J Vet Sci.  2016 Dec;17(4):489-496. 10.4142/jvs.2016.17.4.489.

Two clinical isolates of Mycoplasma hyosynoviae showed differing pattern of lameness and pathogen detection in experimentally challenged pigs

• Gomes-Neto JC
• Raymond M
• Bower L
• Ramirez A
• Madson DM
• Strait EL
• Rosey EL
• Rapp-Gabrielson VJ

• KMID: 2412604
• DOI: http://doi.org/10.4142/jvs.2016.17.4.489

Abstract

Mycoplasma (M.) hyosynoviae is known to colonize and cause disease in growing-finishing pigs. In this study, two clinical isolates of M. hyosynoviae were compared by inoculating cesarean-derived colostrum-deprived and specific-pathogen-free growing pigs. After intranasal or intravenous inoculation, the proportion and distribution pattern of clinical cases was compared in addition to the severity of lameness. Tonsils were found to be the primary site of colonization, while bacteremia was rarely detected prior to the observation of clinical signs. Regardless of the clinical isolate, route of inoculation, or volume of inocula, histopathological alterations and tissue invasion were detected in multiple joints, indicating an apparent lack of specific joint tropism. Acute disease was primarily observed 7 to 10 days post-inoculation. The variability in the severity of synovial microscopic lesions and pathogen detection in joint cavities suggests that the duration of joint infection may influence the diagnostic accuracy. In summary, these findings demonstrate that diagnosis of M. hyosynoviae-associated arthritis can be influenced by the clinical isolate, and provides a study platform to investigate the colonization and virulence potential of field isolates. This approach can be particularly relevant to auxiliate in surveillance and testing of therapeutic and/or vaccine candidates.

Keyword

Mycoplasma hyosynoviae; arthritis; lameness; swine

MeSH Terms

Acute Disease
Animals
Arthritis, Infectious/epidemiology/microbiology/*veterinary
Colostrum
Lameness, Animal/*epidemiology/microbiology
Mycoplasma Infections/epidemiology/microbiology/*veterinary
Mycoplasma hyosynoviae/genetics/*physiology
Specific Pathogen-Free Organisms
Swine
Swine Diseases/*epidemiology/microbiology

Figure

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  Fig. 1 Distribution of experimentally induced Mycoplasma (M.) hyosynoviae-associated clinical cases. Clinical observations were collected daily from 0 to necropsy across all groups. A Chi-squared test was used to compare the distribution of clinical cases (p < 0.05). Overall, a higher percentage of cases was seen in animals inoculated with isolate 3491 than 3496. The intravenous (IV) route led to a more rapid development of clinical signs compared to intranasal (IN) injection. Moreover, IV and 10 mL inoculation with isolate 3491 led to longer duration of clinical disease than 3496 (p < 0.05). The results for the negative control group are not depicted above since there was a complete absence of clinical cases for those animals.

• 

  Fig. 2 Mean lameness score (mean + SEM) across M. hyosynoviae inoculated groups. All observations were taken daily from 0 to necropsy. The clinical lameness scoring system varied from 0 to 3 corresponding to no lameness, slight, moderate, or severe clinical signs. The Chi-squared and the Friedman's tests were used to compare the distribution of severity of cases across groups (p < 0.05). A significantly higher mean lameness score was observed for animals inoculated IN with 10 mL of isolate 3491 than for all other groups between 10 to 14 (p < 0.05). Results for the negative control group are not shown because of the lack of clinical lameness for those animals.

• 

  Fig. 3 Percentage of quantitative polymerase chain reaction assays (qPCR) positive joints for M. hyosynoviae by isolate, individually or combined. Overall, a higher percentage of qPCR positive samples was found in all cases for two anatomical locations: the humero-radial and coxi-femoral joint. However, a broad distribution of this pathogen is seen given that at least 30% of any given joint sample tested positive for the organism. The control group was not included here since none of the joint samples in that group tested positive for M. hyosynoviae by qPCR.

• 

  Fig. 4 Distribution of the percentage of M. hyosynoviae qPCR positive joints by isolate and anatomical location. Significant differences in the proportion of M. hyosynoviae tested positive joints were found when comparing across inoculated groups by anatomical location. Asterisks mark the inoculated groups (isolate and/or volume of inocula) that differ significantly for each joint cavity (p < 0.05). A higher percentage of M. hyosynoviae positive joints was found for the following groups: 5 mL IN 3491, 10 mL IN 3491, and 10 mL IN 3496 for the humero-radial joint, 2 mL IV 3491 and 3496 for the coxi-femoral joint, and 2 mL IV 3496 for the femoro-tibial joint compared to other challenged and control groups (p < 0.05). Data for the control group are not depicted due to the absence of detection for this bacterium.

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  Fig. 5 Box-plot whiskers depicting the comparative analysis of M. hyosynoviae microscopic alterations by joint cavity. Histopathology scores (ranging from minimum to maximum) are depicted across all panels. (A) Scapulo-humeral joints. (B) Humero-radial joints. (C) Coxi-femoral joints. (D) Femoro-radial joints. (E) Tibio-tarsal joints. Statistical analysis was conducted by comparing all groups using the non-parametric one-way ANOVA Kruskal-Wallis test followed by multiple comparisons with Dunn's test. Different letters above the box-plot whiskers data indicate significantly differences across groups (p < 0.05).

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