Vaccination Strategies for Pigs Raised on Small Farms

Use these guidelines to help make sure your animals stay in good health for the show season

Authors: Dave Thompson, MSU Extension Educator; Madonna Benjamin, MSU Extension Swine Extension Specialist; Dan Brown, DVM, 4-Star Veterinarian Services

Why should you consider vaccinating your herd?

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 (such as human influenza), from the sow (such as circovirus), or from other pigs and vectors. Vaccines 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 the lungs, intestines, 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 pig disease cost (due to lost performance, death, or treatment) versus the cost of disease prevention by vaccines, the reported benefits of vaccines consistently exceed their cost by at least 2.5:1 (Miller & Dorn, 1990; Niemi et al., 2018). Exceptions to these findings include vaccines against coronavirus strains that cause porcine epidemic diarrhea (PED) and transmissible gastroenteritis (TGE). These vaccines have not consistently stimulated the correct immune response. Other vaccines that remain controversial for naïve (not previously exposed) herds but have shown promise to stabilize an infected herd include the porcine reproductive and respiratory syndrome (PRRS) vaccines. There are other important reasons for using vaccines to protect your herd. First, swine producers are committed to the well-being of their animals, so it makes sense for them to prevent diseases before their 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. 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 (such as the Veterinary Feed Directive and the We Care initiative) advocated by U.S. meat and dairy producer organizations.

Why should vaccine-based approaches to disease management never precede or preclude vigorous application of sound biosecurity measures on your farm?

Diseases that infect pigs can enter the farm in many forms, including through 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 (Zangaro & Benjamin, 2021) (https://www.canr.msu.edu/news/simple-biosecurity-tips-for-your-small-swine-farm). As prevention typically costs less than treatment, biosecurity should always form the first line of defense against disease on swine farms.

How can you develop a vaccination strategy for your herd? 

No single vaccine strategy 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 naïve 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 2 to 3 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 employees, and other local pig farmers. A general vaccine strategy, summarized in Table 1, 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 the 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 (Table 2). Your vet may recommend use of one or more of these vaccines based on conditions in your area or specific to your farm.

You vet can help identify which diseases are reliably preventable with vaccines and how to obtain the best options for your farm. Michigan State University Extension recommends that you and your vet 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 • Required withholding periods Record this information (as a standard operating procedure, or SOP) and review on a regular basis with your vet to ensure that the plan is up to date. This SOP should be readily accessible to 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. PRRS may require a nuanced approach to vaccine-based prevention as new variants might be less responsive to vaccines currently available. During 2021, 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 (https://www.canr.msu.edu/news/sampling-oral-and-processing-fluids-to-identify-disease-in-pigs), or blood sampling results that show an increase in porcine circovirus type 2 (PCV2) in your herd, even in the absence of clinical signs, might signal an emerging problem that can be prevented by vaccination.

Sourcing and storing vaccines for pigs

Your vet 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. Avoid repeated freezing and thawing of the vaccines since this practice can destroy the biological material contained within them.

Administering vaccines to pigs

Before giving vaccines, read the dosing instructions on the label and confirm the expiration date. Record the day’s date, 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 immunesupporting 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 (Figure 1); a few can be administered intranasally (in the nose) or in water, which can be affected by water treatment protocols. The proper needle size (gauge) and length is based on stage or size of the pig (Table 3). Pork Quality Assurance (PQA) guidelines (National Pork Board, 2022) recommend use of detectable needles when possible. Plan to use each needle no more than 10 times, and discard used needles in a container marked “sharps,” designed to prevent needles from spilling out if the container is dropped or turned over. 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 those caused by 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 the animal involved is a breeding or nonbreeding animal. Always administer vaccines according to the manufacturer’s recommendations and be aware of withholding times for some vaccines. Your vet is the best source of information to consider when developing a vaccination strategy for your farm.