Hello Elley
As you may well have discovered by now, trichomonosis is caused by a microscopic throat parasite, whose actions progressively block the bird's throat so it is eventually unable to swallow food and will die of starvation. It is passed on as a bird, unable to swallow, spits out a piece of food it tries to eat. That piece will then contain the parasite, and if another bird eats the same piece within the following hour or two, it will pick up the parasite as well. With the transmission being fairly instantaneous, hygiene is less important for controlling trichomonosis than it would be in preventing salmonella etc. Still, do keep up with the good hygiene around your bird feeding areas to prevent any other gremlins turning up. Trichomonosis has been known from the pigeon family since time immemorial, and for the past nine years we have also seen it in finches, where it has now become endemic, and has actually caused a nationwide decline in greenfinches.
A very high percentage of pigeons and doves carry the parasite, and many never show outward symptoms. These birds can only pass it on to their own chicks as they feed them with regurgitated food. It is only once a bird is no longer able to swallow that it becomes infectious to other birds at a feeding site. Sadly, any bird that feeds alongside such a sick bird will run the risk of infection. This is why we recommend suspending feeding – at least on horizontal surfaces, as these are where the infected particles will end up – for a while in order not to concentrate the feeding birds into a ‘honeypot’ situation where they would run a higher risk of infection.
Both collared doves and wood pigeons have periodic outbreaks of trichomonosis, where a larger or smaller percentage of the flock will become visibly sick and subsequently die. These outbreaks rarely take out the whole flock, and it may then be years before another outbreak is seen in the area.
Doggie has very helpfully given you the link to the disease pages where you can report this outbreak. Please do so, as reports like yours are essential to our ability to monitor the whereabouts and intensity of known infections, and to identify any new ones that might appear.