Resurgent Mycoplasma hyorhinis causes debilitating arthritis in late finishing

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Infectious arthritis caused by Mycoplasma hyorhinis is gaining ground in hog units where it infects neonatal pigs and develops into severe lameness in market hogs, according Douglas Powers, DVM, veterinarian with Four Star Veterinary Service, Rushville, Indiana.

“Today Mycoplasma hyorhinis is starting to cause a lot more problems,” he said. “We’re seeing issues in the nursery and subsequent issues in the finishing barn with severe lameness, and some even dead on arrival at packing plants.”

Sow transfers to pigs

M. hyorhinis typically enters a sow herd through gilt replacements. It then circulates among the sows and is passed on to piglets in the farrowing house.

“The peak level of infection in pigs is starting around 3 to 5 weeks,” Powers said. “Then it starts to go systemic through the body and causes other issues.

“Early on, you can have some lethargy, fever and pigs not doing well in the nursery. If you follow those pigs downstream, we can start to see some ear-tip necrosis, side sores. Then we start to see the severe lameness in the hind legs and the hocks.”

Damage from severe arthritis

When health issues occur in the nursery, Haemophilus parasuis is the usual suspect. But Powers says an investigation often finds M. hyorhinis is the culprit.

“Some people think it’s a secondary disease, but I think it’s probably primary,” he added. “It can cause quite a bit of health issues on its own, especially in the high-health herds.”

If the infection hits hard in the nursery, it leads to heavy mortality or opens the door for secondary infections, he adds.

“We have theses absolutely perfect, healthy pigs…then all of a sudden they’re lame,” Powers explained. “They’re dog-sitting; they can’t get up; they don’t go to the feed and water as much as they need to; and then they start to get that severe arthritis from the damage.”

The decline continues for the arthritic hogs until market when some of them cannot make it on the truck and become downers.

Death losses due to M. hyorhinis damage can be 4% to 5% during the last 4 weeks in some finisher barns, Powers said.

Testing and treatment

If Powers sees issues in the nursery, he uses a polymerase chain reaction test to check for M. hyorhinis. If the virus is present, he uses an ELISA (enzyme-linked immunosorbent assay) test to see if it is causing clinical disease.

“We will look at those ELISA levels to see what level of infection is in the herd and [if] we need to implement either an antibiotic regimen to control it or a vaccination program,” he explained.

In the future, he sees where elimination of M. hyorhinis in some operations will be warranted.

“Now that we have the ELISA, we can look to see how broad spread it is and see if we can put some programs in to try to eradicate it,” Powers said. “I think eventually that needs to be our goal.”