What causes fever in dogs?

Determining if your pet has a fever can be determined quickly by taking his temperature. Check out our step-by-step guide, here!

Fever vs. Hyperthermia

A dog’s normal temperature ranges from 99.5-102.5 degrees Fahrenheit. A temperature that is 103 or higher indicates an illness with fever or hyperthermia.

A fever is defined as an elevation in a pet’s temperature due to a change in their “set point”, where the body thinks it should have a higher temperature than normal and rises in response.

Hyperthermia is defined as an increase in a pet’s temperature due to external heat influences.

A fever is often due to an underlying disease or illness. As a defensive mechanism, the body tells itself to increase its temperature to help fight disease through numerous different complex pathways. A fever is also commonly referred to as “pyrexia” in the medical word.

In animals, we also often see our pets with elevated temperatures that are not technically a fever, but instead hyperthermia. In cases of hyperthermia, the pet’s elevated temperature is not from an immune response, but instead from being unable to cool itself properly. This happens in situations such as the pet being in a hot car, overexertion, or being outside too long in the sun.

A common example of how pets appear different with a fever vs. hyperthermia is that a pet with a fever is often shivering, whereas, a hyperthermic pet often appears to be panting, distressed, or weak. Their temperatures may be the same in this example, but the underlying causes and treatments can be quite different.

What are the symptoms of a fever?

Due to the change in the internal thermostat, febrile pets often don’t appear overheated. Symptoms of fever in dogs can include:

• Lethargy/Depression
• Shivering/Shaking
• Decreased appetite/Decreased water intake
• Coughing
• Vomiting
• Decreased urination
• Temperature above 102.5 when resting quietly

What are some causes of fever in dogs?

Although many different things can cause a fever, the most common categories are:

• Infection - Different types of infections most commonly causing a fever include bacterial, viral, fungal, tick-borne illness, and some parasitic disease. Some examples of these diseases include pneumonia, parvovirus, distemper virus, leptospirosis, kidney infections, uterine infections, and Lyme disease.
• Inflammation - This is suggestive of a large inflammatory response in the body that is not necessarily related to an infection. Different types of auto-immune diseases or inflammation can cause fevers when the body increases its immune response. Examples of this include Lupus, Immune-mediated hemolytic anemia, and other diseases like immune-mediated meningitis.
• Neoplasia - Cancer causes severe inflammation in the body as well as secondary problems (like infection, for example)
• Drug Reaction or Toxicity - A drug reaction (allergy) or toxicity to known poison can cause a fever
• Vaccination - Due to intentional stimulation of the immune system, vaccines often cause a mild fever 1-2 days after they are given. This is considered a normal side effect in most cases.

How is a fever treated in dogs?

Just like in humans, the underlying cause of the fever is often the focus of treatment for pets with fevers. If an infection is uncovered such as a bacterial or fungal disease, antibiotics or antifungal medications will likely be started. In cases of viral disease, supportive care is initiated, much like in how human flu is treated with rest and fluids. In some cases, antiviral medications may be used as well.

In other situations, like cancer, autoimmune disease, or drug reaction, very specific treatment plans are formed for each pet. These are tailored to the exact disease process as well as their clinical appearance. Treatment may range from hospitalization with IV fluids and medications to outpatient therapy with things like steroids or immune-suppressant drugs.

In any case, however, a fever is an indicator that medical care should be sought. A veterinarian should be utilized to determine the root cause of your pet’s fever so appropriate therapy can be started as soon as possible. Early intervention can be extremely beneficial to prevent dehydration, malnutrition, and help your pet return to normal as quickly and safely as possible.

A word about Hyperthermia (heat stroke) in dogs

In cases of overheating or heatstroke, it is absolutely crucial that the pet receives emergency care immediately. Use your judgment to help you discern this:

• Is the pet visibly panting and overheated?
• Are they conscious or comatose (severe heat stroke)?
• Were they in a hot environment where overheating is likely?
• Do they appear visibly stressed with pale or dark gum color?

If there is any question that your pet may have overheated, take them immediately to an emergency vet and institute cooling by applying lukewarm or cool water to the belly and paws.

Read more:

16 Summer Dangers for Dogs

Parvovirus in Puppies: A Treatment and Prevention Q&A

How to Examine Your Pet at Home: A Step-By-Step Guide

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