Oh poor you and sammy, i am sending well wishes. I know 2 puppies that had this, they were both so ill,critical infact, they were sedated and on IV drips, but they both pulled through and they were only 8 weeks old. The vet told my friend (the owner) that it can be caused by bacteria, airbourne or in the home, im not sure if this is correct? i am praying that sammy will get better soon!
http://vetmedicine.about.com/cs/dogd.../HGEindogs.htm try this link it says about the causes and bacterial infections is on there