H1N1 vaccine for hogs aims to prevent mutated virus

The race to vaccinate humans against H1N1 is the principal focus of health leaders, but a vaccine effort for pigs is about to begin.

Scientists say it will help protect against mutations; H1N1 has shown the ability to infect several species of animals. The virus has been documented in pigs, turkeys and even some household pets, including a pet ferret in Oregon and a house cat in Iowa. Scientists though are most interested in the hog cases.

Carolyn Bridges with the Centers for Disease Control and Prevention said while pork is safe to eat, live hogs need to be watched closely.

"Pigs are susceptible to human influenza viruses, to flu viruses that circulate normally in pigs, as well as to viruses that circulate normally in birds and in poultry," said Bridges. "And they're unique in that way."

Bridges said that makes pigs a natural mixing vessel for various flu viruses. It's possible the human virus could combine with a hog or bird virus inside the pig to form a brand new bug that's more dangerous to humans.

This risk led the U.S. Department of Agriculture to seek a vaccine to protect pigs from the current H1N1 strain. The agency started with what's called the master seed; the USDA's John Clifford describes it as a laboratory culture of the H1N1 virus. He said drug laboratories will use that culture to make the hog vaccine.

"We have provided the master seed to a number of private companies, that can manufacture this particular vaccine for H1N1 for swine," said John Clifford.

He said the vaccine should be available by the end of the year. When Clifford described the effort last September, he said it would be up to hog producers to decide whether to vaccinate their herds.

"Now whether they would need to vaccinate for this novel H1N1 will be directly dependent upon the severity that we see in the human population and whether we start seeing cases in the swine population," Clifford said.

The number of human H1N1 cases has increased rapidly since that September news briefing. The first time it showed up in hogs in the U.S. came at the Minnesota State fair where six pigs tested positive for H1N1. Just this week the virus was also found in a pig herd in Indiana.

That sort of news has convinced at least one major hog company to vaccinate its animals. Minneapolis based Cargill, among it's other businesses, is the nation's 8th largest hog producer. Cargill spokesman Mark Klein said the company plans to inoculate its entire sow herd, about 120,000 pigs.

"One of the vaccine producers has a conditional license and may be able to ship as early as November," Klein said. "We're hoping that's the case because we have our routine semi-annual vaccination program for our sow herds in December. And so we would be looking to incorporate that at that time."

Klein said the mother hogs will pass on their H1N1 immunity to their piglets. The USDA hopes the vaccine will prevent the human strain from gaining a foothold in the hog population and possibly changing into something new. At worst, a new H1N1 virus could emerge that overwhelms the vaccine available now for people. But how likely is that?

Carolyn Bridges with the CDC said any flu virus is constantly changing--even the H1N1 virus in minor ways. But she said in most cases the existing vaccine is still strong enough to handle changes in the virus.

Bridges said more than 99 percent of the viruses seen "are very well matched to the vaccine strain."

It's that one percent that has researchers worried. With over 100 million pigs raised each year in the U.S., including 15 million in Minnesota, they're hoping hog producers use the vaccine when it's ready.

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