Climate Change, Environmental Hazards

Climate Change Bringing Tropical Diseases to Higher Latitudes

Tropical diseases are spreading farther north as the climate continues to warm.
The Anopheles mosquito is responsible for the spread of malaria. Its range may be increasing due to climate change. Photo via Pixabay

It’s been known for a long time—like, since Roman times—that climate change brings disease. Roman aristocrats would move to summer homes in the mountains in order to avoid malaria-transmitting mosquitoes, for example.

But even the appearance of malaria mosquitoes was simply a summer phenomenon that was a regular part of south European climate. Nowadays, we have more to be worried about, thanks to global climate changes.

Tropical diseases like viral illness Chikungunya, West Nile Virus, and Zika; bacterial infection Vibrio vulnificus; and parasitic infection malaria are finding their way farther and farther north as greenhouse gases boost temperatures around the world.

The Asian tiger mosquito and yellow fever mosquitoes infect humans with Chikungunya. The virus had been limited to tropical regions of Africa, Asia, and South America, but as temperatures have warmed, the geographical distribution of these mosquitoes has grown. If climate change continues unchecked, a team at the University of Bayeruth warns, the virus could even spread to southern Europe and the United States.

“People have already been infected with Chikungunya in Italy, France, and Florida,” said Dr. Stephanie Thomas, a biogeography researcher at the University of Bayeruth. “However, such cases are still too rare to play any significant role in our model. The climactic potential for new diseases in southern Europe and the U.S. is probably being underestimated.”

Vibrio illnesses are caused by bacteria that occur naturally in warm ocean waters. Although Vibrio infections have been seen sporadically in warm seas from Texas to Maryland, Vibrio bacteria are spreading north. Vibrio illnesses have even appeared as far north as the Arctic Circle.

We are seeing lots of new hospitable areas opening up for these bacteria,” said Craig Baker-Austin, a Vibrio expert at the UK’s Centre for Environment, Fisheries, and Aquaculture Sciences laboratory in southern England. “Climate change is essentially driving this process, especially warming.”

In Europe, ticks that carry Lyme disease, that once only appeared in southern Europe, are now appearing as far north as Sweden. A region near Russia’s Ural Mountains has seen a 23-fold increase in tick-borne encephalitis over the past 20 years. The sand flies that host the parasite-borne illness leishmaniasis are showing up in north Texas.

“So often so many of the things we talk about with climate change are ‘this is going to be a problem in 2030 or 2050 or 2100, and it sounds so far away,” said Stanley Maloy, a microbiologist at San Diego State University. “But we’re talking about things where our one-degree centigrade change in temperature is already enough to affect infections. We have clear evidence in many cases things are happening already, and they’re tightly correlated to changes in ambient temperature, extreme weather, or water temperature.”

Regardless of whether people believe climate change is real, it’s inevitable that even the greatest skeptics will soon find themselves being affected by the spread of tropical diseases to higher latitudes.

Conservation, Environmental Hazards, Nature, Science, Wildlife & Animal Rights

Bacteria Blocks Zika Transmission by Mosquitos

QK_bacteria_blocks-zikaMosquitos are generally considered a nuisance by everyone, but while they’re simply annoying in the Midwest, in Latin America or Africa they can be deadly. Mosquitos are capable of spreading a wide variety of diseases, such as yellow fever, chikungunya, and, most recently, the Zika virus.

The Zika virus, while not particularly dangerous to adults, can cause a variety of birth defects in children if mothers contract the disease while pregnant. Mosquitos are also notoriously hard to control, which means that preventing the disease from spreading has proven almost impossible.

There may be good news on the horizon, though. A team of researchers has discovered that a common bacteria, Wolbachia, which can be found in many insects but not usually mosquitos, can prevent mosquitos from spreading Zika and other diseases.

Mosquitos carrying the bacteria are less prone to being infected with Zika themselves, and even those that get infected aren’t capable of passing the disease on in their saliva. Best of all, females pass the bacteria on to their young, meaning that it wouldn’t take all that many mosquitos with the bacteria to spread it around throughout the population.

This research has been years in the making, as the team had been studying the effects of Wolbachia on other mosquito transmitted diseases in the first place. The team has performed laboratory tests and some field experiments, and were recently approved to do larger-scale tests in Australia. The results are looking quite positive, but it will still be some time before any kind of bacterial infection program can be put into place.

While it might seem like getting the bacteria out there sooner rather than later would be the obvious choice, there are still a lot of testing that needs to be done. We need to find out, for example, if the bacteria can infect humans as well, and what kind of effects that might have on us. When it comes to impacting the ecological balance, safe is always better than sorry.