Ornithobacterium Rhinotracheale (ORT) infections

Introduction

Since 1991, the broiler industry in several countries worldwide, has been suffering from a phenomenon called "cheesy chickens".The phenomenon is mainly seen during the colder months of the year, and is characterized by high to extremely high condemnation rates in the slaughterhouse. The flocks involved often show very little clinical symptoms during life, so the rejects come as a total surprise.

What are "cheesy chickens"

The name comes from the picture at slaughter: Often there is a cheesy material in the abdomen, but also purulent or foamy material can be noticed (especially during the earlier stages of the disease). Obviously this is not acceptable for sales to consumers, and therefore the affected chickens, or parts of them, are rejected.

Risk for consumers
Although affected chickens do not look nice, there are no indications whatsoever that ORT might be a human health risk.

Aetiology

The bacterium causing "cheesy chickens" is Ornithobacterium Rhinotracheale. ORT is wide-spread amongst broiler breeders and broilers. The presence of ORT only however, will not cause any serious problem. Climatic conditions in the house, and possibly viral respiratory infections as well, play an equally important role in the manifestation of the disease.

Prevention

Make sure there are at all occasions, proper climatic conditions in the poultry houses.
o Prevent cold stress
o Make sure there is an adequate ventilation
o Also relatively short periods with shortage of oxygen or an access of ammonia may have a strong negative effect

Prevent respiratory diseases

o Proper bio-security measures
o Proper vaccination program
o Proper vaccination procedure

Post vaccination reactions may trigger ORT, just as field infections. Recently an ORT vaccine has entered the market. This inactivated vaccine, used twice in parent stocks, should protect the offsprings. Although limited experience is available at this moment, the first results seem to indicate good results.

Therapy

Several antibiotics are used to reduce ORT problems in the field, especially the different types of tetracyclines. The results of this are often questionable, also because ORT is able to develop quickly a strong resistance pattern. A rather late use of antibiotics may lead to a higher risk of residues in the meat.