Animals infected with this baterial pathogen can seem healthy one day and be deceased the next. Learn how to help prevent it.

Understanding why Mannheimia (Pasteurella) haemolytica is considered the most lethal bacterial cause of bovine respiratory disease (BRD) is the first step in helping prevent it.  

How M. haemolytica impacts cattle

From 2011 to 2015, BRD in nursing calves was estimated to cost the beef industry about $165 million annually.1 Of the bacterial causes that generated these losses, M. haemolytica is the most predominant.2

M. haemolytica bacteria are found naturally in the respiratory tract. Dust, stress or viral infections make it easier for M. haemolytica to rapidly reproduce, become more pathogenic and travel from the upper respiratory tract to the lungs. Complicating matters are multiple virulence factors that allow M. haemolytica to avoid the efforts of immune defenses in cattle, making it tougher to cure the infection.

M. haemolytica typically causes acute pneumonia, and other BRD bacterial pathogens are commonly secondary invaders causing more chronic pneumonia.

One thing that separates M. haemolytica from other bacterial pathogens is that it produces leukotoxin, which poses grave threats to cattle:

  • Leukotoxin kills white blood cells.
  • Affected white blood cells destroy lung cells, causing serious lung lesions.
  • Serious lung lesions result in irreversible lung damage and potentially fatal consequences for affected cattle.

Other bacterial pathogens, such as Pasteurella multocida, don’t produce leukotoxin, so they do not pose the threat of severe acute lung damage that M. haemolytica does.

How to protect against M. haemolytica

M. haemolytica is opportunistic. It often takes hold when a viral infection or stress has already weakened the animal’s immune system. It’s better to prevent M. haemolytica than treat it. Vaccines can provide effective protection for cattle from initial viral infections that weaken the upper respiratory tract defenses, which opens the gate for bacteria to get to the lungs.

ONE SHOT® is a vaccine that acts against the unique dangers of M. haemolytica by promoting protection from leukotoxin and bacterial capsular antigens. This diagram demonstrates how it happens:


Mode of Action

STUDY: Significantly reduced lung lesions

ONE SHOT has been shown in controlled clinical studies to decrease the amount and severity of lung lesions in cattle infected with M. haemolytica. That’s because the adjuvanted leukotoxoid from ONE SHOT helps ensure production of predictably higher antibody levels and more effective M. haemolytica protection.3,4 A comparative study of Zoetis products showed that after 21 days of M. haemolytica exposure, ONE SHOT mitigated 74.5% to 79.6% of lesions and prevented 89.4% of mortality within the treatment group.4  

As always, work with your veterinarian to develop the vaccine program that is right for your operation. A veterinarian will help you choose the right vaccine for the right pathogen — key to helping reduce BRD.

Source: Jeff Sarchet, DVM, Beef Technical Services, Zoetis