Recently, the number of vaccines marketed for use in cattle production has increased dramatically. With a host of vaccines and vaccine types to chose from, producers are vaccinating cattle more than ever. Without question, this trend will continue as molecular biology and high-tech research into immunology is applied to cattle disease problems.
But, high-tech will never replace common sense in the fight to reduce health problems in cattle herds.
"Vaccine use is based on the severity of the threat to the herd – and on the prospects of reducing effects of the risk factors," says Bill Kvasnicka, University of Nevada – Reno (UNR) Extension veterinarian. "Usually the decision will be to lower the challenge by management and raise the resistance by vaccination."
Passive immunization produces temporary disease resistance. Antibodies are transferred from one animal to another and give immediate protection. This protection wanes, and the recipient eventually is susceptible to re-infection.
The Best Resistance
Vaccines can be divided into two groups "live" and "killed." Living organisms stimulate the best resistance but may present hazards as a result of residual virulence.
"As we know, it’s now very common to see mixtures of organisms in a single vaccine," says Kvasnicka. "They may protect against several diseases with economy of effort. But when different antigens in a mixture are administered, competition occurs between antigens."
Vaccine producers take this into account and modify their mixtures, says Ben Bruce, UNR Extension beef specialist. "However, vaccines should never be mixed casually or haphazardly, since one component may interfere or inactivate the response to the other ingredients."
Successful active vaccination is achieved only after passive resistance has dissipated because the passive antibodies will interfere with the immune response expected from administration of a live or killed vaccine, says Ron Torell, UNR area livestock specialist, who works out of Elko. "It’s impossible to predict the exact time of loss of the maternal resistance."
Thus, it’s usually recommended that young animals be vaccinated at least twice. Some vaccines will need to be given a second time at six to eight months of age to ensure successful immunization.
Killed vaccines produce a weaker immunity and require frequent administration. Most killed vaccines require two injections at three-week intervals and at least a yearly booster.
"Living vaccines usually produce a long-lasting resistance if initial vaccination is given after the maternal resistance is gone," says Kvasnicka. After initial vaccination with a modified live vaccine, boosters may not be needed yearly, he adds.
Poor management, though, can lead to a high level of exposure and a compromised immune system. Failure to properly immunize puts the herd at increased risk.
In general, according to Kvasnicka, vaccines seldom fail; but vaccination programs sometimes fail.
"Vaccines properly used as a management tool can improve the general health of a herd," he says. "Then the level of resistance will protect the animals from disease when the when the herd is exposed to a challenge."