Graduate student helps survey mosquito population after Hurricane Harvey

Edmund Norris, a graduate student in entomology and toxicology, recently returned from a relief effort to the Houston area to assess mosquito populations after Hurricane Harvey. He was asked to help as a trainee with the Center for Disease Control’s Upper Midwest Regional Center of Excellence, where he is seeking a certification in public health entomology. Norris answered some questions after returning to Iowa.

Edmund Norris

Who sought your help in Texas?

We were invited by the CDC Upper Midwest Regional Center of Excellence, which was contacted by Clarke, a mosquito control company. They asked the CDC Upper Midwest Regional Center of Excellence for possible trainees or volunteers, and I was extremely excited to help the people of Houston and learn more about field work controlling mosquito populations after a crisis. They were wonderful hosts in this training experience.

When did you head down to Texas?

I left for Texas on Sept. 18 and we were expected to be there until the 25th. I was asked to stay longer, but our relief effort has been wrapping up quicker than expected because Clarke was planning to move its operations to Florida, for the relief effort after Hurricane Irma. 

Could you explain your trainee position in the CDC Upper Midwest Regional Center of Excellence?

Obtaining my public health entomology certificate will give me valuable experience and knowledge that will be important in my future career as a toxicologist who aims to work primarily with arthropod vectors of human and veterinary disease.

Mosquitoes collected from a single trap.

What did you do in Texas?

We placed traps in various regions of southern Texas and Houston and its neighboring counties to assess mosquito populations, followed by aerial spraying of sanctioned insecticides that target these mosquitoes. The traps helped us assess the initial numbers of mosquitoes in various regions that experienced flooding after Hurricane Harvey and also check for mosquito species most likely to vector disease. After a large rainfall, it is very easy for large numbers of mosquitoes to reproduce, so our traps allowed us to identify the areas of highest concern. We would then relay this data to field biologists, spray technicians, pilots who would treat specific large areas with aerial insecticide sprays. We are evaluating the efficacy of the spray effort with special equipment and placed post-spray traps to monitor the decrease in mosquito abundance.

How were the conditions there?

There is a lot of flood damage throughout large portions of Houston and the neighboring communities. A majority of houses have large piles of property near the street or driveway that was being discarded due to the recent flood damage. It was really sad to see so many people lose almost all of their possessions.

Have you been finding mosquitoes carrying disease?

We didn’t actively screen for diseases or viruses present within the collected mosquitoes. Instead, we were identifying species that could likely carry disease. We observed a large number of Culex mosquitoes (the type of mosquitoes that can vector West Nile and various other encephalitis-type viruses). Texas has a lot of West Nile disease cases, so it was great to see a significant decline in Culex numbers after our spray efforts. Thankfully, no large numbers of Aedes mosquitoes, which are the major vectors of Chickungunya, Dengue and Zika. Our insecticide spray efforts should prevent these populations from exploding in the future.

What are the living arrangements like?

Clarke was a great host to us, and we were housed at a hotel in the Houston area. We sometimes had to travel a few hours to the field sites.

From your viewpoint, how is the progress on the clean-up going?

The city of Houston has done a great job in the clean-up effort. From what I saw, a majority of the structural damage was cleaned up. There were still significant amounts of standing water pools and flood damage, left behind from the massive flooding. In a few more weeks, most of this flood damage should be cleared away.


How is this experience preparing you for your career?

This experience should serve to be enormously helpful in my future career. I am hoping to be a toxicologist with a special focus on the control of vectors of medical and veterinary disease. I am interested in all things that are involved in combatting mosquitoes, ticks, biting flies and other disease-vectoring insects. By better understanding the field biology of mosquitoes and how field biologists and technicians adequately control them, I hope to more effectively control their populations.