There are a lot of benefits to disease eradication, says Carlos Pijoan, DVM, director of the University of Minnesota College of Agriculture's new Swine Disease Eradication Center. “Eradicating disease is probably the single biggest way we can have an impact on the cost of production, animal welfare and swine employee job satisfaction,” says Pijoan, professor of veterinary medicine. “Our mission is to develop and validate strategies and techniques that will help pork producers eliminate diseases.”
The center is based in St. Paul, MN. Six veterinary staff members are devoted exclusively to swine health issues, he says. Also, a commercial farm has been leased near Morris, MN, to conduct research to help with disease eradication protocols, he adds. More information on the center can be accessed at the college's Web site: www.cvm.umn.edu/sdec .
The center's first goal is to look at eradication of Mycoplasmal pneumonia, says Pijoan, speaking at the first International Symposium on Swine Disease Eradication held during the Leman Swine Conference in Minneapolis.
Why Eradicate Mycoplasma?
Pijoan explains mycoplasma is one of the most insidious pathogens affecting the pig. It is found in the vast majority of hog farms worldwide, causing respiratory problems in growing pigs.
More recently, mycoplasma has been identified as playing a key secondary role in aggravating infections with porcine reproductive and respiratory syndrome (PRRS). It has been linked to a wide variety of other major disease problems including Actinobacillus pleuropneumonia (APP), pseudorabies and even Classical Swine Fever (hog cholera).
Although it has been difficult to document direct costs linked to mycoplasma, it's clear that farms that have managed to break free of the disease enjoy dramatic improvements in performance, especially with growth rates and feed efficiency, states Pijoan.
The Minnesota researcher is not the first to suggest eradication of mycoplasma. In fact, attempts for many years have provided mixed results.
One of the first attempts at eradication was by off-site rearing of litters from older parity sows. It was thought that older parity sows would clear infection so their litters would be free of the microorganism, recalls Pijoan. Many of these newly established herds seemed to be disease-free, but most ended up becoming reinfected.
“Recent work in our group using polymerase chain reaction (PCR) from nasal swabs has found a high prevalence of mycoplasma-positive females of older parities in conventional herds, which suggests that the original hypothesis that these herds were mycoplasma-free may have been flawed,” he says.
Three techniques are being tried to eliminate mycoplasma:
Hysterectomy and off-site rearing: This method used in the specific pathogen-free (SPF) herd programs works well. But it is an arduous task best left to preservation of genetic lines.
Segregated early weaning (SEW): Research has shown that 5-day-old weaned pigs can be reared free of mycoplasma. This technique appears useful for the establishment of new herds, but is not practical for existing herds.
Overall, SEW has proved successful where breeding stock companies have wanted to preserve bloodlines. But many other mycoplasma eradication efforts employing SEW have failed because producers cut corners or the technology simply didn't work.
It is still uncertain if SEW really eliminates the mycoplasma organism, or the prevalence just drops below observable levels.
Depopulation of younger animals: Recent European research has indicated it is possible to eliminate the mycoplasma organism by eliminating all pigs less than 10 months of age from the herd. Under this program, the next step is to stop farrowing and treatment of remaining sows with antibiotics for a two-week period. The plan has apparently worked in small herds.
But Pijoan questions whether European herds have truly eliminated the organism — or if they are just blood test negative and are free of lesions at slaughter. He says recent research at Minnesota has shown animals can be infected by mycoplasma and not develop lesions or blood test positive.
Many questions remain. Reinfections of apparently clean herds could mean that the organism is more efficient than most at area spread, or that it was in the herd all along and expressed itself when the pathogen population or stress reached a critical level.
Still, mycoplasma eradication is a worthy goal because of the bacteria's role as a central immunosuppressor. It produces a cascade of events, precipitates PRRS infection and facilitates pasteurella and APP infections. PRRS infections then lead to infections with Streptococcus suis and Haemophilus parasuis, he notes.
Elimination of mycoplasma would greatly reduce the use of subtherapeutic antibiotics (continuous, low level), cut costs and provide a much healthier hog at marketing, says Pijoan.