When I stayed with my late mother in South
Texas in 2016, there was a
Zika Virus* scare, and so even sweeping the back porch was a fraught exercise in mosquito dodgeball. I remember scurrying about so fast that I likely made more of a mess than I helped.
Spending summers in South Texas at my grandmother's, I was always mosquito-bite ridden. It was annoying, I itched, but I was young. Remember youth? We were never going to get really sick, much less die. But these days I take, and you should take, the threats posed by mosquitoes and ticks very seriously.
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SciLine, of the American Association for the Advancement of Science (AAAS) recently hosted a panel of scientists to discuss said threats ("Ticks, Mosquitoes and Rising Disease Risk"). Some of the takeaways were that
climate change can, but does not necessarily portend, the deletirious effects of mosquito and tick season on a population. Interestingly, changes in land use also play huge factors.
Speaking on the call were Dr.
Erin Mordecai, professor of biology at Stanford University and a senior fellow in the Woods Institute for the Environment; Dr.
Jean Tsao, professor at Michigan State University in the Department of Fisheries and Wildlife and Large Animal Clinical Sciences, and "a disease ecologist studying mainly ticks and tick-borne disease"; and Dr.
Lyric Bartholomay, professor at the University of Wisconsin-Madison in the School of Veterinary Medicine, and an entomologist "who studies those mosquitoes and ticks that impact public health, and how to control them."
The scientists discussed the impact of diseases these insects carry and cause such as the life-threatening
Dengue, which is indicated by symptoms such as vomiting, blood in vomit or stool and weakness;
West Nile Virus, which we have heard about in our state for many years, and causes vomiting, body aches and rash and can be life threatening approximately 1/150 times; and the least known
Alpha-gal syndrome, which Cleveland Clinic defines as "a serious and unusual food allergy to red (mammalian) meat. It occurs in people who have been bitten by certain types of ticks, usually if they’ve been bitten more than once. Ticks are mite-like parasites that feed on blood."
Dr. Tsao said the impacts of climate change vary, and referenced a reporter who had been observing more ticks in Albany, New York.
"I think, in the past 10 years and 20 years, [that area] has seen more blacklegged ticks [also known as deer ticks]. And they’ve been increasing from the east and probably from the south, depending on where you are. In the mountains, in the Adirondacks there, perhaps as
climate change may have helped influence where the ticks can live higher up in the mountains and such. But besides having warmer temperatures, ticks really dry out easily, so it has to be more moist up there, as well, right, can’t be really cold and dry up in the higher mountains. Climate change can certainly, I think, influence, or augment, the effect of land-use change in those areas, but it might not be the most important. That’s what I would say, in some of those areas. But as you get closer to Canada, then it might become more important, certainly."
Journalists got to submit questions, so I wanted to know if mosquito-repellant clothing was truly effective. I had written a blog a few years ago, based on
research out of North Carolina State University, that indicated it is. The answers from the scientists follow:
Does mosquito-repellent clothing work, and is it a good idea?
DR. BARTHOLOMAY: Sure. So our field teams, both in my lab, and I think in Dr. Tsao’s lab, too, are spending their summers wearing those clothes. So we can either purchase the clothes, already with the insecticide embedded in them, or we can spray them after the fact. And so they’re quite effective at keeping the ticks off of us and also repelling mosquitoes. We know that those are really well used by our military as well, and are an important part of the arsenal of protecting people from the types of diseases they might get when they’re deployed.
DR. TSAO: And I’ll jump in and say, I put up this tick suit behind me (shows image). In some ticky areas, we have that, and they are then sprayed with permethrin, right, but I give some to my students, all of them to use. But they are hot. You can’t see all the way down to the legs. So I can imagine, not just they, but other people may not want to wear long sleeve, long pants. And so then therefore, we say, Yeah, you should then use an EPA- registered repellent for your exposed skin, and such. All these measures are to help reduce the risk of getting a mosquito or a tick bite.
DR. MORDECAI: I was just in Costa Rica on a mosquito sampling trip, and, of course, we were very concerned with getting bitten by mosquitoes that might give us Dengue. And we found that if you go to a sporting goods store, there’s a lot of really lightweight clothing that are permethrin-impregnated, so you can buy it already with that, or you can douse your clothes in it, which is really nice. And that, combined with DEET on any of our exposed skin, did a really good job protecting us. The worst hazard we got was when I accidentally stood in an anthill and the ants got all over me and bit me. Apparently, they were not sensitive to the permethrin. Or at least it didn’t keep them from walking on me. Yeah, I think those things are very effective.
Another journalist, from KOPN Public Radio in Columbia, Missouri, asked about the biological or biochemical mechanism behind Alpha-gal.
DR. TSAO: I’m not an expert on that, but what I can say is from what I understand, it is that the saliva of several tick species, but it seems most predominantly with the lone star tick, that there’s a molecule in there that mimics this Alpha, and long word, but a sugar side-chain on non-primate mammalian meat. So not humans, not other monkeys and such, but, let’s say, pigs, cows, deer. They have this sugar side-chain, and something in the saliva of lone star ticks, looks like it. But people don’t know why it is that, for example, not everyone develops this red meat allergy. So I would assume that there are probably some host factors, like not everyone develops a hay fever allergy or a bee sting allergy, but there may be something on the host side, and maybe there’s something on the tick side, too, that we just don’t know. But around the world, there are some other tick species associated with this allergy. In Europe, it is the cousin tick to the Lyme disease tick that’s [the cause]. And some people think that [the] blacklegged [tick] can also be associated with this allergy.
Find CDC current-year West Nile Virus data here, Alpha-gal syndrome data here (the current disease risk is not known, but CDC estimates 450,000 cases), and Dengue data here. Please check CDC data periodically for updates.
* An earlier version of this blog said it was a West Nile Virus scare; no, it was Zika, which WHO declared a global emergency Feb. 1, 2016. The CDC reports that there is no ongoing Zika virus transmission by mosquitoes in the continental U.S.
Artwork:
A giant mosquito trying to attack a French soldier who is protected by a mosquito net. Colour lithograph after H. Stephany, 1917
Watch the full SciLine briefing here.
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