“My dog loves to eat horse manure. Horse poo is safe for dogs to eat, right?”
Wrong
Horse faeces itself is rarely a problem for dogs, though it may cause some mild vomiting or diarrhoea in some dogs. There is however a risk of toxicity if the horse was recently treated with a worming product (containing the active ingredients Ivermectin or
Moxidectin).
Symptoms of toxicity include significant neurological abnormalities such as disorientation, wobbliness, tremors and seizures. Severe cases can also result in blindness.
Certain breeds of dogs (such as Collies, Australian shepherds, Old English sheepdogs) with a multidrug resistant (MDR) gene mutation are extremely sensitive to this class of drugs and therefore more at risk as a much smaller quantity can cause toxic effects.
Of course, if the manure came from your own horse, you are likely to know whether it was recently wormed but dog owners should exercise caution when walking dogs with a taste for horse poo along bridle paths as there is no way to be sure whether any horse manure present contains worming product.