Articles, Blog

Mosquito Meets MODIS: South Dakota Fights West Nile Virus

January 3, 2020

Dakota, a great night at the county fair. The mosquito that transmits West Nile virus
comes out to feed on warm July and August nights like this one, but no one is swatting
mosquitoes. In South Dakota, public health officials, scientists, and communities joined
forces to prevent West Nile disease, and now they’re getting some help from space. West Nile virus is actually a bird virus that
gets accidentally transmitted into humans and horses and other mammals. In this area,
Culex tarsalis is the primary vector for West Nile virus. The conditions in parts of South Dakota seem
to be particularly good for Culex tarsalis and for the mosquito to come into contact
with people. South Dakota has the highest incidence of
West Nile of any state in the country. It’s a bird disease, but it can cause acute illness
in people, it can put people in the hospital. It’s killed 35 people in South Dakota already.
We need good predictors of when the conditions might be right for an outbreak of West Nile
disease. Public health officials estimate the risk
of humans becoming infected by trapping mosquitos and testing them for West Nile virus. But
it’s impossible to get enough data to cover such a large, sparsely populated state. The
South Dakota Mosquito Information System is using environmental data from space to close
those gaps. We came up with some new ideas for how to
develop an improved system for forecasting West Nile virus leveraging information in
satellite imagery. The major goal of our project is to develop a dynamic risk-mapping approach for West Nile virus, and to produce forecasts and risk assessments that are useful to public
health officials and can actually be applied to do a better job of disease prevention and
mosquito controls. The South Dakota Department of Health provides
important data on the location of infected mosquitos and on human cases to Dr. Wimberly
and Dr. Hildreth. The mosquito data allows us to get a very
accurate estimate of disease risk, and the environmental data allows us to extend that
over space and through time. The approach that we’re using for this project
is really to take the mosquito data, the virus data that we have from the various years,
and look at correlations between the years that have a lot of transmission of West Nile
versus low transmission, correlating that to environmental data that’s coming from
the satellite imaging. We’ve used a variety of MODIS products…and
they’ve been particularly valuable because they provide consistent long-term records
of these environmental observations that we can use to study disease over multiple years.
The Landsat satellites have also proved very useful, particularly for trying to do more
detailed, finer-scale risk mapping. We’re looking for patterns, predictive patterns,
much like the weather forecasters are doing. Temperature has really proved to be the most
important variable for West Nile virus in our state. People tend to associate mosquitos
with rainfall and water for breeding sites, but you also have to remember that these mosquitos
are tiny cold-blooded organisms. And as a result all of the processes associated with
mosquitos are all strongly influenced by temperature. Even the rate of development of the virus
inside the mosquito is strongly temperature-sensitive, so that generally when it’s warmer, a mosquito
can transmit the virus more rapidly than when it’s cooler. The combination of the disease data, the environmental data, the climatological data is exactly what we need. West Nile is a very complex disease. What we’re working on right now is putting
out weekly risk assessment reports and we combine that with a risk map based on temperature. We’re trying then to help people take precautions
during those high transmission years, during those peak transmission time periods. The information that we’re getting from
the project are maps of risk factors associated with things that we at the health department
really can’t track or figure out. Things that have to do with climate, lay of the land,
precipitation, what’s growing. And they’re able to pinpoint potential hotspots across
the state of South Dakota. I think this will be absolutely an essential tool in controlling
West Nile here in South Dakota. Our top priority of our program and our mission
of our program is the protection of the public health of the citizens of Aberdeen. We run
a mosquito control program, and it’s an integrated pest management program. I told
our community leaders a number of weeks ago when those threat assessments came in that
we were shifting our efforts now away from nuisance mosquitos onto the Culex and the
virus mosquitos. So we’re really excited about that project. We think it’s going
to be a tremendous help to us. This West Nile NASA project is the first real
project where I’ve been involved where we’ve seen practical use, using our state health
department disease data, correlating with the NASA environmental and climatological
data, to really make some good predictors of a disease that’s really hurting and killing
people in this state. [MUSIC]


  • Reply Riyas Kh January 5, 2016 at 7:09 pm

    Thanks for the information

  • Reply sansaction l January 5, 2016 at 9:06 pm

    or if people would simply let scientists Genetically Modify mosquitos and other organisms so they can easily help people, but nooooo people have some weird problems with GMO -.-

  • Reply Ana Braga-Henebry January 6, 2016 at 4:21 pm

    The video is very interesting and informative. I enjoyed the explanation, the images, and the production quality. Thanks!

  • Reply Michelle Sandifer October 2, 2016 at 4:00 am

    I had west nile one.

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