Cells infected with Hendra virus (left) and with Cedar virus (right).

Cells infected with Hendra virus (left) and with Cedar virus (right).

New bat virus unlocking deadly secrets of Hendra

Australian scientists have discovered a new virus in bats that could help shed light on how Hendra and Nipah viruses cause disease and death in animals and humans.

  • 20 August 2012

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Glen Paul: G’day, and welcome to CSIROpod, I’m Glen Paul. In Australia bats are the natural reservoirs for a range of viruses that can infect and sometimes even kill humans or other animals. These include Hendra, Meningeal, and the Australian bat Lyssavirus. In other parts of the world bats are thought to be the natural host, or involved in the transmission of a range of infectious diseases, including Ebola, Marburg, Rabies, SARS, and Nipah.

Now Australian Scientists have discovered a new virus in bats, named Cedar, after the Queensland location in which it was discovered. The new virus is a close relative of Hendra and Nipah, but with one surprising key difference – the Cedar virus does not cause illness in several animal species normally susceptible to Hendra and Nipah. This tantalising difference may help Scientists understand how to better manage and control its deadly cousins.

Joining me on the phone is CSIRO’s Doctor Glenn Marsh. Glenn, how and when did Scientists first become aware of Cedar?

Dr. Marsh: We became aware of Cedar probably a year, year and a half ago. It was part of a collaborative project we had with Biosecurity Queensland, who has the last two or three years been out sampling bat colonies in Queensland, looking for the presence of Hendra virus. So what they do is they go out, they put plastic sheets underneath the bat colonies of an evening, and then come back the next morning and collect any urine that’s on the sheets. They then take this urine back to the laboratory where they do molecular tests looking for the presence of Hendra virus in the samples.

After they finish looking for Hendra virus in the samples they send them down to the Australian Animal Health Labs here in Geelong, where we carry out a process known as virus isolation, where we put these samples onto cell lines that are susceptible to Hendra virus and try and isolate Hendra virus. Isolation of Hendra virus is not the most successful from these samples, most likely due to the level of virus in the bat urine. On some occasions we’re lucky enough that we can isolate other viruses, many of which are completely unknown to science, with the Cedar virus as one of those.

Glen Paul: So it’s obviously closely related to Nipah and Hendra, so why then doesn’t it affect animals that are normally susceptible to those two?

Dr. Marsh: That’s a very good question. So the work we’ve done on Cedar virus so far has shown that it’s the most closely related virus to Hendra and Nipah that we’ve known. Based on that we have classified it within the henipavirus family, which is that Hendra and Cedar are two members of. However, when we put this virus into several different animal models, and these are animal models that we’ve routinely used for Hendra or Nipah virus research, and when we put Hendra into these animals the animals succumb to fatal infections fairly rapidly. When we put the Cedar virus into the same animals we saw no signs of disease at all. The reason that we saw no signs of disease is unknown at present, and that’s having the ongoing investigations we’ll look at.

Glen Paul: OK, so at this point we don’t know whether it could be harmful to humans or not?

Dr. Marsh: At this point we don’t know whether it could be harmful to humans or not. Those experiments are naturally not experiments you can carry out. But based on what we know about Hendra and Nipah virus, and what we know about the Cedar virus, we think it’s unlikely that it causes significant disease in humans.

Glen Paul: OK. CSIRO already has a vaccine for horses against Hendra in the pipeline, so could Cedar virus pave the way for a vaccine for humans, kind of in the way cowpox did for smallpox?

Dr. Marsh: Cedar virus is very different than Hendra and Nipah virus in terms of the way the immune response is generated against it. Antibodies made against Hendra virus won’t cross-neutralise or protect someone from Cedar virus infection, so therefore the Cedar virus would not make a good vaccine for Hendra virus.
Glen Paul: Oh well, it was just a thought. So where do bats pick these diseases up from, and why aren’t they affected?

Dr. Marsh: That’s a large area of research ongoing in our laboratory at present. Bats are known to be the natural reservoir of many of these viruses, as you mentioned earlier. Bats show no signs of disease from any of these viruses, and how bats can survive with these viruses and not show any sign of disease is an area of research we’re quite interested in at the moment. We have a large group of people who are involved in sequencing the bat genome and doing a lot of immunology work in trying to understand how the bat immune response functions, is it different than what occurs in other mammals, and is this different immune response what allows them to carry these viruses?

Glen Paul: And do you feel bats could be acting as reservoirs for other as yet unknown diseases?

Dr. Marsh: Yeah, we believe bats could possibly be the reservoir for many different unknown viruses. Over the past few years we’ve had significant number of bat urines collected in Queensland that we’ve done virus isolation on, and we’re always amazed at how many different viruses we can find in a single urine sample. For some samples that were collected last year, we could find up to three or four viruses present in some of those samples, which is unheard of in other mammal species.

Glen Paul: What then is the next step with the Cedar research?

Dr. Marsh: So the next step in the Cedar research would be trying to understand why it’s a non-pathogenic, and the hope with that work is that even though we’re trying to work out why Cedar’s a non-pathogenic, what we’re really trying to understand is what makes viruses like Hendra and Nipah so pathogenic, so if we can find out what the differences are between Cedar virus and Hendra virus we should be able to understand what’s different about the two viruses, and then pinpoint the changes in the Hendra virus that makes it so deadly. By understanding what makes this virus cause such fatal disease we’ll be able to develop antivirals or therapeutics that will then be able to target these mechanisms the virus use to cause disease, and hopefully prevent illness in people and animals.

Glen Paul: Well I’m sure we all have our fingers crossed for that. I appreciate you talking to us about it, Glenn, it’s very interesting work.

Dr. Marsh: That’s OK. Thanks for your time.

Glen Paul: Doctor Glenn Marsh. And to find out more about the research being undertaken at CSIRO, and to follow us on other social media, go to www.csiro.au.