The deadly dozen

Now, you know I like a good Doomsday story or conspiracy theory. There are so many ways that humanity could snuff it (not the least through our own stupidity). So it was with some eagerness that I read a recently published report from the Wildlife Conversation Society (WCS), which sounds the alarm on deadly diseases that might be unleashed as a result of climate change. Might have freaked myself out though.

Health experts from the WCS believe there are 12 pathogens that could threaten wildlife and humanity when temperatures rise. We’re so absorbed right now with the financial fracas going on that if we think about climate change, we think of regions heating up, sea levels rising, poor polar bears unable to find ice floes to rest on and so on. But do we ever stop to think about the deadly diseases that we might face? Well, this report sure helped me think about it especially the fact that pathogens, which pose a threat to humanity, have already caused signifcant economic damage. The SARS virus and avian influenza, for example, have already caused an estimated US$100 billion in losses to the global economy.

The report is called The Deadly Dozen: Wildlife Diseases in the Age of Climate Change and it highlights 12 nasty diseases that humanity could soon be battling. Here’s a rundown:

• Avian influenza or H5N1 – we’re already facing this one. So far, the movement of H5N1 has been contained to the poultry trade but changes in climate could bring severe storms and drought, both of which could disrupt the normal movements of wild birds and bring them into closer contact with poultry and domestic bird populations. H5N1 could mutate into a strain that would spread from human to human.
• Babesia – what the? Never heard of it. It’s a tick-borne disease that affects domestic animals and wildlife. Babesia has been pinpointed as an emerging disease in humans particularly in Europe and North America.
• Cholera – a water-borne disease that still affects people in the developing world. The bacterium, Vibrio cholerae, is highly temperature-dependent and rising temperatures are expected to see its spread.
• Ebola – this one scares the bejesus out of me. Ever read The Hot Zone? Ebola has a closely related pathogen, the Marburg fever virus, and both of these pathogens have no known cure. They easily knock off humans, gorillas and chimps. There is evidence to suggest that major outbreaks are linked to unusual variations in rain fall/dry season patterns.
• Internal & external parasites – parasites love warm water and as temperatures rise, these nasties will thrive. Many species of parasites are zoonotic meaning they can spread from wildlife to humans.
• Plague – aka Black Death. Thought this nasty disease was left behind in the 1300s? Think again. Yersinia pestis is one of mankind’s oldest known infectious diseases capable of wiping out huge slabs of humanity. It’s spread by rodents and their fleas and climate change is expected to alter the distribution of rodent populations, which could affect the range of plague.
• Lyme disease – another tick-borne nasty. Tick distributions will be affected by climate change bringing this disease into new regions.
• Red Tides – never heard of this one. With warmer climates, algae will prosper in oceans and create toxins that are deadly to humans and wildlife. These algal blooms are known as “red tides” and can kill off penguins, fish and seabirds.
• Rift Valley Fever – this virus is an emerging zoonotic disease. Humans can catch the virus from butchering infected animals and the disease is fatal. Redistribution of animal populations will most likely take place with global warming, particularly in Africa and the Middle East, leading to a possible increase in this devastating virus.
• Sleeping sickness – I often think I have this, since I can suffer from insomnia but nope. Sleeping sickness, aka trypanosomiasis, is caused by a protozoan and transmitted by the tsetse fly. The disease is endemic in sub-Saharan Africa (covering 36 countries) and around 40,000 deaths occur each year. Once again, climate change could cause a redistribution of the tsetse fly population and affect the reach of this nasty.
• Tuberculosis – bovine tuberculosis has spread since humans started working with cattle. It’s particularly virulent in Africa and can affect humans who drink unpasteurized milk. The human form of this disease can also affect wildlife. With less water, wildlife and livestock will gather and mingle at any water sources they can find and this will increase the transmission of this disease.
• Yellow Fever – I’ve been immunized against this one so I’m hoping it’s a lifelong immunization! Yellow Fever is carried by mosquitoes and as the planet heats up, mozzies will enter new, warmer regions. There’s a strain of Yellow Fever, known as Jungle Fever, which is transmitted from primate to humans and vice-versa courtesy of mozzies.

The report highlights how increasing temperatures and fluctuating precipitation levels will change the distribution of dangerous pathogens. And these pathogens will impact on human health, food supplies and economies. Human and animal health are interconnected so we need to be talking about disease prevention at the same time we’re talking about addressing climate change.