It can be a worrying time if your dog is poorly. If a check over from the vet has revealed your dog has a fever, then you might have a few questions. While some causes of fever can be straightforward to diagnose and manage, others can be much more complicated. Let’s explore fever in dogs in more detail.

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Normal dog temperature

Temperature is regulated by the hypothalamus, an area in the brain. The hypothalamus reacts to chemicals called “pyrogens” in the bloodstream to increase body temperature. These pyrogens are toxins released by infectious agents (like bacteria) or cytokines which are signals released by certain cells in the body. Physical changes start to occur in response to these, such as shivering to generate heat through rapid muscle movements and the diversion of blood away from the skin to prevent heat loss.

Fever is a normal part of the body’s immune response. A raised body temperature is a useful aid for fighting off viruses and bacteria and increasing the activity of the body’s white blood cells. The technical term for fever is pyrexia, and your vet might use both words interchangeably.

Healthy dogs have a body temperature of up to around 38.9oC. This is higher than our body temperatures, which sit around 36.8oC. So even a healthy dog can feel slightly warm to the touch to us.

However, you can accurately measure your dog’s temperature using a digital thermometer. Here’s a step-by-step guide on how to take a rectal temperature from a dog –

  • Follow the manufacturer’s instructions to operate the rectal thermometer
  • Get someone else to hold and comfort your dog
  • Gently insert the tip of a lubricated thermometer into your dog’s anus, pressing lightly towards the inside wall (accidentally pressing it into faeces can give a falsely low reading).  
  • Record the result
  • Praise and reward your dog.
  • If at any point your dog is distressed, stop.

If your dog’s temperature is measuring 39.5oC or above, or if your dog is showing any signs of ill health, then contact your vet for advice.

What are the signs of a fever in dogs?

Depending on the underlying cause, dogs with a high body temperature may have some of the following symptoms –

  • Lethargy
  • Reduced appetite
  • A change in thirst
  • Shivering or shaking
  • Behavioural changes, such as acting more clingy than usual, hiding away or not wanting to go for walks
  • Vomiting and/or diarrhoea
  • Pain (perhaps limping or reacting when touched)

It is important to note that contrary to popular belief, a change in nose temperature or wetness does not confirm whether a dog has a temperature. The only way to confirm a fever is to take your dog’s temperature or get them checked over by a vet.

What are the causes of fever in dogs?

There are many different causes of fever in dogs including –

  • Bacterial, viral, protozoal or fungal infections e.g. pyometra, abscesses, kidney infections, pneumonia and tick-borne diseases
  • Immune-mediated diseases e.g. polyarthritis and steroid-responsive meningitis arteritis (SRMA)
  • Neoplastic (cancer) e.g. lymphoma and leukaemia
  • Miscellaneous e.g. pancreatitis (inflammation of the pancreas), intervertebral disc disease and pyrexia of unknown origin
  • Note – an elevated body temperature can also occur due to stress and environmental conditions

If your dog has a persistent fever, then your vet may need to investigate further to try and understand what the underlying cause is. They will start by examining your dog, checking them over for any indication of pain and any signs of dehydration. They will also record their rectal temperature.

If there is no obvious cause for the fever on physical exam, then blood tests are often advised next

These can check your dog’s organ function and look for signs of anaemia or infection. More specific tests can also be performed on blood samples to look for markers of inflammation (c-Reactive protein) and pancreatitis. Blood cultures might be deemed necessary too, where the blood is checked for bacterial infection.

Urine may also be screened for infection, and to check whether the kidneys are functioning normally.

Survey imaging might be next, which might include chest and abdominal rays and ultrasound scans. These act as a general screen to help look for any abnormalities that could be causing an issue. If the vet finds a specific problem area such as a swollen leg, then imaging will focus on that area.

Depending on the findings of these initial tests, advanced diagnostic imaging such as MRI scans or CT scans might also be needed, along with samples of spinal fluid. This is particularly the case if spinal disease or meningitis is suspected.

Investigating a dog with a fever is a process of elimination, meaning that several tests may be required if the cause of the problem is not immediately obvious.

What is the treatment for fever in dogs?

As there are so many different reasons why a dog might have a fever, there is not one treatment plan. Your vet will let you know the most likely cause of your dog’s problem and the available treatment based on the results of their laboratory tests. This treatment could involve –

  • Antipyretic drugs (drugs that bring the body temperature down) such as non-steroidal anti-inflammatories and paracetamol
  • Antibiotics
  • Antifungals
  • Anti-nausea medication for vomiting animals
  • Intravenous fluids for dehydrated animals
  • Pain relief, including NSAIDs and paracetamol, but also stronger medications such as opioids
  • Surgery (in the cases of pyometra, abscesses, foreign bodies, or disc disease)

Some animals may not require much treatment at all, whereas others may require extensive hospital stays. Your vet will discuss this with you.

The majority of animals do successfully recover from their fever with the appropriate treatment. As with most things, prompt medical attention leads to better outcomes so always speak to your vet as soon as possible if you suspect your dog has an elevated temperature.

Summary

There are a number of causes of fever in dogs, ranging from mild self-resolving viral infections to life-threatening sepsis. Your vet will use examinations and appropriate lab tests to work out what is going on, ensuring your pet receives appropriate care whilst they recover. Hopefully, this blog has answered a few questions for you, but make sure you ask your vet if you still have concerns about your pet.

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