In a rather impressive effort - considering the issues inherent with working with a virus like Hendra virus, the nature of the disease and the low economic value of a vaccine that would only be used in a very restricted geographic area - a Hendra virus vaccine has been released for horses. Equivac HeV should provide a degree of relief to people in Queensland and neighbouring areas who have been battling this uncommon but devastating bat-borne viral infection.
As a virus that comes from wildlife, Hendra virus is tough to contain. Eradicating the virus in the bat population isn't really feasible, and while measures can be taken to reduce exposure, the risk cannot be eliminated in areas where the virus is present. So, finding a way to reduce the risk of a horse developing the disease after exposure is critical, and the logical approach is vaccination.
Vaccination of horses can also play a huge role in protecting people. All human Hendra virus infections (approximately 50% of which are fatal) have come from direct contact with infected horses, so reducing disease in horses should reduce the risk in humans.
As with most vaccines, it's safe to assume this one isn't 100% effective. It therefore may be a great tool, but people can't then ignore all other Hendra avoidance practices. Individuals still need to take precautions when working around horses that might be infected, regardless of their vaccination status. So, while it's important to avoid complacency, this vaccine should provide a degree of comfort to people who have been living with this virus hanging over their heads (both figuratively and literally, as bats fly around) in recent years.
While I guess it's getting beyond the point where Hendra virus infections in horses in Queensland, Australia are considered "news," it's still a highly concerning situation. Infections caused by this fruit bat-associated virus continue to occur in the region and there's no sign that this problem is going to go away any time soon.
In the latest report, two horses from a farm where a horse recently died of Hendra tested positive for the virus. In another location, a dog is being re-tested after a weak positive test. This situation brings back memories of the debate that occurred last year after a healthy dog that tested positive was euthanized as a precautionary measure, despite no information about whether the dog could actually be a source of infection.
Hendra is resulting in profound changes in the horse industry in Queensland. Beyond being a major problem in horses, this virus can be passed from horses to people, resulting is tremendous concerns amongst horse owners and veterinarians. Many veterinarians are refusing to work with horses because of the risk and I assume that some people are selling horses for similar reasons.
Infection control practices can presumably reduce the risk of transmission of Hendra virus between horses and from horses to people, but there's no way to completely eliminate the risk. Fruit bat control strategies get discussed, ranging from removal of fruit trees from horse pasture to reduce fruit bat exposure (logical) to fruit bat culls (highly unlikely to have any longterm effect). At a minimum areas under fruit trees should be fenced off from horses, and it has also been recommended to keep water troughs covered to prevent contamination with excrement from the flying foxes. Ultimately, everyone's holding out for an effective vaccine, which has yet to appear, but work on the vaccine is well underway and the hope is that a commercial vaccine could be released as early as next year.
Bob Katter, an Australian Member of Parliament and leader of the Australian Party, has proposed culling flying foxes (fruit bats) as a way to control Hendra virus, which is spread by these large Australian bats. He's not the first person to make such a proposal, but it's a knee-jerk reaction that in reality doesn't make a lot of sense.
It's not completely clear whether Mr. Katter is proposing a plan to completely eradicate the flying foxes altogether, or to simply let people kill any such bats they find on their property, but neither approach is likely to be effective in terms of decreasing the risk of Hendra virus transmission.
If people kill flying foxes on their property, they'll just be replaced in short order by bats from neighbouring areas.
Trying to eradicate the entire species is a bad idea for a variety of reasons:
- Tinkering with a complex ecosystem doesn't often turn out the way you want it to. Australians certainly know from past experiences that bad things can happen when new species are introduced (rabbits are just one example). The same might happen when a species is removed.
- Eradication of the species is probably impossible or at least very difficult. I don't know much about the reproductive rate of flying foxes, but if the species can reproduce at a reasonable rate, they can probably replace the culled animals unless people are really aggressive and seek out all remote breeding sites. The limitations of culling have been clearly shown in rabies control, where it doesn't do much because culled dogs are quickly replaced by new dogs.
- Eradicating flying foxes would be very expensive. What could that money do if put into research on vaccination, treatment, and other worthwhile ventures? What if efforts were focused on eliminating flying fox roosting sites in horse pastures? Overall, the impact would probably be much greater.
Why stop with flying foxes? Australia has lots of nasty critters, ranging from spiders to saltwater crocodiles. Should we kill all of those too? Dog bites kill more people than Hendra every year. Should we kill all dogs?
Hendra virus is not something to ignore. While infections in horses are rare, they are usually fatal and there's the risk of transmission to people. Human infections are very rare but often fatal. So, ways to reduce infection of horses as a means of reducing both human and horse disease are important, but the slaughter of flying foxes doesn't make a lot of sense.
While you don't want to read too much into a single case, 2012 has started off in a bad way for Queensland horses. Hendra virus was identified in a Townsville area horses that died. This zoonotic viral disease is largely restricted to Queensland, Australia, but it has a high fatality rate in horses (and people). Hendra virus is spread by fruit bats and is an ever-present concern to Queensland horse owners and veterinarians, but a mid-summer infection is quite unusual (remember that it's currently mid-summer in Australia). Most cases tend to occur from July to September - this case is a reminder that seasonal trends are just that: trends, not absolute rules.
Fortunately, the attending veterinarian used proper precautions when handling the horse to limit the risk of zoonotic transmission of Hendra virus. However, there will presumably be an investigation to determine who had contact with the horse and their potential for exposure. There is currently no way to prevent or specifically treat Hendra virus infection. An experimental antiviral treatment has been tried in the past, but it's effectiveness if far from clear.
Last year was quite bad in terms of the number of Hendra cases that were detected in Australia. Let's hope this early 2012 case isn't a sign of things to come.
Dusty, the dog who tested positive for Hendra virus exposure on a Queensland farm, has been euthanized. The owners confirmed through their Member of Parliament that their pet had been euthanized voluntarily, rather than waiting for Biosecurity Queensland to compel them to do so.
Based on publicly available information, this seems like an illogical and unnecessary response, as well as an unethical approach by the government because it did not explain the implications of a positive result when they ask for voluntary testing of the dog.
The family said Dusty was euthanized because "most recent blood tests confirmed that he carried Hendra virus antibodies, which meant he was able to shed the virus to other animals." However, that's false. If government officials told them that, that's incredibly frustrating, disappointing and concerning. Antibodies have nothing to do with being infectious. I carry antibodies in my blood to a wide range of viral diseases that I've had over the course of my life. That doesn't mean that I still have the viruses in m. The presence of antibodies simply means the body has been exposed and mounted an immune response.
All information that I've seen so far indicates that there's no evidence that the dog was shedding virus and therefore no evidence that it posed a potential infectious risk. Furthermore, an experimental study from 1994 showed that infected dogs did not shed the virus. So, unless there are new data that aren't being released, euthanasia is a completely unnecessary and illogical response, probably based more on fear of liability than any evidence or reasonable assessment of risk. It would have been better to quarantine and monitor the dog, to prevent unnecessary euthanasia and to learn more about this virus in dogs.
If evidence indicating a true risk of transmission of Hendra virus from pets exists, this information needs to be released so that other pet owners in Queensland know what the situation is. If not, more common sense needs to be used when dealing with this disease in such animals.
This Worms & Germs blog entry was originally posted on equIDblog on 01-Aug-11.
Neil Fearon and his family have lost three horses to Hendra virus, and are concerned about one other. They are now dealing with the implications of their dog, a Kelpie named Dusty, having tested positive for Hendra virus antibodies in its blood. As I mentioned in yesterday's post, the presence of antibodies in the blood of this dog, detected during voluntary testing as part of the outbreak response, only indicates that the dog was exposed to the virus. Viral shedding was not identified, suggesting that the exposure was a prior event and that an active infection was not present. Despite this, government authorities are requiring that the Hendra antibody-positive dog be euthanized.
Poor communication and mixed messages are often the cause of problems during outbreak management, and this seems to be the case here. Based on the news reports, there are some pretty concerning issues.
Testing of the dog was voluntary and the owner was not notified that euthanasia would be required if the dog tested positive.
- This is rather unethical. People need to understand the implications of outbreak control measures. It's not fair to have such an aggressive response to a voluntary test without proper notification.
Mixed messages are being given about the risk the dog poses to the family.
- Authorities want to euthanize the dog, indicating they must believe there is some risk. However, the owner is very concerned about his 11-year-old son who has slept with the dog in his bed for the last few weeks. Yet, ABC news indicates authorities reassured Mr. Fearon that the risks are minimal. If the risks are minimal from that type of prolonged, close contact during the period when the dog may have been actively infected, it's hard to justify euthanasia after the fact on the basis of the dog posing a risk to people or animals (especially when the virus is endemic in the bat population in the area).
- Why euthanasia is being required seems to be unclear. While fear of Hendra virus shedding makes the most sense, Queensland's chief vet has stated that the dog will be euthanized as a precaution because "As a result of that infection, it may make it aggressive." It seems rather strange to euthanize a dog because of concern that an infection (which may not be active) might cause aggression, with no evidence that disease will occur or that it can cause aggression in dogs. Quarantine and observation would make more sense. There are a lot more dogs that are prone to aggression wandering around Australia.
This type of action drives things underground.
- When overly-aggressive actions are used, and people either don't agree with them or don't understand them, faith in the system decreases. What's the likelihood that people are going to allow their pets to be tested now? I assume it's a lot lower now that they've seen what will happen. So, the ability to determine exposure of other species and the potential risks from other species will be impacted.
Hendra virus is not something with which to play around. It's a very serious disease and one must err on the side of caution. How far you err on the side of caution is the question, and it's a hard thing to determine. It's easy to be very strict when setting rules, and fear of liability or fear of making a subjective decision often override logical thought and discussion.
As a somewhat informed outsider, I have a hard time supporting mandatory euthanasia for a dog that has evidence of previous infection but no evidence of active viral shedding. Yes, no test for virus shedding is 100%, but a pretty high level of assurance can be obtained and the dog can be quarantined for further testing. There's no indication from laboratory studies that I know of that dogs (or other non-bat species) can become longterm carriers of the virus. The owners should be involved in the decision making process and be given enough information to understand the implications of keeping the dog, the risks that might be present, and what they can do to reduce the risks. Government authorities need to clearly state their concerns and the evidence supporting them. With that, it's easier to make a logical plan that protects the public but is also appropriate for the animal and its owners. If the risk is deemed to be real and/or the owners are not willing to accept some degree of risk, then euthanasia is reasonable.
"Kill the dog" is an easy knee-jerk response. I simply don't see the evidence supporting it. Is it possible that authorities have a true reason to be concerned? Sure, but if so, that indicates another communication problem. If there is really evidence that this dog is a concern, this needs to be clearly communicated so people understand what's happening and why such drastic actions are being taken.
This Worms & Germs blog entry was originally posted on equIDblog on 27-Jul-11.
Adding a new twist to the already very concerning situation in Australia, Hendra virus infection has now also been identified in a dog. It's been a bad year for Hendra virus in Australia, with larger numbers of cases of this highly fatal disease in horses in a geographic range that seems to be expanding. Spread by flying foxes (fruit bats), Hendra virus predominantly infects horses, but can be transmitted to people working with infectedhorses.
The Australian Animal Health Laboratory in Geelong has now announced diagnosis of Hendra virus infection in a dog. The dog is from a quarantined farm in Queensland where the virus has been identified in a horse. The dog was healthy and was tested as part of a standard policy to test dogs and cats on infected farms. It's great to see this approach being used, since it helps identify other potential sources proactively - something that is often overlooked in outbreak investigations that focus only on the main species that are already known to be involved.
In this case, the dog had antibodies against the virus in its blood. That means that it was exposed to the virus and mounted an immune response. It doesn't indicate whether it was exposed recently or in the past. Two tests for the virus itself were negative, suggesting that the dog's immune system eliminated the virus (or that the virus isn't really capable of surviving for long in a dog). This is a good news/bad news scenario.
- Dogs can be infected. It increases the range of known susceptible species.
- If dogs can be infected and shed live virus, then they could be a source of infection for other individuals, including people.
- The dog wasn't sick. This might sound like strange "bad news," but healthy carriers of infectious diseases are harder to spot and control than ones that are sick.
- The dog wasn't shedding the virus. That's critical since if dogs can be infected but not infectious (i.e. if they can carry the virus but not transmit it), then they are of limited concern.
- They have been testing farm dogs and cats as a routine measure, and this was the first positive. Infection of pets therefore must be relatively uncommon even on farms where the virus is active.
- The dog wasn't sick. While it's only one case and doesn't guarantee dogs won't be affected clinically, this might suggest that dogs just occasionally get exposed with no disease. Since it's highly fatal in other species, that's a good thing.
What should be done based on this?
- Probably not much more than should have been done before this finding, but it's a good reminder about the potential involvement of other species.
- Dogs and cats should be kept away from fruit bat roosting sites.
- Dogs and cats should be kept away from infected horses.
- If a farm is quarantined because of Hendra virus, dogs and cats should be tested and quarantined. Quarantining the animal while testing is underway helps reduce the risk of an infectious dog or cat (should that occur) transmiting the virus to people on the farm, or wandering away and exposing other people or animals.
- Animals of any type in areas where Hendra virus is active that get sick with signs that could possibly be consistent with Hendra virus infection should be tested.
This should also be taken as yet another reminder that infectious diseases are unpredictable. Considering the potential involvement of different species in a proactive manner as was done here is critical.
Image: Bay Horse and White Dog by George Stubbs (1724-1806)
This Worms & Germs blog entry was originally posted on equIDblog on 26-Jul-11.
As Australia faces a particularly bad year for Hendra virus, with possible expansion of the range of this serious disease, there have been calls for a mass cull of flying foxes (fruit bats). These bats are the reservoir of the virus but also a protected species. The virus lives in the bats and is spread mainly through their urine. Horses that are exposed to bat urine or feces (e.g. grazing under a tree where bats are roosting) can become infected and then serve as a source of human infection. Being a highly fatal disease for which there is no available vaccine, looking at ways to reduce exposure to the virus is critical. When you have a wildlife-associated disease, questions about trying to eliminate the wildlife source often arise. Any discussion of culling wildlife leads to intense debate, and this situation is no different. Some people support culling bats in areas around people and horses, while others are opposed on various grounds, including a lack of evidence that it will be effective.
Can fruit bat numbers really be decreased? A lot of bats would have to be killed to have a significant impact on the population. Bats can reproduce quickly and migrate readily, therefore a single cull may have only a limited and short-term effect. A good understanding of the dynamics of the bat population is required to determine how many would need to be killed in a given area to have any significant impact. As Biosecurity Queensland's chief veterinarian RIck Symons stated "Culling is against government policy. I believe in terms of biosecurity it's counterproductive, because it does stress flying foxes and they're more likely to excrete (the virus). It could be filled by another bat colony the next day and if you're moving them on, you're moving it on to somebody else and it's somebody else's problem, so that is not the solution."
Will a cull actually achieve anything? Even if effective at reducing bat numbers (probably just in the short term), culls don't necessarily have an impact on disease rates. All bats would not be eliminated, and it's unclear whether there is a critical mass of bats that is required to transmit infection or whether a small number of bats distributed across the same region would be as likely to result in infections. Small or temporary decreases in bat numbers may have no effect.
What unintended consequences might occur if a cull is effective at reducing bat numbers? Removing an animal from any ecosystem has an effect, and it's important to be confident that that effect isn't accompanied by problems of its own. I don't know enough about fruit bat ecology to say much here, but if this species is greatly reduced, are there other species that will come and occupy that ecological niche, and might they be associated with problems of their own? Careful scientific study can help to figure this out in theory, but you can never be certain.
Are other control measures, such as removing roosting sites from pastures and other bat avoidance measures, being adequately used? Culls should only be considered when other measures have failed, but it can be difficult to ensure or enforce compliance with these other measures. Certainly, people in endemic areas should remove trees in which bats roost from pastures. However, not all Hendra cases are associated with identifiable roosting sites. For example, one affected Queensland farm does not have any fruit bats residing on the property, but it lies along a common flight path for the bats.
It's easy to talk about avoiding a cull when you're not in the heart of the Hendra epidemic, and I understand the reasoning behind the calls for a cull. Hendra is a devastating disease that's a threat to both horse and human health, and it's unpredictable - and that's scarey for a lot of folks. People that have been exposed face an incredibly stressful period while they wait and see if they've been infected with a virus that kills in ~50% of cases. A vaccine is probably still a couple of years away, leaving a period of continued risk and stress. With such a serious disease, considering culling is reasonable. However, it can't be a knee-jerk reaction to public outcry. It needs to be based on sound science to ensure that if it's used, it will be effective. The impact on this protected species also can't be ignored.
This Worms & Germs blog entry was originally posted on equIDblog on 19-Jul-11.
The latest edition of the journal Emerging Infectious Diseases contains a paper describing the 2008 Australian Hendra virus outbreak in horses and people.
In this outbreak, there were five horses infected and two humans infected. The horses predominantly had signs of neurological disease, not respiratory disease like some other reports describing this disease. Four horses died. One recovered but was euthanized for public health reasons.
Two people became infected after working with the sick horses, which represents 10% of the total veterinary staff that were exposed to the infected horses. Both people started off with influenza-like illness, which seemed to improve initially, but then signs of severe neurological disease developed. They were treated with ribavirin, an antiviral drug, as part of an experimental treatment. One of them died after 40 days of illness, the other person survived.
The authors stressed that the effectiveness of ribavirin could not be determined, but they recommend it nonetheless because of the severity of Hendra virus infection and lack of other options. Ribavirin was also used in the 2009 outbreak, but it is clearly not 100% effective since one person died there also.
A number of concerning activities occurred that put people at risk of infection, including a "percutaneous blood exposure while euthanizing an infected horses" (they didn't explain exactly what this was, but it could have been a needlestick), low use of personal protective equipment, and contact with potentially infectious body fluids. This is unfortunately not surprising since the approach to infection control (particularly in terms of zoonotic infections) is often lax in equine medicine. That certainly has to change, particularly in areas where Hendra virus may be present.
Much more information about how to control this potentially devastating virus is needed. Fortunately, infections are uncommon and it is restricted to a fairly small geographic range in Queensland, Australia.
Image source: http://animalphotos.info/
This Worms & Germs blog entry was originally posted on equIDblog on 27-Jan-10.
A proposed levy on horse owners to fund Hendra virus research has been met with opposition in Queensland. It has been suggested that a $25/horse levy in Queensland would provide needed funding for research into this rare but deadly disease, but this has been opposed by some vets and horse owners. One comment in response to the suggestion of a Hendra virus research levy is that the disease kills humans, so it should be publicly funded. However, Hendra only affects humans who have very close contact with horses, so that's a questionable argument. Also, medical research funding is certainly not overflowing, and the odds of a study such as this getting funded this way may be limited because it is so horse-oriented. I run into the same problem all the time with zoonotic disease research grants. Medical agencies don't want to fund it because it's too animal related, while animal agencies don't want to fund it because it deals more with human health.
Who should fund equine research? Should the government (i.e. all taxpayers) be solely responsible, or should some of the responsibility fall on horse owners, who stand to benefit the most from equine research? This is particularly true for a disease like Hendra that is very rare, currently restricted to one region, and only affects horses and people associated with horses. The rarity of the disease means that industry (e.g. vaccine companies) is probably not eager to fund research (because it would not be profitable). The focal nature of the problem geographically may limit interest from national or international groups. These factors could result in failure to do the necessary research to try to control this deadly disease.
This raises broader questions about funding for equine research. Many people and governments make lots of money from horses, directly or indirectly. You'd like to think that since so much money is made off the backs of horses (both figuratively and in some cases literally), that some of the profits would be put back into helping ensure the health and welfare of these animals. A fraction of a percent of the money generated by horses would be a tremendous asset for equine research, and help make great strides in improving the health and welfare of horses. Unfortunately, such funding is rarely available, and equine researchers are often very limited in terms of the research that can be done with the available dollars. As a researcher, I know the difficulties of finding enough research funding to pay laboratory personnel and grad students, plus perform high quality research. The limited funding that is available is one reason that equine research is now only a fraction of my overall research program. The equine industry as a whole needs to think about its role in research, even if it's from a self-serving standpoint whereby research is funded to help boost performance and profits.
This Worms & Germs blog entry was originally posted on equIDblog on 14-Oct-09.
In the wake of the death of Dr. Alister Rodgers from Hendra virus, there have been increasing calls for the Australian government to put significant resources into Hendra virus research. Various areas need to be investigated, including how this virus is maintained in the bat population, how it is transmitted from bats to horses, ways to treat infection and ways to prevent infection. Vaccination is an obvious topic, and creation of a vaccine appears to be possible. However, as I wrote the other day, there's a question about whether a company would put millions of dollars into development of a Hendra virus vaccine for people, given that the disease is very rare, is currently limited to one region, and only appears to be a risk for people in close contact with sick horses.
One thing that needs to be considered is whether it may be better to develop a vaccine for horses rather than people. Think about it:
- All reported human Hendra virus infections have come from people in close contact with sick horses.
- Human vaccines are very expensive to develop, test, get approved and market.
- Vaccines for animals are much cheaper to make because testing and regulatory requirements are not as strict. (This can lead to marketing of vaccines for animals with limited evidence of effectiveness, but the upside is that vaccines can get to market quicker and with less expense.)
- People are often more willing to get their horses vaccinated than to get vaccinated themselves.
So, even though it might sound strange, development of a Hendra virus vaccine for horses may be a more effective way to protect people.
If this approach is taken, a key step would be continued research into the epidemiology of Hendra virus infection to investigate other routes of human exposure. If people can get infected by other routes, vaccination of horses obviously wouldn't address the entire problem. However, based on what we know currently, vaccination of horses might be the most effective, timely and economic response to this pressing problem.
This Worms & Germs blog entry was originally posted on equIDblog on 04-Sep-09.
Unfortunately, Dr. Alister Rodgers, who had been hospitalized with Hendra virus infection acquired from a sick horse, died yesterday in a hospital in Brisbane, Australia. He was infected last month while treating an infected horse on a farm that was subsequently identified as having multiple horses infected with the virus. Despite experimental ribavirin treatment, he developed the infection three weeks later. He is the second veterinarian from Queensland to die from Hendra virus infection in a little over a year. Four of the seven people known to have been infected by this virus since it first emerged in 1994 have died.
A veterinarian, one of four people in Australia that were under close observation due to exposure to a horse with Hendra virus infection, has developed signs of infection. Dr. Alister Rodgers is now in hospital in critical condition. He had close contact with a sick infected horse three weeks ago - Hendra virus was not considered initially, it was thought that the dying horse had been bitten by a venomous snake. Dr. Rogers didn't wear gloves or a mask when examining the horse because he had left them in his car.
Dr. Rodgers received experimental treatment for five days to try to prevent or reduce the severity of infection. He had returned home from hospital following the treatment only one day before he became ill. It has now been confirmed that he is infected. Only six people have been previously diagnosed with this rare disease; three have died. There were hopes that all of the exposed individuals would escape unscathed given initial tests showing no sign of infection and the experimental therapy, but it's clear now that early detection of infection is not easy.
Image: Coloured electron micrograph of Hendra virus (source: www.csiro.au/science/Hendra-Virus.html)
This Worms & Germs blog entry was originally posted on equIDblog on 21-Aug-09.
Four people exposed to horses infected with Hendra virus in Australia are taking an experimental drug to try to prevent or reduce the severity of infection. All are currently healthy, but it is unknown whether the virus is incubating in them and whether disease may develop. People can be infected with this virus through close contact with infected horses, as was the case with these four individuals. While human infections are rare, 50% of infected people die. Therefore, it's understandable that they would choose to try an experimental treatment.
These people will be treated for five days with intravenous ribavirin, an antiviral drug. There is evidence that ribavirin can kill Hendra virus in the laboratory, but it's not known if it actually does anything in infected people. It has some potential adverse effects, but given the severity of disease and high risk that these people have been exposed, it's certainly a reasonable decision. This treatment was also used in the Hendra virus outbreak in 2008. One person died, one survived after a long stay in ICU, and one did not get sick. It's not known whether the drug did anything to help. The death of the treated person doesn't necessarily mean the treatment is not useful for some people or for certain stages of infection. Hopefully, ribavirin has a better chance of working when infection is only developing, before these people get sick.
This Worms & Germs blog entry was originally posted on equIDblog on 13-Aug-09.
Hendra virus, a virus that can kill horses and people, has resurfaced in Queensland, Australia. This bat-borne disease has caused periodic fatalities in horses and people that work with horses. The latest outbreak is thought to have killed up to three horses and resulted in the potential exposure of at least 30 people. The likelihood of these people getting sick depends on how close their contact was with the sick horses. Close contact with secretions from infected horses seems to be required to transmit disease. One person reported being snorted on by an infected, dying horse and being "covered" in blood, which is certainly concerning. An outbreak last year killed a veterinarian and hospitalized a veterinary nurse.
The farm in question is under quarantine and people that have been exposed are being monitored. There is no treatment for potentially exposed individuals, so they are in the unenviable position of having to wait and see if they get sick.
A virus like this is very hard to control. It's lives in fruit bats and only occasionally crosses into horses. The sporadic nature of disease makes it hard to control and predict when cases will occur. The key is early identification so that there is minimal exposure to other horses and people. People also need to take routine infection control precautions. One veterinarian handled an infected horse without using gloves or a face mask, as recommended, because he had left them in the car. Exposure to a potentially fatal infectious disease is not worth the few minutes of time saved by not following recommended precautions.
This Worms & Germs blog entry was originally posted on equIDblog on 10-Aug-09.
A small outbreak of the potentially deadly Hendra virus was identified in a group of horses near Brisbane, Australia. This virus has caused periodic cases of illness and death in horses, and can be transmitted to people working closely with infected horses. In the latest outbreak, 3 horses have died, making this the worst outbreak since 1994 when 14 horses and 2 people died. Now, a human case has been identified. This person works at a veterinary clinic that treated infected horses. This individual was admitted to hospital overnight but was discharged, so is presumably not very ill.
While Hendra virus (genus Henipavirus) is only found in Australia, it is a good reminder for everyone about the strange nature of some infectious diseases. The natural reservoir of the virus is the fruit bat. It is believed that horses become exposed when infected fruit bats give birth and contaminate horse pastures with uterine fluids. Horses develop respiratory disease ranging from mild to fatal. Human cases have been reported in people working closely with infected horses. A horse trainer and veterinarian's assistant died in the 1994 outbreak. Close contact is required for transmission to people.
Picture: Locations of previous Henipavirus outbreaks (red stars – Hendra virus; blue stars – Nipah virus) and distribution of Henipavirus flying fox reservoirs (red shading – Hendra virus; blue shading – Nipah virus)
It's very difficult to take specific measures to protect horses, people or other animals from sporadic, rare diseases such as Hendravirus infection. However, common sense infection control measures can reduce the risks associated with any animal contact.
- Wash your hands after contact with any animal.
- Avoid contact with sick animals - consider sick animals to be potentially infectious until proven otherwise.
- Remember that new animal diseases are regularly being identified, and that they might be able to infect people.
- People that work in veterinary clinics must be diligent and use good infection control practices because they are at higher risk of exposure to various diseases.