How long does a puppy have to be infected with giardia before it gets sick enough to die

We bought a puppy she was 15 weeks old when we got her .after 12 days she became really sick we took her to vet she had giardia.the next day she passed question is could she have became infected with it and gotten so bad to take her life in a matter of 12 days or did she have to already be infected when we got her?
Asked Jun 17, 2014

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