Any way you look at it, Thor is a herding superstar....
Aussies are a generally hardy breed, however they do have some diseases that can be inherited genetically. This is why all responsible breeders utilise what tests are available before allowing their dogs to be bred.
To do more research on the genetic problems that can occur in Australian Shepherds you can visit the Australian Shepherd Health and Genetics (ASHGI) website. This site has excellent articles by Dr Leos Kral and CA Sharp, a recognised expert in Australian Shepherd genetics.
The current breed average in Australia for hip score results is currently around a total of between 12 & 13 (out of a possible 106 - the lower the better). It has been advised that only those animals with the highest hip's value being less than half the breed average, should be bred.
Tests that you should make sure the parents have had done before buying a puppy include an official hipscore (not just a vet check) and current eye clearance by a registered opthamologist. Preferably also an official score for elbows. On a list of nice-to-have, would be the MDR1 drug sensitivity mutation, Collie Eye Anomoly and HSF4 cataract DNA tests.