Sorry. Language issues. It is what a walker is commonly called in the UK.What is a Zimmer frame?
Yes, Marek's can be detected with a swab. Can do a mouth swab, but a drop of blood is more accurate. Here is one of the independent labs that I have used and I know some others on BYC have used.Can Mareks be found by swab, but even asymptomatic birds will show it's presence, so it's useless except at necropsy?
https://www.vetdna.com/