I've always been conscious of which worm treatments I give Koda because of the MDR1 gene found in many collie type dogs that makes them have a deadly reaction to Ivermectin. Earlier this year I had Koda tested for the MDR1 gene and he came back N/N (Normal/Normal). So I don't need to worry about what worm tablets he has (although I still avoid Ivermectin in general).
Despite that I've just read on facebook about an Aussie Shepherd who was at a herding trial and ate some sheep poo... no big deal right? Well the dog ended up in a coma for 7 days with the official diagnosis being Ivermectin toxicity. Turns out that the sheep used at the trial had recently been wormed with Ivermectin, and apparently for 4 days after treatment, their poo contains lethal doses of Ivermectin to dogs. Because the doses given to livestock are much stronger than what you find in dog wormers, it is not just collie type dogs at risk here!
The dog that ended up in a coma was tested for the MDR1 gene and came back as N/M (normal/mutation).... apparently if she was M/M she'd have died very quickly and if she was N/N she would have still become very sick (perhaps not as sick as she did).
It never even occurred to me that dogs could become sick from ingesting faeces from another animal that has been treated with Ivermectin! Scary stuff!