It is no surprise to see that everywhere you look people are getting scammed out of currency and items just to receive a bite. I myself was taken for 10k silver. It was only after a generous biter sought pity on me did I get vampirism. Afterwords I thought of a very simple solution to prevent any more players from getting scammed.
Make the bite an item that can only be viewed and performed in the trade window. Much like gear or food you have to select out of a long list the things you want to trade. Make the bite a service that shows up in the 'To be traded' column and when both parties agree and submit the bite is performed instantly. Sure you can still have the animation but the disease would already be transferred so if a person tries interrupting the action they won't get away with it.
ESO I implore you to make this fix, I will provide bites once a week without currency exchanged but there are literally thousands of players doing the scam and thousands more getting scammed, enough is enough.