Houndit,
The questions you posed are the reason people have the attitude they're not going to beat the odds. Just because you don't see any symptoms physically in your birds doesn't mean you're safe. The real way to know for sure is to test your birds. This is not a condition that only shows itself one time as cold symptoms, it is a deteriorating disease. Mycoplasma Synoviae will cause your birds to become lame, one day they'll be limping, then a few days later you may find the limping bird dead. Some of these birds don't live to be a year old, and it will kill chicks up to 4 months of age almost immediately. Even the right medication after so much damage is done sometimes won't work to reverse the damage. And just because a bird breaks over into symptoms doesn't always mean that bird is the one that has it, you have to know your birds medically to understand what is going on with them.
I'll give you an example of what I mean, I helped a woman whose birds were tested Positive, we treated her birds and hatched chicks out six months after she was diagnosed Positive and after treatments with what I use. The state came back out and retested her birds, this time her birds tested clean of it. The woman wanted to sell hatching eggs and had people that were waiting for eggs. She sold eggs to someone else I know, who had an Epedemic state of Mycoplasmas in her bird earlier the same year, she got what I use and saved her birds with it, she didn't continue using it, and put it away to use if she ever had the symptoms again, she continued to get eggs from others and hatch them, not giving it a second thought about the eggs she was hatching were from untested flocks, she purchased eggs from my friend whose birds were clean, she incubated those eggs with a bunch of other eggs from untested flocks, the chicks all hatched out together in the same Incubator, after 15 days, my friends chicks died on this woman, and when that happened the woman thought my friends birds were sick, when infact it was the other way around, the other chicks that hatched were the ones that were truly sick and carriers. All chicks would have survived if the woman would have taken the bottle out of the cupboard and used it on them all as day olds, it is used on day olds to prevent the lesions from forming. And its rediculously easy to use, you mix very little in the water for 3 to 5 days, and repeat every 3 weeks for 3 to 5 days until they are over the age of 4 months old, then give monthly for 3 to 5 days, it's that simple.
As far as a bird having it and showing the symptoms getting better, it depends on what you use to treat it with and the strain of Mycoplasmas as to how viralent it is, as far as your other birds getting infected would depend upon if you can control the mycoplasma and use preventative maintance for your other birds as well as your biosecurity. Mites are another issue, they can spread it from one bird to the next, so monitoring your birds for mites is something else we all have to do. I eliminate straw alltogether because straw is hollow and is a great place for mites to harbor, I use pine chips and hay. Easiest way to clean is a garden sprayer with 10-15 percent bleach to water mix, remove the bedding and droppings and the birds to an area like a horse stall for 5 days, saturate their coop including the floor and the ceiling as well as every crack and crevice, treat the birds while they are away, replace their bedding and let the coop air out good in the 5 days, then return them to their coop, and in about 3 weeks treat them again this time in their clean environment, and continue to treat them as well as newly hatched chicks.
I know turkeys can also have Mycoplasmas, I do not know about Ducks, I don't have Ducks or Geese and I do think this would work with Peafowl as well as Guineas. I hope I'm helping, you have to break the cycle and plan to be rid of it. There are others who are using what I use and trying to breed this out of their flocks.
