English shepherds are remarkably healthy dogs, compared to many breeds. I like to think of them as more "natural" dogs than the average breed. This is likely a result of how they were bred and lived for decades on farms. They worked hard - so any physical weaknesses were not tolerated. They sometimes lived on less than an ideal diet, and of course got to sample all the "goodies" to be found on a farm - from livestock droppings to long-dead critters found in the bushes. Females whelped and raised their pups with little assistance from their owners. And genetically, farmers who had a good working dog, would breed that dog to another good working dog, without worrying overly about breed purity. They were looking for working ability, a specific kind of working ability. All this led to the breed we have today, an all-purpose farm dog with a loose-eyed, upright style of work. A dog that wants to work with his owner to do the jobs put before it.
We do know about some health issues in the breed, the most obvious being hip dysplasia. I have seen figures from 10% to 25% of the breed affected to some degree, but I don't think anyone really knows. Many dogs are not tested, and for some of those tested, the results are not made public. The second most common health issue seems to be the MDR1 mutation. Multi-Drug Resistance Type 1 is a mutation found in all the collie breeds, and makes a dog sensitive to several common drugs, most notably Ivermectin. Less common, but still known to be found in the breed, are cancers, epilepsy, and eye diseases.
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