Robust Long-lasting Immunity Needed to Reach Heavier Market Weights

As slaughter weights trend heavier and hog prices increase, the benefit of reducing late-finishing mortality also grows. When pigs die in late finishing, the revenue that would have been generated is lost and the cost of feeding the animal to market weight already has occurred. Choosing the right vaccine to reduce the risk of late-finishing mortality can reap financial benefits.

A vaccine’s duration of immunity (DOI) provides guidance on how long a vaccine is expected to be efficacious. Vaccines with a DOI that covers the entire growing period are expected to provide longer protection, and potentially reduce mortality, in late finishing. This is critical for diseases such as Porcine Circovirus Type 2 (PCV2), which can linger for as long as five months after a pig is infected. This increases the risk of the virus shedding and infecting other pigs, plus it opens the door to co-infections, such as porcine reproductive and respiratory syndrome (PRRS), Mycoplasma hyopneumoniae and swine influenza virus (SIV).

Circumvent® G2 is the only product that provides 5 months of PCV2 DOI, options to use as a one-dose or two-dose protocol, and can be utilized in pigs as early as 3 days of age with the two-dose option.   

How does it provide such long-lasting protection against disease? The vaccine stimulates a robust “Primary Burst” – which is the immune system’s first, critical response to a disease challenge.

When a new, unfamiliar disease antigen is presented, it’s met by a specialized white blood cell called a macrophage. The macrophage collects the invader and delivers the component proteins of the antigen to the nearest lymph node. Within the lymph node, specialized white blood cells, called T cells, are activated by the antigen proteins. The T cells recognize the antigen and are programmed to defend against it.

The more robust the Primary Burst, the more T cells are activated. The more T cells recognize the antigen, the longer and stronger the immune response will be. When real-world disease exposure occurs, T cells at the site of exposure respond quickly. This is called cell-mediated immunity – a strong, rapid immune response.

Signs of a robust Primary Burst that can occur in the first eight to 36 hours post-vaccination include moderate inflammation, mild fever and lethargy. These reactions are the body’s natural response to building strong immunity against the antigen.           

The timing of vaccination and the time it takes to market all pigs in a group should be the first considerations for estimating the benefit of a longer DOI. Seasonality also should be kept in mind because pigs typically grow slower in the summer months. Finally, consider that early vaccination of pigs extends the time the vaccine needs to provide protection. 

January 23, 2015 - Merck