Suffolk-based charity the Animal Health Trust has been investigating SCI since the end of 2010 at five sites across Norfolk, Nottinghamshire, and Suffolk.
The charity is asking owners to stay alert for the signs and seek immediate veterinary attention if they spot the signs in their dog following a woodland walk over the coming months.
Charlotte Robin, SCI research coordinator at the AHT, said: "We had a fantastic response to our request for information from dog owners who had walked at our study sites, but unfortunately this information doesn't yet point to a definitive cause."
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The AHT is advising owners planning to visit woodlands this autumn to ensure their pets are up to date with preventative treatments for external parasites.