Most of us have suffered the intense irritation of a mosquito. Is it more than their incessant buzzing and painful, itchy bites? Although this is a relatively recent concern for people in North America, mosquito-borne diseases cause millions of deaths around the world each year. However, when I was hiking at Elk Island National Park this weekend the potential for disease did not cross my mind as I flailed, added layers of clothing, hosed myself with mosquito repellent, and shortened my walk by about three hours. So what is it that drives the mosquito, and are other animals affected like we are?
As seems to be typical for the world of insects, it is the the females who are the main source of our human issues. They are, in actual fact, doing what any parent would do, working to feed their family. The developing eggs use the protein in the blood as nourishment; the adults, they feed on the much preferred, by us at least, nectar and other plant sugars. (Have you ever wondered what the plant “thinks” about having all these insects eating their sugar?) They track us through exhaled carbon dioxide, body odours, temperature, and movement. So then why is is that I seem to get swarmed just as badly when I’m standing still compared to when I’m moving?
But as I was hiking, I started to wonder: how do other animals deal with mosquitoes?
Well, there are, of course, many animals that eat mosquitoes. I don’t think there is a better site when you are being swarmed by mosquitoes than a swarm of dragonflies darting through the air. But what about the horses, cattle, and birds that are supposed to be the preferred lunch stop for a blood thirsty mosquito?
Generally, there are many examples of relationships between individuals and between species that are feared towards removing parasites, this seems to indicate that some animals at least, are trying to remove these potential sources of disease and irritation, but do mosquitoes actually irritate their other hosts as they do us?
Well, we know that diseases like West Nile virus are transmitted from the birds carrying the disease by those pesky mosquitoes, but I couldn’t find much as to whether the birds mind being bitten in the first place. I did however, find some information about mosquitoes and horses.
To begin with, disease is a big concern. There are three major diseases that can be carried by mosquitoes that have the potential to kill the infected horse, but are the horses irritated by the mosquitoes themselves? According to the Merck Manual of Pet Health, horses can develop an allergy to the bites. As the allergy develops they try to rub and scratch the affected areas, and just like humans this can have some consequences. Excessive rubbing and scratching can result in hair loss, abrasions, and skin thickening.
As I was taking the photo above, I started talking with someone walking her dog, until she had to go because her dog was being swarmed by mosquitoes, particularly on his nose. Admittedly the dog didn’t really look like he cared at the moment, but the person said she tries to keep them off his face when she can.
So, why in the world do we have mosquitoes? They irritate us and other animals, and they spread diseases within species and between species. But remember, aside from a few intense symbiotic relationships, most organisms evolved because they were successful within a particular niche. And despite all the present day control efforts, the mosquitoes seem to return each year with a vengeance.
So what does the future hold for mosquitoes? Well, there is a fair amount of research regarding climate change and mosquito-borne infectious disease, mostly focusing on malaria, and the verdict is still out. The issue, there are so many factors. While some areas are likely to become more prone to mosquito strife, others may become less so. While rates may increase, our control and treatment methods can mask overall changes.
So, can I look at mosquitoes as a marvel of evolution: a successful generalist who has adapted to increasing human presence and our subsequent pest control? They might be, but I don’t have a lot of ethical issues with swatting them as they land on me, or anyone around me; as shown by this one that tried to bite me while I was writing this post.
Gethink, P., Smith, D., Patil, A., Tatem, A., Snow, R., & Hay, S. (2010). Climate change and the global malaria recession. Nature, 465: 342-345. doi: 10.1038/nautre09098
Kahn, C., & Line, S. (Eds.). (2007). Flies and mosquitoes of horses in The Merck/Merial manual for pet health: The complete health resource for your dog, cat, horse or other pets – in everyday language. Westford, Massachusetts: Merck & Co., Inc.
Nadeau, J. & Bushmich, S. (no date). Fact sheet – Mosquito borne diseases: Eastern and Western equine encephalomyelitis and West Nile virus – prevention is just a vaccine away. Department of Animal Science, University of Connecticut. Retrieved from http://animalscience.uconn.edu/extension/publications/mosquito.htm
National Geographic Society. (no date). Mosquito Culicidae. Retrieved from http://animals.nationalgeographic.com/animals/bugs/mosquito/?source=A-to-Z