Summary Porcine pleuropneumonia, caused by the bacterial porcine respiratory tract pathogen Actinobacillus pleuropneumoniae, leads to high economic losses in affected swine herds in most countries of the world. Pigs affected by peracute and acute disease suffer from severe respiratory distress with high lethality. The agent was first described in 1957 and, since then, knowledge about the pathogen itself, and its interactions with the host, has increased continuously. This is, in part, due to the fact that experimental infections can be studied in the natural host. However, the fact that most commercial pigs are colonized by this pathogen has hampered the applicability of knowledge gained under experimental conditions. In addition, several factors are involved in development of disease, and these have often been studied individually. In a DISCONTOOLS initiative, members from science, industry and clinics exchanged their expertise and empirical observations and identified the major gaps in knowledge. This review sums up published results and expert opinions, within the fields of pathogenesis, epidemiology, transmission, immune response to infection, as well as the main means of prevention, detection and control. The gaps that still remain to be filled are highlighted, and present as well as future challenges in the control of this disease are addressed.

iHaemophilus parasuis causes Glässer's disease and pneumonia in pigs. Indirect hemagglutination (IHA) is typically used to serotype this bacterium, distinguishing 15 serovars with some nontypeable isolates. The capsule loci of the 15 reference strains have been annotated, and significant genetic variation was identified between serovars, with the exception of serovars 5 and 12. A capsule locus and in silico serovar were identified for all but two nontypeable isolates in our collection of >200 isolates. Here, we describe the development of a multiplex PCR, based on variation within the capsule loci of the 15 serovars of H. parasuis, for rapid molecular serotyping. The multiplex PCR (mPCR) distinguished between all previously described serovars except 5 and 12, which were detected by the same pair of primers. The detection limit of the mPCR was 4.29 ؋ 10 5 ng/l bacterial genomic DNA, and high specificity was indicated by the absence of reactivity against closely related commensal Pasteurellaceae and other bacterial pathogens of pigs. A subset of 150 isolates from a previously sequenced H. parasuis collection was used to validate the mPCR with 100% accuracy compared to the in silico results. In addition, the two in silico-nontypeable isolates were typeable using the mPCR. A further 84 isolates were analyzed by mPCR and compared to the IHA serotyping results with 90% concordance (excluding those that were nontypeable by IHA). The mPCR was faster, more sensitive, and more specific than IHA, enabling the differentiation of 14 of the 15 serovars of H. parasuis. Haemophilus parasuis is a Gram-negative bacterium commonly found in the upper respiratory tract of the pig, and it was identified in 1910 as the causative agent of a globally prevalent systemic disease of pigs known as Glässer's disease. The more severe presentations of this disease include arthritis, meningitis, polyserositis, septicemia, and pneumonia (1-5). Based on statistics from the United States, H. parasuis is the leading cause of mortality (alongside the porcine reproductive and respiratory syndrome [PRRS] virus) in nursery herds, and it is the third most important bacterial pathogen affecting finisher herds (6). H. parasuis also contributes to a multifactorial porcine respiratory disease complex, the leading cause of mortality in grower-finisher pigs in the United States (7). Diagnostic submissions to veterinary investigation centers of the Animal and Plant Health Agency (APHA) in 2013 and 2014 recorded the highest annual rates of diagnosis of disease incidents due to H. parasuis in England and Wales since 2002 (8, 9). In the third quarter of 2013, the diagnostic rate reached nearly 8% of diagnosable submissions (8,9). This disease characteristically manifests postweaning and is associated with the loss of maternally derived antibodies and the endemic presence of the bacterium in herds (1, 5).Treatment and prevention of Glässer's disease are implemented via strategic delivery of penicillin-based antimicrobials in feed or water. Ongoing treatment may be...

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Copper-zinc superoxide dismutase ([Cu,Zn]-SOD) is widely found in eukaryotes but has only rarely been identified in bacteria. Here we describe sodC, encoding [Cu,Zn]-SOD in Haemophilus influenzae and H. parainfluenzae, frequent colonists and pathogens of the human respiratory tract. In capsulate H. influenzae, sodC was found in only one division of the bacterial population, and although the protein it encoded was clearly [Cu,Zn]-SOD from its deduced sequence, it lacked enzymatic activity. In H. parainfluenzae, in contrast, active enzyme was synthesized which appeared to be secreted beyond the cytoplasm when the gene was expressed in Escherichia coli minicells. The origin of gene transcription differed between the Haemophilus species, but protein synthesis from cloned genes in vitro was comparable. A C-T transition was found in the H. influenzae sequence compared with the H. parainfluenzae sequence, leading to a histidine, known to be crucial in eukaryotic [Cu,Zn]-SOD for copper ion coordination and so for enzymatic activity, to be changed to tyrosine. This is speculated to be the cause of inactivity of the H. influenzae enzyme. Secreted SODs have only been described in a few bacterial species, and this is the first identification of [Cu,Zn]-SOD in a common human upper respiratory tract colonist. The role of secreted bacterial SODs is unknown, and we speculate that in Haemophilus species the enzyme may confer survival advantage by accelerating dismutation of superoxide of environmental origin to hydrogen peroxide, disruptive to the normal mucociliary clearance process in the host.