By Andrew Heck
To jab or not to jab: be it due to on-farm herd management practices or public health concerns, the world is looking for ways to prevent antimicrobial resistance and also overcome a global pandemic. For hog farmers, immunization of pigs and people is improving health and welfare one shot at a time.
During the 2022 Banff Pork Seminar, two presentations related to vaccines highlighted the important role they play in pig production: one by grad student Alison Jeffery on an encouraging development related to managing Streptococcus suis and one by veterinarian Cordell Young on how to maximize your farm’s vaccine program.
While these presentations were video-recorded for virtual participants, those fully vaccinated against COVID-19 were able to attend in-person. This requirement underscores the significant – however heavily debated – role that vaccines will likely play in all industries going forward.
Strep suis vaccine development moves ahead
Streptococcus suis is found in most jurisdictions with well-established pig industries. These bacteria include 29 serotypes or variants and are zoonotic, meaning they can be transferred to humans. For pigs, infection affects the upper respiratory tract, and controlling its spread is usually done with antibiotics. Both sick and healthy pigs can be carriers, and in piglets, there is a risk of arthritis, meningitis and sudden death.
To date, vaccines against Strep suis have been ineffective, but research from the University of Montreal, led by Alison Jeffery, has found that applying an autogenous sow vaccination program increases maternal antibody levels in piglets up to five-weeks-old, depending on the serotype.
Autogenous vaccines rely on isolating bacteria from an individual herd, rather mass production for use on all herds. Whereas conventional vaccines are strictly used to help prevent community transmission or reduce the severity of infection, autogenous vaccines can also be use therapeutically, which is a major advantage for producers.
The process involves the recognition of Strep suis clinical signs in a herd, followed by collecting infected tissues for sending to a vaccine development lab. Development takes place rather quickly and is fairly cost-effective, relative to potential losses due to spreading illness.
“The vaccine induced a significant increase of antibody levels against all serotypes in gilts, compared to placebos,” said Jeffery. “Post-mortem sampling and bacteriology are very important to correctly identify the cause of death in field trials and herd health management.”
Post-weaning piglets are most at-risk of Strep suis infection, but previous research suggests that injecting piglets directly with two doses of autogenous vaccine did not have any effect on improving antibody levels, which hypothetically would have provided those individuals with a better chance at staving off infection. Previous studies relied on autogenous vaccines produced by a single company, so Jeffery decided to look elsewhere for her trial. The newly developed test vaccine was administered to one group of gilts, while another group remained unvaccinated. Then, piglets born to both groups were compared for immune response.
The study results are impressive but will require a deeper dive to fully characterize the clinical protective effect during the nursery period.
“The strains used for autogenous vaccines are isolated on the farm where the outbreak is occurring, so some strains could be more pathogenic than others, and that could have a big effect on the success of an autogenous vaccine from one farm to the next,” said Jeffery. “The herd history with Strep suis could also contribute.”
Using antibiotics to treat Strep suis may appear effective at dealing with clinical signs of illness, but in addition to concerns over antimicrobial resistance, this approach makes it is difficult to identify which serotype of Strep suis is in a herd or if the clinical signs belong to a Strep suis strain at all.
“It can be uncomfortable to ask farmers to move from antibiotics to a vaccine program, because they can see it right in front of them – you can see if the animal gets better,” said Jeffery. “But I think, over time, vaccination programs are going to save producers time and money, as antibiotics cost a lot each year, and now with different regulations worldwide, antibiotics may not be an option we can use easily in the coming years.”
Moving away from antibiotics presents challenges and opportunities, but thankfully, a separate presentation at Banff provided some helpful advice.
Optimizing your on-farm vaccine program
Cordell Young is a partner with Precision Livestock Veterinarians. Young recognizes that vaccine programs are not always cheap, but that their value goes well beyond the price tag.
“Vaccines cost money, unfortunately,” said Young. “They cost probably 40 to 50 per cent of the total veterinary costs for a pig producer in a year. If we’re spending that money, we need to make the most of it, and if we’re not, we’re probably making a bad investment.”
Vaccination offers a wide range of benefits over simple treatment, from total cost to duration of protection, versus the possibility of causing zoonotic disease outbreaks or contributing to antimicrobial resistance and further eroding public trust in the hog sector. That is a lot for any individual producer to consider, but it is vital for the industry to recognize.
And while the benefits are extensive, proper handling and administration of vaccines is important for producers to learn. Improper usage can lead to a host of problems related to animal and human health or could simply render vaccines ineffective, which would equal wasted time, money and effort.
“First of all, start with the right needle. If you go with a half-inch needle into a sow, you’re likely going to inject that vaccine into fat, and it won’t absorb,” said Young. “Alternatively, if you go with an inch-and-a-half needle into a piglet, you are more at risk of breaking the needle and putting the entire industry at risk of political and food safety challenges.”
For vaccines that are ingested through feed or water, other considerations should be made as well.
“These are live vaccines which we cannot use with any other medication or water treatments in the path of those vaccines for 72 hours before or after,” said Young. “They’re great products, and it’s great to be able to put a vaccine through water, but we can kill these bugs. They’re pretty weak bugs in general. Watch the time.”
Freezing is another threat to vaccine stability. They should be stored between two and eight degrees-Celsius – ideally in a refrigerator exclusively dedicated to vaccines – and it is useful to periodically verify the temperature using an infrared laser thermometer. Prior to administering the vaccine, Young suggests letting the product come to ambient temperature overnight, but producers should be careful not to overheat vaccines, as this could cause proteins to become denatured, rendering them ineffective.
Not only correct storage of vaccines, but also vaccine equipment, like syringes, matters. Equipment should be cleaned, dried and covered for optimal performance and to prevent the inadvertent injection of residual harmful bacteria into your herd, which is counterintuitive, but a lot more common than some might assume.
“Bacteria are in these syringes, and we’re seeing resistance,” said Young. “Clearly, just by the fact that they’re there, with syringes containing Class 1 antibiotics, and then we’re injecting that into potentially every pig in a group.”
Every farm is different, and every vaccine program should be tailored to your operation. By closely monitoring your own program, through observation and record-keeping, success should follow.
“Unfortunately, it is a reality that no vaccine will work 100 per cent, providing 100 per cent immunity or protection, and for an unlimited duration of time,” said Young. “However, we want to do everything we can to optimize the response to vaccination to get the most out of our investment.”
COVID-19 vaccines are making meetings possible
As the industry becomes increasingly eager to move beyond COVID-19 restrictions, the call for re-introducing in-person producer meetings grows louder; however, this has proved challenging, given competing ideas about the situation at hand.
The Government of Alberta’s Restrictions Exemption Program (REP), which was first implemented in September 2021 and removed in February 2022, stipulated three conditions for large-size in-person gatherings: full vaccination status, a privately paid negative test result or a medical exemption. Further to this, some venues chose to uphold stricter measures, as was the case with the Banff Springs Hotel, where the Banff Pork Seminar was held. Only fully vaccinated attendees were permitted, regardless of test results or potential exemptions.
Alberta Pork’s semi-annual meetings, taking place in mid-March, mark the two-year anniversary of the initial introduction of restrictions in the province. This year’s meetings will once again take place in-person across the province, after last year’s semi-annual meetings and the two previous annual general meetings (AGMs) were entirely virtual.
While the COVID-19 pandemic is not over, arriving at an endemic situation – where the virus is still present, but stable in terms of case numbers, and more predictable – is a worthwhile and hopefully achievable goal made possible by eventual widespread immunity. Time will tell, but the longer we live with COVID-19, the greater the push will be to accept vaccination as industry-standard, as everyone – vaccinated or not – loses patience with restrictions.
Vaccines are no miracle cure, but they help
Whether for pigs or people, vaccines have the ability to save lives. And for producers, money. But they are neither perfect nor magical, which is why biosecurity measures on-farm and safety measures like masking and physical distancing at meetings are still necessary, even if not everyone agrees on their application. Being safe, rather than sorry, is a reasonable approach when minor inconveniences can protect against potentially life-threatening outcomes.
Perhaps nothing else besides vaccines have created more controversy recently, whether that relates to preventing antimicrobial resistance or supporting public health. Regardless of how they are used, or what anyone believes on a personal level, vaccines are likely the future for the Canadian hog industry and the world.
