Bovine Respiratory Disease (BRD) has been, is now, and for the near future will be the number one problem in calves, stockers, and feeder cattle. Three of the major bacterial causes of BRD are Mannheimia (Pasteurella) haemolytica, Pasteurella multocida and Mycoplasma bovis. This review of clinical signs is intended to help you better understand the disease pattern. For this discussion, we will consider M. haemolytica and P. multocida as Pasteurellas producing similar clinical signs.

Of first importance is the fact that both Pasteurellas and M. bovis are normal inhabitants of the upper respiratory tract (nasal passage, larynx, tonsils, upper trachea, etc). They are opportunistic organisms that rely on stress to suppress the immune system and allow them to “set up house” in the lower respiratory tract (lower trachea, bronchioles, alveolar ducts) and cause clinical BRD. Because of this phenomenon, upper airway swabs for laboratory diagnosis are not reliable. Lower airway transtracheal washings or a broncho-alveolar flush should be used instead.

Clinical signs associated with Pasteurella BRD:
• Appear 5 to 7 days after a stressful event
• Fever of 1040 F to 1060 F
• Clear watery to heavy yellow or green nasal discharge
• Moist cough with shallow rapid breathing
• Depression, and an unthrifty appearance
• Anorexia
• Arched back with an expiratory grunt due to inflammation of the pleural lining (chest cavity)

Clinical signs associated with Mycoplasma bovis BRD:
• Tend to appear 20 to 45 days following a stressful event
• Fever of 1030 F to 1050 F
• Moist muzzle
• Moderate increase in respiration
• Frequent, harsh hacking cough
• Depression, and an unthrifty appearance
• Anorexia
• Other
            o Tilted head due to inner ear infection
            o Swollen joints generally forelimbs

An understanding of clinical signs will be useful in determining the vaccine needs of the herd.