Veterinarians voice concerns over decline in vaccinations. Case reports rise 2.5% nationwide.
Even though 30-50% of healthy hogs carry erysipelas, the bacterial organism seldom causes much more than mild disease.
We get mild erysipelas breaks about every year. But for some unexplained reason, every 7-10 years the disease strikes with a vengeance, says James D. McKean, DVM, Extension swine veterinarian, Iowa State University (ISU).
This summer there were numerous reports of serious problems on farms and at county fairs across Iowa and southern Minnesota, he reports.
Hogs are normally sent to slaughter at the conclusion of county fairs. In some cases this year, however, officials had to retain pigs at the fairgrounds for up to 30 days. That's because some pigs in a group broke with erysipelas and the whole group had to be vaccinated. Vaccinated pigs then had to be retained to adhere to drug withdrawal times, explains Brad Thacker, DVM, ISU researcher and animal scientist.
On the farm, there have been some problems in younger finishing groups down to 60-80 lb., but the majority of outbreaks are in the heavier market weight finishers, adds Paul Yeske, DVM, Swine Vet Center, St. Peter, MN. Reports also indicate few problems in sow farms other than those seen in new gilt introductions.
Treating heavy finishers can be troublesome as outbreaks sometimes occur at the time of sales, says Yeske. In these cases, injectable penicillin can be used but be careful to avoid potential residue problems.
“Treating the entire group of animals in the early stage of infection is important,” says Yeske. “In groups where vaccine can be used without withdrawal concerns, then also vaccinate the entire group with the killed vaccine at the time of treatment.” Naxcel (Pharmacia Animal Health) has been used on groups that are close to marketing and need a shorter withdrawal period.
Yeske's list of clinical signs includes:
Death loss of 0.5-2% occurring overnight in apparently healthy hogs;
Pigs that are obviously sick with high body temperatures of 104-107° F;
Pigs depressed and off feed;
Low level of activity;
Lameness with extremely painful joints;
Generalized reddening of diamond-shaped skin lesions that don't usually show up until late in the outbreak; and
Condemned carcasses at slaughter (it's much easier to see skin lesions once hogs are dehaired).
The diamond-shaped lesions can appear any place on the body, says McKean. The lesion results in blockage of the blood supply, causing death of diamond-shaped patches of skin.
McKean and Yeske agree that most of the erysipelas outbreaks appear to have occurred in unvaccinated herds. But there have been reports of breaks in improperly vaccinated herds, too.
There have been some sow infections, but most cases have been in finishing pigs, as is expected, since erysipelas is basically a grow-finish disease, points out McKean.
Vaccination for erysipelas has dropped from 81.6% of operations to 72.9% of operations from 1990 to 2000, based on national estimates for erysipelas vaccination from USDA's last three National Animal Health Monitoring System (NAHMS) swine studies, says NAHMS official Eric Bush, DVM.
The drop in vaccination is most pronounced in larger operations, says Bush. The change in percent vaccinating is -8.2, -13.9 and -25.1% for operations with <250, 250-499 and 500+ breeding females, respectively.
“In 1990, erysipelas vaccination was clearly associated with herd size, increasing from 80.7% to 97.2%,” reports Bush. In the Swine 2000 report, there is no major association between herd size and frequency of vaccination for erysipelas.
The percent of all operations reporting erysipelas diagnosed in any group of pigs has risen from 4.6% in 1990 to 7.1% in 2000.
McKean advises:
Ensure the products being used and the timing of vaccination are providing good protection;
Provide an adequate amount of protection for late finishing pigs into the fall when most erysipelas outbreaks will normally subside; and
Review their vaccination program with their veterinarian so that the herd is protected through the winter — and to get ready for next spring.
“Continue to vaccinate. Don't quit just because you think the season for erysipelas is over,” stresses McKean. “Especially this year, that would be the smart thing to do.”