A highly virulent organism. A new barn. A large number of piglets dying of meningitis.
Although Streptococcus suis (Strep suis) was not a new problem for the Pipestone System, a new serotype began causing major problems one to two years ago and required a new solution, said Scott Dee, DVM, director of research for Pipestone Veterinary Services, during the American Association of Swine Veterinarians annual meeting on March 8 in Atlanta, Ga.
“We had been exploring alternative approaches and began thinking, ‘what about a Streptococcus autogenous vaccine using this new isolate?’” Dee said.
Admittedly, Dee and colleagues were skeptical about an autogenous Strep suis vaccine based on past results and information.
“With all the pressure on antimicrobial use, as well as the pressure of this new pathogen, we thought we better look at this again,” Dee said. “We did not want to rely on the preventative use of antibiotics to solve this problem.”
A mission to prove efficacy
One of the things Pipestone set out to do with their research program on autogenous vaccines was to prove efficacy, Dee explained.
“We ran two experiments that basically looked at the efficacy component of an autogenous Strep suis type 1 vaccine made by Newport Laboratories,” he explained. “We had 100 pigs that were vaccinated and 100 pigs that weren't vaccinated.”
Dee worked with Newport Laboratories to develop a challenge to evaluate these two groups of pigs.
The results showed a significant reduction in mortality and clinical scoring in the vaccinated group as compared to the control group.
“It was a bit of an eye opener because a lot more pigs died in the non-vaccinated group or had more clinical issues than the vaccinated group. Maybe there was something to an autogenous strep vaccine after all? Better adjuvants? More accurate isolate selection?” Dee said.
During their second research trial, they divided the pigs into four groups: vaccinated sows, vaccinated pigs, vaccinated sows and vaccinated pigs, and no vaccine. Using the same challenge model and the same homologous strain, they conducted the study similar to the first one. The results? They saw benefits again in the groups that used the vaccine.
“We saw the most improvements in the sow-vaccinated group of pigs and the sow- and pig-vaccinated group. However, all vaccinated groups were better than nothing,” Dee said.
Delivering the vaccine through the sows had the best results. Dee said this was exciting because it costs less and takes less time to vaccinate the sows and have them deliver the immunity through colostrum rather than vaccinating all the pigs.
Realizing the challenge model was artificial, the Pipestone team is beginning to evaluate the vaccine under real-world conditions.
“The challenge was given intramuscularly and intraperitoneally, which we liked because it was very robust. But that's not the natural route of strep infection,” Dee explained. “Now we are evaluating the performance of vaccines under natural challenge conditions where Strep suis is allowed to pass from pig to pig the way it does in the real world.”
The preliminary information is similar to what they saw in the first two trials. He said sow vaccination appears to have a repeatable benefit, trial after trial.
“Vaccination is always better than doing nothing. That's quite repeatable as well,” he said. “It really depends on your budget and how many shots you want to give.”
Dee believes this is one way to reduce the use of critically important antimicrobials in a preventative manner, which is a common process in swine farms.
“There's a place for the strategic use of antimicrobials. We don't really agree that preventative is one of those. What can we do outside of just giving everybody a shot of a critically important antibiotic? This is not a viable, long-term alternative,” he said.
Pipestone has been utilizing this autogenous Strep suis vaccine at problem farms since the first two trials were conducted.
“Clinically, we’ve had a nice response,” Dee said. “It seems to be working well. It has helped us control the problem and given us a new tool.”
He added testing efficacy will be a standard procedure for their research team if they pursue additional autogenous vaccines to battle other organisms in the future.
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