Vaccination Strategy Helps Keep Hog Herd Healthy
Published: Friday, January 6, 2023
The following is from Dave Thompson, Michigan State University Extension educator; Madonna Benjamin, Michigan State University Extension swine veterinarian; and Dan Brown, 4-Star Veterinary Services, Holland, Mich.
Many diseases in pigs can be prevented or their effects minimized by vaccines formulated specifically for use in pigs. These vaccines provide a management tool that, when used properly, can greatly reduce reliance on other medications including medically important antimicrobials.
Protecting your swine farm from entry and spread of diseases is critical. Sometimes, despite excellent biosecurity and animal husbandry, pigs can become infected by a disease transmitted by humans (human influenza), from the sows (circovirus), or from other pigs and vectors. Vaccines are used to prepare your pigs for that possibility by priming their immune system in ways that help them fight off or neutralize the disease or its effects, thus minimizing damage it may cause to lung, intestine, or other critical organs.
Most commercial vaccines widely used in pigs have consistently demonstrated excellent efficacy against the bacteria or viruses they target. In surveys designed to determine the cost of pig diseases (i.e., lost performance, death, treatment costs) versus cost of prevention by vaccines, the reported benefits of vaccinating consistently exceed their cost by at least 2.5:1.
Exceptions to these findings include vaccines against coronavirus strains that cause PED and TGE. These vaccines have not consistently stimulated the correct immune response. Other vaccines that remain controversial for nave herds, but have shown promise to stabilize an infected herd, include the PRRS vaccines.
There are other important reasons for using vaccines to protect your herd. First, swine producers are committed to the wellbeing of their animals. From an animal wellbeing perspective, it makes sense to take actions proved to prevent diseases before your animals contract them. For example, the disease Erysipelas will cause a high fever and lesions on the skin.
As a result, pigs go off feed and some experience pain in the joints. These conditions are fully preventable by vaccinating against Erysipelas. Second, vaccines reduce the number of pigs that will contract diseases such as Erysipelas and influenza that can be transmitted to and cause disease in humans.
Third, preventing disease by vaccination usually allows animals to be raised using less antimicrobials, including those that are medically important (i.e., used to treat serious infections in people).
Reducing large-scale use of medically important antimicrobials, including many of those given as feed or water additives, helps prevent the emergence of antimicrobial-resistant strains of pathogenic bacteria and fungi. This is critical for preserving the long-term efficacy of those agents for future use in both animal and human medicine. This concept is central to the objectives of responsible antimicrobial use programs advocated by U.S. meat and dairy producer organizations.
Diseases that infect pigs can enter the farm in many forms, including other pigs, contaminated feed, delivery trucks or equipment, rodents and other wildlife, and people. They can also come in attached to dust particles that blow in from neighboring farms. These sources of disease are almost impossible to eliminate entirely.
However, in many infectious diseases, the infectious dose (amount of virus particles or bacteria required to cause disease) largely determines the disease outcome. An infectious dose can be reduced dramatically by consistently practicing preventive farm biosecurity measures.
As prevention typically costs less than treatment, biosecurity should always form the first line of defense against disease on swine farms.
Vaccination strategy
There is no single vaccine strategy that fits all farms. Disease risk can vary based on geographical areas and pig flow patterns, including entry of new stock. Also, vaccine selection and dose regimen are often dependent on pig age and breeding status.
Gilts are typically vaccinated prior to farm entry and again prior to breeding because they may be nave (not previously exposed) to current diseases on the farm. Vaccines can provide a quick immune response including antibodies in the colostrum that are passed from the gilt to their first litter.
Because maternal antibodies wane in the first two to three weeks after birth, piglets will likely require another vaccine at weaning. For these reasons, the best advice regarding vaccine products, dosage and timing, along with information on the risk of specific diseases in your area, will likely come from your veterinarian. It is also useful to consider information provided by your vaccine supplier, swine breeder, feed mill and other local pig farmers.
A general vaccine strategy includes important diseases that can be prevented using commercially available vaccines. Combination products are available for most of these common diseases, the use of which brings the added benefits of reducing labor, handling stress on the pigs and number of injection site lesions.
Vaccines are also available for diseases that occur less frequently in U.S. pigs or occur frequently but, for various reasons, don't provide consistent protection from disease. Your vet may recommend use of one or more of these vaccines based on conditions in your area or specific to your farm.
We recommend that you and your veterinarian work together to develop a vaccination strategy that includes such information as disease/vaccine, vendor(s), dosing schedule, amount/site/dosing procedure, possible injection site reactions to be prepared for, and required withdrawal periods. This information should be recorded (as a standard operating procedure or SOP) and reviewed on a regular basis with your veterinarian to ensure that the plan is up-to-date. This SOP should be readily accessible for you, farm staff and anyone else who may need to fill in for you and provide pig care over an extended period.
Management by vaccination of some pig diseases is not straightforward. Porcine Reproductive and Respiratory Syndrome (PRRS) may require a nuanced approach to vaccine-based prevention as new variants might be less responsive to vaccines currently available. During the past year, we have witnessed the emergence of new strains has caused high mortality in sow barns, nursery and grower finishers. If your herds are likely to be exposed, consult with your veterinarian on a vaccination program for weaned, breeding and incoming animals.
Decisions around vaccination might also benefit from the type of information obtained through surveillance methods that measure disease presence or response. For example, processing fluid, oral fluid or blood sampling results that show an increase in PCV2 virus in your herd, even in the absence of clinical signs, might signal an emerging problem that can be prevented by vaccination.
Storing vaccines
Your veterinarian is the best source of advice regarding where to purchase vaccines. Store vaccines according to label instructions and always check the expiration date. Most vaccines consist of biological materials suspended in aqueous solvents and are best stored in the refrigerator. Repeated freezing/thawing can destroy the biological material contained in the vaccine; and should be avoided.
Administering vaccines
Before giving vaccines, be sure to read the dosing instructions on the label and confirm the expiration date. Record the date given, pig ID, vaccine administered, lot number, expiration date, dose volume used and the name of the person delivering the vaccine. Pigs should be healthy at the time of vaccination. Don't vaccinate an animal running a fever. Make sure the intended injection site is clean.
Most vaccines have withdrawal times; usually this period is 21 days following injection. This information is clearly stated on the product label and must be followed. Be aware that efficacy of some live vaccines can be compromised by pre- or co-administration of certain antimicrobials.
Zinc deficiency can also compromise vaccine efficacy by virtue of the immune-supporting effects of this trace mineral. Your veterinarian will be able to answer questions regarding withdrawal time requirements and possible interactions between vaccines and antimicrobials or trace minerals.
Most vaccines currently used in pigs are administered into muscle (IM) or just beneath the skin (SC) a few inches behind the ear; a few can be administered intranasally or in water which can be affected by water treatment protocols. The proper needle size (gauge) and length is based on stage/size of the pig.
PQA guidelines recommend use of detectable needles that are 16 gauge or larger. Plan to use each needle no more than 10 times, and discard used needles in a marked "sharps" container designed to prevent needles from spilling out if the container is dropped or turned over (PQA PLUS Site Assessment Guide 3.0).
You should never use a bent needle. If a needle breaks during injection and you are unable to remove it, mark the area with a bright color label and alert anyone who might purchase the pig or transport the pig for slaughter. Make sure the butcher is aware of the needle and its approximate location.
Summary
Most important diseases that infect pigs, including pathogenic viruses and bacteria can be prevented or their effects reduced by vaccines.
Along with a sound biosecurity program, vaccines are the most cost-effective tool for preventing serious disease outbreaks on your farm. In most circumstances, vaccines are effective only when administered before exposure occurs to the specific pathogen it targets.
The type of vaccine and dose regimen used can be highly dependent on the stage of pig development, and whether it is a breeding or non-breeding animal.
Always administer vaccines according to the manufacturer's recommendations and be aware of withdrawal times. Your veterinarian is the best source of information to consider when developing a vaccination strategy for your farm.
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