I question the dearth of data in Kentucky.
Agreed - the sudden scarcity starting right at the KY - TN border is VERY suspicious, and I don’t think KY is doing something drastic, such as massive pesticide spraying.
One thing that is interesting, though, is the lack of mosquitos I saw (or felt!) during the times I was in Philippines: Davao (including rural areas outside of Davao, Cagayan De Oro and a trip across central Mindanao, Cebu (again including a couple rural areas, and a boat trip to a couple outlying smaller islands), and Manila (ok, that was all city). I would speculate that the ever present chickens get a lot of them. I don’t think they (RP) have ticks?
Here (mid-south) we have 9 free-range chickens, and we get very few of the larger (1/8” dia. or more) ticks since we started raising more than 3-4 chickens. Some numbers of the really tiny species show up, though. We still get lots of mosquitos too — there are way too much woods and other area(s) nearby for the chickens to get more than a tiny fraction of what flies in when we go out. I make sure to get plenty of the 40% DEET repellent when stores have deals on it!