Have to agree with Caroline (wildliferescuer) on this one as I've had a least one fledgling greenfinch affected recently by Trichomoniasis - had to take in all my feeders and disinfect them, then not put them out for at least 2-3 weeks after that
The finch in question has now disappeared (no doubt died somewhere) but there have been a couple more cases reported in my village as well.
Having witnessed my fledgling greenfinch with this deadly disease the symptoms that I observed in it's later stages were - general dopeyness, would sit for ages in one spot tilting it's head to one side, eyes closing and a gagging motion with it's beak, puffed up and generally looking really poorly
I've been advised that it will take approx 3 weeks to actually kill the bird and it's transferred through their spit, so any feed that the poorly bird has been in contact with (or water) will spread the disease to others.
Perhaps you could find out if your neighbour has observed any of these particular symptoms in his visiting birds?