Hmm
In that year was there ever a time when it was feed a live food item?
Was there ever a introduction of a new tank mate that had not been treated for parasites?
Some animals can live there complete life span with parasites and have no trouble. They say that most fish in the wild have parasites.
I truly think that if every predatory wild caught characin owner would treat there fish for parasites at least on a yearly basis that these problems would go away.
My oldest tat has been in captivity since late 2007. And i have personally seen parasite med's stop this behavior on more than one occasion.