I am so sorry for your loss..
Are you aware of the MDR1 gene in collies/shelties/aussies?
Was Ele ever tested to see if she was a carrier?
My aussie tests out 'mutant/mutant' for the MDR1 gene, which means she is a carrier, would pass it on to her offspring, and there is a long list of drugs that are big no no's that would probably kill her.
Ivermectin (as in Heartguard) is only one of them.
I would highly suspect and would bet my life on it, that she had a toxic reaction to the vac's given to her (an mdr dog could possibly take it once or twice, and then not tolerate at another point) and the Ivermectin.
If your vet was giving your collie Ivermectin (as in heartguard), sorry but they are severely under informed and boy I would be ON that guys doorstep telling him so.
I would honestly ask them if they 'knew" of the MDR1 gene in the above mentioned dogs, bet he hasn't.
Some of the drugs that are no no's are listed on this website
www.busteralert.org (I think that's the site)
Again, I'm so sorry for your loss
diane