Elizabeth Castro Salas: Tequila bats and coronaviruses

Elizabeth Castro Salas: Photo courtesy of Elizabeth Castro Salas

Click here to listen to the full podcast episode

Elizabeth Castro Salas: Tequila bats and coronaviruses

While we can agree that bats probably don’t deserve the reputation they get from horror movies, they are carriers of many diseases. And while they don’t necessarily get sick, they can act as reservoirs for infectious agents and can pass them on to humans and other animals. This includes coronaviruses, of which the most famous is SARS-CoV-2, the virus that causes COVID-19. 

It’s still not clear whether bats played any role in the current pandemic. But to discover more about how these animals pick up and transmit infections, Elizabeth Castro-Salas at the Instituto Politécnico Nacional in Mexico City is studying coronaviruses in Mexican tequila bats, looking for signs of viral genetic code, in the form of RNA, in their poop. First things first, though - tequila bats??

Elizabeth: They're these small bats that feed on nectar an pollen but mostly they pollinate the Tequila Agave. So without these bats, there wouldn't be no tequila in Mexico.

Georgia: Oh, Wow. So they're important then.

Elizabeth: Yeah. They're very, very important.

Georgia: Is It as glamorous as it sounds, are you going and just picking up bat poo in the field?

Elizabeth: Yeah, it is very fancy. So yeah, we go to the field, we're actually going to work in Baja California Sur. So it's in the coast of Mexico and we trap the bat without harming it and we take it out. We put it inside this fabric bag so they can breathe, but not go away. And we wait for them to poop inside and we collect it and put it in RNAlater you know, for preserving the RNA, the viral RNA specifically, we want that. So when we are at the lab, we extract the viral RNA and then through PCR, we are going to detect viruses from the family Coronaviridae.

Georgia: So you're going to be looking at viral load in this fece, so what are you hoping to find out then?

Elizabeth: So we think that different events like migration, lactation and pregnancy could affect the immune system. Therefore the bat won't be able to control viral replication. So we think that bats arriving just from migration will shed more viruses into the feces. But we also expect that with time, as they recover and rest, there will be less virus shed in the feces. So we're going to analyse non reproductive bats, just arriving from migration and in different points of time as well, to see that recovery and to see if that correlates with the viral shedding in the feces. And for example, we think that maybe pregnancy and lactation will also be affected. So we are going to study also females in those reproductive states.

Georgia: Let's take a step then and just talk about bat immunity in general. Because they've got a reputation as the the hub of a lot of nasty diseases that humans don't really want to get, but can. So how can bats have done alright with Corona viruses and Ebola and all sorts?

Elizabeth: Yeah, that's amazing right? I wish I had their immune system. Well, they have like a reduced inflammatory response, but they also can control viral replication, like I said, so, yeah, they don't respond with inflammation to pathogens. So it's like they have the door open to enter the body, but once they're there viruses, for example, the replication is controlled by interference. They interfere with viral replication. So it's amazing because they can harbour the virus, but the virus cannot replicate, so therefore it cannot harm them. So normally even if they harbour the virus, it won't be shed into the environment. So there's no risk normally for humans and other animals

Georgia: In general, how do viruses jump from bats to people when it does happen?

Elizabeth: Okay. Yeah. A lot of people think that just because the animal has the virus, a whole pandemic is going to start. But we know that viruses are everywhere, in the water, in the soil, a lot of animals have them, not just bats, pigeons, cats, dogs, they're everywhere. So we need more than just the virus in an animal, right. We need that animal to be immunosuppressed, for example, and to get infected. And then that animal has to shed the virus into the environment. And that virus also has to survive in the environment. And also, when it survives, another animal or person has to be in contact with it and be also susceptible to the virus to get infected and maybe to be like this intermediate host and to pass it onto other species like the human. So it's a lot of things that have to happen. So it's very rare. Normally there's no threat to humans. So we think that what has happened recently is with climate change and habitat devastation, these types of events have occurred more often giving rise to zoonotic diseases.

Georgia: When you start getting a few more answers, what kinds of implications is this going to have for bat conservation? Because they're not doing great, are they?

Elizabeth: Yeah, totally. I think that we have to be very careful when we publish the results because we don't want to continue with the persecution of bats. So we think if we demonstrate that these events have an impact on the immune system and viral shedding, we will understand better the zoonotic outbreaks. And we will also generate more information so that people understand that they have to respect their habitat and that we can coexist without risk. Because most people are afraid they're going to get ill from a disease they got from a bat, but that normally doesn't happen. Like I said, there's a lot of things that have to happen for a zoonotic outbreak to take place.

Georgia: Right. Yeah. Because if it was easy It would probably happen all the time. Seeing as there's so many bats, so many humans and so many diseases.

Elizabeth: Yeah. All the time and it wouldn't happen just with bats, it would happen with pigeons, with pigs, with birds everywhere all the time. Yeah.