folks from colorado   where are these fleas coming from? say parire dogs colony in colorado spring plauge infested now  that  scarey  but how?

Fleas can show up for no reason .. even a new cat can infest an entire barn and area .. 

Simple de-infestation ... buy you some common table salt in the kitchen type 

round paper cans ... cheap.. so buy $20 worth .. 

Shake salt every where you think there is a flea in the barn and on the path to house 

and barn ... 24-36 hours later no fleas ... do again in 10 days for rehatch on fleas 

If they’re really bad ask your vet for Fipronil spray for your dogs/cats and sprinkle dimotacious(not sure if I spelled that correctly) earth around your yard. Fipronil is the main ingredient in most all flea medicines. DE is non toxic to animals but kills fleas. Also good for ants. I usually buy the food grade just to be extra cautious. It’s pretty cheap too.