If you suspect your dog is showing signs of SCI, contact your vet immediately. 

The most important thing is to take seriously the signs of sickness, diarrhoea and lethargy in your dog, especially if they start within 72 hours of a walk in a woodland area. 

There is no new information on SCI but advising dog owners of the clinical signs remains vitally important. We wish to continue to raise awareness of SCI amongst dog owners to help save dog’s lives.

Seasonal Canine Illness (SCI) shows with clinical signs of sickness, diarrhoea and lethargy, within 72 hours of walking in woodland areas, usually during autumn.

What is SCI?

Seasonal Canine Illness (SCI) is a mystery illness affecting dogs during the autumn; no one knows what causes it. It is normally characterised by vomiting, which may be accompanied by diarrhoea and lethargy and these clinical signs are usually witnessed within three days of having roamed in a woodland area.

Unfortunately, in some cases, SCI becomes severe very quickly and, sadly, some dogs do not survive. Cases have been reported all over the UK, are generally seen from August onwards, peak in September and may be seen in to November.

What advice is there for dog owners?

  • Be vigilant

    Closely monitor your dog’s health in the hours and days after a woodland walk, especially if you normally do not walk your dog(s) in the area

  • Use a lead

    Keep your dog on a lead during a woodland walk so that you can keep an eye on them at all times

  • Don’t hesitate

    Go to your vet immediately if you think your dog could have SCI – prompt veterinary attention could make the difference between life and death. If dogs get veterinary treatment quickly, they tend to recover well after a week or so.

  • Keep hydrated

    Make sure your dog is offered water before you set off on foot, especially if you have travelled a long way in the car for your walk. Keeping hydrated may help if your dog is affected by SCI.

  • Think about mites

    Harvest mites have been commonly noted on dogs suffering from SCI, so it may help to preventatively spray dogs against mites before a walk. It is important to use a spray rather than a ‘spot-on’ product as the chemical barrier of a spray may be more effective at preventing a mite infestation and can be applied directly to the more exposed areas of the feet, legs, chest and belly. Your vet will be able to advise on the correct products.

  • Tell others

    Help to raise awareness of the disease amongst fellow dog owners. 

All dogs can be affected by SCI

In 2009 cases were first reported in the UK

Can SCI affect all dogs?

SCI can affect dogs of any size, shape or sex; however a study by the Animal Health Trust found that smaller dogs may be more likely to be affected.

Dogs are also more likely to get the disease if they are allowed off the lead, especially if they are new to the woodland area (e.g. if they are not ‘local dogs’).

What is the treatment for SCI?

As the (infectious, or ‘toxic’) cause of SCI is unknown there is currently no specific treatment for the disease, but vets can try to alleviate the signs of SCI. As dogs will lose a lot of fluid with their gastrointestinal upset, it is often important to hospitalise them and rehydrate them on a ‘drip’.

Dogs will often be feverish and, as bacteria may be involved, vets may prescribe antibiotics. Most vets in affected areas have become familiar with the disease over the years and therefore normally take swift action. If dogs get veterinary treatment rapidly, most will recover from SCI.

Are there any patterns between SCI cases?

The only thing owners and vets regularly see on affected dogs are harvest mites (known as ‘chiggers’, which are orange in colour). However, it is currently unknown whether these mites are involved in the transmission of the disease or whether they just happen to be abundant at a time of the year when the disease strikes. 

How many cases are there of SCI?

It is difficult to accurately report the number of cases as there is no known cause of SCI, there isn’t a definitive diagnosis to confirm cases. Therefore, many cases are likely to be underdiagnosed.

What is significant is that although the total number of SCI cases in the UK appears to remain high, there has been a dramatic decrease in the number of fatal cases since 2010, when the condition first became prominent. We believe that this is probably due to increased awareness of the condition around affected areas, and that dog owners now know to contact a vet promptly if they spot any of the clinical signs. 

When was SCI first discovered?

The first reports of SCI can be traced back to around the autumn of 2009, when dogs were reported to have died after being walked in woods on the Sandringham Estate in Norfolk, East Anglia, as well as at several other woodland sites elsewhere in England.

Press Enquiries

The AHT has no new information on SCI, but the advice to dog owners provided on this page remains vitally important. We do not wish to answer press enquires on SCI at this time.

Information for vets

Seasonal Canine Illness (SCI) is a recently emerged disorder of unknown aetiology in Great Britain.

SCI is particularly associated with dogs being walked in woodland areas in the autumn months, and presents as a sudden onset syndrome of vomiting, diarrhoea and lethargy, which if not treated appropriately may proceed to recumbency and death.

Most cases do recover over a seven-10 day period, especially when receiving re-hydration therapy.

The current case definition is acute onset gastrointestinal signs in dogs, between 24 and 72 hours of having walked in a woodland area.

The clinical signs include:

Vomiting, diarrhoea, lethargy, abdominal pain, anorexia, pyrexia, and muscular tremors.


No cases of Seasonal Canine Illness have been referred to the Animal Health Trust, however based on clinical reports from cases treated by veterinary surgeons close to sites in East Anglia, the Midlands and Nottinghamshire that have been treating cases, the most common treatment is intra-venous fluid therapy, supportive care and in some cases, antibiotic-therapy.

Unfortunately the Animal Health Trust, as a specialist referral centre, cannot offer advice on the specific treatment of patients as they are not animals under their care, however if you are a veterinary surgeon and wish a patient to be referred to the Small Animal Referral Centre, please contact the Centre on: 01638 552700 or email: