Canker (Trichomoniasis) is a Protozoa. (a one cell organism)
There are many strains of canker some are deadly (John Jones strain killed about 93% of the birds infected) other strains kill none.
Studies have found that Trichomoniasis is one of the biggest killers that pigeons can contract. Because of the many strains and some can have an affinity for different parts of the body they can go unnoticed. While many have the belief that canker is only the yellow cheesy growth that can be seen in the mouth or on the navel.
It has been found in the crop, intestine, liver and in some cases muscles.
For the most part these are harmless organisms that just about all pigeon have mostly living in the crop. It seems that outbreaks of the disease occur when the pigeons are under stress (breeding or racing) or when a new strain is introduced into a loft.
Drugs for treatment Aminonitrothiazole, Ronidazole
Keeping your birds healthy is just as important as buying a good pigeon.