Any article that starts out with this: "There have been many reports this week of the heartworm drug Trifexis® being responsible for the deaths of 700 pets this year" without any cites or substantiation of any kind... not reliable right off the bat IMO.
We don't use or dispense Trifexis so no personal experience but this rumor gets re-circulated every once in awhile and every time it does people on the vet subscription sites all say they've never seen a death associated with it. The original incident that kicked it off was I believe 3 puppies from one litter who all died of myocarditis who had all received Trifexis within something like the previous 3 weeks prior to their deaths (all in different households by the time of their deaths IIRC). There have not been any other claims as far as I'm aware that Trifexis has been associated with myocarditis, and there are plenty of other explanations for myocarditis in 3 littermates... parvoviral myocarditis or a genetic heart defect to name two right off the top of my head.
Unfortunately when bad stuff happens, people look for something to blame, and people are very, very good at drawing correlations even if there's no evidence of causation. Dog with cancer died after getting Trifexis? It was the Trifexis! I wouldn't be afraid to use this in my dogs.
