Whether you have a legal obligation you’d have to consult a real estate lawyer.
If you’re legally obligated then you’d be morally obligated. We have a moral obligation to follow the law.
If you’re not legally obligated, I fail to see a moral obligation. Woods and deer are the places where ticks carrying Lyme disease could be found. These are inherent risks in these areas that common sense should inform people about. And as you also say, you may have contracted it there or somewhere else. Anytime someone is in any wooded area, they should be aware that there may be Lyme disease carrying ticks present. This is a risk that is associated with an entire region, not particular to your house/property. I don’t see why you’d have to reveal your medical information to a third party in this set of circumstances.
