The objective of this investigation was to study the pathogenesis of experimental Mycoplasma hyosynoviae arthritis in pigs. The experimental inoculations were designed to provide information about systemic spread, the persistence of subclinical infection, and the length of time for which the mycoplasma is cultivable from synovial fluids and other tissues. In this article we report on the clinical response to infection and the results obtained from re-isolation attempts.In three inoculation experiments with M. hyosynoviae, clinical arthritis was produced by intravenous and by intranasal exposure as well as by pen-contact in 12 out of 23 exposed pigs. The infection was transmitted from persistent carrier pigs to non-infected pigs by pen-contact. The incubation period until development of clinical arthritis was 4-9 days for all routes of exposure, and the symptoms were of variable severity. In half of the cases the onset was acute and the lameness severe, typically involving the hindlegs and with affected pigs assuming a dog-sitting position. A systemic phase was found in the majority (86 %) of the pigs. However, the infection was in two cases established in the tonsils without detection of a systemic phase. An apparent persistent infection of the tonsils became established in all the pigs.M. hyosynoviae spreads via the blood to different organs from which it could be re-isolated during the acute phase of the infection. In general, M. hyosynoviae was recovered from joints from day 3 until day 21 post-exposure, but longer persistence of viable mycoplasmas in joints or regional lymph nodes in the chronic phases of the infection appeared to have taken place in a few pigs. U.S. Copyright Clearance Center Code Statement: 0931-184X/99/4606-0317 $14.00/0 318 HAGEDORN-OLSEN et al. The aim of this study was to investigate the pathogenesis of M. hyosynoviae arthritis. It was the objective to produce arthritis by intravenous (iv.) and intranasal (in.) inoculation, and by pen-contact exposure to pigs in the acute phase of the infection or by pen-contact exposure to chronic carrier pigs. The experiments were designed to provide information about: (i) the incubation time and the clinical course of the infection; (ii) the systemic spread of the mycoplasma, and (iii) the isolation rates of M. hyosynoviae from joints and tonsils during the assumed acute, subacute and chronic phases of the infection. Materials and MethodsPigs and inoculation material Naturally farrowed crossbred (Yorkshire-Landrace) pigs, originating from six litters from two weanerproduction herds known to be infected with Mycoplasma hyopneumoniae, were used. The pigs were moved directly from the sow at 25-28 days of age to an experimental isolation unit at the Royal Veterinary and Agricultural University, Copenhagen, where there was no contact with other pigs. The pigs were proved free from M. hyosynoviae by 2-4 consecutive cultivations of tonsillar scrapings before they were used for the experiments. The pigs were free from any clinical signs of illness and wer...

Abstract. Necrotizing osteomyelitis and fibrinopurulent arthritis with isolation of Actinobacillus pleuropneumoniae serotype 2 is reported in two pigs from a herd with lameness and mild coughing problems among 8 to 12-week-old pigs. Application of fluorescent in situ hybridization targeting 16S ribosomal RNA of A. pleuropneumoniae in formalin-fixed tissue was performed to verify the association of A. pleuropneumoniae with the bone and joint lesions. By in situ hybridization A. pleuropneumoniae was demonstrated as multiple microcolonies or single cells dispersed in focal fibrinonecrotizing pleuropneumonia, in joints with arthritis, and in bone necroses including lysis of growth plate and suppurative inflammation in the adjacent trabecular metaphysis, thus demonstrating that well-known infections manifest new, unusual lesions.

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Oligonucleotide probes targeting 16S ribosomal RNA were designed for species-specific identification of the porcine mycoplasmas Mycoplasma hyopneumoniae, Mycoplasma hyorhinis and Mycoplasma hyosynoviae using a fluorescent in situ hybridisation assay. The specificity of the probes was evaluated using pure cultures as well as porcine tissue sections with artificial presence of mycoplasma, and the probes were found specific for the target organisms. The assay was applied on sections of 28 tissue samples from pigs infected with one or more of the three Mycoplasma species as determined by cultivation. M. hyopneumoniae and M. hyorhinis were identified in accordance with cultivation in lung sections from nine pigs affected by catarrhal to purulent bronchopneumonia. Likewise, in eight cases of fibrinous pericarditis, M. hyopneumoniae, M. hyorhinis and M. hyosynoviae were the infectious agents according to cultivation and were correctly identified by in situ hybridisation. Out of 11 joints cultivation positive for M. hyosynoviae, the probe was only able to identify M. hyosynoviae in eight cases probably due to a low number of microorganisms in the tissue sections. The in situ hybridisation assay is well suited for use in diagnostic and experimental work as well as a tool for pathogenesis studies.