I believe one of my chickens has this illness. I see there are injectable antibiotics and wanted to ask if there is: a) a cost effective one that is readily available b) is there long term risk of cross contamination c) would it be best to euthanize the bird? She's displayed the symptoms since last Friday but has appeared to get slightly better with Calcium, vitamins and warm soaks. I originally thought she was egg bound (she is at the age to start laying) and last night was the first time I heard rattles in her breathing. Any advise would be great! Mycoplasma synoviae Synonyms: MS, infectious synovitis, synovitis, silent air sac Species affected: chickens and turkeys. Clinical signs: Birds infected with the synovitis form show lameness, followed by lethargy, reluctance to move, swollen joints, stilted gait, loss of weight, and formation of breast blisters. Birds infected with the respiratory form exhibit respiratory distress. Greenish diarrhea is common in dying birds (see Table 1). Clinically, the disease in indistinguishable from MG. Transmission: MS is transmitted from infected breeder to progeny via the egg. Within a flock, MS is spread by direct contact with infected birds as well as through airborne particles over short distances. Treatment: Recovery is slow for both respiratory and synovitis forms. Several antibiotics are variably effective. The most effective are tylosin, erthromycin, spectinomycin, lincomycin, and chlorotectracycline. These antibiotics can be given by injection while some can be administered in the feed or drinking water. These treatments are most effective when the antibiotics are injected. Prevention: Eradication is the best and only sure control. Do not use breeder replacements from flocks that have had MS. The National Poultry Improvement Plan monitors for MS.