The need for a coordinated effort to track and manage emerging and domestic swine diseases has long been realized. However, a Minnesota herd's recent experience with high mortality from imported pigs has resulted in a renewed call for action.

When Jerry Torrison, DVM, visited one of Jim Lewis' finishing barns near Welcome, MN, in April last year, he already knew the Canadian-born feeder pigs were infected with a couple of domestic swine disease agents.

Rigorous Sampling Process

Torrison looked further by sending twelve pigs to the University of Minnesota Veterinary Diagnostic Laboratory (MVDL). The group represented dead pigs, downer pigs, normal-appearing pigs with a deep cough and normal pigs. MVDL pathologist Kurt Rossow, DVM, conducted a series of diagnostic tests. Polymerase chain reaction (PCR) tests were positive for Bovine Viral Diarrhea (BVD). Test results were also positive for Haemophilus parasuis, Type 2 porcine circovirus and H1N2 swine influenza virus (SIV).

MVDL Director Jim Collins, DVM, contacted regulatory officials and sent samples to USDA's Plum Island Diagnostic Laboratory in New York for further testing. PCR and virus isolation testing both confirmed that the pigs were indeed positive for BVD.

BVD is normally a cattle disease, but it has also been found to occur naturally in pigs, explains Torrison. Pigs don't normally show signs of BVD unless infected congenitally (acquired during development in the uterus).

The concern was that BVD comes from the pestivirus family that also includes classical swine fever, otherwise known as hog cholera, a foreign animal disease. Lab work at Plum Island ruled out hog cholera.

Haemophilus parasuis and SIV were also previously identified by Fairmont, MN, veterinarian Mark Wagner.

Haemophilus parasuis serotype 13, an uncommon serotype in the U.S., was repeatedly isolated in testing despite intensive antimicrobial therapy, says Torrison. This points to the major role the bacteria apparently played in this case, he stresses. Minnesota diagnosticians plan further testing of this serotype.

Large Losses Incurred

Torrison notes it has not been determined if BVD played any role in the high mortality in the Canadian feeder pigs.

The pigs were placed into one of three finishing barns in late March 2004. In all, 637 of the 999 pigs in the shipment died.

“All but three of the pigs died in April and nearly all in a two-week window,” observes Lewis. “After the disease went through, mortality essentially ended.

“What made this situation so scary was that the pigs were placed on medication within 24 hours of the first mortalities, and nothing we did with medications seemed to have an impact,” he adds.

The deaths and related treatment costs and production losses resulted in an actual financial loss of $62,000, according to the Minnesota producer.

Mortality rates were normal for the two other finishing barns on the same site. Those barns housed pigs born locally.

USDA's National Animal Disease Center at Ames, IA, is in the process of further defining the nature of the infection and the possible role that BVD may have played in the outbreak, observes Torrison.

He applauds Plum Island's quick response to the disease threat. The lab is working on further genome characterization of the BVD virus.

Program Needs

The Minnesota case highlights the fact that the industry lacks a coordinated, comprehensive and real-time surveillance system for emerging and domestic swine diseases, according to a committee report of the United States Animal Health Association (USAHA).

Recommendations to USDA for a program that would meet the needs of the pork industry were identified and detailed in a 1999 report by the Swine Futures Project, a government-industry partnership.

To rectify the situation, the USAHA passed a resolution during its annual fall meeting calling for USDA to work through its National Center for Animal Health Surveillance and the Center for Emerging Diseases at Fort Collins, CO, to establish a program. The effort is to bring together industry and state animal health officials to develop a defined mechanism to deal with emerging swine diseases.

“I think the important thing is that there be some sort of a definitive system for looking at these potentially emerging diseases, and if it is an emerging disease, that we get on top of it right away,” adds Tom Burkgren, DVM, executive director, American Association of Swine Veterinarians.

“The incident in Minnesota is only an example of the process that is needed, and helped to underscore the importance of detecting, investigating and responding,” notes Paul Sundberg, DVM, vice president, Science and Technology, National Pork Board.

“The pork checkoff is ready to help USDA understand how the industry works so they can develop a mechanism that is seamless and responsive to the industry,.” he says.

“We lack a scripted response as an industry for emerging diseases, and that is a highly significant need,” responds Torrison.

The case highlights the point that there are no regulations to deal with disease issues that don't fall under the category of foreign animal diseases.

“One of the lessons we hoped we would learn from PRRS (porcine reproductive and respiratory syndrome) is that we need to have an infrastructure and a mechanism that is up to the challenge of a new domestic disease, because such diseases can still be economically devastating to an individual producer, and potentially to the industry,” says Torrison.