
Hi Sylvia,
kc is highly contagious and by the time we notice coughing/sneezing the dog(s) have already been harbouring the virus for several days. In that case, all the puppies are likely to have contracted it but may just show symptoms at differing stages and also to differing degrees.
It is an airborne virus - possibly brought into the household inadvertently by a visitor on their clothing (if they for eg. were in contact with an infected dog and had it's saliva on them) or perhaps an infected dog has breached their garden fence. The parents may not show signs because they have perhaps had the disease in the past and have built up enough of an immunity to it to either be unaffacted or only very mildly so. kc is potentially very dangerous to young puppies and any elderly or infirm dogs. I've known of a few litters similarly affected but fortunately if they are around the age of 6 weeks or so and already in robust health etc., then when treated promptly they are less likely to suffer severe complications. Just sounds like very bad luck :( Hope they all turn out to be OK. regards, Teri