A presentation at the Ohio Dairy Management Conference Dec. 18 gave a much-needed review of the important principles and guidelines relative to vaccinations of livestock animals.
Paul Hass, who is in the department of veterinary preventive medicine at Ohio State University, gave a concise and clear explanation of most kinds of vaccinations, how they work and why they sometimes do not work.
I think you’ll find it worth reviewing.
I have added clarification and additional explanations to his outline.
Livestock biosecurity. With today’s heightened awareness of biosecurity issues, it is important for livestock producers to remember that the program you put into place to shield your livestock from diseases includes much more than vaccinations.
Biosecurity must include complete isolation of new or returning animals for at least two weeks, preferably longer.
Biosecurity also includes keeping unauthorized visitors from coming into contact with livestock, and keeping other disease vectors such as insects, rodents, birds and predators away from susceptible individuals or groups.
Your biosecurity program may be focused on eradicating a known disease problem such as Johne’s Disease, or it may be focused on a more generalized concept of keeping new problems such as new serotypes of bovine viral diarrhea from becoming established.
Whatever the situation, you must understand the role of vaccinations, isolation, visitor screening and security and other methods in applying a complete biosecurity program to your herd.
Vaccine limitations. No vaccine is 100 percent effective.
Each herd has different disease infection profiles.
Unless there is a disease outbreak, it is difficult to assess the effectiveness of vaccination programs.
One thing is certain, vaccinations will never be a substitute for good livestock management.
Your herd veterinarian is the best person to design a vaccination program for your situation.
Be sure to work closely with your veterinarian and follow the program he or she prescribes for your livestock.
Vaccine terminology. The following are some terms you should be familiar with as we discuss vaccinations in dairy herds:
* Antigen – a foreign substance that stimulates an immune response, such as a bacterium, virus or toxin.
The antigen is what stimulates the immune response to a vaccine.
* Vaccine – a suspension (mixture) of an antigen that is given the animal to stimulate an immune response. Vaccines can be either killed or modified live.
* Killed vaccine – In killed vaccines, the disease agent is killed. It requires two doses given two to four weeks apart to build immunity.
These vaccines take three to four weeks to get protection.
Killed vaccines are generally safe for pregnant animals, but they have decreased ability to stimulate cell-mediated immunity (more on that later).
* Modified live vaccine – the disease agent is grown under conditions that causes it to lose its ability to produce disease.
This modified disease agent reproduces inside the animal and usually requires only one dose if administered at the right time.
Some modified live vaccines are not safe for use in pregnant animals.
Modified live vaccines produce both humoral (more on this later) and cell-mediated immunity.
* Bacterin – a killed vaccine made from bacterial products, for example, the clostridial bacterins.
* Vaccination – the exposing of an animal to an antigen by injection, intranasal administration or by oral administration.
* Immunity – the ability of an animal to produce antibodies to specific antigens.
* Active immunity – the animal produces immunity as the result of infection or vaccination.
* Passive immunity – the animal receives immunity from outside the body.
Examples include immunity from ingestion of colostrum or from one of the oral or injectable antibodies.
* Antibodies – large protein molecules that are specific for a particular antigen.
These antibodies attach to the antigen and limit its ability to cause disease.
* Humoral immunity – the antibodies are circulating in the blood.
* Antibody titers – the measurement of the quantity of antibodies in the blood. Elevated titers can be the result of disease infection or vaccination.
* Cell-mediated immunity – certain white blood cells present in the blood or body tissues that attack and destroy disease-causing agents.
Some infections require both antibodies and cell-mediated immunity to control them.
* Mucosal immunity – antibody that is produced on the surface of the intestine, nasal passage, lungs or reproductive tract.
Intranasal and oral vaccines induce mucosal immunity.
Response factors. The age of the animal is a major factor in immune response to vaccination.
Calves are born with very little immunity. The colostrum milk antibodies provide disease protection for six to eight months.
These same colostrum antibodies also interfere with response to vaccination of calves and young heifers.
Vaccinate dry cows to increase protection from colostrum against such calf diseases as bacterial scours.
Oral and nasal vaccines can be effective in newborn calves because they provide mucosal immunity.
Heifers’ immune systems reach maturity at about the time of puberty, eight to 12 months of age.
Animals vaccinated before four months age should be revaccinated after six to eight months of age.
Pregnant animals should not be vaccinated with live virus vaccines, unless specifically labeled safe.
Stressed animals will often have reduced response to vaccination. Newborn calves often do not respond, even to oral or intranasal vaccines.
Animals that are already stressed from moving, dehorning, weaning and castration, or already sick animals will have a reduced response.
Air temperatures above 85 degrees Fahrenheit also will reduce response to vaccination.
Good nutrition is required for a proper immune response, including copper, zinc, selenium and vitamin E.
Rations that cause acidosis (too high in starch, too low in fiber) will reduce response.
Handling vaccines. Proper handling of vaccines is critical to success.
Keep vaccines cool, but do not allow them to freeze. Always read and follow all label directions.
Give injections in a clean, dry area of the neck or shoulder.
Use new disposal syringes or multidose syringes that have been cleaned with hot water only.
Modified live vaccines need to be handled with extra care.
Never mix two vaccines in the same syringe. Once mixed (these vaccines come as two bottles that are to be mixed together before use), use the live vaccine within one hour.
Keep vaccines out of sunlight.
Vaccine failure. There are several reasons why vaccinations may fail or appear to fail.
Sometimes animals develop an overwhelming infection or encounter such a virulent form of the disease pathogen that the vaccination antibodies are not adequate to protect the animal.
Sometimes a slightly different serotype of the disease comes along that is not affected by the vaccination antibodies (one example of this occurs with bovine viral diarrhea).
If you vaccinate stressed animals or animals still protected by colostrum antibodies, the response may be reduced.
Improper handling of vaccines will reduce or completely destroy effectiveness.
Animals that are already infected with the disease will not usually develop immunity in time (an exception to this is with oral or intranasal vaccines, which give an almost immediate immune response).
Failure to give the followup dose of killed vaccines is a common cause of vaccination failure.
Vaccine consideration. Bacterial diseases you may want to consider vaccinating for:
* Clostridial diseases.
* E. Coli diseases.
Viral diseases for which you may want to vaccinate:
* Bovine viral diarrhea (BVD).
* Infectious bovine rhinotracheitis (IBR).
* Parainfluenza 3 (PI3).
* Bovine respiratory syncytial virus (BRSV).
(The author is an agricultural extension agent in Columbiana County. Questions or comments can be sent in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)