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Identifying autoimmune diseases in dogs and cats

Autoimmune diseases occur when the immune system attacks normal body tissues by mistake because it thinks that part of your body or process is a disease and tries to fight it; a well-known example in humans is type 1 diabetes. Like us, animals can experience autoimmune diseases that are complex and challenging to diagnose. They can affect a range of body systems, causing a wide variety of clinical signs, many of which are found in more common disorders. Autoimmune diseases can be life-threatening, so it’s important to identify any unusual changes in your pet and seek professional advice from your veterinarian to ensure timely diagnosis and treatment.

Autoimmune diseases are often referred to as an ‘immune-mediated’ disease in veterinary medicine (for example, immune mediated thrombocytopaenia or lack of platelets). These diseases can be ‘primary’, with no identified cause, or ‘secondary’ to a trigger such as infections, cancer, or even certain medications. Many factors can lead to autoimmune diseases but in dogs there is a strong genetic basis, with higher rates in particular pure breeds.

What is an autoimmune disease?

The most important thing to know if your pet has an autoimmune disease is that the treatment is very different depending on whether an underlying secondary cause can be identified. Autoimmune disease is a diagnosis of exclusion. This assessment will involve a range of tests, which may include blood tests, biopsies (or multiple biopsies), bone marrow sampling or imaging such as radiographs and ultrasound. If no obvious trigger is found, your pet may be given medications to suppress their immune system and stop it attacking the body’s own cells. It will be necessary for the pet to then have ongoing monitoring as immune suppressive drugs can make the body more prone to infection.

Early diagnosis by your veterinarian is important, so seek immediate advice if your dog or cat shows the clinical signs of any of these autoimmune diseases:

Immune mediated haemolytic anaemia

This attacks the red blood cells which are responsible for delivering oxygen to the body’s tissues. Predisposed breeds include Cocker Spaniels and Poodles. This condition can cause the following clinical signs in dogs and cats and can present as a medical emergency:

  • Fatigue
  • Pale gums
  • Depression
  • Weakness
  • Lethargy
  • Poor appetite
  • Weight loss
  • Exercise intolerance
  • Rapid breathing
  • Rapid heart rate
  • Fever
  • Black stools
  • Red or purple spots on the body
  • Bruising
  • Collapse

Immune mediated thrombocytopaenia

This destroys the body’s platelets, which are responsible for blood clotting. This condition occurs in dogs, particularly in Whippets and Greyhounds, and causes the following clinical signs:

  • Uncontrollable bleeding with even minor injuries
  • Bruising of the skin and gums
  • Blood in the urine or stools
  • Nose bleeds
  • Pale gums
  • Lethargy
  • Weakness

Immune mediated polyarthritis

This occurs most commonly in dogs and attacks the joints, causing an inflammatory response with the following clinical signs:

  • Reluctance to walk
  • Altered gait or lameness
  • Multiple swollen painful joints
  • Fever
  • Lethargy
  • Inappetance (lack of appetite)
  • Vomiting or diarrhoea

Pemphigus foliaceus

This is the most common autoimmune skin disease in cats and dogs (although it is rare). It attacks the biological ‘glue’ that holds the skin cells together, causing the following clinical signs:

  • Crusting lesions of the nose, face and ears
  • Thickening of the footpads
  • Fever
  • Loss of appetite
  • Depression

Autoimmune diseases in dogs and cats can cause a range of severe clinical signs, but many of these clinical signs are not specific to the disease and so the diagnosis of an autoimmune disease is usually one of exclusion – your veterinarian must rule out other conditions that would require very different management before treating an autoimmune condition. This means the cost of initial assessment can be quite high, as can ongoing treatment with medications that suppress your pet’s immune system, with long-term monitoring in case of flareups when this medication is tapered off.

Your pet may go into remission (where the disease is controlled and the clinical signs are reduced or eliminated), but autoimmune conditions may require lifelong treatment and monitoring.

Consider how you can be confident that you can provide your dog or cat with the veterinary care they need if any specified illnesses or accidental injuries occurred. Consider RSPCA Pet Insurance to assist toward eligible vet bills.

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Dr Rosemary Elliot 

Dr Rosemary studied veterinary science at the University of Sydney after having established her career as a clinical psychologist, and has qualifications of BVSc (Hons), MANZCVS (Animal Welfare), MPsych (Clin), BA (Hons) as well as previously establishing her career as a clinical psychologist. Her experiences during veterinary training fostered an ambition to focus directly on animal welfare and ethics, with a particular interest in animal sentience and the human-animal bond. Currently working in small animal practice, Dr Rosemary combines her psychology background and veterinary skills to contribute to and promote animal welfare, and regularly contributes quality content to RSPCA Pet Insurance's Pet Care blog.