Hendra Virus

by Rie

The furor surrounding human vaccinations seems to have died down in the US. Excellent timing to throw my hat in the ring. Fewer voices except for the most invested – what could go wrong, right?

It helps that I’m a vet student. And I’m at that stage where I am forming my opinions based on what I am taught, the facts I am presented and have seen, and the stories I hear. I’m not yet so completely certain of fact that anecdotes do not sway me but I am not so green that every sob story does. Also, animals become vaccinated just as humans do but, since the chunk of humans who care about humans is significantly larger than the humans who care about animals, the spitting, hissing vitriol is far easier to wade through.

I am also a writer (but that depends on your definition) and am aware of how words colour your sentences; I know when your truth becomes a half-truth in the face of objectivity and I’m relatively immune to it.

TL;DR for those who don’t know what’s going on: Hendra virus is deadly to people (50%) and horses (70%) but it’s really too rare to tell how bad it is statistically. The pro-vaccination camp believes that the vaccination is very important in controlling the disease. The anti-vaccination camp believes that the vaccination is more dangerous than the disease. The anti-vaccination camp also believes that Big Pharma and the veterinary proponents of vaccination are only out to make money off of the fear. MPs are getting dragged in because veterinarians are refusing to see horses that haven’t been vaccinated.

It’s really way too complicated for a succint TL;DR.

RTL;DR: If you have a horse, it’s either you vaccinate or you do. And you probably have strong feelings about it.

Everything I will cite here will be something you can click through to for free. I don’t have much vested interest in this issue. It’s just…an interest, really. I don’t even want to become an equine vet. But I am a vet student, as I have mentioned and I will become a vet.

And I’m not looking to even draw a conclusion. Have you read my blog? I wish I could draw conclusions but am the sort who would happily sit on the fence forever. There is no judge here, just a slightly interested member of the jury.

Also, this blog post is not meant to be your go-to for information. It’ll hardly be exhaustive. I will put links at the bottom to government websites. If you don’t trust the government…I’ve got nothing. I am not going to recommend Facebook pages as a source of information.

Man, so many disclaimers.

So, here we go. Let’s review.

I: Some Microbiology

This is what I know. Hendra virus is a Paramyxovirus. This means that it is an enveloped RNA virus. Being enveloped means that it’s fragile in the environment (counter-intuitive, I know). Being an RNA virus means that it’s more prone to mutation than DNA viruses which is irritating when you’re trying to vaccinate against them. Fortunately (or unfortunately, depending on the camp you’re in) they have glycoproteins on their bacterial envelopes. These glycoproteins are used in the formation of the controversial Hendra virus vaccine, Equivac. And by controversial I mean that when I Google Hendra virus vaccine, I get conflicting reports all on one page. And there’s the whole debate thing.

Hendra virus, as of today, can only be found in Australia. It was first recognised in 1994 and has since killed 4 out of the 7 people it’s infected. No big deal, right? Well…

II: Outbreak?

It’s considered endemic in Australia. The epidemiological definition: the disease is always around but occurrence is typically low. All this means is that, if you’re in Australia, your horse can theoretically get infected, although cases have only been seen in Queensland and New South Wales. It’s considered endemic, I think, because Hendra virus is carried by bats and the virus has been demonstrated in all species of flying foxes in Australia (and even Papua New Guinea – who knew?). Horses get the disease from exposure to anything contaminated with flying fox urine, faeces, birthing products, and spats (chewed up and spat out plant material). And, no, you cannot suggest we kill all the bats in Australia but that’s for another day.

Humans can’t get the virus from bats yet (thank goodness) and an infected human can’t spread it to another human, so there’s also that. But, fun fact, dogs, rabbits, and rats can apparently be infected. Go figure. There have been two dog deaths so far.

And horses? 53 cases and 95 deaths since 1994 as of now (I had to count this manually, darn it, so I may have missed one or two. I may update the figure when I find a very recent figure). That’s way more than 7 cases but there are so many horses in Australia. Is this a big deal?

III: Points of Contention

The first is this: only 7 people have ever been infected since 1994. In 1994, it was a horse owner assisting a vet necropsy and a horse trained and stable-hand force-feeding an infected horse. In 2004, it was a veterinarian performing a necropsy on an infected horse. In 2008, it was a veterinarian and nurse performing a nasal lavage (putting water up the nose and getting it back out – it’s diagnostic). In 2009, it was a veterinarian performing endoscopy on an infected horse.

Vets are way, way overrepresented in this small sample. You might not be surprised, then, that some veterinarians have quit equine practice because they’re worried. (I know the title of paper says ‘Unexpected Outcomes’ but is it really that unexpected?)

There are two things this aspect of the debate seems to point to:

  1. Hendra virus is less likely to affect members of the public anyway, so why the fear-mongering about children/loved ones/anyone except a vet getting infected?
  2. Vets should just use the appropriate protective personal equipment (PPE) if they don’t want to get infected

This seems legitimate. But I think this is where many members of the public confuse what risk means. When public health officials conduct a risk analysis, they’re not thinking, “Oh, how likely is it that these people will be infected?”, they’re asking, “How likely is it that these people will be infected? If they’re infected, how bad will it be?”

Death is a pretty bad outcome, so where high mortality rates are involved, the risk is bumped up regardless of how common the disease is. (If you’re interested, you can check out how the Australian government conducts import risk analysis. It’s quite similar.)

I do agree that horse owners can evoke their free will to decide on their personal acceptable level of protection. I think this is where vets and their clients butt heads the most (based on unofficial stalking of Facebook conversations). Clients seem to be able to empathise that their vets are uncomfortable but they cannot suggest anything but PPE.

They are right, though. PPE is important. From personal experience, we spent almost the entirety of our Veterinary Public Health lectures talking about PPE. We even spent an hour learning how to put it on properly and spent another hour in class devoted solely to PPE.

(PPE is cumbersome. I hated it. No one ever goes, “I’ll just go lounge around in my PPE now.” Also, PPE can fail. This is especially true with animals since they’re more likely to knock veterinarians around than humans are likely to knock their doctors around.)

I can’t speak for all equine veterinarians but I think they have a pretty risk averse stance. We, as students, have been informed of our rights to refuse to treat an animal we believe carries the risk of Hendra virus.

Perhaps it would be more accurate of the public, then, to accuse veterinarians of being cowardly? I mean, it’s not just their own death, veterinarians would be legally responsible for the welfare of those working for them. They’re also liable for the client’s safety.

In this, I’m probably biased to veterinarians. If I were in that situation, I don’t feel it would be unfair for me to put myself over a person’s horse. If the horse wasn’t valuable, why would I risk it? If the horse was very valuable, why would I risk it? There’s no one size fits all approach.

Then, there’s the issue of prevalence. Why vaccinate so often for a disease rarely seen? I found this most interesting because of its parallels in human medicine. Remember the Disneyland measles outbreak from early this year? It’s all about herd immunity (I like the diagram in this link).

What’s even more fascinating is that Hendra is an emerging disease. It hasn’t even made its rounds yet. We don’t know the full extent of what it can do. There are a lot of what-ifs that can be used to colour the conversation here: What if it ends up spreading from horse to horse (there’s already some evidence for this, although it hasn’t been replicated in experimental conditions)? What if mortality among children is higher? What if the virus ends up being used for bioterrorism?

It would be difficult to make the case to vaccinate with a problematic vaccine, though. So, let’s say we can all agree that vaccination is necessary even with a disease of low prevalence. What do we do about the reports that the vaccine can kill?

(Again, the parallels with human medicine is fascinating.)

The vaccination schedule is as such: One vaccination at day 0 and another between day 21-42. Afterwards, a booster every 6 months is required.

The talk of boosters only being required once yearly seems to be an issue among horse owners. (It’s still officially required once every six months now.) It appears that the idea emerged around the end of 2013 but the Australian Pesticides and Veterinary Medicines Authority (APVMA) has not approved it. I cannot adequately cite this, though. One article I found quotes Equine Veterinary Association president Dr. Nathan Anthony and the AVA’s FAQ brochure mentions it briefly.

And that’s problematic because people are worried that they’re over-vaccinating their horses. Of recent note is this article quoting a CSIRO scientist.

It would be correct to characterise the APVMA as risk averse, possibly explaining the slow change in vaccination policy. The window of 6 months the horse may or may not be susceptible is way too long. And the uncertainty for something with the consequence of death is unacceptable.

There’s such a berth of anecdotal evidence, though. The way the Facebook conversations are going, I thought everyone was having a problem. This part was tricky. Many appear to fault their veterinarians for not noticing the causality. The general sentiment appears to be, “My horse showed symptoms of x after the vaccination. My vet thought it was something else. My horse died. It was clearly the vaccination.” There’s also the spotlight on the cases that did go wrong.

APVMA’s take on it? The vaccination is largely safe. I believe them. Do I think you should believe them? Yes. Do I think the people on Facebook are liars? Nope. Because truth and lies all have to do with perception. Maybe veterinarians should take extra care to detect subclinical illness, so owners can be adequately informed. (Is that a legitimate statement?)

I do agree that a balance has to be struck between the risk of vaccinating and the risk of not vaccinating. That statement is such a cop-out, though. Does that mean yes or no? Seriously.

But it was APVMA’s figures that ultimately made me look at the unofficial reports askew. I lean, again, toward vaccination. (I must be such a typical veterinary student.)

What I don’t understand is if the vaccine reactions can be managed. I haven’t seen a heard a lot about that. (Something I shall have to look into further. A little beyond the scope of this increasingly lengthy blog spot.)

IV: Vets are Killing Our Horses

This is technically not a point of contention directly relevant to the vaccine but everything I’ve written above culminates to this.

Horse owners are demanding that vets be required to treat their horses regardless of their vaccination status. Vets are standing their ground. As I’ve mentioned, it is within their rights to refuse to treat.

The question is simply this: why? Wouldn’t vets be expected to be treated if they were sick? Why should their horses be allowed to suffer? Why should they be bullied into vaccinating? Clearly, vets are trying to make money here. They must be exploiting a loophole somewhere.

There is our stalemate. Something that cannot be quantified easily. Here’s what I couldn’t look up. I can’t tell who’s right here.

I agree that no animal should be allowed to suffer. But, then, I think to what I know. If the horse hasn’t been vaccinated and is in a known Hendra area and Hendra is on my differential list, I’d be scared. Hendra varies in presentation, how will I know unless the horse is tested?

If I were feeling particularly brave, I’d don the whole suit and treat the animal (which is what some vets do agree to do). If I weren’t, I’d try to refer the horse.

What if I can’t refer the horse?

That prospect scares me. What if I forget to put Hendra on my list and I show up and it is Hendra? Well, yeah, I’ll be wearing PPE but what if I encounter a failure? What if I’m careless because I didn’t think it was Hendra?

I can imagine a bunch of horse people showing up and telling me I’m incompetent. That I shouldn’t be an equine vet.

And, so.

V: Conclusion

I won’t be an equine vet.

How anticlimactic.

If you were expecting a dramatic conclusion with sweeping statements and black and white boxes, you’ve got the wrong blog.

Here are the facts:

  1. Hendra virus exists. And it can kill.
  2. There is fear among veterinarians. Whether you think this is warranted or not can be discussed for…ever because it depends largely on the individual.
  3. Further to point 1, veterinarians are liable for the safety of their staff and their clients.
  4. The vaccine can be a financial burden.
  5. The vaccine still appears to be largely safe despite anecdotal evidence.

The stalemate exists because parties on both ends feel backed into a corner. It’s easy to empathise with the horse owner whose horse died because the vet wouldn’t show up. It’s also easy to empathise with the vet who can’t justify showing up for the safety of himself and the people around him.

It feels as if the conversation can be distilled to this:

Client: More horses are dying because you aren’t showing up.

Vet: I’m not showing up because you’re not vaccinating. Why aren’t you vaccinating?

Client: Because my horse might die if I vaccinate. I’m not paying money for my horse to die.

Vet: What would you do if I died?

Client: Put on PPE. You won’t be exposed, then.

Vet: But what would you do if I was exposed and infected? It’s not as if everything is predictable once I put on PPE.

Client: It’s not like everything is predictable once I vaccinate.

Vet: So, what would you do if I died?

Client: What would you do if my horse died?

There has to be a way to more effectively manage risk, then. Something more effective than vaccination.

What’s that alternative?

Holy moly, writing that took longer than I thought.

I was hoping to address how I feel personally about vaccination in general. Doing that, however, seems to compromise the analysis of this situation (which is still developing! How exciting.)

Disclaimers. Disclaimers everywhere. I’ll come back and revise for typos. This was written very quickly by most standards. (Some people spend ages writing things like this. Much respect. I thought it would be easier.)