These are made in England from recycled materials, mainly old fire hoses and the leftover leather from Rolls Royce, BMW, and others like Burberry.
We visited while on honeymoon so I could pick something out in person, they have a really cool facility built out of hay bales and then plastered over and run on mostly solar power and are really cool people in general.
I’m pretty sure it isn’t part of any normal testing. Maybe if there were symptoms in the donor that indicated rabies or their family noted they had interactions with wild animals, but typically I think it’s mostly hepatitis, HIV, syphilis, toxoplasmosis, cytomegalovirus, chagas, and west Nile that are always checked for.