Hot dogs – the causes of fever and increased body temperature
It’s time for your dog’s annual physical examination. Your dog excitedly jumps into the car, leaps across your vet’s waiting room to greet other dogs and hops up and down on the clinic scale. By the time the veterinarian or veterinary technician takes your dog’s vital signs, your dog’s temperature is elevated. That higher temperature is probably due to excitement, but what makes it different from a fever? Or heat stroke? Suppose your pet is ill, but also nervous about their trip to the veterinarian – how do you sort out the causes of an increased temperature in that situation?
In order to determine the cause of increased body temperature, we need to review some definitions as well as understand how the body regulates temperature.
Hyperthermia refers to an increase in core body temperature for any reason. Hyperthermia can be further divided into pyrogenic hyperthermia, or “true” fever, and nonpyrogenic hyperthermia.
For a dog’s body to function efficiently, the body needs to maintain a core temperature in a very tight range, between 99 F and 102 F. The body has many mechanisms to respond to changes in environmental temperature in order to maintain this range, such as shivering, panting and posture changes. The hypothalamus is the part of the brain responsible for temperature regulation, acting as an internal thermostat.
The hypothalamus can reset the body’s temperature in response to substances called exogenous pyrogens. Examples of exogenous pyrogens (causes of fever) include infectious agents such as bacteria, tissue inflammation and certain drugs. The hypothalamus “turns up” the internal thermostat in response to these substances, causing a true fever. There is good evidence this response can be beneficial, although prolonged high fever needs treatment. True fever indicates a problem elsewhere in the body, and many true fevers subside when the underlying cause is addressed.
Nonpyrogenic hyperthermia occurs when the body cannot rid itself of excess heat. The classic example of nonpyrogenic hyperthermia is heat stroke, but other lesser known causes include seizure activity, brain tumors involving the hypothalamus, and exercise.
Treatment of increased body temperature depends on the underlying cause. Some veterinarians question whether low-grade, true fevers should be specifically treated, since evidence suggests that the fever may be beneficial. However, all clinicians agree that fevers above 106 F, and fever lasting more than two or three days require attention. For nonpyrogenic hyperthermia, the use of cooling measures, intravenous fluids, and oxygen are indicated.
As we learn more about how the body adjusts and regulates its temperature, as well as the myriad of substances involved in fever development and perpetuation, we can better assess the best way to treat (or not treat) elevated body temperature. Morris Animal Foundation’s Golden Retriever Lifetime Study will help us better understand the causes of fever, and if and how best to treat them.