MPR: Pseudorabies

Pseudorabies
By Mark Steil
March 15, 1999

State officials are scrambling to find out why a hog disease known as pseudorabies spread rapidly this winter in southern Minnesota's prime pork-raising areas. Over 200 infected herds are quarantined and officials expect to find more animals with the virus.

For More Information
See the section on the Minnesota farm crisis.

QUARANTINED HOGS ARE NOT a total loss; producers can still sell them for slaughter. The virus does not affect humans so the meat is safe to eat. But the disease can kill hogs, and for those that survive it adds thousands of dollars to the cost of getting them to market. Southern Minnesota producer Kurt Unke has seen the bills pile up.

Unke: Just all the blood testing itself and the time to get it done. And of course the vaccine expense. And your pigs do not grow as good when you have pseudo.

Those slower growth rates require more feed to get the animals to market weight. The extra cost is an added blow to hog farmers already facing depressed market prices. The disease also limits some of the available markets for Minnesota pork producers. Unke says South Dakota officials refuse entry to pseudorabies infected hogs because they're concerned the virulent Minnesota strain will spread to their herds:

Unke: Even though we raise as good a hogs as anywhere in the country, you have another state say "well we don't want Minnesota hogs because of the pseudo. " That's bad.

The disease strikes hardest at young pigs, killing many at birth. Pseudorabies less-frequently kills adult hogs, but it has done that this winter in southern Minnesota. The virus is spread readily through saliva and mucus, but it can also travel through the air. Once infected, a hog carries the virus the rest of its life and may pass it on to other animals, including cats and dogs.

The disease got its name from the rabies-like symptoms it produces in dogs, such as foaming at the mouth. State veterinarian Tom Hagerty says the number of infected hog herds in Minnesota had been declining steadily this decade. In fact, officials had hoped to eradicate the disease by next year, something which seems unlikely now. Hagerty has theories, but doesn't know what caused the winter flare-up.

Hagerty: Whether it was the fact that we have had and experienced a great deal of swine influenza which we know will trigger the pseudorabies. Or if just the fact that producers were unable or unwilling to maintain their vaccination schedule.

Hagerty speculates low hog prices forced producers to cut costs, with pseudorabies vaccinations among the items discarded. Hagerty says since last fall, records show the amount of vaccine sold is not enough for the number of hogs in the state. Producer Kurt Unke says some farmers wonder about other reasons for the outbreak.

Unke: We have done a lot of expansion in this area in the last five to seven years.

Some believe the growth of the hog industry contributed to the pseudorabies outbreak. Unke farms in Martin County's Rutland township, one of the most hog-intensive townships in the state's top pork-producing county. New hog farms dot the landscape. Pseudorabies is rampant and farmers speculate the hog buildings are just the right distance apart to provide a stepping-stone-like path for the virus to travel. State veterinarian Hagerty says the problem with the stepping- stone theory is that no one knows if the virus can ride the wind from farm to farm, because it's not certain just how far it can travel.

Hagerty: People talk about quarter mile, one mile, maybe a mile and a half. But I don't think that there's ever been a good enough study done to say that the virus will go X number of miles under certain environmental conditions.

Another theory is that the virus was carried from farm to farm by vehicles. Hog producer Kurt Unke suspects the semis used to transport hogs to market.

Unke: In the wintertime it's very hard for the trucker to keep the truck spotless, washed, disinfected, cleaned-out in between different farms. I guess my concern is that there's always a possibility of transferring, whether it's pseudo or any other bug the industry can get here, without having the trucks cleaned, washed, disinfected in between groups.

State veterinarian Hagerty says state law requires that trucks be disinfected after hauling quarantined hogs. But he says whether truckers follow that requirement is mostly on the honor system.

Hagerty: I know we do not have the personnel to do any sort of enforcement of that. I would say there has been very little enforcement of that requirement.

It's also possible that the southern Minnesota outbreak is a new, more virulent strain of pseudorabies. The virus has mutated in the past, most recently in the 1960s. Researchers say chances that something similar has occurred this winter are remote, but they are isolating and studying the virus to make sure.

Mark Steil covers southwest Minnesota for Minnesota Public Radio. You can reach him at msteil@mpr.org.

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