Hi all,
I wanted to update this thread in case people are searching for help. It's a good news story!
So Marilyn started to get worse and eventually she had not eaten for a couple of days. I had tried to give her the Metronidazole in food but it tastes so bad she would not eat it. I cut 250mg tablets into quarters, coated them in lard so she couldn't taste it and managed to force them into her beak. As soon as I let her go she would flick the medicine out again. I decided to get serious with her. I crushed the tablet and slurried it up with veg oil, then caught her and used a plastic pastette to squirt it into the right side of her throat. She did not like it but had no choice but to swallow it. I did the crazy pigeon thing (desperation...) and she was getting about 100mg each day. The vet had said to treat for 3 weeks: I managed 20 days during which she had a poor appetite as metronidazole apparently makes everything taste horrible. On the 10th day she went into moult and lost her tail/neck feathers so looked awful. She was still gurgling and shaking her head throughout so I really thought it was not working. But her appetite came back OK; I fed her alone so the others couldn't dominate and scoff it all.
It's now three weeks since I finished the treatment. I have not seen her shake her head for at least a week and her breathing is clear. She would appear to be better! The vet had said it takes a while to shift the plaques so I guess that was it. She's still getting her own special breakfast (sweet corn, pomegranate, BOSS, grain porridge and yoghurt), feathers have almost grown back in and looking lovely. I was worried the medication/lack of appetite might ruin her moult but looks fine. She's not laying but that's normal for this time of year. After almost a year of violent head shaking, the chicken is cured. And if it recurs, I have plenty more Flagyl and a delivery system!
Thank you everyone for your help/support; it's really so helpful that you are there.
Love from Marilyn too!