Seasonal Canine Illness is a relatively new illness about which we frustratingly still don’t know a whole lot. However, the good news is that although we still don’t know the exact cause, we have become a lot better at treating it and the majority of dogs with SCI now survive. 

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What is Seasonal Canine Illness (SCI)?

Seasonal Canine Illness is a syndrome that first appeared in 2010. It seemed to affect dogs who had been mainly walking on the Sandringham estate in Norfolk. Shortly after this, cases started being reported in other areas of woodland mainly in East Anglia, Nottinghamshire and Lincolnshire. Since 2010 there have been cases every year, mainly between August and November but peaking in September. The signs of seasonal canine illness (mainly vomiting and diarrhea) are very common in dogs and can be caused by a whole range of things. But the things that link cases of SCI are the time of year in which they occur, and the history of having been walking in woodland within 72 hours of becoming ill. 

What are the signs of SCI?

Dogs affected with seasonal canine illness become suddenly very ill with vomiting, diarrhea, severe dehydration, abdominal pain and sometimes muscle tremors. The diarrhea and vomit will often contain blood, which can be very scary to see. The illness usually starts within 72 hours of a woodland walk, and can become very severe within a few hours. Many dogs are already quite profoundly dehydrated by the time they arrive at the vet practice.

Is it treatable?

Yes! Although we don’t know exactly what causes SCI, we can treat it by managing the symptoms. Intravenous fluids are given to combat the dehydration, anti-nausea medication can be given to ease the vomiting and nausea; pain relief can be given to help the abdominal pain and antibiotics are often given also. Although there is no solid evidence that a bacterial infection is involved, in a dog that is so ill, it is often prudent to cover all eventualities. The majority of vets consider that an antibiotic is unlikely to do harm to these patients, and may well help. With prompt, aggressive treatment, most dogs with SCI will make a full recovery within 7-10 days. 

The good news is that as the years have gone by, we have got better and better at treating this. When the Animal Health Trust (AHT) first started compiling data on this in 2010, they found that 20% of affected dogs died in the first year. However, 2 years later only 2% of affected dogs were dying. So our increasing understanding of the disease and the publicity around it has really helped. 

What causes it?

Unfortunately, we still don’t know for sure. As soon as this disease first emerged in 2010, the AHT in Newmarket, started compiling data and trying to figure it all out. They did fantastic work and came up with some credible theories, most of what we know now about the disease is thanks to them. But, unfortunately, they were forced to close in 2020. As a result, the research remains unfinished and no definitive conclusion has been drawn. We do know that the cause of SCI is likely to be something that these dogs are exposed to during their woodland walks. Some early theories were that it was due to mushroom poisoning, or algae. But the most enduring theory is the possible link to harvest mites. 

What are harvest mites?

Harvest mites are tiny, orange insects found on long grasses and plants. They are mainly active in the autumn months (around harvest time, hence their name!). They like to hop from the end of long grasses onto passing dogs. Once on the dog they like to find thin skinned areas such as in front of the ears or between the toes, where it is easier for them to feed, and they stay there for 2-3 days. You may be able to see harvest mites on your dog if you look closely. They will look like a little cluster of tiny, orange dots on your dog’s skin. In 2013 it was noticed that a large majority of dogs presenting for treatment of SCI had visible harvest mites on their skin. 

Does this mean that harvest mites cause SCI?

Not necessarily… harvest mites have been around for a lot longer than seasonal canine illness. Dogs have been exposed to harvest mites for a very long time without any problems, and indeed there are probably lots of dogs every year who are exposed to harvest mites without becoming ill (not all harvest mites live in woodlands for instance!). So no one really knows why this particular set of circumstances of dogs being exposed to harvest mites, in woodland, from 2010 onwards has suddenly become a problem.

Perhaps some of these particular harvest mites are carrying a virus that they can pass on to dogs? Perhaps they are feeding on something in particular in the woods that is triggering this reaction in dogs? Or perhaps it is all just a coincidence? It would be so lovely to have some answers after over 10 years of dealing with this disease. But unfortunately we really just don’t know. 

Is my dog at risk of getting SCI?

If you walk your dog in wooded areas between August and November, then yes, your dog could be at risk. Being vigilant about the signs of this disease is very important as the sooner these dogs get treatment the better. So knowing your dog is at risk means you can take steps to minimise the chances of this happening. 

How can I prevent it?

There is no definite way of preventing it, but you can take steps to minimise the risk, as follows:

  • Avoid long walks in wooded areas in the Autumn months, if possible. 
  • If it is not possible to avoid wooded areas, keep your dog on a lead and keep walks as brief as possible, sticking to designated paths. 
  • If you are going into woodland, you can apply insecticide sprays (talk to your vet for the most appropriate product) to your dog’s face and paws about 1-2 hours before the walk. This may prevent the harvest mites from latching on to your dog. These sprays are not licensed for prevention of harvest mites, but it does kill other types of mites and we think it is the most likely out of all the available parasite treatments to help with this. The spray is much more effective than spot on products, especially if it is applied directly to where the harvest mites are most likely to attach. However, because they are off-license, your vet will need to prescribe them.
  • If you spot any harvest mites on your dog, after a woodland walk or otherwise, wipe them off with a damp cloth as soon as possible.

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