Mosquitoes, Wild Pigs, and How Urban Planning Can Help Mitigate Disease

The first major professional conference that Pallavi Kache ever attended was an international symposium focused on wild pigs.

Kache, now a doctoral candidate in the Department of Ecology, Evolution, and Environmental Biology, was a fellow at the Centers for Disease Control (CDC) in Atlanta at the time, working on how to mitigate the spread of brucellosis, a bacterial infection that can spread from pigs to humans. And one of the most important populations to work with to help in that effort is wild pig hunters.

In the years since, Kache has turned her focus to mosquitoes, and specifically Aedes mosquitoes, which are prevalent in tropical, urban environments and responsible for spreading well-known viruses like dengue, yellow fever, and Zika. This fall, she was the lead author on a paper in Nature Ecology and Evolution that explored novel ideas around how the design of cities contributes to the risk of mosquito-borne diseases. The idea behind Kache's research is to use urban design to confront Aedes mosquitoes. We caught up with Kache to discuss how her career took her from the CDC to Columbia (the university), as well as Colombia (the country), where she completed a Fulbright fellowship in 2020.

Can you explain the gap that your paper is trying to address?

In its early years, the field of urban planning focused on how to build cities that could avoid disease. Avoiding cholera, for example, was an important concern for urban planners in New York City. But over time, with basic sanitation problems solved, the concern has dwindled somewhat. A few years ago, when I first started looking into this topic, it really surprised me to find that contemporary urban planning was not really grappling with the rise of infectious diseases, and how to prevent their spread.
 
So that’s the goal of this paper: To jump start conversations with geographers, urban planners,  and urban ecologists—people who think about the design and function of cities—and move toward an urban planning that aims to prevent mosquito-borne diseases, which are a growing issue in cities around the world.
 
The paper that was just published is the first chapter of my dissertation. It’s a conceptual framework. The rest of the chapters of my dissertation are about the ways we can begin implementing the framework laid out in this paper with different scientific and statistical methods.

What makes the disease-spreading Aedes mosquito so good at surviving in cities?

They’re highly adapted to humans as their primary source of food, and they lay their eggs in and around human-made buildings and dwellings. They can breed in habitats as small as a bottle cap’s worth of water. That makes management and control of their populations incredibly challenging.

What led you to study this topic?

I’ve always lived in major cities. I’ve lived in Austin, Atlanta, New York, Geneva, and Bogota. And everywhere I’ve lived, I’ve loved walking through the city, observing and absorbing the history, and architecture of different neighborhoods. Thinking about the similarities and differences between those urban environments was what got me thinking about public health in urban environments more broadly.

You did a fellowship at the CDC in Atlanta before starting at Columbia. What were you working on there?

I was working on bacterial diseases that are transmitted from livestock to humans, for example zoonotic pathogens like anthrax. I also worked on the Ebola outbreak that happened in West Africa from 2014 to 2016.
 
I also worked on one disease called brucellosis. That ended up being a really fascinating project to work on because it's sometimes transmitted from wild pigs to humans and the highest risk population is wild pig hunters. So I was working with a population I never really expected to be working with in rural Georgia.

Did you go on a wild pig hunt? 

I didn't go on a hunt. But I did talk to a number of hunters and the first professional conference I went to was the international wild pig conference. It was in Montgomery, Alabama. I was about 22. I learned a lot about understanding different peoples’ traditions and practices, what they love doing, their culture. And how scientists and public health professionals need to be able to listen and learn from the communities we are working with. 

How did you decide to pursue a PhD?

I got a master’s in infectious disease epidemiology from Columbia. And in doing that I realized that there are so many things we still don’t understand about what is causing new zoonotic diseases to emerge. Things like deforestation, urbanization, and climate change. 

I found that to really understand these diseases, we need to better understand the cascading effects of how humans are changing the planet, and for that I turned to a PhD in disease ecology. 

Can you tell us some of the big findings from your research so far?

I’m looking primarily at dengue in Colombia, and trying to identify the key factors that are leading to its rise in areas across the country. In one chapter of my dissertation, I focus on how extreme weather is affecting the spread of dengue in cities. Analysis is still ongoing. But one thing that’s been important in our findings so far is that cities that have not experienced outbreaks of dengue in the past because they are at high elevations are starting to experience outbreaks because of more extreme temperatures that are occurring due to El Niño cycles. But those cities may not have enough resources or public health infrastructure in place to mitigate outbreaks. We also found that droughts are really important, a topic that I explore in another chapter. Because people are inclined to store water during periods of drought (and mosquitoes are breeding in that water), we see spikes in dengue rates three or four months after a drought.

In another chapter, my research focused on Ibagué, a city in the Andes Mountains. The city has undergone a lot of changes recently and so we were interested in seeing how water infrastructure across different neighborhoods may be affecting how people store water in their homes, which is driving differences in the numbers of mosquitoes in those different neighborhoods. In Ibagué, there’s a long history of not having access to water consistently, so people have built up a culture of storing water in their homes, because of their memories of that precarity. Any kind of public health measures need to take that cultural and social memory into account.

You’ve done some illustrations to accompany your own stories through the years. How did you start doing that work?

I've always been interested in design. I've been working kind of at the intersection of design and science communications for a while. While I was at the CDC, I actually designed some flyers with preventative messages for wild pig hunters. And those are actually up on the CDC website. I just got a job at the CDC as an officer with the Epidemic Intelligence Service. I’ll be starting there after I finish my PhD in the spring.  So, who knows, maybe more of my illustrations will end up on the CDC’s website in the future.