As with the large creatures, the smaller ones, no matter how annoying, are having young also. This would include the flea and tick. A good flea and tick repellant will work well to keep Rover from bringing home that unwanted companion. I suggest asking your vet which ones they prefer. The same goes for fleas.
Fleas are more dormant in the winter and flourish for the duration of the summer.
I recently attended a plague seminar and found out that Colorado is second, behind New Mexico, for plague cases. Many of these cases are restricted to prairie dog colonies and to a lesser degree various wildlife. When a prairie dog colony is infected by the plague, it takes about two weeks for the entire colony to be wiped out. When an animal investigates an old den, the flea hops on the new host, ready to repeat the cycle. Buy a good solid I.D. tag and securely attach it to the collar.