One thing to consider about ick or other paracites, is their geographical origin.
An ick varient fron Michigan or New York which has evolved to live in certain temps, temps from 50-to 80F may be the perfect reproductive range, but temps above that range may be limiting or lethal
An ick variant that comes from Panama or northern S America may have evolved to tolerate and reproduce, in a drastically different range.
Water temps often swing from lows of mid 70sF to mid 90sF in those countries. So a rise in temp that inhibits New York ick, may be just what Panama ick need.
And with importation of fish from all over the world, the possibility of parasites hitch hiking is highly likely.
I have collected fish in Panama where the water in certain places was bath water hot.
And commonly had fish arrive with an ick spot or 2, in nature ick is an irritant, but once put in the confines of a tank it becomes epidemic and deadly.
For the use of heat with these wild fish, the rise in temp needed would have done more harm to the fish, than the tropical ick.
I have also heard of an ick strain from Lake Tanganyika that has the ability to handle increased osmotic pressure (the mineral content of the lake is dense), so if that African strain is suspected, increased salinity may be needed.
Most research on ick, has been done by north American fish farm interests, so the strains that have developed in warmer countries may have not been taken into account.
