Infection of the pig by the tiny bacteria, Mycoplasma hyosynoviae, can be a real frustration for producers. The organism is ubiquitous (meaning everywhere), and it is likely that all herds are infected. Some herds never see clinical signs and some are plagued with it, especially in early finisher or when introducing new breeding stock.
Case Study No. 1
A producer receives 700 weaned pigs from the same, single-source sow farm every eight weeks. The sow herd is negative for porcine reproductive and respiratory syndrome (PRRS), but positive for Mycoplasma pneumonia. Piglets weigh 16 lb. at weaning, and nursery performance is fantastic with less than 2% mortality. Piglets are vaccinated for circovirus, erysipelas and Mycoplasma pneumonia.
Four weeks into the finishing phase, the producer notices lame pigs. It is always rear leg lameness with no visible swelling initially. Left untreated, the stifle (knee) joint eventually becomes very swollen, and the pig has to be euthanized because it becomes unable to rise. Incidence ranges from zero to 5%.
Case Study No. 2
A 1,500-sow unit receives breeding-age replacement gilts from a gilt developer unit every month. The gilts are PRRS- and Mycoplasma pneumonia-negative. Within a week of arrival, the producer notices gilts that are “toe-tapping lame.” My veterinary colleague, Dr. Steve Henry, says, “They look like a 14-year-old girl in her first pair of high heels, just a little wobbly.” Unfortunately, as in Case Study No. 1, if left untreated, the stifle joint swells to the size of a softball or bigger, the gilt eventually refuses to stand, and requires euthanasia. Incidence was usually less than 2%.
In both cases, diagnosis of M. hyosynoviae infection is made by gross lesions on postmortem and histopathology (tissue examination).
Although the Mycoplasma hyosynoviae organism lives in the respiratory tract of the pig and is spread via inhalation, it damages the joints, usually the stifle. Pigs show shifting lameness, which progresses to a stiff gait, then to dog-sitting and finally to recumbency. The pigs generally do not run a fever, and they often don’t lose weight until they can no longer get to the feeder comfortably. Initially, the stifle joint does not appear swollen, as it is covered by heavy muscle.
Often, at this point, producers call the veterinarian when the stifle joint is already very swollen and the joint is filled with pus. Treatment is not successful, and the origin of the problem is more difficult to determine by postmortem exam. If a postmortem is done earlier in the disease process, the joint fluid may be blood-tinged and the synovial membrane (lining of the joint) reddened and thick, but the surface of the joint cartilage appears normal. This is important because the condition is often confused with OCD (osteochondrosis dessicans), in which the cartilage is abnormal.
Successful treatment of M. hyosynoviae takes careful observation on the part of the producer. Affected pigs must be identified early and treated with a combination of injectable corticosteroid to reduce the swelling and the immune system’s reaction to the organism and antibiotic to kill the organism. Penicillin generally does not work, but the organism is usually sensitive to tylosin, lincomycin or tiamulin. Mycoplasma can be confused with erysipelas, Hemophilus parasuis, OCD and trauma. Treatment and prognosis for each is different.
Many have tried feed medication to prevent the disease with limited success. The no-brainer recommendations are:
- Avoid mixing and fighting. Move pigs pen for pen from nursery if possible; don’t resort.
- Feed-susceptible pigs ad-lib.
- Maintain stable environmental conditions for temperature, humidity, air quality and airflow.
The outcomes in the cases outlined above have been somewhat successful. In the first case, the producer has eliminated mortality associated with M. hyosynoviae by aggressively treating individual pigs at the first signs of lameness. Treating the first cases aggressively may help prevent more clinical cases as incidence is lower. Feed antibiotics were unsuccessful.
In the second case, the incidence was lower, but lowering stocking density and increasing feed upon arrival have reduced the incidence even further. Early identification and treatment have been key to animal recovery.