As the UK temperatures continue to climb, it is essential every dog owner knows how to recognise the signs of heat-related illness, and how to effectively cool their dog in an emergency. Whilst these presentations are aimed at veterinary professionals, we’re making them available here too for anyone who is interested in our work.
ALWAYS seek veterinary advice if you are concerned your dog has developed heat-related illness. Less than half of the dogs that progressed to the severe form survived, so getting effective, early treatment is crucial.
Lots of myths get shared about cooling hot dogs, and sadly there isn’t much published evidence on which cooling methods work best! Our current understanding is that if your dog has overheated, but is still conscious, the most effective methods of cooling are to either immerse them in water (cold tap water is perfect), or wet them (with whatever water you have available) and fan them – air conditioning is perfect if you’re transporting them to the vet. If your dog has overheated and has lost consciousness, it is ESSENTIAL that you protect their airway, and don’t let them inhale any water. Dogs that have lost consciousness will cool far more slowly, so it is even more important to use effective cooling methods, such as spraying with water plus air movement.
Cooling methods used in dogs with heat-related illness under UK primary veterinary care during 2016-2018.
In this presentation, Emily shares the provisional results of our study exploring the cooling methods reported to have been used in the veterinary records of UK dogs presenting to their vet with heat-related illness. We also present the current evidence-base for cooling methods that are available for hot dogs, and discuss the importance of effective cooling.
VetCompass Clinical Grading Tool for Heat-related Illness in Dogs – a novel tool to support clinical decision-making in primary-care practice.
In this abstract, Emily introduces our VetCompass Clinical Grading tool, which we hope will allow dog owners and veterinary professionals to recognise heat-related illness earlier, and hopefully support more effective management of this life-threatening condition.
We’ve condensed our research so far into an article for the Kennel Club, sharing updates on the recognition of heat-related illness in dogs, the breeds at risk, and the most common triggers of this life-threatening condition.
First published in the May 2021 edition of the Kennel Gazette. Copyright The Kennel Club Limited. Reproduced with their permission.
As summer finally arrives, we’re asking all dog owners to remember that
Dogs die in hot cars and on hot walks!
If your dog’s exercise has been limited by the UK’s lockdowns, or they have perhaps developed a little “lockdown bulge” they will be at greater risk of developing heat-related illness as the weather starts to warm. So make sure you can recognise the early signs, and always have a plan to cool your dog in an emergency.
Our latest paper reports the most common signs of heat-related illness in dogs, abnormal breathing (excessive panting, and/or difficulty breathing) and lethargy (unwillingness to exercise, play or interact, changes in behaviour and tiredness). Crucially, dogs that are presented to vets showing just these early signs, were far more likely to survive.
When dogs presented to their vet with signs of severe heatstroke (neurological changes including multiple seizures, loss of consciousness or being comatose, bleeding disorders including passing vomit or diarrhea with blood, and organ damage), less than half survived (just 43.2%).
We are urging ALL dog owners to familiarise themselves with the EARLY signs of heat-related illness, as spotting these and taking appropriate action – cool your dog and seek veterinary advice – could save your dog’s life!
The AMAZING Camilla from the VetCompass team has turned our findings into this brilliant info-graphic, which we encourage you to download in full and share with as many dog owners as possible, as the UK weather starts to turn warmer!
We will be presenting this tool in the BSAVA 2021 Clinical Abstracts in May, and will be sharing our findings on cooling methods used by UK vets, so watch this space for more updates over the coming months!
Almost exactly two years ago we published our post – Dogs don’t just die in hot cars (to date our most widely read blog post!). Amidst the usual summer “Dogs die in hot cars” campaigns we warned owners about the risk of heat stroke triggered by exercise, and shared a particularly heart breaking story from a trainer who lost his dog after a seemingly routine training session in mild heat. We can now share an update on this important message, including the dogs most likely to be affected by exertional heat-related illness – aka heat stroke following exercise.
Of the events where a trigger was recorded in the history, 74.2% occurred after exercise.
Exposure to hot weather alone triggered 12.9% of events and travel or confinement in a hot car triggered 5.2% of heat-related illness events. Other triggers included confinement in a hot building (e.g. a conservatory), undergoing treatment at a veterinary clinic or professional grooming parlour, and sadly becoming entangled in blankets or bedding.
The risk of death following exercise induced heat stroke was similar to the risk of death following vehicular heat stroke, with around 10% of events resulting in fatality. The risk of death following heat stroke triggered by confinement in a hot building was significantly higher, with a third (33.3%) of events resulting in the dog’s death.
Exercise triggered over 10 times as many canine heat-related illness events as hot cars, and caused 8 times as many deaths.
The risk is year-round!
A key result from this project was the year-round risk of exercise induced heat stroke. Exertional heat-related illness affected dogs during every month of the year, with fatalities in January and every month between March-October.
In contrast, vehicular heat-related illness and environmental heat-related illness occurred only between March and September (the UK’s spring to summer period). This mirrors the results we reported earlier this month, that internal car temperatures exceed 35°C between April and September . Vehicular heat stroke deaths occurred between March and July, adding further evidence to support our recent call to launch the “Dogs die in hot cars” campaign earlier in the year. Environmental heat stroke deaths occurred from May to September, and building entrapment fatalities occurred between June and September.
Which dogs are most likely to develop exertional heat stroke?
We previously reported that Labrador Retrievers had no greater risk than crossbred dogs for developing heat-related illness in general. However, this is not true for purely exertional heat-related illness, Labradors were twice as likely to suffer from the condition. The Chow Chow, Bulldog, French Bulldog, Greyhound, Springer Spaniel, Cavalier King Charles Spaniel and Staffordshire Bull Terrier were all found to be at increased risk of exertional heat-related illness when compared to the Labrador, with these breeds plus the Pug, Boxer, Golden Retriever and Border Collie at increased risk when compared to crossbred dogs.
Younger dogs (under 8 years old) were at increased risk of exertional heat-related illness, as were male dogs and neutered dogs. Overweight (both obese and large for their breed) dogs were also at increased risk, as were brachycephalic dogs in general.
This finding reflects the situation in humans, with young athletic men at greatest risk of exertional heat stroke, either following sport or after working in hot environments.
Which dogs are most affected by hot weather?
The breeds most at risk of environmental heat stroke – heat-related illness occurring after being exposed to hot weather alone without exercise – were the Chow Chow, Bulldog, Pug and French Bulldog. Again, dogs were found to have similar risk factors to humans for environmental heat stroke, with older dogs (aged 12 years or over) 3 times as likely to develop the condition.
The risk to flat-faced dogs
Brachycephalic, or flat-faced dogs, had two times the risk of environmental heat stroke and three times the risk of vehicular heat stroke when compared to mesocephalic dogs (e.g. those with a medium skull shape, like the Labrador or Springer Spaniels).
Flat-faced dogs are known to overheat at relatively low ambient temperatures (e.g. 21-22°C ), due to their limited capacity to cool via panting. Our findings suggest they are at increased risk of all types of heat-related illness, so efforts to change current breed standards and “breed to breathe” should be prioritised in the face of rising global temperatures.
How do you keep your dog safe?
The crucial thing is to know your dog.
Be able to recognise when your dog is getting hot – are they starting to pant, lying down more, seeking shade and cool surfaces to lie on. Know if your dog will run until they collapse, as these “eager to please” dogs like the Golden Retriever, Springer Spaniel and Staffordshire Bull Terrier are particularly at risk when out walking, running or even playing in warm weather.
If you own a flat-faced dog you need to be extra cautious in any situation where they could be exercising or exposed to a hot environment. Consider carrying water with you so you have a means of cooling them if you need to.
If your dog is older, you need to be particularly cautious in hot weather. Just like humans, older dogs struggle to control their body temperature in hot weather, so you need to check that your dog is actually drinking enough, keep an eye on them sunbathing in hot weather, and consider using paddling pools and frozen treats to help them stay cool.
Dogs die in hot cars, but in the UK more dogs die after exercise, even during cooler months. Think carefully before taking your dog on a long walk in hot weather, and if you’re heading to the beach, make sure you can keep them cool and out of the sun.
Our latest study looked at temperatures falling outside the range of 8-25°C . Broadly speaking, 25°C is the upper comfortable threshold for dogs to control their body temperature, slightly above the upper limit for some brachycephalic dogs to cool themselves unaided. This range is also the temperature threshold for the storage of many veterinary and human drugs, outside of which they can lose their efficacy with potentially dangerous consequences. An additional threshold over 35°C was included, at which point all dogs struggle to thermoregulate, particularly when enclosed in a car with no air movement.
The internal temperatures of four cars were monitored over a two-year period. This allowed us to monitor the temperatures 24 hours a day (no dogs were kept in the cars for the purposes of the study!). By the end of the study period, we had between 7300 and 17800 individual temperature readings for each month of the year. This allowed us to look at the impact of time of day and seasonality on internal car temperature.
UK car temperatures
Internal car temperature ranged from -7.4°C to 54.5°C with temperatures dropping below 8°C in every month except June and July. Temperatures exceeded 25°C in every month of the year and above 35°C from April to September. And whilst early mornings were generally cooler, temperatures over 35°C were recorded between 8am and 9pm.
The highest temperature recorded was 54.5°C
It is also worth bearing in mind that the risk may extend beyond stationary vehicles. Sitting in traffic on a hot day, or an air conditioning system failure could also be lethal for dogs trapped in the car.
This study highlights the year round risk to dogs in cars and the need for constant vigilance. This is particularly the case for those breeds and types of dogs considered more at risk of heatstroke, such as brachycephalic, overweight and older dogs.
The study highlights that the risk to dogs in cars is year round, not just restricted to the traditionally warmer summer months. Heat-related illness can be fatal so whenever dogs are in cars, owners should be cautious. Whilst traditionally the advice is to avoid exercise during the midday heat, peak car temperatures occurred between 14:00 and 17:00 hours from March to October. So late afternoon, from spring to autumn is the most at dangerous time for dogs in cars.
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:
You may have been wondering where we’ve been and what we’ve been up to, as it seems an age since we last shared any updates on our canine heatstroke research project…
Well, we finally have some exciting news!
Hot Dogs at BSAVA Congress 2020
Last month Emily presented two abstracts (preliminary findings) at the British Small Animal Veterinary Association’s annual Congress. Whilst the live event was an early casualty to the COVID19 lockdown, the abstract session was moved on-line in May, reaching a virtual audience of over 160 veterinary professionals from around the world.
The first abstract summarised our first study using the VetCompass TM database, reviewing the anonymised veterinary records of over 900,000 UK dogs to explore canine risk factors for heat-related illness. This abstract can be downloaded in text form below, or you can watch a recording of the presentation.
The second abstract explored the “triggers” for heat-related illness in UK dogs, reporting the most common reasons dogs develop heatstroke, and which reasons had the highest risk of causing death. This abstract can be downloaded in text form below, we hope to be able to share the video soon.
Findings from our VetCompass study will be published 18th June at 4pm!
Finally, our first Hot Dogs VetCompass study will be published TOMORROW AFTERNOON, where we report the incidence, fatality rate and canine risk factors for heat-related illness in UK dogs (the full paper of the first abstract). Thanks to a Dogs Trust Canine Welfare Grant this paper is Open Access, meaning you will be able to read the full version for free just as soon as it is published!
Watch this space for updates, we’re hoping it’s going to be a busy summer sharing our research, to help you make safer choices for your dog.
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.
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.
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?
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.
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 average car is a metal box with glass windows. Metal is an excellent conductor of heat, meaning heat can pass through metal easily, think of your kitchen saucepans. Glass is a poor heat conductor but allows sunlight to pass through. This means that light energy from the sunlight enters the car through the windows but then gets trapped as heat by the glass. Some of this heat will be lost through radiation and conduction into the surrounding air, but if sunlight continues to fall on the car, it will continue to heat and in summer, this happens far quicker than heat can be lost to the environment; the reason greenhouses are so effective. The net result is your classic summer hot car.
The typical British summer is an unpredictable affair. Whilst temperatures regularly reach 20oC or more, often we have consistent cloud cover, intermittent rain or high winds to keep things feeling fresh, and stop cars turning into ovens. Last summer, we experienced one of the first prolonged heatwaves of this century, with temperatures regularly hitting 30oC and endless blue, cloudless skies. We have become complacent. Our dogs are typically part of our family, so we like to take them with us, whether we are taking them for a walk, for a day out, or travelling somewhere. The problem is, on a typical sunny day of 21oC, your average family car will reach temperatures of 31oC in 10 min. As the outside temperature climes to 31°C, the internal temperature of the car can reach 54°C. 80% of that temperature rise happens in the first 30 minutes.
We’ve all seen the adverts, surely no one would be so stupid…?
Since 2016, summer has been heralded by the “dogs die in hot cars” campaigns supported by a number of charities to increase awareness of the risk of leaving dogs in cars in the summer, and yet last year (2018) the RSPCA received 8290 calls, an increase from around 7800 calls concerning heat exposure in animals 2017. In a single weekend, over the 2018 May Bank holiday weekend, 217 calls were made by people concerned about dogs left in hot cars. One London police force was even offering a ‘free ventilation service’ if dogs were left in cars during the hot weather (by breaking the window).
So why do people leave dogs in hot cars? A two-minute trip into the shop for a couple of forgotten items can easily become ten minutes. When questioned, owners gave a range of excuses, from “My dog is white, he’ll be fine” to “We feel bad leaving him at home on his own all day.” “We didn’t think we’d be long.” “It’s OK, I’m a vet”. No doubt, the vast majority of people do not want to harm their dog, but simply do not think. When leaving the car, the air con or open windows from travelling can make the car feel relatively cool. However, left in the sun for any length of time, even with the windows cracked slightly, it will get hot. Shade can help to keep the car cooler, but as the sun moves round, the shade can quickly disappear.
A human in a similar situation would begin to sweat to try and lose heat. Dogs don’t have the ability to sweat, they will pant, but as the temperature continues to rise, panting becomes less effective, and once the car temperature exceeds body temperature (around 38oC) there is nothing the dog can do to cool down. Unless the dog is actively cooled (see below) their body temperature will rise with the car temperature, and once they exceed 41oC, they are likely to develop heatstroke.
Heatstroke – the problem
Heatstroke isn’t the same thing as sun stroke, or heat cramps, or heat exhaustion. These conditions can often be treated with cooling, plenty of fluids and rest. True heatstroke causes multi-organ failure. Picture an egg in a frying pan, you crack the egg, the yolk is yellow but the egg white is clear and jelly like. Once the egg starts to heat, the chemical structures of the proteins start to change, the egg white becomes firm and changes colour. Now imagine this happening to the proteins within the body. As body temperature exceeds 41oC the stomach and intestines stop functioning, so the dog may vomit or pass bloody diarrhoea. The kidneys stop working, so despite fluid therapy the dog is unable to flush out the toxins from all the cellular damage taking place around the body. If the dog’s brain overheats, they may start fitting, or fall into a coma. The mortality rate for dogs with heatstroke is up to 63%.
Don’t risk it.
Don’t keep your dog in the car and never leave them unattended. Even in the shade, car temperatures can increase quickly, and shade may disappear. Leaving windows partially open has little effect on car temperature. If you are stuck in traffic or travelling, have the air conditioning on to keep the car cool and make sure windows are shaded from direct sunlight. Don’t assume your dog in the car boot area is fine because you are, check them regularly, your air conditioning may not reach the boot. Ideally, leave your dog at home in hot weather. Car shields and shades may help to keep the car cool by reflecting the sun’s rays, but some may also act as an insulator, particularly if the car is already hot inside. If you have no alternative other than to keep your dog in the car, open all windows, open the boot, try and maintain airflow, park in shade, and don’t leave your dog. Stay with them so you can be absolutely sure they are OK.
If you see a dog in a hot car, the advice is to phone the police. Heatstroke can kill quickly. A dog that is suffering from heatstroke needs to be actively cooled and taken to the vets. Active cooling is key. Even before setting off to the vets, use water to splash the dog’s legs, belly and throat area, get them out of the sun and into the shade, and if possible move them somewhere with good air flow – this might be in a car with the air conditioning already blowing. To give you an idea, the army have been known to use the downdraft from helicopter rotor blades to create airflow over soldiers with heatstroke. Next, getting to the vets as quickly as possible is the current best advice. Avoid using ice or very cold water, as this can do more harm. When your skin is cold, the blood vessels constrict, which can make it harder to cool the dog, and increase the risk of them going into circulatory collapse (shock).
There is no guarantee any dog will survive heatstroke, so the best way to keep your dog safe is to prevent it.
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:
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.
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.
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
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.
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:
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).