Intestinal and external parasites Both rising temperatures and increased rainfall help the parasites to survive. They are an increasing problem for humans and animals

Lyme disease Changes in population patterns of white-tailed deer and white-footed mice have promoted a spread northwards of the tick-borne disease in the US and into Canada

Plague It kills people and animals and is spread by rodents and fleas, which are altering their distribution amid warmer conditions

Red tides These algal blooms can kill people through the spread of brevetoxins, domoic acid and saxitoxins. Their biggest impact is on the loss of natural resources

Rift Valley fever The virus has significant health, food security and economic impacts, especially in Africa and the Middle East

Sleeping sickness It is transmitted by the tsetse fly, distributions of which are changing

Tuberculosis People catch TB through drinking milk from infected cattle. As rivers dry up because of warming, livestock will be forced to drink in the same places as infected wild animals

Yellow fever Mosquitoes, which carry yellow fever, are expected to spread to new areas as rainfall patterns and temperatures change