What Are the Symptoms of Fever in Dogs?

Written and verified by the vet Juan Pedro Vazquez Espeso

Last update: 27 December, 2022

Fever in dogs is, without a doubt, the most frequent illnesses in veterinary clinics’ day to day work. It’s usually a sign of some sort of illness, either infectious or otherwise. Furthermore, fever carries a series of associated symptoms, which are quite characteristic.

Given the high frequency with which fever occurs in animals, it’s important to know the symptoms that this produces in their bodies. Keep reading if you want to know what the symptoms of fever in dogs are.

What is fever?

Fever, as we all know, has to do with body temperature. For that reason, to begin with, you should be aware of the normal body temperature of the species that we’re going to talk about today: dogs.

In dogs, veterinarians consider a temperature between 100.4 F and 102.2 degrees Fahrenheit to be normal. So, fever occurs when there’s an increase in this temperature. To be a bit more technical, we can define fever as a disorder of the thermal regulation that forces the animal to adapt to a temperature level that’s higher than normal.

Unlike hyperthermia, where the source of heat is exogenous and the regulatory mechanisms of body temperature – the hypothalamus – work properly, in fever there’s a change in these mechanisms.

When the hypothalamic thermostat is altered and 105.8 degrees is considered normal, then 102.2 degrees Fahrenheit (which would be the usual temperature) is interpreted as hypothermia. So, the body will work at a metabolic level to increase those degrees of difference.

Causes of the fever

Most of the causes of fever are usually septic and infectious, both localized and generalized. For example, an infected wound can produce this scenario. There are also non-infectious events that cause fever. We’re talking about the following:

• Certain tumoral processes, especially with rapid growth
• Vascular hemolysis
• Heart attacks
• Even an intramuscular injection with local reaction can produce fever

Considerations, fever and hyperpyrexia

The symptoms produced by the fever will depend, fundamentally, on two factors:

• The characteristics of the animal: This pathological process isn’t the same in puppies as in adult dogs. Nor will a healthy dog have the same symptoms as a sick one.
• Type of fever: A slight fever of a few tenths of a degree can produce some symptoms that aren’t noticeable at all. On the other hand, a pronounced fever, called hyperpyrexia in medical jargon, will cause more evident symptoms.

Symptoms of slight fever in dogs

Fortunately, this is the most common occurrence. On most occasions, fever in dogs that’s seen to in a consultation usually doesn’t exceed 104 degrees. What’s more, in some cases, this fever appears as a coincidental finding in a veterinary exam without the owner having perceived anything.

In these sick dogs, the following symptoms can be noticed:

• Slight decline and apathy.
• Lack of appetite, as the dog may even reject the food completely.
• Dry and hot truffle. This isn’t always indicative of fever, but sometimes there’s a direct relationship with it.
• Slight dryness of the mucous membranes.

Symptoms of hyperpyrexia

When a dog’s body temperature exceeds 104 degrees, then we’re looking at a high fever or hyperpyrexia. In these cases, animals usually show more accentuated symptoms. Likewise, hyperpyrexia can endanger the dog’s life, so speedy treatment is necessary.

A dog with hyperpyrexia will show all or some of the following symptoms:

• Very pronounced dryness in the mucous membranes. When touching these tissues, they feel completely dry.
• A decrease in the amount of urine produced, as well as an increase in its concentration. Very dark and odorous urine is typical.
• A marked decline in the animal. There may even be a decrease in reflexes and a lack of response to external stimuli.
• Loss of muscle mass and anorexia. It’s usually very evident to the naked eye and comes on very noticeably.

Prevention and speed

In general, these are the most common symptoms that produce fever in dogs. Despite these general guidelines, it’s necessary to emphasize that each animal is different. A dog may not show any symptoms at all, while another will be listless and with no energy for several days.

In cases of hyperpyrexia, the symptoms reveal that the dog’s life may be in danger, so a visit to the vet should be immediate. We hope that this advice will be useful to you in detecting the symptoms of this process in dogs early on.