Seasonal Canine Illness is a potentially life-threatening disease with no known cause. It affects dogs that have been walked in woodland areas 1-3 days before becoming unwell. Symptoms start with vomiting, diarrhoea and lethargy.



Seasonal Canine Illness affects dogs during the autumn months. Cases start in August, peak in September and end in November, leading to the name ‘Seasonal Canine Illness.’



SCI was first identified in 2009 in dogs that had been walked on the Sandringham Estate in Norfolk. About the same time, dogs walked in Thetford also in Norfolk, Clumber Park and Sherwood in Nottinghamshire and Rendlesham Forest in Suffolk, were also reported to have symptoms consistent with Seasonal Canine Illness.


So far, research has ruled out contaminated water sources, fungi and natural flora as potential causes and man-made poisons. Mites have been suggested as a trigger, specifically harvest mites which are also seasonal.

However, many dogs will pick up harvest mites while out walking and never become unwell, so the real cause remains a mystery.



Look out for sudden gut upset, vomiting and diarrhoea. Other signs include lethargy, abdominal pain and loss of appetite. Dogs may have very high temperatures, suffer from shaking or trembling and occasionally dogs may have a rash over the abdomen and limbs.



Because the symptoms of SCI look similar to those of many other diseases, making a definitive diagnosis can be tricky. Other conditions with similar symptoms often need to be excluded.



Many dogs are sick enough to require treatment in veterinary hospital.


  • treatment can consist of intravenous fluid therapy and medications such as anti-sickness drugs to make the dog feel more comfortable


  • antimicrobials can be prescribed but are not always needed


  • some dogs will be well enough to go home with oral therapy


  • if harvest mites are present then your vet may advise specific treatment, with sprays are generally considered more effective than spot on therapies.


Spread the word

Increased awareness of Seasonal Canine Illness has resulted in quicker treatment for dogs. In 2010, around 20% of dogs developing this disease, died as a result of it. Thanks to increased awareness and prompt treatment this figure was only 2% in 2012. With speedy veterinary treatment most dogs make a complete recovery over 7-10 days.


Preventative Measures for Dog Owners


Remain vigilant

Check your dog’s health in the hours and days after a woodland walk, especially if walking your dogs in a new area. Unfortunately SCI can become severe very quickly and for some dogs it is fatal. Prompt veterinary attention could mean the difference between life and death for your dog.


Use a lead

If on a woodland walk keep your dog on a lead so you can monitor them closely


Act quickly

Visit the vet if you think your dog may have Seasonal Canine Illness. Dogs who get treatment quickly, tend to recover well after about a week.


Keep hydrated

Make sure your dog is offered water before a walk and in hot weather (or on long walks carry a portable drinking bowl for them). Keeping hydrated could help if your dog is affected by SCI.


Think about mites

Harvest mites have been commonly observed on dogs suffering from SCI.


Preventative spray

It may help to spray dogs against mites before a walk.




First Aid for Pets provides this information for guidance and it is not in any way a substitute for veterinary advice. The author does not accept any liability or responsibility for any inaccuracies or for any mistreatment or misdiagnosis of any person or animal, however caused. It is strongly advised that you attend a practical First Aid for Pets course or take our online course to understand what to do in a medical emergency.

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