Hopefully by now, most people have seen the warnings that dogs die in hot cars. They die of heatstroke because trapped within a car, with little or no air flow, they get hotter and hotter. Once their internal blood temperature exceeds 41^oC their internal organs become damaged and begin to shut down. This can take minutes.

But hot cars are not the only reason dogs die from heatstroke. Increasingly, hot countries are reporting that exercise is the major reason dogs get taken to the vets with heatstroke. Now in the UK we’ve been lucky.  Traditionally, the UK doesn’t see much hot weather, and when we do, it usually doesn’t last long before we get rain, wind, sometimes even the odd summer snowfall!

But this is changing.  Climate change is increasing the number and frequency of abnormal weather events.  Look at 2018, at home in the Midlands in March it was -7^oC. Three months later it hit 32^oC on my driveway. Three months is 90 days.  Heat acclimatisation takes around 60 days.  I remember de-icing the car on Easter weekend, so before the prolonged period of heat hit, we didn’t have 60 days to acclimatise to the heat, and neither did our dogs. Already there have been reports of dogs presenting to veterinary practices suffering from heatstroke following exercise, one dog lost their life following a walk in the heat.

Heatstroke happens when exercising dogs get too hot and stay hot.

Dogs and temperature

Unlike horses and people, dogs can’t sweat.

Unlike horses and people, dogs come in an enormous range of sizes, colours, coat types and length, breeds and personalities. Ok, people and horses are also pretty variable, but you don’t often see a x40 difference in body weight like you do in dogs.

Because dogs can’t sweat, and because they are so variable, there is NO SAFE TEMPERATURE.  In our research we saw dogs reaching a critical temperature (over 40.6^oC and up to 42.5 ^oC when measured with an ear thermometer) at every race we attended over a two year period.  At every race.  Some races it was snowing, the hottest race was 15.4^oC. We’ve spoken to canicrossers (people who run with their dog in harness) who have seen dogs collapse from heatstroke with snow on the ground (on-going project so no reference yet!). Yet we’ve also seen dogs competing in long races in the middle of summer crossing the line safely.

There is no easy way to predict which dogs will overheat.

You need to know your dog. Some dogs will tell you when they’ve had enough. They’ll lie down, or seek shade, or just flatly refuse to move! But some dogs will run until they drop, so they need to be managed with exercise only in the cooler mornings and very late evenings.

A cautionary tale

Danny lost his beautiful dog Brodie in June 2018.  The temperature was 19^oC. Brodie wasn’t working hard.

[Videos – click the links to view]

WARNING this may be distressing to hear: Danny after Brodie collapsed

This is what he was doing before he collapsed; listen to Brodie’s breathing at the end of this video, something wasn’t quite right: Brodie training

Brodie collapsed shortly after this video was taken.  Tragically he died from heatstroke.

Danny has kindly allowed us to share Brodie’s story, because like us, he would like to see canine heatstroke become a thing of the past.  Heatstroke kills dogs. Veterinary hospitals report mortality rates of up to 63% in dogs with heatstroke.

Your dog won’t die from a missed walk, or run or training session.  If they get heatstroke: flip a coin. Heads you win, tails they lose.

Dog’s cool in a number of ways.

Like us, dogs have a number of ways to cool down if their core temperature gets too high.

• Radiating heat into the air around them – the hotter the air, the more humid the air, the less this happens.
• Conducting heat to their surroundings – if the ground is hot this won’t happen.
• PANTING! Air in the lungs is moistened, meaning water evaporates as the dog pants. If the dog can’t move enough air, or if the dog is in a humid environment, this becomes ineffective.

So if it is hot and humid dogs will struggle to cool.

But even if it’s cold and dry, if your dog can’t move air, their main cooling mechanism isn’t working.

Panting, some key facts

In order to pant, dogs need to be able to move air.  Anything obstructing air flow, will limit the effectiveness of panting and therefore cause the dog to overheat more quickly (see below for respiratory disease).

• Brachycephlic breeds
• Laryngeal paralysis (see below)
• Tracheal collapse
• Any respiratory disease, or heart disease that affects normal breathing.

In order to lose heat through panting, dogs need enough water in their body to moisturise the air.   A dehydrated dog will conserve water and produce less saliva, and not moisturise the air in their lungs as much as a well hydrated dog.  Unsurprisingly, they get hotter quicker when exercising.

• Vomiting
• Diarrhoea
• Anorexia (not eating)
• Being in a hot environment
• Urinating more frequently (diseases like diabetes, Cushings, hypothyroidism, renal disease can all cause this)
• Not being given enough to drink or something nice to drink

Anything that could make your dog even slightly dehydrated could increase their risk of heatstroke if they are exercising. The same as people!

How do I know if my dog has a respiratory condition?

Usually, this is fairly obvious. If you’re sat on your sofa watching television, can you hear yourself breathing? No? Good, this is normal! Noisy breathing happens when there is turbulence in the respiratory tract.  This could be a narrowing, a flap of tissue, or liquids like mucous or pus. Narrowed airways may cause wheezing, or whistles. The classic noise is snoring.  If you can hear your dog breathing when they are at rest (and awake), this isn’t normal.

However, this isn’t always the case. My family dog Holly (the Goldie here) had laryngeal paralysis (LP).  This is a disease one respiratory specialist vet described as “something that can be diagnosed whilst walking past a dog in the street”. They’re normally noisy.

[Videos – click the links to view]

Extreme laryngeal paralysis – this is an advanced case.

Cyanotic dog with laryngeal paralysis – note the blue tongue!

LP dog at the vets – not so obvious, panting, but listen to the forced exhale.

Holly wasn’t a noisy breather. She panted quite a lot but never made ANY noise.  I am a vet, and I missed it.  She started collapsing on walks. She would go very pale, collapse, and then about 5 minutes later get up and be fine! I checked her, found nothing. Checked her again, found nothing.  Then one day I was there, her heart rate was over 300 beats per minute and that’s not normal! So I referred her to a cardiologist thinking she must have a heart problem, they eventually examined her airway with an endoscope and found her LP. Her diagnosis was made almost by accident.

Because we then knew she had a respiratory problem we were careful with her.  We kept her cool, we kept her walks short, we kept her weight as low as we could. Because of my background, I knew she was at an increased risk of heatstroke, so I made sure she wasn’t put at risk.

If you are worried about your dog, get them checked by a vet.  If they find nothing, but you are still worried, get them checked again.  Don’t be afraid to ask for unusual things.  If your dog’s problem happens during or after exercise, ask if you can walk them in the car park and have them examined during and after exercise.

If you know, or suspect, that your dog is suffering from any kind of respiratory problem, be extra careful. Keep your dog cool in the warm weather and don’t risk exercising during the heat.