Seeing sick birds boosts canary immune system
Seeing sick people can make you feel unwell yourself sometimes, but it might also, scientists are showing, augment your own immune system to better defend you should they come too close! That’s certainly the case for canaries at least, as Sally Le Page has been hearing from the University of Connecticut’s Ashley Love...
Ashley - For our experiment we had birds that were sick, so they are infected with this bacterium. And then we had healthy individuals on the other side of a divider. And then across from those two groups, we had birds that were either just staring at healthy neighbours or birds that were staring at sick neighbours so they could see sort of a visual cue of disease.
Sally - What does a sick bird look like?
Ashley - Sick canaries, when they're infected with bacteria, tend to look a little bit fluffed out, so they're a little puffy. They look tired, they don't want to move. Sometimes they just hang out by the food bowl, which I also do when I'm sick. I just sit around with snacks!
Sally - So you've got these healthy canaries that are looking at either sick or healthy birds opposite them in the room. What did you test?
Ashley - We looked at a few different components of innate immunity, which is just a non-specific component of your immune system. We found an increase in a specific cell type called a heterophile, which is similar to neutrophils that humans have, and this cell's really important in early inflammation responses so it's sort of like your first line of defence that goes out to the site of infection. And then the one other thing we looked at was called compliment activity, and this is really important for breaking open foreign cells like bacteria. So yeah, we found that seeing sick individuals was changing the immune system.
Sally - Could these changes make it harder for those birds to get infected?
Ashley - We haven't tested to confirm whether or not this increased immunity actually benefits the birds, but that's something we're working on right now.
Sally - It's astonishing to think that what the birds can see is linked up to such a different part of the body like the immune system. While Ashley's team haven't yet pinned down how that link is happening, it's possible that seeing sick birds is stressful, which triggers stress hormones that amp up the immune system - just like humans watching a horror movie triggers an adrenaline response, which amps up our heart rate. So that might be how the birds are responding to sick individuals, but why are they responding?
Ashley - That's a great question. So we don't know for sure. We think it could be that avoiding individuals obviously can help prevent you from becoming infected. But there's also costs associated with that, so birds aren't getting to engage in social interactions, they might miss out on foraging opportunities. So if there is this little immune boost that they're getting from seeing sick individuals, it might potentially protect them and allow them to still interact with other individuals.
Sally - And how strong is this effect?
Ashley - The response is sort of incredible just because it's happening at all. I don't think it's as strong as say, you know, a vaccine, or I think taking pre-emptive medicines to protect yourself. But I think it's sort of a short-term boost that probably helps a wild organism. I don't know about humans...could give a short burst of immune benefits to humans as well, but not as strong as probably some of the medicines and pre-emptive medicines we give.
Sally - What made you even think of looking at how social interactions can affect the immune system?
Ashley - I've been studying wildlife diseases for a while and I came across this paper that was a study in humans where they showed human participants images of sick people, so coughing and sneezing people with rashes. And what they found was that those participants that were seeing images of sick people had a boost in immune function. So I thought that was super fascinating and was really curious if that was going on in other organisms as well.
Sally - And of all the organisms you could have picked. Why canaries?
Ashley - Well I was currently working with canaries at the time and since I was already working with a disease system that caused these obvious visual signs or symptoms of disease, we thought it would be the perfect system to test these questions in!
Sally - And how many beds do you have in at once?
Ashley - At the time of this experiment we had a little over 40 birds. But now we - well, since we've been studying reproductive effects in mothers we've been breeding birds, I think, we're over a hundred birds now. It's a lot of canaries!
Sally - A swarm of canaries! Oh, that must be amazing.
Ashley - Yeah, the noise that they make carries down the hallway. So I think the other labs that work in our building might be a little bit frustrated with that!