In both dogs and humans, a fever is the body's way of fighting infection and inflammation. There are a number of potential reasons why your dog has a fever. Most fevers require a veterinarian's attention.
Causes of Fever in Dogs
A fever is an elevation in body temperature caused by the immune system's response to a perceived threat. Body temperature is regulated in the hypothalamus, sometimes called the body's thermostat. Pyrogen, a fever-inducing substance, causes the white blood cells to produce substances that prompt the hypothalamus to elevate the body's temperature. A fever is the body's attempt to kill pathogens like bacteria and viruses using warmth.
Hyperthermia is not quite the same as a fever; it's an elevation in body temperature due to external heat. Hyperthermia may lead to heatstroke.
A fever itself is not a disease, but a symptom of an illness in the body. Fevers are most commonly caused by infections. Other potential causes are less common. In some cases, the veterinarian cannot determine the cause of the fever and will refer to it as a fever of unknown origin, or FUO.
Infections are responsible for most fevers in dogs. Infections may be bacterial, fungal, or viral in nature. Many bacterial infections occur due to a wound or abscess on the skin or in the mouth. Internal bacterial infections like pneumonia, leptospirosis, urinary tract infections, and tick-borne diseases can also lead to fever.
Some fungal infections like coccidioidomycosis (valley fever), blastomycosis, histoplasmosis, and disseminated aspergillosis are known to cause fevers in dogs. Ear infections often cause fevers. They may be bacterial and/or fungal infections.
Exposure to toxins and poisons may cause dogs to develop fevers. These may include toxic foods, hazardous chemicals, and poisonous plants. Be sure to contact a veterinary facility immediately if you suspect your dog has been exposed to a toxin.
A dog may develop a low-grade fever following a vaccination. Most vaccine-related fevers are mild and self-limiting. However, some dogs experience vaccine reactions that require veterinary care.
Immune-mediated or autoimmune diseases confuse the immune system, causing it to fight against itself. The body attempts to destroy its own cells because the immune system thinks the cells are foreign. This immune system process may cause a fever.
Cancer (neoplasia) can sometimes be responsible for a dog's fever, especially leukemia, lymphoma, and liver cancer.
How to Tell If Your Dog Has a Fever
A dog's normal body temperature ranges between about 100 and 102.5 degrees Fahrenheit. This can be measured rectally using a battery-operated digital thermometer from a drugstore.
You cannot gauge a dog's body temperature by feeling the nose; a healthy dog's nose can be warm or dry.
The only way to determine if your dog has a fever is to check a rectal temperature. A dog with a fever may or may not exhibit other signs of illness, including:
- Shivering or shaking
- Glassy or red eyes
- Warm ears (warmer than usual)
- Decreased appetite
A dog with a fever will need to see a veterinarian for treatment. Contact your veterinarian for advice if your dog has a body temperature over 103.5 degrees Fahrenheit. Mild fevers may go away on their own with supportive care at home, but your veterinarian can help you determine the best steps to take.
Contact your veterinarian immediately if your dog has a fever over 104 degrees Fahrenheit. Never give your dog over-the-counter medications like ibuprofen or acetaminophen as these are toxic.
The exact treatment for a fever depends on the underlying cause. You can help your vet by providing detailed information about your dog's recent activities. Be sure to mention injuries, exposure to toxins, and contact with other animals.
The veterinarian will begin with a physical examination. Next, the vet may recommend lab tests, radiographs, or other diagnostics to look for the cause of the fever. In the meantime, the dog is treated symptomatically to provide comfort.
Most fever cases require some form of supportive care to manage symptoms and promote recovery. This may involve hospitalization, intravenous fluids, and various medications. Antibiotics are used for bacterial infections and antifungal drugs are used to treat fungal infections, but additional treatment may be needed to address the source of the infection. For example, wounds and abscesses may require surgery.
How to Prevent Fevers
Since most fevers are caused by infections, you may be able to prevent them by detecting the infection early. Be sure to visit the vet if your dog has a wound so it can be treated before the infection begins. Contact your vet at the first signs of illness to prevent minor infections from becoming serious. Be sure to take your dog to the vet for routine wellness exams. Your vet may be able to detect the start of a health problem before it causes a fever.