President Donald Trump's executive order last month reduced the cap of refugees allowed into the United States from 110,000 to 50,000. That means that fewer refugees will be resettled into areas like St. Louis.

But the cap also is curtailing disease research across the country. To understand diseases that are widespread in poor, war-torn countries, scientists study refugees from those nations that are infected with those diseases.Among them is Soumya Chatterjee, an assistant professor in the Department of Internal Medicine at Saint Louis University. Chatterjee studies tuberculosis, a disease that kills more people than HIV and is a leading cause of fatality in developing countries. Trump's order makes it difficult for him to enroll participants in his study.

Only one vaccine for tuberculosis exists, but it doesn't work for those living in developing countries. The reason is unknown to scientists, but last month, Chatterjee began a study to confirm a leading theory that could explain why the vaccine is ineffective for some populations. In places where tuberculosis is widespread, people are also exposed to large parasites, called helminths.

Chatterjee spoke with St. Louis Public Radio's Eli Chen to explain why his work depends on refugees. Here is their conversation:

Soumya Chatterjee: [Helminths] are transmitted in areas with poor sewage disposal, when people walk bare feet, eating contaminated food that contain parasites, so then the parasite develops inside of your body. So what it does is, over the long term, it affects your immune system. You don’t respond as well to other pathogens, like tuberculosis, as you would have if you were not infected.

Eli Chen: Your research on tuberculosis depends on refugees who come to St. Louis. Where in the world do these refugees come from and why are they so important for your research?

SC: They come from areas of the world that are dealing with a lot of strife, a lot of political instability. And most of the countries they come from are located in the Middle East and in Africa. Before they come to the U.S., they actually have to be, for a fairly long period of time, in a refugee camp while they’re being cleared for entry in the U.S. And while they’re in the camps and when they were in their countries of origin, a lot of these people have been exposed both to tuberculosis and the worms which we call the helminth parasites.

The other piece of studying the dynamics of infection and immunity in people with tuberculosis is to try and understand the role of the environment. The refugees are a unique population in that regard because they were exposed to these infections when they were in that high prevalence environment. And now they have been removed from that environment.

And so we can now study their immune responses in a very systematic way because whatever infections they’ve come in with into the U.S, that is what they have. They won’t get any further reinfection with these parasitic diseases.

EC: How difficult is it for you to find participants for your research?

SC: It was very difficult when I started here in 2015. Because refugees are [a] very special population who have gone through tremendous amounts of strife and life events that can only be described as traumatic, it’s a difficult population to research on. You have to be cognizant of what kinds of things you’re asking refugees to do for your research. Thankfully, my research did not interfere in any way with the care they were going to receive at the [City of St. Louis] Department of Health and it was essentially to collect blood and stool from them to study their immune responses and the presence or absence of parasites in their stool. I was able to then convince the International Institute, which relocates the refugees here, as well as the Department of Health, but them being on board was the initial part of the story. We also have to go through what is called an IRB approval, which stands for Institutional Review Board, which looks at all the clinical research studies. Those are research studies involving human subjects. Saint Louis University IRB had to go through my application and approve that, then we had to sit down with lawyers from Saint Louis University and the Department of Health and make sure all the i’s were dotted and t’s were crossed because this is essentially a partnership between two institutions which have really not partnered up in a systematic way before. So once those approvals were in place, we finally were able to start the study. And we just started in January.

EC: The president’s executive order severely limits the travel of refugees from predominantly Muslim countries. Tell me how that could really hurt your research.

SC: Refugees being banned from these countries will put this study on hold. I don’t know for how long. Because I know that the refugee program itself has been suspended for at least three months. And especially because refugees are [mainly] coming from these seven countries, I think our enrollment will suffer tremendously.

EC: So that could mean further delays in trying to find a vaccine for this population, is that right?

SC: Yes, that is absolutely correct.

EC: What is your plan if there continue to be restrictions on refugee travel?

SC: Uh...I actually do not have a backup plan at this point. This was a very specific question. And it would have led to, we believe, very unique results. So I’m just hoping that the ban gets lifted and we can start the study again. Otherwise, I think our human subjects, our research will suffer.

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