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Melanie Cole (Host): New viruses found in free-ranging Burmese pythons raise questions of disease risk to native snakes and other species. Invasive pythons have been devastating to the ecology of Southern Florida. And while some of the immediate effects of an invasive species like the Burmese python may be more obvious, others such as the introduction of novel pathogens and diseases, are less obvious, but can be equally problematic and are harder to recognize and monitor.

Welcome to UF Vet Med Voice with the University of Florida College of Veterinary Medicine. I'm Melanie Cole. And joining me today is Dr. Rob Ossiboff. He's a Clinical Associate Professor of Anatomic Pathology at the University of Florida College of Veterinary Medicine, and he's here to highlight emerging pathogens and invasive species, the impacts that include disease risks, as well as environmental effects.

Dr. Rob Ossiboff, it's a pleasure to have you join us today. As we get started, this is such an interesting topic, can you please tell us a little bit about the Burmese python, for example, and a little evolution of invasive species, how they have affected the ecosystems of Florida?

Dr Rob Ossiboff: Absolutely. So, the Burmese python, as many of you have probably seen pictures before, they're incredibly large pythons that are native to southeastern Asia. And they have established themselves in South Florida, throughout the Everglades starting in the first animals that were observed in the late 1970s, 1980s. And then, in the early 1990s, they were really started to be seen in higher numbers and, later that decade, actually became a sustainable breeding population. And those animals have done a number on the ecosystem of South Florida. They have affected the numbers of normal species that they're either eating or being affected by having decreased diet, because the snakes are actually eating their diet.

But one of the other things that the Burmese pythons have introduced into the state of Florida are a couple of diseases. And one of the big diseases, we know that they have introduced this novel pentastome parasite. And that is a parasite that affects the lungs normally of the Burmese python. But that parasite has spilled over into our native species and is actually spreading north through the state beyond the range of Burmese pythons, so that is an introduced disease because of these snakes. And then recently, we did a large study to determine if those Burmese pythons are present in the Everglades also were carrying different viruses, particularly serpentovirus, which are a known important pulmonary pathogen of captive snakes, yet we don't know so much about them in wild snakes. So, we decided to screen those Burmese pythons for the presence of these viruses. And we actually found quite a high prevalence and a variety of different viruses in those snakes.

Melanie Cole (Host): Wow. So, tell us the implications of that. I'd like you to speak about the projects that you're involved in and these studies and the collaboration, but speak a little bit about the implications of serpentovirus and these other invasive species and pathogens that you're seeing, and what do you see as an implication into the wider environment and ecosystem.

Dr Rob Ossiboff: So for the serpentoviruses in particular, these are viruses that we have known about for less than 10 years. The first ones were described in 2014 in a couple of different python species in captivity. And in captive pythons, they can cause really high rates of morbidity and significant mortality in affected animals.

What these viruses mean for wild snakes isn't entirely clear. We know that there's a lot more viral diversity out there now than we used to know. And even in captive snakes, the diagnosis of a viral infection is not always a fatal diagnosis. But we weren't sure then potentially what these viruses would mean to the Burmese pythons. And of the several hundred animals we sampled, about 25% were positive for the virus. We did necropsy or postmortem examinations on a subset of snakes, and we really only found mild oral inflammation in these individual snakes. So, it seems like these viruses to the Burmese pythons aren't a big deal.

The bigger concern is what risk these viruses play to our native species. Is it possible that these viruses of the Burmese pythons can spill over into our native snakes, some of which are threatened, such as the indigo snake, others are decreasing in numbers such as the pygmy rattlesnake? And what potential these viruses may hold for our native species?

The good news is, is that when we did swab 200 native snake species, we did not find any of the Burmese python viruses in the snakes, but we did find different serpentoviruses in the native snakes of Florida. And that's another important finding in terms of the ecosystem because we don't entirely understand what finding these viruses in our wild snakes when they seem to be healthy means. Are these low level infections that aren't going to cause disease? Or are these infections that with appropriate stress on the animal, whether it be to decreased temperatures in a cold winter snap, or if there's any sort of environmental stress, if that can actually allow them to break with disease? And we do see this in wildlife, that species can introduce novel pathogens, including viruses that spill over into native species and then what risk that poses for the native ecosystem.

A lot of the work I do here at UF, you know, my particular area of interest is diseases of reptiles and amphibians. And as we are in the state of Florida, invasive reptiles species are a huge concern. It goes much more than just the Burmese pythons. We have invasive iguanas, we have invasive tegus; we have invasive anoles, the brown anoles that are present aren't supposed to be; cuban tree frogs when it comes to amphibians. All of these different species can have impacts on the native species and the native ecosystem, depending on what niche they're inhabiting or what they may be eating. And all of these species have the potential to introduce novel disease, and we've documented novel diseases in almost all of these species. And it's something that's important to assess and consider when you are doing risk analysis of the introduction of invasive species into certain ecosystems is what other confounding factors may come along with the invasive species that aren't just directly related to the animal itself.

Melanie Cole (Host): This is so interesting. Dr. Ossiboff, you had a collaborative project with other academic institutions. Can you please tell us a little bit about this? How did it come about? And tell us about the study.

Dr Rob Ossiboff: Absolutely. So, this was a large scale collaborative project. And it actually initially came about because one of the collaborating institutions on this study had captive Burmese pythons on grounds to be used as research animals. And so, these were animals that were collected in the Everglades, brought into captivity, and then maintained in captivity for a number of months as they were being set up to be used for studies to help better understand the biology of these invasive snakes. And it actually happened that there was an outbreak of viral disease in this captive colony of snakes in Florida that had origins in the Everglades. And when we did the analysis on those snakes, we found it was one of those serpentoviruses in those snakes. And it was actually a serpentoviruses very commonly seen in pet pythons. So, our initial concern was, is this virus potentially circulating in the Everglades? And if so, how did it get there? Was it introduced by potentially pet snakes or, you know, what impact may this have, positive or negative, on the Burmese pythons?

Further analysis of that outbreak at the local research facility showed that those snakes likely got infected by being exposed to an animal keeper that also had pythons at home and some of those pythons at home probably had this viral disease and it was passed to the research colony. But that's what started this collaborative project. And anytime you're working in a large national park such as the Everglades, you need to work with the appropriate people.

So, we here at the University of Florida, we can do so much in terms of diagnostic testing. When it comes to field work, we need to have help in terms of the people that are out there all the time and doing this type of work. So, we collaborated with the Florida Fish and Wildlife Commission, United States Geological Survey, USDA as well as collaborators at Colorado State, who were also doing some of this virus work, and some other individuals, other places as well.

And through this, we were allowed to really do this large scale study. We looked at samples from over 350 pythons and over 200 native snakes, and none of that really would've been possible without the collaborative effort of everyone working together.

Melanie Cole (Host): Dr. Ossiboff, as we wrap, and we don't yet know the complete implications of the Python viruses to the South Florida ecosystem, I'd like you to give us some parting words about further studying the importance of these kinds of studies on that ecosystem and really ecosystems all around where we're seeing invasive species and the possible emerging pathogens that can come from them as an example of where invasive wildlife species can introduce those pathogens to a native environment. Tell us a little bit about what you would like the takeaway message of this podcast to be, what you would like other vets to know about your studies, your clinical trials. Really, any key takeaways.

Dr Rob Ossiboff: Sure. I think the most important thing is we don't understand exactly how significant these viruses are to the Burmese pythons. And they're likely co-evolved and they likely have little clinical significance to the actual Burmese pythons. But understanding how viruses and their hosts persist and interact in the environment is an important thing. You know, how long do these snakes stay infected? Can they get sick clinically? How is the virus maintained in the population? How is it passed from individual to individual? And then, again, what risks are there for closely related species in the area surrounding it? Can this virus get into native species? What are the implications if it does get into native species?

The take-home message in terms of invasive species and ecosystems really is that biology is incredibly complex. And when we try to determine the risks that invasive species may play, we invariably miss many important factors that go into the entire interactions of that host with the biological system. And we know there are other instances, instances on the whole, on the globe, in fungi, in amphibians, so Batrachochytrium fungi, were introduced by different species, including invasive species for the salamander chytrid. We know that bacteria can be introduced by invasive species, we're experiencing some of that in the state of Florida now, and viruses can be introduced. And it's really important to understand the potential implications of this because, while this virus may not be a highly pathogenic virus to the host that introduced it, there may be a time when that type of virus is introduced. And studies such as this need to constantly be happening for us to understand what normal viruses and bacteria and parasites may be present in wild animals and how those may change with stress and in situations where the environment is changing.

Melanie Cole (Host): So interesting. Dr. Ossiboff, thank you so much and I hope you'll join us again and update us as you learn more because this is such a fascinating topic. Thank you so much again. And for more information about the University of Florida College of Veterinary Medicine, please visit vetmed.ufl.edu/uflachievers. And to listen to more podcasts from our experts, you can visit vetmed.ufl.edu.

That concludes today's episode of UF Vet Med Voice, brought to you by the University of Florida College of Veterinary Medicine, advancing animal, human and environmental health. I'm Melanie Cole.