I assume his lease probably addresses sub-leasing, as well.He has a good case but it will take a while for him to follow the legal process and get these parasites out of his home.

And like some body-snacher flick this parasite has taken over the "wholesaler" space all but totally, zombified creature feeding on your capital vs brains although they do consume a considerable amount of ones patience as well. 

But they are the worst and most terrible parasites to our society.

Unfortunately this way is often taught by parasitic gurus and put into practice by their victims.

(In Ohio, unless the tenant recently moved to the state you can require that the letter be from an Ohio health practitioner)The tenant is required to have a legitimate relationship with the healthcare provider... you don't have to accept any old website certificate: ask the tenant and the provider if the tenant sought out this provider specifically to obtain an esa and if the tenant has been seen by the practitioner before or since.You may ask for vet records showing that the animal is in good health, free of parasites and has all required vaccinations.

If you just rely on the current landlord for information they could be lying to you just to get the renter out of THEIR hair.These parasites can pop up anywhere.

I don't know how easy it is to sell a house that comes with parasites on tap.  

Secondly I have been advised by my Dr to be tested for mold, parasitic, allergic or breathing problems.

That's how parasites work. 

It's unsolicited and effectively being a parasite.