A second Clark County herd of pigs has tested positive for pseudorabies, State Veterinarian Dr. Robert Ehlenfeldt says.
Eleven animals on a Loyal farm tested positive at Wisconsin Veterinary Diagnostics Laboratory. The 20-animal herd has been quarantined. The herd was tested because it had been in contact with the original infected herd; a boar from that herd had been brought to the Loyal farm for breeding. The Loyal farm is outside the five-mile radius around the first infected herd in Greenwood.
"This only tells us we have two infected herds," Ehlenfeldt says. "We'll continue our investigation to see if we have other infected herds and try to find the source of the infection."
The Department of Agriculture, Trade and Consumer Protection will work with the owner to develop a plan to destroy the animals and clean and disinfect the property. Because there is no human health risk, the animals can go to slaughter for food.
Quarantines will be delivered in the next few days to farms with swine within five miles of this second herd. There will be some overlap with the original five-mile quarantine area, Ehlenfeldt says. A quarantine stops movement of live hogs onto or off the farms, except for slaughter.
Herds on these premises will be tested for pseudorabies by May 5 and quarantines will be released for farms where herds test negative. Swine within two miles of the infected herd will be retested 30 to 60 days after the infected farm is cleaned and disinfected. It's not yet known how many swine herds there are in this five-mile area.
Ehlenfeldt said the U.S. Department of Agriculture is deciding whether Wisconsin can maintain its pseudorabies-free status for trade purposes now that a second infected herd has been found. To date, only Michigan has banned Wisconsin swine from import into that state. Other states have not imposed bans or additional testing requirements for Wisconsin swine.
In other developments, crews from the state and federal agriculture departments were in Clark County Monday and Tuesday drawing blood samples from 32 swine herds that are within five miles of the original infected herd. Those test results are expected by the end of the week. In the meantime, state and federal animal health officials will be examining records and talking with producers, market operators and others to try to find the infection source.
The original herd is expected to be eliminated this week.
Confirmation of positive test results was received April 16 for the Greenwood herd and work began immediately to find and arrange testing of herds within five miles. Pseudorabies is caused by a virus that enters the pig's system through its snout and is passed between pigs in mucus and saliva. It can be passed between pigs in close physical contact or in shared food that has been contaminated with mucus and saliva. Manure that's contaminated with mucus and saliva and tracked between farms may spread the infection, and in very rare circumstances, the disease may be airborne up to a mile.
Pseudorabies often kills newborn pigs, and causes abortion or stillbirth in sows, but usually causes only respiratory symptoms in healthy adult hogs. They can carry the virus without symptoms and without transmitting it until stress or other factors activate it.
Other species including cattle, goats, sheep, horses, cats and dogs can contract the virus from pigs, most commonly by bites. They die within 48 to 72 hours, often showing symptoms similar to rabies, although the virus is not related to the rabies virus. These other species do not transmit the disease.
Although pseudorabies was first detected in the United States nearly 200 years ago, it only began causing significant swine losses in the early 1960s. Wisconsin's infection rate peaked in 1989 with 60 infected herds, and the last case in Wisconsin was reported in 1998.
Besides the disease threat, pseudorabies poses an economic threat to producers, because a loss of Wisconsin's pseudorabies-free status would mean they have to test for the disease before shipping animals out of state. In 2005, Wisconsin producers shipped 182,000 swine out of state. Wisconsin's pork production in 2005 was worth $120 million, with a total swine herd of 430,000 animals.