Concerns, symptoms and treatment contained in the thread introduction
Map of areas in the USA where plague has historically occurred is at post #9
Historical information about past known plagues and number of fatalities is at post #17
H/T to Whenifhow
Flea meds for dogs are neurotoxic. I’d focus on making homemade concoctions like garlic oil and rubbing it on the dogs. There are other essential oils that fleas also hate, can’t remember what they are but search online, then mix drops of these oils with a carrier oil like coconut or olive (usually the essential oil is too strong to use alone) and apply and brush into the dog’s fur. Some smell so nice and strong that you literally don’t need much - insects, when they hate a smell, don’t come aboard. So doggy isn’t greasy at all. Just has a slight scent of whatever.
One of Tony Hillerman’s detective novel The First Eagle includes a description of how the local public health department handled the problem by seeking out the source and destroying the animals that are vectors.
that book was published awhile back, but I suspect it's still being done, not just for plague but for the mouse borne Hanta virus that pops up every decade or so.