Immunosuppression is a reduction in the effectiveness of the immune system, either caused by disease or deliberately induced by medication. In veterinary medicine, immunosuppressive drugs are used to treat immune-mediated diseases (where the immune system attacks the body's own tissues). An immunosuppressed pet is more susceptible to infections and may respond poorly to vaccines.
Conditions that cause natural immunosuppression in pets include: canine distemper virus, parvovirus, FIV (feline immunodeficiency virus) in cats, FeLV (feline leukaemia virus), severe stress, malnutrition, and some cancers. Cats with FIV and FeLV require special management because their reduced immune function makes them vulnerable to infections that healthy cats would fight off easily.
Deliberate immunosuppression is used medically to treat immune-mediated conditions — diseases where the immune system has misidentified the body's own tissues as foreign and is attacking them. Immune-mediated haemolytic anaemia (IMHA), lupus, immune-mediated polyarthritis, and pemphigus are examples where the immune response itself is the disease and must be suppressed to prevent organ damage.
Common immunosuppressive drugs in veterinary medicine include corticosteroids (prednisolone), ciclosporin, azathioprine, mycophenolate, and lokivetmab. Pets on these medications are often on modified vaccination protocols and should be monitored carefully for signs of infection, as they cannot mount normal responses to pathogens.
📌 Key Facts
Natural causes: Parvovirus, FIV, FeLV, severe stress, cancer
Common drugs used: Prednisolone, ciclosporin, azathioprine
Risk while immunosuppressed: Increased susceptibility to infection
Frequently Asked Questions about Immunosuppression
Q: Can my immunosuppressed pet be vaccinated?
Modified-live vaccines (which contain a weakened live virus) are generally avoided in immunosuppressed animals as the immune system may not control even a weakened pathogen. Killed vaccines may be used depending on the situation. Your vet will advise on an appropriate vaccination strategy during treatment.
Q: Are cats with FIV dangerous to other cats?
FIV is transmitted through deep bite wounds — the concentrated saliva exposure of a serious fight. Casual contact, shared food bowls, and mutual grooming are very low risk. FIV-positive cats can often live safely with FIV-negative cats if the cats are compatible and fighting is not an issue.
Q: My dog is on prednisolone — does this mean they are immunosuppressed?
At anti-inflammatory doses, prednisolone modestly suppresses immune function. At immunosuppressive doses (typically higher), it significantly reduces immune responses. Your vet will monitor for signs of infection and may recommend precautions such as avoiding dog parks and contact with sick animals during treatment.
⚠ Medical Disclaimer: This glossary entry is for educational purposes only
and does not constitute veterinary advice. Always consult a licensed veterinarian for diagnosis
and treatment of your pet's health conditions.