Francesca Tomasi received her B.A. from the University of Chicago and is now a microbiologist.
If you live on the east coast like I do, you have probably been wearing sweaters and boots all week, walking around with an umbrella shielding you from the sky’s torrents. The dark, chilly days have probably dampened (no pun intended) your hopes of a May filled with sunshine, birds chirping, and morning dew on green grass. You also probably have not seen a single mosquito yet.
Mosquitoes consistently rank among the least liked organisms in the world, along with ticks, leeches, and cockroaches. They buzz in your ears when you’re trying to sleep, they make your skin itchy and bumpy, and worst of all, they carry diseases – malaria, yellow fever, chikungunya, West Nile, various encephalitis-causing viruses, and now Zika.
Experts have been cautioning for months that Zika will eventually make its way to the United States as the days grow warmer and mosquitoes take over the outdoors. Until recently, the good news about Zika transmission in the US was that the virus was only transmitted by Aedes aegypti, a mosquito species limited to southern states and the Gulf Coast. This would limit the geography of the infection. Last week, however, researchers detected Zika in another mosquito, Aedes albopictus, the world’s most invasive mosquito species. More commonly known as the “Asian tiger,” A. albopictus is a little more ubiquitous, as its geographic range extends farther north than A. aegypti’s, offering the potential for Zika to make its way up to New England.
Standard mosquito control – that is, chemical sprays – can eliminate all kinds of mosquitoes in any population. Researchers are also experimenting with genetic mosquito control. Besides that, however, A. aegypti and A. albopictus have some different behavioral patterns from each other that will require different elimination protocols. As we have seen with the unprecedented spread of Zika through Brazil, A. aegypti does well in urban environments, where it can lay eggs in any pool of water, from overturned bottle caps to puddles. Meanwhile, Asian tigers are more “outdoorsy,” laying their eggs in tree stumps and birdbaths, preferring wooded forests to concrete jungles.
Detecting Zika in a new mosquito species does not necessarily mean the disease will spread the same way. It is reasonable to hypothesize that A. albopictus will serve as an effective vector for insect to human transmission, but further research needs to be done to determine just how competent the Asian tiger is at spreading Zika. Some scientists are already speculating that A. albopictus will actually be worse at spreading Zika amongst humans because of its different behavior patterns from A. aegypti. Albopictus, for instance, feeds on any mammal it comes across and is not as well-adapted to human targeting as A. aegypti; once it commits to an individual, A. albopictus sucks exclusively on that individual’s blood. On the other hand, A. aegypti is more wanton, taking morsels from multiple different individuals until it is full. This promiscuity makes A. aegypti a particularly good disease spreader.
So far, the CDC has not detected any Zika transmission by mosquitoes in the United States. When the current weather gives way to a hot and humid summer, however, things may change pretty quickly. Knowing that a more broadly-prevalent mosquito species is harboring Zika is important as public health departments across the country gear up for mosquito season.