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What you need to know to keep your dog safe in the heat this summer

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Finally, the sun is starting to make a regular appearance in the UK again. The annual #DogsDieInHotCars campaign has officially launched (more on this shortly), which means summer is coming! And we have a new publication to share with you and some tips for risk assessing your dog’s safety in the warmer weather.

Our latest research paper reviewed all of our previous findings to identify the risk factors for severe and fatal heat-related illness (HRI). We also explored two important additional factors for UK dogs: location, and ambient temperature. If you want to read the full results they are available open access here:

Risk Factors for Severe and Fatal Heat-Related Illness in UK Dogs—A VetCompass Study

So which dogs are at greatest risk of heat-related illness?

Our previous research showed that overall, HRI is more likely to affect certain breeds (the Chow Chow, Bulldog, French Bulldog, Pug, Golden Retriever, Greyhound and Cavalier King Charles Spaniel to name a few), dogs with flat-faces (brachycephalic dogs), overweight dogs, older dogs, large breed dogs and purebred dogs in more affected. We also know that exercise is the most common cause of HRI in UK dogs, triggering almost 75% of cases, and some breeds (those listed above plus the Labrador Retriever, English Springer Spaniel, Staffordshire Bull Terrier and Border Collie) are more likely to develop HRI due following exercise.

But it is important to recognise that HRI is progressive disorder, meaning dogs start with mild disease but can progress to more severe, potentially fatal disease if their temperature continues to climb or remains too hot for too long. Over 90% of dogs presented for veterinary treatment with mild to moderate signs of HRI survived, whilst more than half of those presented with severe disease died. Our latest research paper specifically explored the factors that make severe and fatal HRI more likely once a dog is affected.

Which dogs are most likely to develop severe disease?

Severe HRI is characterised by vomiting and diarrhoea with blood present, repeated or continuous fitting (seizures), neurological damage (such as loss of consciousness and uncoordinated movement), bleeding disorders and kidney and liver damage. Less than half of the dogs with severe HRI will survive, despite veterinary treatment. If your dog develops HRI, the following factors make it more likely that they will develop severe disease:

AGE: Dogs aged 4 years or over (and particularly those aged 12 years or over) at more likely to develop severe HRI than dogs aged under 2 years of age. This is likely due to a number of reasons related to both lifestyle and lifestage. In people, young men are more likely to develop HRI caused by exercise because they are more physically active (either due to sports or physically demanding job roles). Older people are more at risk of environmental HRI (HRI triggered by heat waves or just hot weather) because they cannot cool down as effectively as mechanisms such as a sweating become less effective with age as heart function deteriorates. We suspect the same is true for our canine companions (whilst dogs do not sweat to cool, they still rely on mechanisms that need strong blood flow). Certainly older people and animals struggle to keep cool in the heat, and this is worsened by conditions such as heart disease, obesity, and breathing problems.

BODYWEIGHT: Dogs also have to obey the laws of physics so bigger, heavier dogs will get hotter quicker during exercise (more muscle to generate heat), and lose heat more slowly than small dogs. Dogs weighing under 10kg are less likely to develop severe HRI, and this is because they can cool more quickly, so don’t stay hot for as long as larger dogs. It could also be because small dogs are more likely to be carried, so if they get too hot we can pick them up, which helps to stop them getting hotter on walks.

EXPOSURE TO HEAT: This one is important. Dogs don’t die just in hot cars. Anything that causes a dog’s body temperature to rise and remain high can potentially lead to HRI, including hot weather, hot cars, hot buildings, being trapped in hot blankets, getting stressed at the groomers or at the vets, and most commonly getting hot whilst exercising. Dogs left in hot cars are more likely to develop severe disease compared to dogs that develop HRI following exercise. Why is this important? Because the key factors here IS YOU! If you leave your dog in a hot car, they are alone. Dogs don’t have thumbs, they can’t open the window to escape, you are leaving them to cook. UK cars can reach over 50°C, and can reach that temperature rapidly in direct sunshine. In comparison, dogs that develop HRI following exercise are usually with their owner, so you have an opportunity to spot the early signs of mild to moderate disease and take action before the disease can progress to the potentially deadly severe form.

That’s not to say that exercise induced HRI isn’t deadly, in fact more dogs died due to HRI following exercise than died following vehicular HRI, because the vast majority of dogs affected by HRI in the UK were triggered by exercise. So you can make a real difference here, and if the weather is heating up, stop and think carefully – if in doubt, don’t take them out!

This year (2022), the Dogs Die in Hot Cars campaign has been expanded to include this new message, Dogs Die on Hot Walks, all down to our Hot Dogs research.

Which dogs are most at risk of dying from HRI

Unsurprisingly, dogs that develop severe HRI are most likely to die. In fact they have 65 times the odds of death compared to dogs that only develop mild disease – and remember these are all dogs that presented to a vet for treatment. So knowing the early signs of HRI, and taking action to prevent the condition from worsening by cooling, stopping exercise, getting the dog into a cool area and seeking veterinary treatment can save your dog’s life.

Again, older dogs (this time dogs aged 8 years or older) are more likely to die if they develop HRI. This is likely due to a number of factors, including the fact that older dogs are more likely to have underlying health problems that impact their odds of survival.

Dogs with flat faces (brachycephalic dogs) are more likely to die if they develop HRI. This one is really important. Note that being flat faced DID NOT increase the risk of developing severe HRI, and whilst we can’t prove why, we have a theory we urge all flat-faced dog owners to consider. The first sign that indicates your dog is too hot is panting. In a healthy dog with a healthy respiratory tract, panting is normal and incredibly effective at cooling. If your dog has ANY kind of respiratory disease – specifically brachycephalic obstructive airway disease or BOAS – then panting is not as effective (so they don’t cool as quickly) AND panting requires more work, meaning the muscles driving panting can end up generating more heat than the panting can lose. In severe cases (again BOAS but also laryngeal paralysis), panting can cause further narrowing of the airway, leading to a lack of oxygen, which can lead to cardiac arrest and ultimately death.

A French Bulldog panting before BOAS surgery to open up their airways. Note the very narrow nostrils that restrict airflow.

Not all flat-faced dogs have BOAS though, so this isn’t quite enough to explain this finding. But, remember the signs of moderate HRI include excessive salivation and vomiting, and can include fitting and collapse. Flat-faced dogs are at increased risk of aspiration pneumonia following vomiting (basically inhaling the vomit into the lungs causing massive damage to the lung tissue), which will again lead to a lack of oxygen, cardiac arrest and ultimately death. So if you own a flat-faced dog, you need to take even mild signs of HRI really seriously, and seek veterinary advice immediately as your dog is three times more likely to die than most.

Does it matter where my dog lives?

Perhaps not as much as you might think, and UK region didn’t increase the risk of either severe or fatal HRI for dogs affected by HRI. But we did find that dogs living in London were more likely to develop HRI than dogs living in the North-West. Overall, around 1 in 2500 dogs developed HRI in the UK during 2016, in London this increased to 1 in 1250 dogs.

The proportion of dogs affected by heat-related illness by UK postcode region during 2016.

We also found that dogs living in London were more likely to develop HRI following confinement in a hot building. Nationally, only 3% of canine HRI cases were caused by hot building confinement, but in London that figure rose to 7.6%. We suspect that the urban heat island effect (lots of concrete, tall and terraced buildings, and not enough trees) contributes to this finding. We also found that dogs living in London were much less likely to develop HRI following confinement in a hot car, the reason for this isn’t clear but may be due to different transport preferences with significantly fewer London households owning a car.

So, how hot is too hot?

We get asked this question A LOT, and I’m afraid we have come to the challenging conclusion that it’s just not that simple. We can’t give you a number. This is where risk assessment comes in. Lets take the Hot Dogs team as an example. Anne competes in both canicross and bikejor with her dogs, and is incredibly active and physically fit. If you send her out for a 5km run in 20°C, she’ll be fine (FYI she wouldn’t be taking her dogs at that temperature!). Emily is a self confessed sofa pumpkin (we explained this term previously), she hasn’t competed in any sports for many years now and is no where near as active as Anne and not very physically fit. She also has asthma, so there’s an underlying respiratory disease to consider as well as a greater bodyweight (ahem!). Firstly, Emily couldn’t run 5km even with zombies chasing her. If she tried, there is a very real risk she would develop HRI not matter the ambient temperature. Our dogs are just as variable, they will react differently to ambient temperatures depending on a whole host of factors including bodyweight, breed, skull shape, general health, physical fitness, acclimatisation, hydration status and even diet.

Even more concerning, in our latest paper we reported the highest daily “feels like” temperature (this is “wet bulb globe temperature”, which takes into account air temperature, humidity, wind speed and solar radiation) recorded at the nearest weather station to each HRI event we studied. The average (median) temperature was just 16.9°C. The lowest temperature was 3.3°C (for an exercise induced HRI case), whilst the highest temperature was 23.1°C. These are not high temperatures. In Israel a similar study found that 85% of HRI cases occurred on days with a feels like temperature of 24.1°C, so dogs in the UK develop HRI at much lower temperature than dogs living in hotter climates.

When judging temperature conditions for your dog, you also need to consider how temperature is being measured. We used local weather station data, meaning the temperatures were recorded in the shade. Your back garden, in full sun, with fences or hedges reducing wind and airflow, could be significantly hotter than the “feels like” temperature being reported on your weather app or weather forecast. If you have a lot of tarmac or artificial grass in your outdoor space, this will cause further heating and can even cause contact burns if your pet walks or lies on a hot surface.

So how do you keep your dog safe this summer?

Firstly, if in doubt, don’t take them out. No dog will die from a missed walk, but exertional HRI can be fatal. If you are travelling with your dog, then ensure you have carefully planned your journey and can take action should you break down or get stuck in traffic. Never leave your dog alone in a vehicle that could overheat.

Consider the conditions and the recent weather conditions:

  • Sudden hot spells are most dangerous as you dog can take about 6 weeks to acclimatise to heat.
  • Consider the time of day, early mornings are typically cooler, as usually the temperature drops overnight. Evenings can be hot and in particular the ground (where your dog will be walking/lying) may be very hot.
  • If you can exercise your dog in shaded areas like woodland, this can help limit their heat exposure.
  • If you are planning intense exercise with your dog, frankly anything over 10°C should be prompting a risk assessment.

Is your dog at greater risk?

  • Are they an at risk breed?
  • Are they flat-faced?
  • Do they have a respiratory condition such as laryngeal paralysis or BOAS?
  • Have then recently been unwell, this includes dehydration from not eating, vomiting or diarrhoea?
  • Are they physically fit?
  • Are they overweight or obese?
  • Are they a large breed dog?
  • Do they have a thick fluffy coat (this is particularly important for exercise, not so much for lazing around)?
  • Are they older?
  • If you answer yes to any of these questions then you need to take extra care when considering activity in even warm weather.

Make sure you can spot the early signs of HRI:

Being able to recognise the signs of mild HRI may save a life:

  • SPOT THEM – spotting the early signs will give you time to take action.
  • STOP THEM – from getting any hotter, e.g. stop the exercise, get them out of the hot car/building/garden.
  • SAVE THEM – seek veterinary treatment and cool them (using water)
Mild heat-related illness signs. Seeking veterinary treatment at this point will save lives.

Consider how you would respond if you dog developed HRI:

Things to consider include:

  • Access to water for cooling – cold water is ideal, so could be a stream, a lake, even a water trough or water from a bottle (although for big dogs a lot of water may be needed).
  • Transport to a vet – can you lift and carry your dog? If not, how far do you plan to be from a vehicle or help if your dog were to collapse?
  • Access to veterinary care – the UK (and international) veterinary profession is suffering from a serious workforce shortage, meaning some practices are struggling to provide a full service, and many practices are unable to take on new clients. If you are on holiday or away from home for the day, where is the nearest veterinary practice that could treat your dog in an emergency?

Unlike many conditions, you can protect your dog from heat-related illness, so make sure you take the risk seriously this summer and know the early signs so you can take action if the need arises. Remember, if in doubt, don’t take them out.

Hendricks napping on a hot day, staying safe by keeping cool out of the sun.
Research news

Baby its cold outside – Is the winter weather keeping your dog inside and inactive? You may regret this in the summer…

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As much of the UK feels the chill of winter, it might be tempting to hide back under the duvet, snuggle up to your canine companion and hibernate until spring arrives. But how much exercise your dog does now, could make all the difference in the summer when the weather heats up. In this post we’re going to explore some of our recent research findings relating to weather and canine activity.

After keeping you all waiting for far too long, we finally had an opportunity to analyse the results from the canine activity survey we ran in 2018. Thanks to the incredible generosity of the on-line canine community, we received over 3000 responses to our canine activity survey where we asked you to tell us about your dog, about their activity routines and how the weather impacted their exercise. You can read the full results here:

Exploring Owner Perceptions of the Impacts of Seasonal
Weather Variations on Canine Activity and Potential
Consequences for Human–Canine Relationships

In this post we’re going to focus on the winter weather results from our survey

  • 64% of dog owners surveyed said ICE reduced their dog’s activity
  • 48.2% said COLD reduced their dog’s activity
  • 25.3% said RAIN reduced their dog’s activity

We also explored which dogs’ activity levels were most impacted by cold, wet, icy winter weather:

  • Small dogs (under 10kg) were most impacted by winter weather.
  • Both brachycephalic (flat-faced) and dolichocephalic (long-nosed) dogs were more impacted by winter than dogs with a mesocephalic (medium – like Labradors and spaniels) shaped skull.
  • Older dogs (8 years and older) were more impacted than young dogs.

And which dogs were less impacted by winter weather:

  • Dogs that competed in canine sports were less impacted by winter weather.
  • Dogs that were routinely active for 2 hours or more per day were less impacted by winter weather.
Dogs that participated in canine sports were less impacted by winter weather.

When individual breeds were compared, the results were frankly unsurprising; Yorkshire Terriers, Whippets, Chihuahuas, Greyhounds and Pugs were the breeds most likely to miss out on exercise in winter weather.

Smaller dogs, and breeds such as Chihuahuas were most likely to miss out on exercise in winter. Pepe here would rather stay in bed.

At the other end of the spectrum, Huskies, working Cocker Spaniels and Springer Spaniels were less impacted by winter weather (and all these breeds were compared to the Labrador Retriever).

Daisy and Skye ready for some night-time running in their hi-vis jackets – safety first girls!

Overall, 50% of respondents agreed that they use dog-jackets and coats to keep their pet warm during exercise in the winter. We also asked which dogs were most likely to wear a coat in the winter:

  • Dogs weighing under 10kg
  • Brachycephalic and brachycephalic cross breed (e.g. Jugs, Pugaliers and Lhasaliers) were more likely to wear coats compared to mesocephalic dogs.
  • The dolichocephalic breeds Whippets and Greyhounds were the breeds most likely to wear a coat.

So why does this matter?

As you will by now be aware, this is a blog all about hot dogs, so why are we harping on about cold dogs all of a sudden? One of the ways of keeping your dog safe in the hot weather, is to prepare them for the heat. We know that overweight dogs are more likely to develop heat-related illness because the extra fat they carry makes it harder for them to cool down (we explain this in more detail in a previous post). We also know that unfit dogs will get hotter faster during exercise, so keeping your dog fit during the winter means they will be better prepared to cope with sudden hot spells in spring and early summer. So if your dog does less exercise in the winter, they will be less fit in the summer and they could put on some excess weight, both of which will make it much harder for them to stay cool.

Even in sub-zero temperatures Hendricks still needs to stop to cool down in a nice muddy puddle.

We should also pause here, to remember that dogs can still develop heat-related illness in the winter! In one of our previous studies we reported that dogs were presented for veterinary treatment of exercise-induced heat-related illness all year round, and one of those dogs died as a result of their exertional heat-related illness in January. Just because its cold, there is still a risk of overheating, especially for dogs with underlying diseases that affect their breathing, so make sure you can spot the early signs of heat-related illness so that you can take immediate action.

We do however recognise that there are times when it isn’t safe to exercise a dog in winter weather. If your dog is older, has mobility issues, or underlying heart or lung disease then you may need to speak to your veterinary professional about ways to help them stay safe during wintery walks. We’re also not suggesting putting yourself or your dog at risk heading out into a blizzard, or onto icy roads and pavements. We also recognise that exercising your dog in the dark can be a serious personal safety issue, particularly for women, so you need to put your own wellbeing first when deciding when and where your dog can be active.

Dogs can also develop hypothermia (the opposite problem to heat-related illness – becoming too cold) especially smaller dogs, older dogs and those with underlying health issues. There are additional winter hazards related to ice and snow that can result in injuries, and even toxins such as antifreeze that pets may encounter in winter which can be extremely dangerous if ingested.

So how can you help your dog to remain active through the cold, dark, wet winter months?

  • Consider if a coat or fleece will help them stay active.
  • Wipe your dog’s paws and belly after walking to remove any traces of grit, salt and ice.
  • Find ways to stay active at home or in the garden.
  • Consider an alternative winter activity like hydrotherapy to help maintain fitness if you can’t get outside as often (ensure you have checked with your vet that this is safe first).
  • Join a canine sports club to keep you motivated!

We found dogs that took part in canine sports (like canicross, agility and field sports) were less likely to be impacted by winter weather, so if you need some added motivation to keep moving with your canine companion consider joining a local club?

These two are raring to go, even on cold, frosty, misty mornings.

We also investigated the impact of summer weather on canine activity, so we’ll share another post in spring to explore those findings ready for the hot weather. In the meantime, if you can’t wait for more Hot Dogs research findings you can read our recent papers open-access here:

Full results from the survey discussed in this post:

Exploring Owner Perceptions of the Impacts of Seasonal
Weather Variations on Canine Activity and Potential
Consequences for Human–Canine Relationships

Our latest research exploring heat-related illness in UK pets. This paper uses the SAVSNET database of primary-care veterinary practice patient records to explore heat-related illness in all pets, including cats, rabbits, guinea-pigs and ferrets:

Surveillance of heat-related illness in small animals presenting to veterinary practices in the UK between 2013 and 2018

Anne has also been busy researching working trial dogs:

Kinetics and Kinematics of Working Trials Dogs: The Impact of Long Jump Length on Peak Vertical Landing Force and Joint Angulation

Of course some breeds are most at home in winter weather. Ares the Alaskan Malamute says bring on the snow!
Research news

Hot dogs – the UK dogs most likely to experience heat-related illness

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After what feels like an eternity (and is in fact just under 2 years!) we can FINALLY share the first set of results from our Hot Dogs VetCompass project – exploring the risk factors, incidence and fatality of heat-related illness in UK dogs.

The paper is fully open access, so you can either view it on-line here:

https://www.nature.com/articles/s41598-020-66015-8

Or download the PDF here:

Incidence and risk factors for heat-related illness (heatstroke) in UK dogs under primary veterinary care in 2016Download

We have a conversation article that summarises the key findings available here: https://theconversation.com/nine-dog-breeds-at-higher-risk-of-heatstroke-and-what-you-can-do-to-prevent-it-139501

Or, for the super short version, check out our infographic, designed by Becky – www.PawPrintsPosters.com

Research news

Getting hot under the collar – allowing your dog to pull on a collar and lead could be causing damage and increase their risk of heatstroke.

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You only need to step inside a pet shop to see the vast array of collars, harnesses and leads available to dog owners. Owners can choose a particular look, colour scheme and material type. But amongst all of this, there is a more serious question of the role of the collar and the impact it may have on the dog. Historically, collars were used as a means of identifying a dog as being owned. Today, in the UK, as in many countries, it is a legal requirement for a dog to wear a collar and tag to provide key information about the dog, in order to identify the owner and to return it should it become lost. However, collars are now commonly used as a means of restraint and control for dogs to make sure they don’t wander off when out for a walk.

choc lab in collar

The problem is that the neck is a pretty sensitive area of the body, and many dogs pull on the lead. Ultimately, the neck connects the head to the rest of the body, carrying some pretty vital anatomical features such as the spinal cord, major blood vessels, the windpipe and the food pipe. Serious damage to the spinal cord in the neck can result in paralysis, or even death. Similarly, damage to the windpipe can impact a dog’s ability to breath or even result in choking, another potentially fatal injury. Linking to our normal research area, heat-related illness, compression of the windpipe can impact a dog’s ability to breathe effectively, impairing their ability to cool. When it’s hot outside, allowing a dog to pull on a collar and lead could potentially result in them over heating more quickly.

Sport_bulldog (2)

In fact, when questioned, almost 50% of owners suggested that their dogs pulled on the lead. This might range from a consistent light pull, to an owner being ’towed’ up the street by an overzealous dog. And of course, there is the sudden jerk on the lead from a normally calm dog, as a cat goes running across the road. On the other end of the lead is the owner, perhaps getting a little impatient at the 17th lamppost being sniffed, and offering a quick tug on the lead, or the frustrated individual jerking the lead to remind their dog to listen and behave. In all these instances, the resulting impact is a pressure applied to the dogs’ neck.

Two aspects are worth exploring; the impact of the type of collar – are some better than others? And the impact of the force applied – is a light pull on the lead less likely to cause harm?

loose lead walking (002)

Anne has been exploring just this topic, using pressure sensors attached to various styles of collar to test how much force then could be applying to our dog’s necks. Because of the risk to the dogs’ neck, and to retain consistency, a model neck (plastic pipe) was used instead of actual dogs. Working with Dr Mandy Roshier and Prof Donal McNally from the University of Nottingham, eight different collar types were tested. These were chosen to represent the range of commercially available types rather than focusing on specific brands: a rope slip lead, leather and thread, plain webbing, webbing padded with neoprene, thicker neoprene padded sports, wide lurcher, rolled collar and check chain.

The forces tested aimed to replicate a light pull on the lead (40N), a strong pull on the lead (70N) and a lead jerk (~141N).

The collars reacted differently in both the way the pressure was distributed and the amount of pressure applied to the model neck, the pressure increased as the force applied to the collar increased. Arguably the most interesting and valuable finding was that the pressure exerted on the neck model ranged from the lowest, 83kPa at 40N to the highest, 832kPa at 70N across the range of collars. To put this into context, in humans, pressure over 33.3 kPa has been shown to increase intraocular pressure (pressure within the eyeball which can lead to pain and ultimately blindness) and compress blood vessels, limiting blood supply to tissues. Tourniquets used in emergency situations to stop serious blood loss following trauma are used at a pressure of 33.3kPa on the arm and 40.0kPa on the thigh. In horses, pressures above 30kPa under the saddle are associated with back pain.

30kPa is enough pressure to strangle a human, and 230kPa is enough pressure to crush a human’s windpipe.

In short, no single collar tested provided a pressure anywhere near low enough to remove the potential risk of injury when pulling on the lead. Where dogs pull on the lead or the lead is jerked, there is a risk of injury to the neck for all collar types and styles tested, even where collars are padded or wide fitting. Collars are a great way to display tags and add a little personal flare to your dog. But for restraint and control, a non-restrictive harness is a much better option, and in hot weather a harness is definitely the safest option.

The full article is available here as a pre-print copy: FINAL Canine collars – an investigation of collar type and the forces applied to a simulated neck model

dogs-on-a-walk

Research news

What is a “normal” body temperature?

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If you’ve read any of our posts so far you will know we are all about monitoring body temperature, specifically as a means of understanding heatstroke risk in exercising dogs. As our fabulous friend Dr Jackie Boyd likes to remind dog owners:

“You cannot manage what you do not measure and monitor.”

Whilst Dr Boyd is referring to measuring food in relation to canine nutrition and weight management, the same applies to body temperature. You can only be sure your dog is not over heating if you measure their body temperature. You can only be sure your temperature management strategy is working if you continue to monitor their temperature. We’ve previously shared some advice on methods of monitoring body temperature in dogs and other animals, and we have an update coming on this topic very soon! Crucially though, if you’re going to measure your animal’s temperature, you need to know what the numbers mean, and how to react appropriately.

The “normal” range

For almost every measurable aspect of an animal, from age, height and weight, to temperature, heart rate or urine production, there are “normal” reference ranges. In theory, these are statistically calculated limits of the normal population; in other words, 95% of healthy animals will fall within this range – there are always extremes that don’t fit the normal limits.

light-sepia-household-thermometer-166493

Google “normal temperature for a human” and you will see the top result, Wikipedia, reports “The normal human body temperature is often stated as 36.5–37.5°C”. It goes on to mention that “In adults a review of the literature has found a wider range of 33.2–38.2°C (91.8–100.8°F) for normal temperatures, depending on the gender and location measured.” A study recently found that the long established “normal” body temperature for humans is too high, highlighting the continued use of out of date normal ranges by medical professionals all over the world. This situation is mirrored in animal species. Textbooks state the normal range for various biological parameters in almost every species, but rarely state where this reference range has come from, how old it is, which animals were used to establish it and how their temperature was measured.

Our primary interest is canine health and welfare, so this all started when we tried to find a reliable source stating the normal resting temperature for a healthy dog. We struggled. Every textbook listed a slightly different range, 37.9-39.9°C on one website, then 38.2-39.2°C in a veterinary nursing textbook. The most recent reference we found was in a paper measuring rectal temperature in 62 dogs presenting to a veterinary hospital for routine health checks, who reported a normal range of 37.2 to 39.2°C. However, this did not report how this range was calculated, so without details of the statistical methods used to determine this range, it can not be considered truly valid.

Where does this leave us? Well, at the moment, we don’t actually have a robust, recent, reliable normal reference range for canine body temperature, when measured with a rectal thermometer. Three different sources state that 39.2°C should be considered the upper limit of normal, so we are fairly happy to accept that as our upper limit. What we do have, is a scientifically calculated normal reference range for canine ear temperature – because we calculated it! We measured ear temperature 416 times, from 157 healthy dogs attending various canine sports events over a two year period. Importantly, these dogs were not at the vets, so whilst they may have been excited, they were not stressed or scared. We calculated the normal range to be 36.6-38.8°C.

FINAL Establishing a reference range for normal canine TMT (you can read our published study here in the un-formatted version)

download
37.2 to 39.2°C is the current best estimate for normal rectal temperature in dogs.

Returning to rectal temperature, we know from our research, and from studies done by various other research teams around the world (Zanghi, 2016; Gomart et al., 2014), that ear temperature tends to measure around 0.4-0.6°C lower than rectal temperature. So, the rectal range of 37.2 to 39.2°C then quite nicely reflects our ear temperature reference range, just 0.4-0.6°C higher. This is the range we would consider to be most appropriate for interpreting canine body temperature, when measured with a rectal thermometer.

Equine body temperature

horse legs

Because we are both slightly mad, some might say obsessive, we couldn’t stop at establishing a normal reference range in just dogs. Oh no, we had to look at horses too. Whereas a dog may try to escape, sit down, or worst case scenario bite should they resent having their rectal temperature measured, a horse can, and if suitably aggrieved will kick you. This can be catastrophic. So if you’re going to risk your life measuring your horse’s temperature, and there are plenty of reasons you should be doing this, we felt it our duty as scientists to ensure you have a means of accurately interpreting the result.

We started by trying to find the evidence behind the “normal temperature range” for horses. We failed miserably. Once again, whilst plenty of textbooks, websites and other studies investigating equine temperature all state what the normal temperature range for a horse is, none of them reported where this range came from. Similar to the situation in dogs, if you don’t know where a reference range came from – how many horses were included, what part of the world, what breeds of horse, who took their temperature, how was their temperature taken – how can you be certain it is relevant to your horse? The simple answer is, you can’t.

stabled horse

So we decided to establish our own reference range. The horses at our University Equestrian Centre are cherished; the team caring for them will (and have!) battle blizzards, tropical storms and heat waves to ensure these horses are fed, watered, comfortable and loved. Part of their routine husbandry includes temperature monitoring, and yes, being University horses they do have to work for their living, so they are often used in non-invasive research work like our study comparing rectal temperature to eye temperature (measured with a non-contact infra-red thermometer, and coming soon!). Working with Dr Carol Hall and Dr Anne Stevenson, we collated rectal temperatures taken from 41 of the horses on the yard, measured at rest during a number of projects and routine monitoring. This gave us over 600 resting, healthy horse temperatures, all measured with a digital rectal thermometer by a familiar person, in the comfort of their stable. Knowing the horses were relaxed and not stressed is important, as stress can influence temperature in horses and other species.

We used a statistical method to then determine our horse’s “normal” temperature range, basically the middle 95% of the temperature readings. On our yard, this was 36.0-38.0°C. The upper limit is particularly important, as it is around 0.5°C lower than most of the previously published normal temperature ranges for horses. When an animal’s temperature exceeds this upper limit of normal, they are considered to be hyperthermic, too hot. The temperature reading alone can not explain why the animal is too hot, but it is an important indicator that something isn’t quite right (or, the horse has been exercising or in a hot environment). The term pyrexia, or fever, describes an animal that is too hot due to illness, this could be an infection, inflammatory or painful process. A low grade fever is where an animal’s body temperature is just slightly increased above the normal range and can be an early indicator of disease. It is therefore important that the normal reference range is accurate, otherwise these early indicators of illness can go unnoticed.

It is worth noting again, that the method of temperature measurement used is really important to consider when assessing your animal’s health. True core body temperature can only be measured using invasive, or ingestible devices. Rectal temperature remains the most accurate estimate of core temperature in most animal species (thankfully in humans non-contact thermometers appear to be as reliable!), but even the depth of rectal thermometer probe placement can have an impact on the resulting reading. A difference of 1cm can impact the temperature reading in chinchillas, whilst inserting a probe to 15cm or deeper in horses is likely to result in a higher temperature reading being obtained. Whilst we have no published evidence to support our theory, we suspect inserting a rectal probe to 15cm or deeper may also increase your risk of being kicked, so our normal temperature range is based on a 5cm thermometer depth.

If you monitor body temperature in two different ways you will get two different results. We know ear temperature is typically 0.4-0.6°C lower than rectal temperature. So it is important that you use the same method of temperature measurement each time if you are going to monitor your animal for changes in body temperature. That said, if you are ever worried about your animal’s temperature, use a rectal thermometer as this is still the most reliable estimate of core body temperature. Also, see your vet. Both high and very low body temperatures can be fatal in all species, so if your animal is unwell DO NOT delay seeking veterinary treatment. 

Our equine paper is available to read and download (free!) on the publisher’s site until 8th March 2019:

Establishing a yard specific normal rectal temperature reference range for horses. 

After this time, if you do not have access to the Journal of Equine Veterinary Science, then you are of course welcome to read the full article in the unfinished form below (this is the accepted manuscript, just not formatted into the journal’s style).

Establishing a yard specific normal rectal range horses FINAL.

We are hoping to recruit horses from all around the world to our next equine temperature study, so watch this space for further details if you would like your horse to take part!

horse-sleeping

 

Research news, Uncategorized

Hot Dogs – investigating the epidemiology of canine heatstroke presenting to UK primary care veterinary practices

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The Hot Dog’s team (Emily and Anne) are now working with Dan O’Neill from the Royal Veterinary College on a UK wide canine heatstroke study. The study will use data from the Vet Compass™ database to review the clinical records of over 900,000 dogs registered with UK primary-care veterinary practices for heatstroke events. As well as canine risk factors (e.g. breed, age, sex and bodyweight), additional information will be collected to establish the incidence, fatality rate, seasonality and underlying causes for canine heatstroke. Understanding the risk factors of heatstroke specific to the UK dog population will provide evidence to better support educational campaigns aiming to reduce or prevent this potentially fatal condition.

This project has been funded by a Dogs Trust Canine Welfare Grant.

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The results of this (likely two year) project will be published in an open access journal, so the link will appear here on the Hot Dog’s site as soon as it is available!

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Research news

The Journey So Far – access to our research papers

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Thanks for joining us!

We have started this blog to share our research findings with the wider dog owning, dog working, and dog competing community.  Apologies for the lack of content at the moment, but we hope this will soon change!

For now, here are some of our recent research findings and publications in an openly accessible format, along with links to the published works (which are sadly mostly behind paywalls):

FINAL Heatstroke – providing evidence based advice to dog owners.

Link to published version

FINAL Establishing a reference range for normal canine TMT

Link to published version

FINAL Factors affecting canine temperature after canicross racing

Link to the published version

FINAL Investigating the use of non-contact infrared thermometers in cats and dogs.

Link to the published version

FINAL Canine collars – an investigation of collar type and the forces applied to a simulated neck model

Link to the published version

Incidence and risk factors for heat-related illness (heatstroke) in UK dogs under primary veterinary care in 2016  (open access click to read)

Our Conversation UK articles:

How to stop your dog getting heatstroke – according to science

If your New Year’s resolution is to get fit, your dog may be your perfect training partner

Dogs don’t just die in hot cars – here’s how to stop them overheating when exercising

Nine dog breeds at higher risk of heatstroke – and what you can do to prevent it

Conference presentations:

Anne presented our preliminary findings on “Non-invasive temperature monitoring of canine athletes” at the Canine Science Forum in 2018.

Anne also presented “Investigating non-invasive methods of monitoring body temperature in in a range of domestic species” at the British Society of Animal Science annual conference in 2019.

Emily presented initial findings from the Hot Dogs VetCompass project to the British Small Animal Veterinary Association annual congress in 2020 (available to watch here).

If you have any concerns about your dog’s health please consult your veterinary surgeon immediately.  This site is designed to provide information and share knowledge regarding heatstroke, but is no substitute for veterinary care for your dog