Q&A: LEAP Student Fellow Lauren Killingsworth Maps History and Tensions of Biological Control

Lauren Killingsworth is an M.D.-Ph.D. student at Yale School of Medicine in the Department of History of Science and Medicine and a student fellow with the Law, Environment & Animals Program (LEAP) at Yale Law School. She centers the non-human in her interdisciplinary scholarship on emerging infectious diseases, environmental history, and public health. Killingsworth is also a recipient of a 2024 LEAP Student Grant for her work examining the practice and history of biological control, the use of living organisms (such as mosquito-eating fish and parasitic insects) to eradicate vector-borne diseases. With her grant, she studied the archives of the World Health Organization (WHO), National Agricultural Library, and the Smithsonian Institution to examine the history of and ethical dilemmas raised by biological control techniques. Killingsworth discusses her archival research.

What is the history of biological control? To what extent is this practice employed today?

Biological control can mean different things, but generally it refers to the use of living organisms (such as parasitic fungi, bacteria, or even fish) to control disease vectors. I first got interested in it because I was looking at some old journals from colonial India under British rule in the early 1900s and was intrigued that they kept mentioning fish being a useful, naturalistic method for malaria control. I did some more digging and realized the use of specific species of fish to eat mosquito larva, which can help with malaria prevention and other vector-borne diseases, was — and actually still is — a relatively common practice in many parts of 

the world. What does it mean for some forms of disease control to be more natural? These fish were often posited as a natural method to use instead of chemical methods, often for interesting reasons: In colonial India, the British saw the use of fish as a way to covertly control malaria without angering the local indigenous people. So there was a darker side of this practice because you basically have British officials seeing fish as a means of skirting around public resistance to putting chemicals in their rice paddies or fountains. The idea was, “We’ll just put fish in the wells, and no one will notice.” But of course, the local people did notice. 

There was also conflict around the ecological disruption caused by introducing non-native species into new areas. Another example of this situation was the Rockefeller Foundation, which was the major global health philanthropy in the 20th century, shipping millions of an American fish species to India, which caused lasting environmental problems. And in California, a newt species is now endangered partly because these mosquito-eating fish were introduced into their habitat in the 1920s. These measures have lasting consequences.

Turning to today, there are a lot of methods being used with varying degrees of success. There's been a lot of interest in genetically modified animals, particularly modifying mosquitoes carrying dengue. There have been efforts to use bacteria to sterilize mosquitoes, too. Another part of my project looks at the beginning of this “sterile insect technique” as they call it, which has an interesting intersecting history with atomic energy.  The technique was seen as a way to promote the peaceful use of atomic energy, since insect vectors were sterilized using radioactive isotopes. These biological control techniques became a part of international diplomacy during the Cold War.

You combed through the archives of the World Health Organization (WHO), National Agricultural Library, and the Smithsonian Institution for evidence of biological control experiments. Why did you choose these organizations in particular? What did you find?

The WHO had a significant interest in these naturalistic or biological methods, which was very much a response to rising concern about DDT toxicity and the growing environmentalism movement in the 1960s. What does it mean in the international context that policymakers and global health leaders are starting to focus on alternative methods of vector control, especially the problem of pesticide resistance? I was curious about how biological control was seen as something of a permanent solution to vector-borne disease — a nuclear option in a way. They were benefiting from and relying on nuclear technologies and this idea that you could completely eradicate a species. 

I wanted to look at the WHO’s archives because many people involved in the biological control projects I've seen had their foot in the door of the WHO at one point or another. Around 1950, a scientist at the WHO introduced a parasitic fungus from Malaya to the remote South Pacific Tokelau Islands. He thought this fungus (which preyed on mosquitoes) could help eradicate the island’s lymphatic filariasis problem. This idea that you can collect, transport, and release a fungus to an island to control a mosquito vector was fascinating, especially given the scale on which these projects were occurring. 

I found a lot of interesting material at the National Agriculture Library. It’s in Washington, D.C. and has all the records of the U.S. Department of Agriculture (USDA) and a lot of records from the WHO because they are very much in conversation with one another. The project I examined at the National Agriculture Library is quite interesting: it took place in the 1950s and was the first experiment using the sterile insect technique, which at the time used radiation to sterilize insects. The idea is that, if you release a ton of sterile male insects into the population, when the insects mate, they won't be able to produce offspring. The founder of this method was a USDA scientist, Edward Knipling, so I looked at his papers to understand the work. There, I found something I didn’t expect: records of the initial islands in the Caribbean where they tried these projects and conversations between the governments of these islands and the USDA, which was quite eager to trial these methods. In a different trial in Mexico, I found evidence that the Mexican environmental department was not at all interested in being a guinea pig for the United States’ agricultural experiment.

The material I've been looking at most recently has been the records of the U.S.-Mexico Commission on the Eradication of Screw Worm, which is a bit of a mouthful. The screw worm is a parasitic wasp — basically a flesh-eating maggot — that affects humans and animals, but the main concern is cattle. From the 1960s until the early 2000s, there was a mass initiative where the U.S. operated within Mexico to set up a factory to produce sterile versions of these insects. With that came all sorts of interesting public health ephemera and material that have been left at the National Agricultural Library archives: I got to look at the original tubes where people sent these insects in all the original packaging, the little tweezers they used to pick out the bugs, and all the signs and logos associated with the project.

I also went to the Smithsonian, which wasn't part of my original plan, but I realized there might be something there. I'm glad I went because I didn't realize the extent to which the Smithsonian and other natural history museums throughout the 20th century had been involved in projects that spanned across human, environmental, and animal health. I found records at the Smithsonian that I would characterize as early recognitions that the health of the environment has an impact on the health of people, which is a big part of biological control work. It raises big questions: To what extent humans can control their environment and other animals? Is this a good or a bad thing? 

I’ve seen projects the Smithsonian has worked on that cut across the sciences. For example, I've been looking at their records of this place called the Center for Short-Lived Phenomena — a great name — that’s interested in recording information about climate, biology, anthropology, and geophysics, which seem totally unrelated. But the point of this organization was to look for similarities and connections between things like volcanic eruptions, migrations of birds, migrations of insects, and changes in human populations. They were also obsessed with biological control; they even published fun books meant for elementary schoolers that mentioned these new “Super Bugs.” It was helpful for me to think about how these things enter into popular culture and the everyday.

Your project also interrogates the ethics of biological control. Based on your research so far, what conclusions, if any, have you drawn about the ethical permissibility of these practices?

As a historian, I've been interested in thinking about the ethical questions that these projects raised in their own time, which are not usually explicitly in the archives. I surprisingly haven't seen anything asking, “Is it ethical to eradicate a whole species?” But what I have seen is scientists and local people voicing concern about the ramifications of these projects or how they're being done. I'd like to look more at the records of the project I mentioned between the U.S. and Mexico, especially on the Mexico side, to see more about this resistance or uncertainty about the project.  I've seen one letter that clearly expressed hesitancy about new methods being trialed in their country. They asked, “Why not try this in the southwestern United States?” which is a very fair question. With the work I did previously on fish, there was clear resistance from Indian fish scientists, Indian medical officers, and local public health anti-malaria organizations because they depended on local fish for food and for malaria control. Local organizations actually started breeding local fish and set up a whole system within India to transport these “indigenous fish” as they called them across the country via train in little aquariums to distribute the fish as a way to combat the introduction of foreign species being sort of pushed upon them by this American quasi-imperial philanthropy. I'm curious to see if that sort of resistance comes up more the further I get into looking at the U.S. and Mexico. Zoonotic disease in general is always very political, and oftentimes there are these difficult questions about whose rights you're prioritizing. 

As someone who's also doing an M.D., I’m thinking about how to tie this all in and bring it back to medicine. One of the things I'm interested in is ecologies and how they impact disease. Towards the middle and end of the 20th century, a lot of medical professionals and scientists became interested in ecology and started to speak in terms of ecological-thinking about communities and disease. Some people go as far to say, “Maybe we shouldn't be eradicating disease because disease is a natural part of ecology.” 

I see connections between that and this biological control work. I'm now looking at armadillos as models for leprosy, which ends up being surprisingly political because people blame armadillos for causing leprosy outbreaks in the southwest. I’m still figuring out where my dissertation will be, but I'm hoping it includes animals and humans and their messy intersection at infectious disease control.