How long do mycoplasma-negative herds stay negative?

Most hog farms successfully stamp out mycoplasma pneumonia when they work with their veterinarian to eliminate the disease. The challenge is preventing reinfection.

If the herds remain negative after the first 8 months, they became reinfected at a much slower rate over a much longer time than the herds turning positive in 8 months, reported Paul Yeske, DVM, Swine Vet Center, St. Peter, Minnesota.

Yeske and his colleagues looked at all the clinic’s herds taken through a mycoplasma-elimination program. They rated the success of each effort and plotted over time when the herds turned positive, which they called the decay rate.

81% elimination success

They noted a distinct difference between herds that used a closure plan with medication (water medication for sows and injection to piglets) for the elimination versus just medication (injection of both sows and piglets).

“On herds using a closure and medication plan, we were 81% successful,” Yeske said. “In herds with medication and no closure, we were at 62% success.”

The clinic’s protocol for whole-herd elimination required all pigs on the farm to receive a vaccine injection followed with a second dose 2 weeks later. In elimination with no herd closure, animals that become infected with mycoplasma can shed the organism for up to 8 months.

“I believe what happens with no herd closure is some of the herds decay rapidly because we never got mycoplasma totally eliminated,” Yeske said. “If they make it to 8 months, the pigs were done shedding and the herd was able to stay negative going forward.”

More negative herds in future

“Mycoplasma elimination is one program that’s been widely done in a relatively high number of herds and has been successful. I think we will see more and more people adopt elimination and see more herds go to mycoplasma-negative pigs because of the economic benefits with grow-finish production,” he explained.

“The good thing with mycoplasma is we have the tools to eliminate and successfully keep it out of our herds for a long time.”