if your dog is severly dehydrated and skin and bones, and refusing to eat and drink, you may have to force some water and food, like eggs or probiotic yogurt down it's throat, to keep it alive. dose it with fendbendazole for 3 to five days and in a roll. giardia is another very common parasite that is everywhere and a pain in the arse. repeated treatments may be required. giardia is nearly impossible to test positive for at a vet. many vets are entirely incompetent anyway.
http://www.dog-health-guide.org/causesofgiardiaindogs.htmlhttp://www.firstchoicenaturals.com/resourcearticles/giardia.php