Can human lice shampoos kill dog fleas?

No, you need to use a treatment supplied by a vet - and please understand if you sea a flea on an animal that is only a female feeding, the majority of the flea population is actually in the animals beading. Therefore it is no use just treating the animal you have to treat you house and the animals beading too.....a vacuum cleaner is the best defence against fleas - hoover and clean daily and wash/replace the animals beading regularly.