The disease has been reported in chickens and turkeys. CRD is specific disease caused by one of the group of organisms known is pleuro pneumonia like organism (PPLO), but more closely defined is Mycoplasma; the particular organism directly associated with CRD isAlycoplasma gallisepticum with or without any secondary complications. According to I he recommendation of FAQ committee meeting held in May l969, the term “Avian Respiratory Mycoplasmosis” (ARM) be used in uncomplicated outbreaks involving only pathogenic avian PPLC (Mycoplasma) and the term CRD be used when PPLO infection is superimposed with other condition in I eel ion is superimposed with other condition.
The mortality entirely to CRD is negligible, but it is important because it predisposes the birds to infection for other disease producing organisms.
M. gallisepticum is transmitted through eggs but organisms can also pass from bird to bird through nasal discharges and through droppings. It can also be transmitted by hands, feet and clothes of attendants of visitors. Symptoms: Uncomplicated CRD is frequently sub-clinical. When symptoms are present they are normally milk in nature and include coughing, sneezing, and a nasal discharge. In turkeys, sinuses are frequently swollen. On postmortem examination the trachea may be found inflamed and the air sacs thickened with pus. The condition affecting air sac is often referred as “air sac” disease but it is more pronounced when other factors including bacteria, complicate the original CRD infection.
The- organism has long incubation period of 10 to 30 days. Therefore only few outbreaks-seen in birds under 4 weeks old
Prevention and control:
As uncomplicated CRD is not a major problem today, it may be necessary to protect only against the probable complicating factors. Increased ventilation without drafts reduces the spread and severity of CRD. Buying replacement stock from CRD free source greatly reduces the risk of spread. A very high standard of hygienic condition is of course, supremely important.
The tetracycline group of drugs is useful in treatment, if given continuously for over a week, as soon as disease’s seen in flock, at the rate of 100-400 g per ton of feed. It can also be given through water. Nitrofurans especially furazalidone is very effective. Streptomycin may be injected in sinuses after removal of mucous by spraying in turkeys are helpful.