Free Endotoxin

Endotoxins are the lipopolysaccharide components of gram-negative bacterial cell walls. They are released by the bacteria when they die or when the cell wall is damaged. They trigger an inflammatory response where they occur in the body and they can cause fever, low white cell counts and abortion. These problems can result in lowered milk production, loss of a calf, and a weakened immune response in the cow. All of these physically stress the animal, and lower production.

Free Endotoxin Content in Vaccines

Free endotoxins circulate in an animal without being bound to an adjuvant. They can enter an animal with the vaccine administration or can be released when a bacterial infection is treated with antibiotics. A bacterial infection treated with antibiotics kills the bacteria rapidly and they release large amounts of endotoxins into the animal when they die. Free endotoxins are also present in nearly all gram-negative vaccines. When bacteria are killed and placed in vaccines a binding agent called an adjuvant is used to keep them anchored long enough to stimulate the immune system. Unfortunately it is impossible to bind all pieces of the bacteria, and prevent cell wall breakage while manufacturing vaccines--these unbound pieces of bacteria are free endotoxins.

The amount of endotoxins in a vaccine is variable. Although it is not possible to eliminate all free endotoxins from gram-negative vaccines, the amount in a vaccine is usually less than the amount of endotoxin resulting from a natural infection. It is important to limit the amount of free endotoxins (whether from vaccinating, injury, or infections), in an animal because they can accumulate with each vaccine given and cause health problems.