Seasonal Canine Illness (SCI) is an uncommon but potentially serious condition affecting dogs, typically during the late summer and autumn months. It causes sudden gastrointestinal signs, including vomiting, diarrhoea and lethargy, which are often reported within 24–72 hours of a woodland walk.
The exact cause of SCI remains unknown. Several possible environmental and infectious factors have been investigated, but none have been confirmed as the underlying cause. Although SCI is rare, affected dogs can become seriously unwell and should be assessed promptly by a vet.
Abdominal pain
Fever
Muscle tremors
In more severe cases, dogs can become seriously unwell and may deteriorate rapidly.
These signs are not specific to Seasonal Canine Illness and can occur with many other, more common conditions. A veterinary examination is therefore important if a dog develops sudden gastrointestinal illness, particularly following a woodland walk during the autumn months.
If your dog develops vomiting, diarrhoea, lethargy or other signs of illness after a woodland walk, contact your vet promptly and mention the recent woodland exposure. This is particularly important if your dog is repeatedly vomiting, cannot keep water down, appears dehydrated, has abdominal pain, or is becoming weak or depressed.
SCI is rare, and these signs can have many other causes. However, because some affected dogs can deteriorate quickly, early veterinary assessment is advisable rather than waiting for symptoms to worsen.
There is no specific test that can confirm Seasonal Canine Illness (SCI). A diagnosis is based on the clinical signs and history, while ruling out other possible causes of sudden vomiting and diarrhoea. Your vet may recommend blood tests, urine or faecal testing and, depending on your dog's signs, diagnostic imaging to help investigate other possible causes.
Because SCI does not have a definitive diagnostic test, your vet may need to consider a range of possible causes before reaching a diagnosis.
There is no specific treatment for Seasonal Canine Illness, as the underlying cause remains unknown. Treatment is therefore supportive and depends on how severely your dog is affected.
This may include:
Fluids to correct dehydration and support circulation
Medication to control vomiting
Pain relief where needed
Correction of electrolyte abnormalities
Nutritional support
Close monitoring of dogs that are more severely affected
Dogs with significant vomiting, diarrhoea or dehydration may need to be hospitalised for intravenous fluids and monitoring.
There is currently no proven way to prevent Seasonal Canine Illness, as its underlying cause remains unknown.
During the late summer and autumn months, some sensible precautions include:
Consider reducing woodland walks, particularly in areas where SCI has been reported.
Keep your dog on established paths where possible.
Check your dog thoroughly after woodland walks and remove any debris from the coat.
If you are concerned about SCI in your area, your vet can advise you about any local concerns and appropriate precautions. These measures may reduce exposure to potential environmental factors, but there is currently no evidence that they reliably prevent SCI.
With early and appropriate veterinary treatment, most affected dogs recover well. However, Seasonal Canine Illness can progress rapidly and, in severe cases, can be fatal.
If your dog develops sudden vomiting, diarrhoea, marked lethargy or other signs of illness following a woodland walk, prompt veterinary attention is essential.
Written by Gillian Burkhill, Veterinary Surgeon, Animal Trust Vets CIC | Published September 2026 | Review date September 2029 | This advice is for UK pets only and is not a replacement for seeing a vet
