Penn State study finds deer infected with COVID-19 at high levels, hitting 80% last hunting season

This story comes from our partners at WPSU.

Two tigers at the Pittsburgh Zoo tested positive for Covid-19 recently, after displaying symptoms. They’re just the latest examples of animals in captivity who have been infected with the novel coronavirus. There’s a lot of concern about wildlife now, too.

Suresh Kuchipudi, a professor of virology at Penn State, is one of the lead researchers of a study of SARS-CoV-2 in white-tailed deer in Iowa in 2020-21. They found that the number of deer samples that tested positive increased over time, reaching 80% by the end of the year.

WPSU’s Anne Danahy spoke with Kuchipudi about the findings.

LISTEN to their conversation

Anne Danahy: What was your reaction when you saw that while at first you were getting samples and there were no positives earlier in the spring, and then all of a sudden it doesn’t just go up, but it goes up by a lot?

Suresh Kuchipudi: It is quite astonishing, to be honest, to see the level of the positivity among deer that we saw. While there are indications that white-tailed deer are susceptible, and there might be natural infections happening. But being able to detect the viral nucleic acid in tissues of the deer at that level is quite stunning. And we weren’t expecting to see that level of positivity among those samples.

Danahy: Are there any hypotheses about what’s going on?

Suresh Kuchipudi is a professor of virology at Penn State and one of the lead researchers on a study of SARS-CoV-2 in white-tailed deer in Iowa. Photo: Penn Stat

Kuchipudi: So the first point is why there were so many deer were infected at that point in time. I think there could be a number of factors that may have contributed to this incredibly high level of positivity.

Those included the time of the year, which is the peak hunting season, also coincided with the time when Iowa has the highest human cases of COVID-19 among people. So naturally, there is a high level of infection burden among the human beings.

Then the other aspect is hunting disrupts the movement of deer, so they probably are moving into places where they may have had a higher chance of exposure.

The other aspect is also, when the weather turns cold in Iowa in November, December, there is not much food left for deer to eat.

They probably are looking for everything or anything that they could possibly eat, and try and reach places where they might find something to eat.

So I believe all of these factors may have contributed to this high level of positivity among deer.

The interesting observation that we made was that there were not just one but there were multiple independent spillover events into deer. So at different locations simultaneously across the state, which would indicate that there were spillover events of virus transmission from humans to deer was happening in different locations at the same time. They were all independent.

Then the second point is that there was the human to deer transmission, but also followed by deer to deer transmission in these locations. The reason we were able to say this is we have analyzed the virus genomes from the deer samples. Then we compared them with the virus sequences from human cases around the same time in the same locations.

We were able to match the genetic information of what was infecting people at that time, was also indeed what was infecting the deer. That was the real power of this scientific investigation.

Danahy: Do you know how is it spreading from humans to deer?

Kuchipudi: Yeah, that’s a great question. We don’t precisely know exactly what are the possible ways in which the virus is transmitting from the deer. It is probably less likely that it is a direct interaction between a person and the deer.

But we could hypothesize several ways in which this can happen. The reason is that, based on experimental studies, we know deer are highly susceptible. They could be very easily infected if there is a source of the virus.

I think several activities that could make the virus accessible to the deer. Many different attractions of humans, for example, feeding the deer or throwing a half eaten apple, or leftover food or… so we call them as fomites, the inanimate objects that may have been in contact with people, but then subsequently, the deer got in contact with them.

Danahy: So your study was in Iowa, and there are other studies in Ohio. Is it safe to assume, though, that it’s happening all places where deer are?

Kuchipudi: I think we have now three independent pieces of evidence. One is our study where we demonstrated the viral nucleic acid in the deer and followed by the Ohio study, which also did the same in a different location, different timeframe.

There was also the USDA study which found antibodies in four states that included Pennsylvania, Michigan, Illinois and New York. Now, if you take it collectively, that makes six different states. So based on that observation and the fact that deer are, now we know, highly susceptible, the white-tail deer, I think it is highly likely that this must be happening everywhere where there are susceptible deer populations.

Danahy: It’s frightening, but it’s so interesting and fascinating that you were able to find this. Anything else?

Kuchipudi: While we have a reasonable mechanism internationally or globally, to monitor the way the virus is changing — so we have started off with the original Wuhan version of the virus. Then there were several variants emerged in different parts of the world.

The reason that we came to know about them is there is a mechanism that is monitoring the genetic analysis of the viruses from people from different parts of the world. We are monitoring how the virus is changing.

So now the important aspect is that, whether it is humans or white-tail deer or other animals, when a virus continues to circulate in a given species, it is likely to change and it will continue to mutate. While we do not know exactly how it might end up, either it could become more serious or less serious. But it is always important to monitor so we are prepared. Otherwise, we might be caught up by surprise.

We have to really struggle: ‘How do we deal with this?’ I think the important aspect is now to be proactive. So we continue to monitor how the virus might be changing in the animal population so that we are informed and we could also be better prepared with the necessary tools and the strategies that we need in case if there is an emergence of a variant that has increased pathogenicity to people or could potentially undermine the current vaccines that we have in the U.S.