Heatstroke In Dogs And Cats

Dogs and cats are unable to cope with this rising temperature as we humans because humans have sweat glands all over the body while in case of dogs and cats they are present only in paws and nose.

Summer in Pakistan is crossing 40 degree centigrade daily according to Pakistan Meteorogical Department (PMD). The animals and humans are highly vulnerable to the weather harshness. The pets demand food, shelter and care to avoid these weather peaks.  To cope with rising environmental temperature, they have to rely on panting and external cooling. As increase in environmental temperature is directly proportional to increase in body temperature that ends generally with situation called as Heatstroke if left unnoticed. Heatstroke is more than normal body temperature resultantly harming to the body tissues. Heatstroke is characterized by when dog’s boy temperature rises greater than 105.8°F while in cats more than 104-105°F. Death rates are high as much up to 62% if owner delays in taking their beloved pets to the owner. The underlying mechanism involves imbalance insufficient heat dissipation. Here in this short communication, brief discussion of heatstroke in dogs and cats is being presented.

What is heatstroke?

Heatstroke is actually hyperthermia i.e. elevation in body temperature. Hyperthermia is of two types. It may be either pyrogenic or nonpyrogenic. If the body temperature rises due to any infection which is usually referred as fever. While in case of nonpyrogenic hyperthermia animal’s temperature elevates than normal and body fails to return at normal level. Its causes include the damage to hypothalamus or any variation in body’s regulatory system to return temperature to normal.

Types of heatstroke?

Heatstroke may be exertional or nonexertional. Exertional hyperthermia occurs when animal’s, especially dogs plays or work in environment, which are not acclimatized. Nonexertional heatstroke is caused by animal’s inability to dissipate heat because of lack in shade or water, decrease in airflow or increase in environmental temperature and humidity. Heatstroke is nonpyrogenic nonexertional hyperthermia.

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Pathogenesis:

Thermoregulation, acclimatization, production of heat shock proteins (HSPs), acute-phase response (APR), acute-phase response (APR) are some of the factors which are responsible for imbalance between heat generation and dissipation.

Thermoregulation:

Thermoregulatory center of hypothalamus maintains the body temperature within a narrow range (called as “set-point”) by keeping the balance between heat production and dissipation. Heat is produced either endogenously (heat generated from metabolism) or exogenously (heat generated from environment). Heat is dissipated from the body by 4 mechanisms i.e. conduction, convection, radiation, and evaporation. When body comes in contact with any cooler surface conduction occurs, i.e. heat is transferred from hot surface to cooler surface (e.g. placing the animal on cold steel table). Transfer of heat when air flows over the body is called as convection, e.g. placing the animal in front of fan, this cool air will warm down the animal’s body. Evaporation is the process of changing body’s fluid into water, this process plays a vital role in dissipating body heat when environmental temperature rises above 32 ℃ (89.6 ℉). Evaporation occurs as perspiration (sweating) in humans, although perspiration occurs in dogs and cats via foot pad but it is not sufficient to cope up with the rising temperature, rather than they used panting to dissipate their body heat.

Peripheral and hypothalamic heat receptors are activated on elevation of blood temperature of 1℃ (1.8 ℉) ultimately leading to activation of hypothalamic thermoregulatory center. This results in increase in blood supply to the body tissues by efferent reposes of this center such as cutaneous vasodilation and constriction of renal and splanchnic blood vessels. Panting center receiving neurogenic signals from hypothalamus starts the initial mechanism of heat dissipation in dogs by panting. Tachycardia also occurs to maintain the body temperature. If there is dehydration then it will impair the function of evaporation because there is less water to make it vaporize and cool the body.

Acclimatization:

It is a physiologic process of body to adapt the changing environment or climatic change. Usually animal took 10 to 20 days to partially adapt to changing environment but it can take up to 60 days for complete acclimatization.

Acute Phase Response (APR):

APR is a systemic controlled set of reactions which are activated as a result of inflammation protecting against tissue injury and promoting the healing. The APR is initiated and modified by cytokines and cytokine modulators. Interleukin 6 produced as a result of heat stress is the major APR inducer. It regulates the response by controlling the levels of the inflammatory cytokines and stimulates production of antioxidants & acute-phase proteins that are anti-inflammatory. The systemic inflammatory response syndrome, sepsis, septic shock, and stress response are all varying degrees of the APR. An exaggerated and inflammatory APR is involved in the development of heatstroke.

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Heat shock Proteins (HSPs):

HSPs increases the potential of enzymes to work during heat extremes. nearly all cells of the body produce HSPs in response to instant increases in temperature and other stressors, acting as ‘protein chaperones’ or ‘molecular guardians’ which instigate a state of cellular tolerance to help keep intracellular function and structural protein integrity.

 

HSPs facilitate protein mend, modulate and provide protection against apoptosis. These proteins may also help in maintenance of antioxidant pool and protection against oxidative stress. HSPs also provides protection against arterial hypotension and cerebral ischemia.

 

Predisposing factors:

  • A hot humid environment with meager ventilation (e.g. high temperature or leaving the pet in unventilated room or car)
  • Inadequate shelter
  • Limited supply of drinking water
  • Obesity
  • Flat face breeds are more prone to heatstroke like Bulldogs, Pugs, Persian and Himalayan Cats
  • Long hair breeds are more susceptible than short hair breed like Persian
  • Young age is comparatively more prone
  • Excessive exercise

Signs and symptoms:

  • Panting, which increases more than normal
  • Drooling, salivation
  • Restlessness
  • Tachycardia (Increased heart rate)
  • Diarrhea and vomiting
  • Epistaxis (bleeding from nose)
  • Dizziness, staggering
  • Lethargy, weakness
  • Muscle tremors
  • Seizures
  • Collapsing and lying down
  • Dysuria to anuria (Little to no urine production)
  • Coma
  • Death (if not treated)

Emergency first aid at home?

The first step toward saving pet is getting animal to normal to their body temperature as soon as possible because deaths rates can be decreased from 62% to 39% according to a study after adapting following precautions before taking pet to the vet.

  • Pour or spray cool water on the animal’s fur and skin.
  • Place the animal in front of fan to aid heat dissipation process.
  • Don’t use the ice-cold water or ice otherwise it will exacerbate the problem.
  • Take TPR (temperature, Pulse, Respiration) of your pet, if you are trained for this
  • Take your animal to nearest veterinarian immediately
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Feeding in case of heatstroke?

Following natural foods can be used to keep your pet cool in this hot weather;

Proteins: beef, beef liver, chicken eggs, cow’s dairy, salmon

Carbohydrates: yam, white rice, white potato, pumpkin

Fruits and vegetables: carrots, pineapple, raspberry, cabbage, cauliflower, cucumber

Preventive measures:

Following measures can be adopted by pet owners to avoid heat stroke;

Don’t leave the animal in car:

No, don’t even think you will be back in few minutes. Temperature in cars rise multifold and there is no proper ventilation when you leave your car. It’s better to leave your pet at home when you are going somewhere or go places where he can be with you.

Keep your home cool:

If you are leaving your pet alone at home then make sure that there is proper cooling at home. Leave the air conditioner or fan on with drapes off.

Watch when exercise:

in hot and humid environment limit your exercise. Try to do exercise at cooler time of day like early morning or evening. Carry enough water with you adequate for both of you.

Examine the pavement:

have you ever tried to walk bare footed on concrete floor or road in hot summer day? Your pet’s paws are just also sensitive to this heat as your bare feet are. Try to walk on grass or any other surface which stays cooler to avoid blistering on paws.

Offer excessive water and shade:

Don’t leave your pet stay longer outside. When he is there make sure is continuous supply of water and enough shade. Trees are better shade providers than dog/cat houses because these houses can trap the air but there is continuous supply of fresh air in case of trees.

Groom your pet:

Get rid of mats or tangles if you pet have long hairs. Clip or shave the long hair from animal’s body after consulting the vet, because the fur which keeps the animal warm in winter sometimes make him cool in summer.

Ayesha Qayyum

Ayesha_Qayyum

M.phil Chemistry, University of Agriculture university, Faisalabad

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