How are human and animal diseases in general affected by the climate becoming “wilder, wetter and warmer?” New research shows that ticks have spread over larger geographical areas in Norway and that climate and environmental changes, access to host animals and demography affect tick distribution in Norway. Furthermore, local climatic conditions can have a decisive influence on the ability of the tick to spread dangerous viruses. The climate can also play a role in the spread of gastrointestinal infections.

The effects of climate changes are the easiest to detect and are probably most pronounced near the geographical distribution limits of the infection or for the vector which carries the infection.

Ticks are champions at spreading diseases, expanding in both poor countries and rich ones, and delivering an extraordinary menagerie of bacteria, protozoans, and viruses. In a 2010 report on the dangers of ticks, the Institute of Medicine, the health arm of the National Academy of Sciences, declared the animals, with what sounds almost like admiration, “the Swiss Army knife of disease vectors.”

IT’S STARTLING to look at the graphs of tick-borne diseases over the past few decades. They’re mostly going in the wrong direction. The research on Lyme disease is fairly recent, sparked in the mid-1970s after a cluster of children around Lyme developed fever and aches. They were diagnosed with juvenile arthritis—a peculiar diagnosis for so many children in one place. Their parents searched for an explanation, and eventually Allan Steere, a doctor at Yale, figured out that they suffered from an infectious disease. The fact that they all came from a rural part of the state suggested that an insect or some other animal had delivered the infection. In 1982, Willy Burgdorfer, an entomologist with the National Institute of Allergy and Infectious Diseases, discovered corkscrew-shaped bacteria in black-legged ticks from Long Island. He exposed the bacteria to serum from people with Lyme disease and discovered that their antibodies swarmed around the microbes. That was a sign that these bacteria—which would later be named Borrelia burgdorferi after him—were the cause of Lyme disease.

Since Burgdorfer’s discovery, Lyme disease has spread relentlessly. New York and other northeastern states started recording new infections in the eighties. In the Midwest, Lyme disease came to light around the same time in Wisconsin and began radiating out from there. Today it can be found as far west as California, as far south as Virginia, and to the north across the border into Canada. Each year, 38,000 people in the United States are diagnosed with the condition. The list of symptoms includes fever, aches, fatigue, and, if left untreated for a length of time, arthritis, heart arrhythmia, and neurological damage. Lyme disease is rarely fatal.

More ticks.

These diseases are caused by viruses, bacteria and parasites, and affect more than one billion people, mainly in the tropics, where the most vulnerable developing world populations are concentrated.

But the map of tropical diseases like malaria, Chagas’ disease, sleeping sickness, leishmaniasis, schistosomiasis and dengue fever, is starting to change.

Tropical diseases transmitted by vectors like mosquitoes, flies, ticks or snails are directly affected by conditions in the ecosystems they inhabit, such as changes in humidity, water levels, temperature or rainfall, experts explain.

“Global warming is ‘tropicalising’ subtropical regions; rising temperatures could bring an explosion of parasite and insect vectors that are expanding into North America, the Southern Cone of South America, Australia and New Zealand,” Costa Nery said.

One sign of this, said the president of the SBMT, is the spread of leishmaniasis in Europe by travelling persons and dogs. He explained that the disease, which is endemic in southern Europe, could continue to spread northward if temperatures keep rising.

At the same time, climate variation in the tropics and its effects on the frequency of flooding and drought “could also modify the dynamic of the transmission of diseases,” with the emergence of vectors that alter the population’s immunity and resistance.

Via IPS covering the 18th International Congress on Tropical Medicine and Malaria, held Sept. 23-27 in Rio de Janeiro.

Fantastic read: “Mosquitoes and NIMBYism” at The New Yorker.

Scary news from Down Under, a new disease seems to be erupting, killing humans and livestock. Cause is increased heat and flooding, making a perfect incubator for the virus.

“It started with Vic Rail’s horses, in September 1994. First one, then another, they died horrible deaths, 13 horses in all over the span of just two weeks, frothing from their noses and mouths, thrashing in agonizing pain. Then Rail died too.

Weeks later Australian officials isolated a newly discovered virus they ultimately named Hendra, after the Brisbane suburb where Rail and his horses died. For 17 years, Hendra virus smoldered in its host population of fruit bats killing nearly 50 horses and claiming three more human lives.

Then in May, something happened.

Flying Fox, a type of bat, in Australia passed deadly virus to humans

It was as if Hendra virus awoke from a slumber and roared fully into life. There have been more outbreaks of Hendra in 2011 — 18 at last count — than in the 16 previous years…

“The interesting change was the big floods in January,” said Raina Plowright, a disease ecologist at the Pennsylvania State University’s Center for Infectious Disease Dynamics. “Floods are expected more frequently with climate change — so, if they are linked, climate change may increase disease.”

Hendra virus is just one of a number of newly emerged zoonotic diseases, so called because they have their origins in animals but somehow make the leap to humans, and in doing so, wreak enormous havoc. While zoonotic diseases may sound exotic, one of the most devastating is also one of the most familiar: AIDS, which made the jump from primates to humans sometime at the beginning of the 20th century, and now kills an estimated 2.7 million people a year. Hendra, far newer but fearsomely lethal, has claimed the lives of four of the seven people infected.”

Climate Central