Episode Summary

Rodney Rohde, Ph.D., Regents’ Professor and Chair of the Medical Laboratory Science Program at Texas State University discusses the many variants, mammalian hosts and diverse neurological symptoms of rabies virus.

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Ashley’s Biggest Takeaways:

  • Prior to his academic career, Rohde spent a decade as a public health microbiologist and molecular epidemiologist with the Texas Department of State Health Services Bureau of Laboratories and Zoonosis Control Division, and over 30 years researching rabies virus.
  • While at the Department of Health Lab, Rohde worked on virus isolation using what he described as “old school” cell culture techniques, including immunoassays and hemagglutinin inhibition assays.
  • He also identified different variants of rabies virus, using molecular biology techniques.
  • Rohde spent time in the field shepherding oral vaccination programs that, according to passive surveillance methods have completely eliminated canine rabies in Texas.
  • In the last 30-40 years, most rabies deaths in the U.S. have been caused by bats.
  • Approximately 98% of the time rabies is transmitted through the saliva via a bite from a rabid animal.
  • Post-exposure vaccination must take place before symptoms develop in order to be protective.

Featured Quotes:

Early Career

Rodney Rohde in the lab.
Rodney Rohde in the lab.
Source: Rodney Rohde, Ph.D.
I actually love talking about this part of my career because it was so fundamentally important to where I am today. So just for some context, I did my bachelor's degree in microbiology and a master's degree in virology. And over that 6.5-7-year period, I actually had plans to work at a hospital medical laboratory. But what I learned quickly when I graduated is that I hadn't gone through a medical lab science program. So, I didn't have the credential, and I couldn't sit for a credential. As you may know, you can't work in a hospital lab without a credential.

So, what I did—to my parents, surprise, like, ‘oh, great, you've been in school for 7 years, and you can't find a job,’—is I quickly went and talked to some professors. And they talked to me about the Department of Health, which is only about 1 hour from the university. And so, I started applying for jobs at the Department of Health Laboratory. And fortunately, I was accepted. I spent about a year in newborn screens, which was interesting, because I had never worked in those areas, but ultimately, where I wanted to be was microbiology and virology.

So, once I was in, I started immediately looking for positions in microbiology and virology. And the first move I had was into an area called virus isolation. And this was fantastic. I spent about 3 years in this area. And it's every potential virus, that a person can be infected with. Hospitals that had problematic specimens, or they couldn't figure out what it was, they would send to the Department of Health. And so, I got to use old school cell culture. We did tons of immunoassays, lots of monoclonal antibodies, hemagglutinin and human neuraminidase inhibition assays. This was prior to molecular really taking off in the in the early 90s. So, I'm really fortunate because I spent the early part of my career kind of pre-molecular, and just as it was coming on, I was right there.

Examples of oral rabies vaccine sachets, coated with attractant to bait coyotes and fox.
Examples of oral rabies vaccine sachets, coated with attractant to bait coyotes and fox.
Source: Rodney Rohde, Ph.D.
While I was doing that, because rabies and arbovirus were such a unique and large area for concern, they had their own department. And again, right place at the right time, Texas was undergoing 2 rabies epizootics—epidemics in animals—1 was in the south part of Texas towards the Gulf of Mexico, and 1 was in west central Texas. And these became public health emergencies. The governor actually declared them public health emergencies. Three people died of rabies, and 1000s of animals, including the livestock, were being impacted by this deadly disease. And because of all that, there was this opportunity that the Department of Health alongside CDC and the Canadian Ministry of Natural Resources had been doing what's called oral rabies vaccination programs.

So, the idea is that you drop vaccines in these little sachets, these little packets that are coated with attractants and smells that animals can actually sense, and you drop them from airplanes, and you blanket a region. We were the first program in the U.S. to get approval to do this for coyotes and fox, which were the primary vectors for canine rabies in Texas.

Rabies Diagnostics and Variant Identification

Rohde preparing to board plane for oral vaccine drop to eliminate canine rabies in Texas.
Rohde preparing to board plane for oral vaccine drop to eliminate canine rabies in Texas.
Source: Rodney Rohde, Ph.D.
What was interesting was, because we were putting these vaccines on the ground, and it was targeting canine rabies, we needed to know where the viral front was either advancing or retreating. And so that's basically what I did. Every time an animal was submitted for testing its brain material, they would [create] a GPS marker. So, you kind of knew where the animal was submitted from. And then I would do the typing.

There are various [rabies] variants. Everybody knows that term now because of COVID, but we were doing this 30 years ago. And so, the primary wildlife reservoirs are canine, skunk, raccoon—and then there are some others that you see in different places, like Arctic Foxes up in the Canadian area, and a variety of bat rabies virus variants.

At the beginning, I was doing monoclonal panels, but they weren't totally clean. Eventually, we went to DNA sequencing, which came on board right as I was ending my career and moving to Texas State for academia.

I got the type the Sonora dog rabies variant from Mexico or Latin America, or the Arctic fox [rabies variant], or the raccoon variety that's on the east coast.

Rabies Variants, Transmission and Impact on Humans and Animals

So, much like other viruses, people don't know this sometimes, but rabies kills in almost all instances if you're not vaccinated. But there are different variants. You can have a canine strain in a cow. Or you can have a bat strain in a cow or a horse, or a dog or a cat. So, any warm-blooded mammal is susceptible to the virus, but it can be different variants, much like you can have flu A, flu B and so forth.

I often describe it as a fascinating and one of the most diabolical viruses out there. Just really interesting to work with.

In the U.S., for the last 30-40 years, most human rabies deaths have been bat associated.

It’s usually because if a bat actually had bitten somebody or [there had been] an exposure, because they're so tiny and their incisors are so small—it's like a hypodermic needle—it's not like you've been mauled by, you know, some wildlife or rabid feral dog or something. Most people they put their hands in a woodpile or dug around the tree or something, and they thought they got scratched and didn't care about it. And then unfortunately, 2 weeks later, they had symptoms.

Bat bites have been the most common cause of rabies deaths in the U.S. for the past 30-40 years.
Bat bites have been the most common cause of rabies deaths in the U.S. for the past 30-40 years.
Source: Flickr

A good point about rabies dimension: here we are talking about zoonotic disease and vector borne disease that is going to be really difficult to eliminate rabies completely because there's always a wildlife reservoir. And even if we eliminate all the terrestrial, 4-legged animal variety of reservoirs, you're still going to have bats (which are not land locked—they fly) reintroducing the virus into animals and/or humans.

The primary route of exposure is direct, usually through a bite. And then once it gets into that particular site, wherever it's at—it could be your pinky, your toe, your face, whatever part of your body gets bit—the virus will multiply locally in those cells and eventually get into the peripheral nervous system.

Then it'll move towards the central nervous system and move throughout that nervous system to the brain, and then it'll actually retrograde go back through the body. So, another interesting thing about rabies is it does impact the brain, and ultimately, you succumb to it through common comatose and other issues. But at the end stage it also can kind of retrograde move back through the body and end up in organs. So, I've had some unfortunate cases where someone donated their organs, and they didn't know this person had died from rabies, and [the recipient] got rabies through organ transplantation. Four or 5 people died that way, if you can believe that.

Rabies Pre- and Post-Exposure Vaccination in Humans and Animals

The rule of thumb is that if you get vaccinated before symptoms show up, then you can be protected [via] circulating antibodies.

When I was working in that area, we all had pre-exposure vaccination. We would receive 1 vaccine kind of for those accidents where you weren't sure if you'd been exposed. So, if you work in a rabies lab or you are a veterinarian or maybe a wildlife biologist, or something like that, you typically are going to have pre-exposure rabies vaccine just to be careful.

Once you know you've been exposed, you can receive that vaccination. And it's a series of vaccines. It's not in the stomach anymore that that's gone away decades ago. It's all in the arm. You do sometimes receive post-exposure prophylaxis right in the wound site, where they'll put a little bit of the vaccine because it can tie up and neutralize the virus before it gets into circulation. But you're still going to get the IM—the intramuscular shots—throughout several weeks.

Most of the time, it's of the attenuated and/or the protein kind of subunits, including with the oral vaccine. They'll use VRG, it's actually part of the nucleoprotein. And so, they'll have different makeups. It kind of depends on the country you're in and what you're going to utilize in those different countries. In the U.S., most of the time, it's a form that's not going to be living. It's not a live vaccine; it's attenuated and/or subunit vaccine.

In my experience, there's a lot of anxiety around [rabies], because, let's be frank, it's not a great way to die. It's a pretty tough neurological way to go. And, as I mentioned, once you get beyond a certain point, if you have not had vaccination, you're going to approach 99% mortality in most cases. So, it's very difficult to do much about it, once symptoms start.

Rabies Symptoms

In general, most of the time, if you get bit, and you go through the process, the progression of the disease is going to be about a month—3-4 weeks is typically what you're looking at. Now, there are some of these weird exceptions, and they're actually documented in the literature. We've had cases where we believe people got bit, and they ended up dying several years later from rabies. We're not sure why that occurred. But we do know the further away from your brain you're bitten, the longer it takes. So just kind of common sense. If you get bitten on your little toe, it takes longer for that to reach your brain. If you get bitten in the face, that's an immediate worry.

For most people, there's going to be very common symptoms of the acute phases. You know, like a lot of things, they might have a headache, they might have flu like symptoms and nausea. There's tingling and kind of strange sensations at the bite site.

Longer term, as it goes forward, it can really go between [a person is] here, lucid and talking to you, and then 5 minutes later, they've kind of slipped off into another world. So, there's some mental involvement because of the viruses, pathology.

There are issues with being afraid of water. So, for whatever reason, swallowing water is an issue. So, when I was doing some of the meetings, I went too early in my career, I always found it fascinating that in certain cultures where rabies is kind of rampant, people would actually set out buckets of water around their living spaces to ward off wild animals because they're basically afraid of water.

Sometimes people will go to the dentist thinking they have some kind of impacted problem with a tooth or something. In some cases, you'll see the patient has actually gone to the dentist before the doctor. And unfortunately, that means the dentist and the dental hygienist are now receiving post-exposure prophylaxis to because they've had their hands in their mouth..

So, just some interesting signs and symptoms. And then, ultimately, when it gets into the brain and starts doing what it's going to do, typically, they slip into a coma. And it stops the heart at some point. And you have other organ involvement or kidneys are starting to shut down and things like that as well. But kind of a tough pathological route.

Science Communication

I don't know if there's a more important issue right now, in all honesty across the world. There's so much misinformation and disinformation and sometimes outright falsehoods around different diseases, whether they're infectious or chronic, and different scare tactics around vaccines or with therapies. And so, it's definitely become a passion of mine, to help raise the health literacy of my family, my friends, my students, my colleagues and anyone and everyone that I can reach.

Having a platform like ASM and really any opportunity—different podcasts, different articles, different colleagues that I have the privilege to work with, like yourself, and others that are with ASM—to just do that work. It's a work of passion, for sure. So important.

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