It's hard to think about mosquito-borne disease season here at the moment, with temperature's still going down to freezing, but the highly concerning Eastern equine encephalitis (EEE) has been identified in a Marion County, Florida horse. This mosquito borne viral disease is highly fatal to both humans and horses. (People don't get it from horses. Rather, they get exposed the same way horses do, a bite from an infected mosquito).
Mosquito borne diseases are quite variable geographically, both in terms of where and when they occur. EEE is fortunately very rare around here, but it's a bigger concern in some other areas, particularly the southeastern US and US seaboard.
We won't likely see mosquito borne diseases like EEE and West Nile virus infection around here for a few months, but in other areas, the risk period has already begun. Knowing what diseases occur in your area, what diseases occur in areas you might take (or send) your horse to and when those diseases occur is important. That's one of the reasons we recently launched WormsAndGermsMap. The location of this case can be found there.
Spring’s slow arrival has brought many things. Disappearing snow, a hint of green in the grass... and a greater risk of disease outbreaks in horses. Outbreaks can occur at any time of year but we often start to see certain infectious diseases ramp up as horses start moving around more at the start of training, racing and showing seasons.
A tentative diagnosis equine herpesvirus I (EHV-1) neurological disease in a horse has resulted in a precautionary quarantine of a barn at Aqueduct racetrack in New York. This virus is a concern because of the potential for serious disease (e.g. the affected horse died) and the potential for large outbreaks. However, concern needs to be tempered by awareness that this virus is widespread in the horse population and that single, sporadic infections are more common than outbreaks.
At Aqueduct, horses in the barn in which the affected horse was housed are not permitted to race, and may only train after the general horse population is off the track. Rectal temperatures of horses from that barn are being checked twice a day to help detect any new cases as soon as possible. Usually, this type of outbreak response goes on for 21-28 days after the last identified case, but the planned time frame hasn’t been stated here.
Too often, we see one of two things happen when EHV-1 is identified. Traditionally, little was done in the hope that nothing bad would happen. More recently, the pendulum has swung the other direction and people often completely freak out over it, panicking and implementing measures that are over the top.
Like most things, a happy medium is needed, with enough attention (and common sense practices) to reduce the risk of further cases, while no causing undue hardship to those affected. It’s not always an easy balance to find. As someone who is frequently involved in these situations, it’s tough to figure out where to draw that line, especially when you have multiple different agendas, perceptions and degrees of risk tolerance. Taking a draconian approach (lock all the horses in the barn until further notice) is the easy way out, but it rarely makes sense. Being more balanced and less restrictive creates some risk for people making those decisions (because if something bad happens, they’re probably going to be blamed) but the easy-way-out is rarely the best-way-out.
The response at Aqueduct seems to be well balanced.
- They’ve identified a potential problem.
- They’re trying to determine if there are more cases (although I’d take temperatures of all horses on the track, not just that barn. You need to know if it’s escaped from the index barn.)
- They’re communicating.
- They are taking reasonable measures with the highest risk group (horses from the affected barn).
- They’re not taking the easy, knee-jerk response of totally restricting horses in that barn, rather they are using common sense practices to limit the risk of further exposure should any other horses in the barn be affected.
Most often, these incidents end up being single cases. However, by the time you realize something is going on, it’s possible that multiple horses have already been infected and are getting ready to become sick and/or be able to transmit the virus further. A short period of relatively aggressive but reasonable precautions is usually the key in outbreak management, and hopefully nothing more will come from this.
The location of this outbreak can be seen on the Worms & Germs Map at http://www.wormsandgermsmap.com
Most of the time, when we talk about the parasite Dirofilaria in animals, we’re talking about Dirofilaria immitis - a.k.a. heartworm. However, it’s not the only member of this parasite family that is found in dogs and cats. Another one, Dirofilaria repens, is present in pets in many regions, and it can also spread to people via mosquitoes.
A recent report from Belarus, highlighted in ProMed-Mail, describes 21 cases of dirofilariasis caused by D. repens. Interestingly, this is a relatively new finding for the area, as the disease was not reported in Belarus before the mid-1990s.
This parasite naturally infects dogs, cats, and a variety of wild carnivores like wild canids (e.g. wolves, coyotes, foxes). Mature worms live in tissues under the skin of a suitable host, where they produce larvae (microfilaria). These larvae enter the bloodstream and can then be taken up by mosquitoes that bite the host. If a mosquito feeds on an infected animal and then a person, it’s possible to transfer the larvae to the person. People aren’t natural hosts, and the parasite almost never develops into its adult state. However, as the parasite undertakes its futile migration through a person’s tissues, trying to find a place to mature, the body mounts an immune response. This results in local inflammation, typically causing the development of little tissue nodules. Very rarely, more serious infections can occur, in which case surgical excision of the nodule, with or without antiparasitic drugs, is the typical treatment.
Heartworm prevention practices should also prevent establishment of D. repens infections in dogs. Control of the parasite in the dog population is an important control measure in areas where it exists, but if the parasite is also present at high levels in wild animals, that complicates things. Basic mosquito control and avoidance measures also make sense.
Image source: http://www.cdc.gov/dpdx/dirofilariasis/index.html
A recent rabies death in a Russian man highlights multiple screw-ups that led to the man’s death.
A 50-year-old man in Smolino Kovvrosko, Russia was bitten by his cat at the end of February.
- Problem #1. The cat was presumably not vaccinated against rabies. Vaccination is not 100% protective but it’s pretty likely this was an unvaccinated animal. If the cat was vaccinated, the chance of it having rabies would have been very low.
The man went to the local "medical assistant," but rabies prophylaxis was not given.
- Problem #2. Here was the opportunity to initiate the discussion about rabies. This would involve querying the health status of the animal and quarantining it for 10 days to see if it developed signs of rabies (which would indicate the need for post-exposure treatment). These things weren't done.
A few days later, the cat started acting strangely. A local vet euthanized the cat. Rabies was not discussed.
- Problem #3. Malpractice. Plain and simple. A cat with neurological disease needs to be considered a rabies suspect. Bite history must be queried before euthanizing an animal. If rabies testing had been performed or if rabies had been mentioned as a possibility, the man might have been treated.
At multiple time points, there were chances to identify the potential for rabies, but multiple people screwed up and the man died as a result. Rabies is virtually 100% preventable with proper post-exposure treatment, but virtually 100% fatal by the time someone develops disease.
Clinical guidelines are fairly new (and limited) in veterinary medicine, although they’re widespread in human medicine. Following up on recent guidelines for diagnosis of treatment of urinary tract infections in dogs and cats, a working group from the International Society for Companion Animal Infectious Diseases (ISCAID) has completed guidelines for the treatment of a common type of skin infection in dogs, superficial folliculitis (pyoderma).
No, not what I write (although I certainly get enough emails suggesting otherwise... and I'm sure another round of interesting emails is going to be coming at my way shortly).
In the past, and even sometimes still today, public health has had to deal with the phenomenon of having "chickenpox parties." These are events held by well-intentioned but grossly-uninformed parents who deliberately expose their kids to a child with chickenpox in order to "get it over with." Yes, the children will get chickenpox and yes, the children will become nicely immune to the disease thereafter. Most of the time, it’s not really a problem, but then there are the times when a child develops serious (and potentially fatal) complications from chickenpox. Or when one child picks up chickenpox and spreads it to a high-risk child who then develops complications. It went so far at one time that at least one person was selling lollipops laced with chickenpox over the internet (until it was pointed out that this was essentially a bioterrorism activity).
We now have the analogue being recommended in dogs. The basic idea is to take young puppies to an area where distemper virus or parvovirus is likely present, so the puppy will be exposed and vaccination won’t be required.
Sure, it might work.
- The puppy might get exposed to enough virus to develop an immune response but not cause disease.
- Or the puppy might get sick and require expensive veterinary care.
- Or the puppy might get sick and die.
- Or the puppy might do any one of the three above and also spread the virus to other susceptible dogs, whose owners didn’t make the conscious - and dumb - choice to purposefully expose their dogs to these potentially fatal viruses.
Do vaccine reactions occur?
- Of course.
Are animals vaccinated more often than needed?
- Probably. Vaccination intervals are increasing so progress is being made. However, confusing the debate about how long we can go between vaccines with whether dogs should be vaccinated at all is dangerous. There's no doubt that young animals need proper early-life vaccination to prevent these potentially fatal infections.
Does the benefit outweigh the costs?
- Absolutely. Vaccination has controlled some incredibly important infectious diseases.
- Choosing not to vaccinate in response to internet rumours isn’t logical and it puts lots of animals at risk.
- Also, decreasing population vaccination rates increases the disease risk to the dog and cat population overall, since fewer protected animals means more chance of disease circulating from animal to animal to animal before it can be stopped. It’s like the “Wakefield effect”: the surge in some vaccine-preventable diseases attributed to the now-discredited (and former doctor) Andrew Wakefield, whose flawed and unethical research fed the anti-vaccine movement with since-retracted data.
Vaccination of young animals is critical for the control of certain infectious diseases. Recommending otherwise is illogical, and when it’s done by people who should know better, it’s unethical. Hopefully this doesn't get to the point where we need to start tracking the animal equivalent of the Jenny McCarthy Body Count.
A cluster of Brucella canis infections has raised concerns in Calgary, Alberta, and hopefully will prompt more discussion about importation of dogs.
Brucella canis is a bacterium that can infect both dogs and people, although it’s natural host is dogs (more specifically, dogs that are not neutered or spayed). Human infections are quite rare but they can be nasty, and therefore need to be taken seriously. Infections are sporadically identified in dogs in Canada, but it seems to be a very rare disease overall, and most cases I’ve dealt with have been in dogs that were imported.
The latest incident involves identification of brucellosis in five dogs. The first case, not surprisingly, was imported, having come from somewhere in the southern US. Three other dogs also from the southern US had contact with the first dog. The fifth case, concerningly, was a local Alberta dog that had contact with the first dog. There seems to have also recently been another unrelated Brucella canis infection in a local dog that originated from Mexico.
The main human health risk associated with Brucella canis is contact with breeding animals, as the bacterium is shed mainly in vaginal discharge, placental and fetal fluids, semen and aborted fetuses. Contact with dogs that have given birth or aborted is the main concern. The bacterium can be shed in urine, but that seems to be less of a concern, particularly with otherwise healthy dogs. The risk to the general public is therefore quite low, but it’s important to try to control this bacterium because of the potential for serious human disease.
Brucellosis is just one of many potential disease risks with imported dogs. As I’ve discussed previously, there is little to no control over importation of dogs and little comprehensive guidance for people who are importing them. This is a big reason why we are seeing certain "foreign" diseases in dogs in Canada (e.g. leishmaniasis). We sorely need a comprehensive approach to dog importation to help reduce the risk of disease entry and help people who choose to import dogs do so safely.
This cluster of infections can also be found on our new disease tracking site, http://www.wormsandgermsmap.com.
A few questions were sent in by a reader regarding a recent post about rabies in a Texas animal shelter. They’re good ones so I thought I’d cover them here.
I'm a little confused by this. Weren't these shelter dogs vaccinated?
- Probably not. Many shelters don’t vaccinate against rabies. There are a few reasons for this:
- One reason is cost. From a shelter standpoint, rabies vaccination may even be considered of less importance compared to vaccination against diseases that are more common causes of illness in shelters (such as parvo).
- A big reason is that in most regions, rabies vaccines must be given by a veterinarian, and many shelters don’t have much veterinary involvement.
- Another consideration is that even if animals are vaccinated in the shelter, they are not considered protected until 28 days after vaccination.
- Yet another thing to consider is whether vaccination would have changed anything. Vaccinated dogs would still require a 45 day observation period. That’s much easier than a 6 month quarantine but still problematic and could lead to euthanasia for logistical reasons.
How exactly were these dogs exposed?
- Good question. It depends how the shelter was run and whether dogs were mixed together or socialized in groups. Sometimes, all dogs end up being considered exposed unless shelter personnel can definitively state that they know a particular dog didn’t have contact with the rabid dog. It’s often hard to say that with confidence, so by default they consider all dogs exposed.
What about vaccinated pets (dog and cat) that live in homes but go outside in suburban or rural environments? How do we know, for instance, that an indoor/outdoor cat hasn't come into contact with a rabid wild animal or feral cat? Do owners of indoor/outdoor cats really know where their cats go and what they do or who they associate with when they're out all day long? And, what about dogs that go out for their last potty break, unattended, in the fenced backyard at night when the wild critters come out? How do we know, really, that our pets haven't been exposed to rabies?
- We don’t. That’s an inherent risk in life, and a reason that we push for vaccination of all pets. Vaccination isn’t 100% but it will greatly reduce the risk of an animal developing rabies.
- This is also one of many reasons to make sure animals aren’t allowed to wander outside unsupervised.
A single rabid animal has lead to plans to euthanize 40 dogs at a Texas animal shelter. It’s very similar to a situation I discussed with vet students recently, and it’s one that raises a lot of emotions.
The brief version...one rabid dog was identified in the shelter.
- This means that consideration has to be given to who (people and animals) was exposed to the dog.
- If the shelter cannot state with confidence that a particular dog was not exposed to the affected dog (e.g. if they don’t strictly cohort groups and/or follow these practices), then it’s considered exposed. Fortunately, only 40 of the over 300 animals at this shelter were deemed potentially exposed. It’s not clear if this is because some dogs were considered unexposed or, more likely, that all dogs were considered exposed but cats were kept separately and therefore not exposed.
- A dog that’s been exposed to rabies needs a 45 day observation period (if properly vaccinated) or 6 month quarantine (if not known to be properly vaccinated) or euthanasia.
What are the odds that any other dogs were actually infected? Very low.
Is euthanasia, then, a reasonable response? Unfortunately, yes, in many situations.
This is where people start to get upset. Why euthanize these perfectly healthy dogs if none were likely going to get rabies and you can simply quarantine them?
At a basic level, I agree. But, when you think about it more, these actions make sense.
- Yes, the dogs could be quarantined, but how? That would involve keeping them in the shelter for 6 months, since fostering out rabies-exposed dogs would be hard to justify.
- If they quarantine them in the shelter, they essentially have to keep the shelter closed since it would make no sense to bring in more dogs (that would have to be strictly isolated from the others) and there’s probably little or no room for added dogs anyway.
- As a result, instead of being admitted to the shelter, the animals might be euthanized on the doorstep, since there’s often not a "plan B" for sheltering.
So, does it make sense to shut down the shelter for quarantine? That’s hard to justify. The net impact on dogs (both those in the shelter and those that would be admitted) plus considerations of shelter operations (e.g. lots of presumably unvaccinated people having to work with potentially exposed animals) need to be part of the discussion.
Unfortunate as it is, this is often the response. Ideally, there’d be a way to isolate these dogs and continue shelter operations (and pay for the extra costs associated with doing this). In the real world, this is rarely an option.
All of this could potentially have been prevented if the affected dog had been properly vaccinated by its original owners.
There have been a few reports of equine herpesvirus (EHV-1) neurological disease over the last couple of weeks and some other cases that have been less well publicized. Hopefully it’s all just been a blip on the radar and not a sign of things to come as equine events start to ramp up at this time of year. However, it would be good for racetracks to take these cases as reminders of the ever-present risk of EHV and the need to try to prevent problems.
Some tracks have taken this issue seriously and are working on infection control and outbreak response plans. In response to one outbreak, a Minnesota track is building an isolation area for infected horses and implementing a variety of infection control measures.
Too often, the response to EHV-1 is only reactive: when there's no immediate problem, people don’t do anything, and when there is a problem, people freak out (and it’s hard to do things right when people are freaking out).
We need a happy middle ground that includes a reasonable response plan (effective and realistic) and proactive measures to both reduce the risk of an outbreak and to facilitate response.
Racetracks are starting to understand the need, although the response is variable. The number of outbreaks and the potential implications of them (e.g. sick or dead horses, cancelled racing, horses banned from going to certain tracks) means that it is in the horse owners’ and tracks’ best interests to do things right. What constitutes "right" is a moving target, though, and some people just don’t want to bother.
You can virtually guarantee that there will be EHV-1 outbreaks at racetracks this summer. A limited number of horses will die but there will be massive disruption based on quarantines (sometimes reasonable, often excessive) and other fall-out.
While there’s no way to completely eliminate the risk of EHV in horses, there are many things that can be done to reduce the risk of an outbreak. Some are relatively cheap and easy, such as
- Ensuring that horses with signs consistent with EHV-1 are promptly examined and isolated
- Avoiding shipping horses from sales directly into racing barns
- Cohorting groups on tracks as much as possible to contain incidents to individual barns
- Fostering routine infection control practices by people who frequently move between barns like veterinarians, farriers and riders/drivers
Other measures may take more time, effort and planning, such as creation of isolation areas and development of clear outbreak response plans. One of the most important things that can be done, however, is improving communication and trust. Often the biggest challenges in outbreaks involve poor communications, such as unwillingness to report cases, egos and agendas that get in the way of effective and timely response, and various other related problems that can be fixed by people thinking and talking to each other.
Some tracks are doing a good job of thinking proactively. Many are taking the "head-in-the-sand" approach. Any track could run into a problem, but my money’s on bigger problems occurring at the tracks that don’t take this problem seriously.
Unfortunately, we’ll be talking more about EHV-1 outbreaks this summer.