Mycoplasma hyosynoviae arthritis on the rise in North America

Monday, August 4, 2014

Improved diagnostics aside, there has been a definite increase in M. hyosynoviae arthritis in our herds and treatment is often unrewarding

by ERNEST SANFORD

I have previously written about Mycoplasma hyorhinis in this column (Better Pork, August 2011) and mentioned that there is an overlap in clinical disease presentations caused by M. hyorhinis and M. hyosynoviae as they both cause arthritis (actually polyarthritis), although M. hyorhinis also causes a generalized polyserositis similar to that caused by Haemophilus parasuis (Glasser's disease) and Streptococcus suis.

Clinical signs. Lameness, joint swelling and pain resulting in altered gait are the usual clinical signs caused by M. hyosynoviae. Lameness in the hind limbs, especially the hock joints, is most easily observed in pigs with M. hyosynoviae arthritis, but all limbs can be involved. Rectal temperature remains normal or may be slightly elevated. Pigs may go off feed or have a reduced appetite, although difficulty in accessing the feed trough might be the reason for reduced feed intake. Morbidity is variable and direct mortality is rare. Some pigs may have to be removed from the pen, sold to the barbecue market or culled because of lameness.

Epidemiology. M. hyosynoviae colonizes the nasal passages when sows pass the organism over to their offspring soon after birth. The organism sits there until something triggers its spread systemically via the blood stream, ending up in the joints where it creates arthritis. Whereas M. hyorhinis generally causes arthritis in pigs less than 10 weeks old, M. hyosynoviae causes synovitis/arthritis in somewhat older pigs at 12-24 weeks of age.

Clinical cases and diagnoses of M. hyosynoviae arthritis have increased dramatically over the last decade. Part of this increase is due to a marked increase in diagnostic capabilities via molecular biology techniques, specifically PCR. Previously, diagnosis was accomplished by taking a culture of the M. hyosynoviae organism, which is technically challenging and unreliable unless sophisticated laboratory facilities are readily accessible.

Diagnostics. Diagnosis is accomplished by selection of clinically lame pigs for identification of M. hyosynoviae in the joint fluid. Your herd veterinarian would choose acutely affected, untreated pigs to aspirate synovial fluid from joints and submit this to the diagnostic laboratory for detection of M. hyosynoviae infection by PCR. It is often preferable, however, to submit an entire affected leg to the laboratory or to submit one or more live, acutely clinically affected pigs to the diagnostic laboratory for a complete diagnostic workup. More recently, oral fluids sampling (rope testing), which can capture one or several pens of pigs, has been the most reliable sampling technique for identifying M. hyosynoviae in a population.

Treatment and control. Acclimatization of replacement gilts and boars, which includes adequate exposure to resident recipient herd organisms, is an essential part of prevention measures. Startup herds are more prone to having M. hyosynoviae outbreaks when offspring reach the grower-finisher stages in the barn. Antimycoplasmal antibiotics, including draxxin, enrofloxacin, lincomycin and tiamulin are effective against M. hyosynoviae, but early treatment is necessary to avoid development of chronic lameness.

Treatment is often unrewarding. Tylosin is reported to provide variable results. NSAIDs (nonsteroidal anti-inflammatory drugs), such as metacam and aspirin, reduce swelling and pain associated with the lameness. There are no commercial vaccines available for M. hyosynoviae arthritis. Autogenous bacterins can be made, but reports have indicated they have not had much success.

The incidence of M. hyosynoviae arthritis has been increasing over the last decade in Canada and the United States. Part of the increase is due to improved diagnostic techniques, principally the introduction of polymerase chain reaction test for identification of the M. hyosynoviae organism. Improved diagnostics aside, however, there has been a definite increase in M. hyosynoviae arthritis in our herds. BP

S. Ernest Sanford, DVM, Dip. Path., Diplomate ACVP, is a swine specialist with Boehringer Ingelheim Vetmedica (Canada) in Burlington. Email: ernest.sanford@boehringer-ingelheim.com