Seasonal Canine Illness

WHAT TO LOOK OUT FOR (Courtesy of the Animal Health Trust)

There is no new information on SCI but the advice to dog owners provided on this page remains vitally important and we wish to continue to raise awareness of SCI amongst dog owners to help save dog’s lives. The below FAQs aim to cover any questions you may have about the disease and the AHT’s involvement.

To see our information for vets, click here.

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.


Poster – download our poster to help raise awareness of SCI


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.

What has been the AHT’s involvement?

The AHT was alerted to a recurrence of dog deaths at Sandringham in 2010 and asked to investigate. The AHT collated information about SCI for several years in the form of an owner questionnaire aimed at dog walkers at five study sites, which were not the only places to have experienced SCI, but were the first ones reporting significant numbers of SCI cases during the autumn months.

From this and other information from treating veterinary practices, the AHT’s researchers looked into the potential link between SCI and harvest mites as a possible cause. There is currently no licensed product which protects against harvest mites, however fipronil spray, which is only available from veterinary practices, may provide some protection.

Although the AHT conducted a short pilot trial in 2013 to assess how easy it was for dog owners to access and use this spray on product, a larger study is still needed to confirm or deny if the product will have any impact on reducing harvest mite infestations and/or reducing the number of SCI cases.

The AHT have further analysed samples from affected dogs, carried out post-mortem investigations and have been instrumental in getting samples (blood, mites etc) to other laboratories for analysis.

What is happening now?

The AHT is as interested as ever in identifying the cause of, and ideal treatment for, this mysterious disease. However, it has had to stop its SCI investigation due to shortage of funds and resource constraints and is currently reviewing if and how a new research project could best be instigated. Even if such projects are successfully funded, it may take several years to correctly identify the cause of this mystery disease.

The most important thing that can be done to help save lives today is to raise awareness of SCI amongst dog owners. All dog walkers should be aware of a sudden illness after a woodland walk, typically including sickness, diarrhoea and lethargy, and to seek veterinary attention immediately.

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.