Mycoplasma hyosynoviae infections in finisher pigs with arthritis

Since 2001 GD Animal Health in the Netherlands runs a monitoring system on pig health. One pillar of this system is the recording of all telephonic questions concerning health issues. Since 2013 lameness turned out to be the main subject of these questions. A detailed telephonic survey in 2014 revealed that most of the questions on lameness concerned finisher pigs between 3 and 5 months of age. The symptoms reported were acute lameness in more than one leg and swollen joints and bursas. However, rectal temperature was normal and mortality low. Predominantly hindquarters were affected. According to literature, these symptoms are associated with a Mycoplasma hyosynoviae (M. hyosynoviae) infection. However, in the Netherlands, this pathogen is rarely confirmed in pigs. Another possible cause might be osteochondrosis or a combination of both. In order to establish whether M.hyosynoviae plays a role in the described problems, selected pigs submitted for post mortem investigation were specifically examined.

Pigs, between 3 and 5 months of age, submitted for post mortem investigation to the GD Animal Health laboratory, with a history of acute lameness and swollen joints were selected for further investigation. Samples were taken from the affected joints and sent to the laboratory of the Tierärtzliche Hochschule in Hannover, Germany to demonstrate M. hyosynoviae by culture. Joint tissue and adjacent bone tissue were also assessed histologically for signs of inflammation and osteochondrosis.

In the period June until December 2015 19 pigs (from 10 herds) with lameness were investigated pathologically. From 36 joints a smear was cultured. M. hyosynoviae was detected in 8 joints (6 pigs from 4 herds), Streptococcus suis in 7 joints (3 pigs / 2 herds), mixed culture in 6 joints (5 pigs / 4 herds) and no bacteria were found in 7 joints (6 pigs / 4 herds). Results form 8 joints (3 pigs / 2 herds) are pending. All joints with an M. hyosynoviae infection showed indications of osteochondrosis and all but one also presented clear signs of arthritis consistent with a M. hyosynoviae infection.

From the results of this limited survey, it can be concluded that M. hyosynoviae most likely plays a significant role in acute lameness of finishers pigs between 3 and 5 months of age in the Netherlands. Osteochondrosis might be a cofactor in the pathogenesis. However, further investigation is needed to clarify the role of M. hyosynoviae and to establish appropriate preventive measures.

Disclosure of Interest: None Declared.