Glad to report that my goose has now fully recovered but it took a LONG time.
After reading your post John, I did some research on the tetracyclines and spoke to the Waterfowl Trust in the UK. Then I asked my vet if she could order some for us which she happily did. This we had to administer orally via a syringe for a full month before her eyes stopped being gunky. She'd lost a lot of weight too. However, with lots of TLC and special food treats throughout July I'm happy to report that she has now gained back her weight, her beak is now normal colour and she looks just like the others in the flock.
One other goose seemed to be showing early signs so we gave her the tetracycline for 3 days which knocked the infection on the head.
One of our Muscovies also got it so she needed the medication soaked into bread every day. That took two weeks to clear.
No signs in the Indian Runners, the Pekins or the
chickens thank goodness.
So, a happy ending.