Arthritis caused by Mycoplasma hyorhinis and Mycoplasma hyosynoviae continues to be an ongoing issue for pork producers and veterinarians. In addition to the economic loss (up to $23 per pig)⁸, there is the issue of decreased animal welfare due to reduced locomotion, pain, and general discomfort and sickness⁶.

Studies have indicated the within-herd prevalence of sow lameness to range between 8.8% and 16.9%6. When considering all cases of lameness in swine, it is estimated that approximately 26% are a result of Mycoplasma infection².

Mycoplasma can affect pigs of all ages. Sows are presumed to be the primary carriers, with piglets being affected prior to weaning or via horizontal transmission post-weaning. There are numerous factors affecting whether or not a pig infected with Mycoplasma develops lameness, including; age, immunity, virulence factors and/or infection pressure, and, in some herds, stress and low general resistance⁵.

A small, fragile, bacteria-like organism, Mycoplasma hyosynoviae is easily spread in the air and feces. It has been suggested that it can spread in the wind between farms. Mycoplasma hyorhinis, can cause respiratory disease and, occasionally, lameness7. In evaluating 431 cases of lameness seen at the Iowa State University Veterinary Diagnostic Laboratory, between 2003 and 2010, M. hyorhinis was diagnosed more frequently in animals 10 weeks of age or younger, while M. hyosynoviae was more common in animals older than 10 weeks^3.

Mycoplasma spp.-associated arthritis is more commonly seen in gilts than in boars, particularly in older animals⁷.

Pigs infected with M. hyorhinis will generally begin to show clinical signs of polyserositis and polyarthritis 3 to 10 days after exposure. The pathogen tends to primarily affect 3 to 10 week-old pigs, although occasionally, older animals may be affected. Infected pigs may appear lethargic and unthrifty, have swollen joints, and be unwilling to move³. The pathogen colonizes the upper respiratory tract of pigs. Acute inflammation of the serosa of body cavities and synovium may occur, and if not stopped can become chronic¹.

M. hyosynoviae tends to affect older animals, generally between the ages of 3 to 5 months. Infected pigs may appear to be uncomfortable, with swollen joints and stiff movement. Many animals will recover without treatment, although clinical signs may persist, especially if there is co-infection or joint lesions present3. Arthritis tends to show up 2 to 3 weeks following initial exposure, and the infection is often located in the tonsils. An acute infection will last approximately 2 weeks, during which time the pathogen may spread to the joints and various tissues. In some cases, infection will persist to adult age and become systemic⁴.

Diagnosing Mycoplasma spp. is best done via real-time PCR, which can be conducted directly on clinical specimens, joint or nasal swabs, or tonsil scrapings. Danielle McKeown, Diagnostics Manager at Cambridge Technologies, explains their approach: “We offer a Mycoplasma Multiplex qPCR that identifies and quantifies the amount of Mycoplasma hyopneumoniae, hyorhinis, and/or hyosynoviae present in a given sample. We are able to conduct this test in a matter of hours. If the sample is negative for these three Mycoplasmas, we also offer a Mycoplasma species PCR that detects any Mycoplasma spp. that may be present in the sample. We can then conduct 16s sequencing to help us identify the specific species of Mycoplasma.”