Studying intrauterine vaccines for sows

Studying intrauterine vaccines for sows
Apr 14, 2020

Scientists at VIDO-InterVac are looking at the immune response and impact on piglet development of providing a vaccine formulation along with artificial insemination

By Jackie Clark
Staff Writer

Researchers at Saskatchewan’s Vaccine and Infectious Disease Organization – International Vaccine Centre (VIDO-InterVac) are conducting experiments on intrauterine vaccination. The technique could make vaccinating pigs and other livestock easier and more effective.

“Pigs aren’t like cattle and horses where you can put them in head gates and get them immobilized,” Dr. Heather Wilson, a research scientist at VIDO-Intervac, told Most pigs are bred using artificial insemination (AI), and during that process they go into a lordosis state. The pig will “freeze up, so for about five minutes they’re really safe to approach.”

This lordosis state presents an opportunity for farmers to vaccinate the sows without adding an extra management step.

“We were trying to think of ways to work with the industry … trying not to give anybody extra work,” Wilson said.

Also, though traditional vaccines may give a strong antibody response in the blood, “needle vaccines or intramuscular vaccines don’t do a terrific job providing protection at the exterior parts of the body, the mucosa,” Wilson explained.

The mucosa includes the mouth, nose, and reproductive tract. Because the uterus is a mucosa site, intrauterine vaccination also provides protection at the other mucosal sites, she added.

“If you can protect the mucosal sites, you’re stopping the virus or bacteria from actually getting into the body, rather than an intramuscular vaccine, it mounts a really nice immune response but it waits until (the body) gets invaded,” Wilson said.

Intrauterine vaccines provide “very good immune protection in the blood as well,” she added.

There is potential to protect both the sow and her piglets from invading pathogens.

“Initially we started looking at this as protection for the sow, but any time you get a really good immune response in the mom, if the animal is suckling, which the piglets are, they actually get good antibody protection by taking in colostrum as well,” Wilson explained.

The researchers started by conducting experiments with a primary vaccine.

“We did some research where we only administered the vaccine with semen into the uterus at one dose,” she said. This helped ensure the formulation didn’t have a negative impact on sperm, developing fetus, or piglets.

“But when we looked at the immune response, it was modest at best,” Wilson said.

It was encouraging that the intrauterine vaccine didn’t negatively impact fertility, but clear that multiple doses would be needed for a better immune response.

Normally, swine producers would want to vaccinate at AI and provide a booster once the piglets were weaned and the sow came back into heat. This process, however, takes months.

For research purposes “we gave the first intrauterine vaccine and we purposefully used killed sperm,” Wilson explained. This meant the sow would go back into heat three weeks later, and the scientists repeated the process with killed sperm to provide a booster.

Three weeks later the process was repeated again, this time with live sperm alongside a third dose of the vaccine.

“It worked out really well, the gilts had their piglets and they appeared healthy,” Wilson said.

The sows who had the intrauterine vaccination had the same number of piglets as the control group, but the piglets in intrauterine vaccinated sows were slightly lower weight.

“That could be because of that manipulation with the sperm. So the next set of experiments would look at the growth kinetics. Change the formulation a bit and see how they do,” Wilson explained.

The researchers were encouraged that gilts seemed to have good immune response, but weren’t able to challenge them with a virus that was in the vaccine. They conducted a challenge study on piglets that had been born to sows that had received intrauterine vaccines with porcine epidemic diarrhea virus (PEDv) antigens instead.

“Within three days of age, we challenged those piglets with PEDv infection … we did actually see a little bit of protection against the disease,” Wilson said.

The results are promising, and the researchers are now looking at how they might run a challenge study on the sows. Next steps also include investigating growth kinetics of the piglets, to ensure there’s no negative consequence to intrauterine vaccination.

If successful “we’d like to expand into other animals that use artificial insemination,” like turkeys or dairy cattle, Wilson said.

The vaccine formulations could be mixed directly with the semen and applied by producers when they are inseminating animals. 

“The semen producers might start looking at using intrauterine vaccine part and parcel with their semen, kind of a value-added product,” Wilson said.

chayakorn lotongkum\iStock\Getty Images Plus photo

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