Mycoplasma. Mycoplasma gallisepticum is a common, highly infectious disease that causes severe breathing difficulties in chickens and can take weeks of antibiotics to resolve. Mycoplasma species are, however, notoriously difficult to completely eradicate and may recrudesce later in time.hickens are fun, interactive pets to keep but can be prone to disease if not cared for in the correct manner. Unfortunately for their owners, chickens do not tend to show any sign of disease until they are very ill, at which point quite intensive treatment may be required to rectify the problem.