To my knowledge, dogs don't get Posion Ivy…..
As far as Fleas.... while we don't have a big problem here in No. California... I do need to use flea protection.. at times....
To be on meds for heartworm is responsible... and I would never take a chance...
Liver problems with Basenji is not uncommon... that to me is the biggest plus for blood work up at least once a year... especially with our old Basenjis... some as with the Kidney's starting to shut down... my 15 1/2 yr old has been Kidney failure (nothing to do with Fanconi, but just old age) for almost the last year.... we have kept her going to SUBQ fluids since we found this out... and while I would do no more then this, since she accepts the fluids well (we at this time give fluids 2 to 3x's a week...) we take each day as a bonus day until the time she is ready to cross the bridge....
As far as flea meds.... if they don't have fleas... I would not worry about it.... of couse different then meds for heartworm... since that is a mosquitos born problem...