Blood and mucous in the faeces is generally indicative of colitis, that is, inflammation of the colon (lower intestine). This can be caused by parasites (worms), bacteria, allergies, diet or stress. Adult dogs should be wormed every 3 months, so if your dog isn't up to date, get yourself some wormer from the vet. Any change in diet should be done gradually over time - slowly introduce more of the new diet and cut back the old diet. Think about any stressful events or changes your dog may have been exposed to lately. If the blood and mucous continues, or your dog shows any signs of illness - lethargy, inappetance, diarrhoea, vomiting, you should seek veterinary attention.
