Feel­ing the heat

Dogs feel the heat too and ac­cess to wa­ter is cru­cial, es­pe­cially for ac­tive hunt­ing dogs, as vet­eri­nar­ian Dr Karen Davies ex­plains.

Field and Game - - VET ADVICE - With Dr Karen Davies

Ris­ing tem­per­a­tures and longer days dur­ing sum­mer are a risk for dogs, par­tic­u­larly ac­tive ones like hunt­ing dogs.

When a pet’s body tem­per­a­ture rises through ac­tiv­ity, they re­lease ex­ces­sive body heat through pant­ing and their paws. Un­for­tu­nately, in high en­vi­ron­men­tal tem­per­a­tures, the pet can­not eas­ily lower their body tem­per­a­ture and heat­stroke can de­velop. Heat­stroke can be eas­ily pre­vented if early signs of heat stress such as ex­ces­sive pant­ing and agitation are ob­served and man­aged early. A dog’s nor­mal tem­per­a­ture is around 38°C and when it rises to 40°C there is a prob­lem.

Hyper­ther­mia is de­fined as an el­e­va­tion in body tem­per­a­ture above the gen­er­ally ac­cepted nor­mal range of body tem­per­a­tures; although pub­lished nor­mal val­ues for dogs and cats vary slightly, it usu­ally is ac­cepted that body tem­per­a­tures above 39°C are ab­nor­mal.

Hyper­ther­mia can be cat­e­gorised into ‘fever’ and ‘non-fever’ hyper­ther­mia: fever hyper­ther­mia re­sults from in­flam­ma­tion in the body (such as se­condary to a bac­te­rial in­fec­tion); non-fever hyper­ther­mia re­sults from all other causes of in­creased body tem­per­a­ture.

Heat stroke is a form of non-fever hyper­ther­mia that oc­curs when heat-dis­si­pat­ing mechanisms of the body can­not ac­com­mo­date ex­ces­sive heat; heat stroke can lead to mul­ti­ple or­gan dys­func­tion, also termed heat ex­haus­tion or heat pros­tra­tion.

Tem­per­a­tures of 41°C or higher, with­out signs of in­flam­ma­tion, are sug­ges­tive of ‘non-fever’ hyper­ther­mia.

Malig­nant hyper­ther­mia is an un­com­mon ge­netic non-fever hyper­ther­mia that can oc­cur. It is of­ten seen in pigs (es­pe­cially black ones) and deer, stressed prior to be­ing dis­patched. This ef­fec­tively cooks the beast from the in­side out and the meat will ei­ther go to jelly or be in­cred­i­bly tough.

Other causes of non-fever hyper­ther­mia in­clude ex­ces­sive ex­er­cise, ex­ci­ta­tion, stress and a num­ber of un­der­ly­ing ill­nesses.

The fol­low­ing in­for­ma­tion pri­mar­ily re­lates to non-fever hyper­ther­mia.

Breeds

May oc­cur in any breed but long-haired breeds, dou­ble coated breeds, and short-nosed, flat-faced (known as ‘brachy­cephalic’) breeds are at greater risk.

Mean Age and Range

All ages can be af­fected but sus­cep­ti­bil­ity is greater with young and old dogs. Young dogs tend to over ex­ert them­selves while older dogs may have un­der­ly­ing dis­ease.

Causes

Iden­ti­fi­able un­der­ly­ing causes in­clude ex­treme weather, be­ing locked in car or other con­fined area with­out ad­e­quate ven­ti­la­tion, ex­ces­sive ex­er­cise and re­stricted ac­cess to wa­ter.

Signs

Signs are vari­able but the clues are there: pant­ing, ex­ces­sive drool­ing, in­creased body tem­per­a­ture (hyper­ther­mia), red­dish or pale gums and moist tis­sues of the body suck as the mu­cous mem­branes or a bluish dis­coloura­tion of the skin and moist tis­sues, which is caused by in­ad­e­quate oxy­gen lev­els in the red blood cells.

A rapid heart rate or ir­reg­u­lar heart­beats, shock, breath­ing dis­tress and vom­it­ing or pass­ing blood or black, tarry stools could also in­di­cate non-fever hyper­ther­mia.

Dogs can also suf­fer small pin­point ar­eas of bleed­ing, seizures, mus­cle tremors or ap­pear wob­bly and unco-or­di­nated, as if drunk.

Risk fac­tors

Risk fac­tors for dogs in­clude a pre­vi­ous his­tory of heat-re­lated dis­ease, age, obe­sity, a thick coat of hair and de­hy­dra­tion.

Treat­ment

If you recog­nise symp­toms of heat stress in your dog you should act im­me­di­ately to cor­rect its body tem­per­a­ture. Bath the dog in cool wa­ter (this should be easy for duck hun­ters in the field) and ap­ply air­flow, whether in front of a fan or the vent in the car. Do not use cold wa­ter or ice as this will cause blood flow to pull away from the skin, pre­vent cool­ing and make the hyper­ther­mia worse. A shiv­er­ing re­sponse also is un­de­sir­able, as it creates heat.

Stop cool­ing pro­ce­dures when body tem­per­a­ture reaches 39°C to avoid drop­ping too low and seek vet­eri­nary care. Most af­fected pets will need in­ten­sive care for sev­eral days.

No spe­cific drugs are re­quired for treat­ing in­creased body tem­per­a­ture or heat stroke; your vet will make choices based on what they see when they ex­am­ine your pet.

De­spite treat­ment there are pos­si­ble com­pli­ca­tions that can prove fa­tal, some days af­ter the event. It de­pends on the time lag be­tween the cause of the hyper­ther­mia and treat­ment, how high your dog’s tem­per­a­ture was and how long it re­mained el­e­vated.

One episode of hyper­ther­mia or heat stroke in­creases the like­li­hood of fu­ture episodes, so the best medicine is preven­tion.

Preven­tion

Avoid work­ing your dogs on hot days (see the chart) and en­sure only short stints, with plenty of wa­ter, elec­trolyte re­place­ment and time in the shade. En­cour­age them to take a dip in wa­ter even if they aren’t re­triev­ing.

If your dog must be crated, en­sure good air­flow and plenty of shade, even on the back of the truck, in­vest in cool mats for the crates and never leave your dog in the car. Re­mem­ber to watch sur­face tem­per­a­tures too, a dog can’t run on burnt feet.

Vet­eri­nar­ian Dr Karen Davies owns and uses hunt­ing dogs and has broad­ened her ex­per­tise to in­clude an­i­mal re­ha­bil­i­ta­tion, an­i­mal phys­io­ther­apy and an­i­mal hy­drother­apy ser­vices. Read­ers of Field & Game Mag­a­zine can draw on her ex­pe­ri­ence and ex­per­tise by sub­mit­ting ques­tions to edi­tor@fiel­dandgame.com.au Karen can be con­sulted at Di­rect Vet Ser­vices, 8/22–30 Wal­lace Ave, Point Cook, VIC; Email: di­rectvet­ser­vices@big­pond.com or Tel: (03) 9369 1822.

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