The question is how well it is regulated. I don't know anything about the business. But I'd assume that with the right kind of regulations it can be controlled. E.g., require prostitutes to register. Registering should include a short course about basic rights and hygiene. They should have to go to regular health checks (maybe once a week), which should also provide access to social and legal counselling. The brothels should be required to keep track of anyone who works there and make sure that anyone working there has done those checks. This should be _regularly_ checked by the authority. Violations should be harshly punished.

Of course there is a risk if you over regulate it that there will still be black market prostitution happening. Especially if those regulations result in a price increase. Which regular health checks and access to social/legal counselling would certainly do.