Quote Originally Posted by frawri
I was told that since one of my dogs is a hearding breed. That those you mentioned can hurt my dog. Because hearding dogs can be sensitive to these ingredients and adverse reactions cause them to be at risk. Have you had any problems with these meds, looks like you have a Border Collie.

The sensitivity that you refer to is a known mutation commonly called MDR1. This mutation affects the blood-brain barrier and thus *numerous* otherwise safe drugs are toxic. I think it's prevalence has been exaggerated, and I don't think it has been documented (officially anyway) in *all* herding breeds by any means. (Here's an interesting article: http://www.pnas.org/cgi/reprint/101/32/11725 )

Research out of UC-Davis and other institutions has shown that the heartworm preventive dose is sufficiently low to not elicit a reaction in known sensitive (MDR1) dogs. I don't know what HW preventative you are using now, but it is more than likely also from the avermectin class of drugs, which includes Ivermectin. Personally I would only worry about the possibility of a reaction to avermectins if I had a herding breed undergoing heartworm treatment. This involves much higher doses of the drugs.

The MDR1 mutation is of concern to HW drug manufacturers and they do actively address it. Specifically they test their products on lines of Beagles (usually) that have been bred purposely to carry this mutation. Not sure how reassuring that is, as it is kind of sad, but it is the truth. (These animals are not abused by any means, but they also do not have what you and I would think of as the ideal life...)

Bottom line: The greater risk to your herding dog is undergoing heartworm treatment if he or she is not put on an effective preventative. I would not worry about possible reactions from any of the three HW preventatives I have mentioned here. I give my herding breed (yes, he is a border collie) Sentinel every month and I'm very confident in doing so.