Evaluation of the Efficacy of a Vaccination Program against Actinobacillus pleuropneumoniae Based on Lung-Scoring at Slaughter

Porcine pleuropneumonia is of serious concern regarding lung health in pig production. Besides optimizing hygiene and pig management, specific vaccination against the causative agent, Actinobacillus pleuropneumoniae, is an important tool in the fight against this disease. As porcine pleuropneumonia may present with different clinical courses of disease, it is not always easy to objectively assess herd lung health state or to monitor improvements following specific therapeutic or prophylactic measures. Here, the effects of specific vaccination on lung health in a chronically diseased farrow-to-finish farm in Lower Austria experiencing an acute episode were monitored by means of an app-based electronic tool, enabling the scorers to document lung pathologies real-time at slaughter. At the time, when vaccination measures took effect, percentages of lungs affected by dorsocaudal pleurisy had decreased from 43 to 5 and the APP-index from 1.2 to 0.1, respectively. But not only pleurisies were diminished, also incidences and severities of bronchopneumonic alterations had dramatically decreased and exhibited interesting trends when set in connection to clinical signs. Overall, vaccination measures against Actinobacillus pleuropneumoniae proved to be very effective in restoring herd lung health.

Immune status improvement in piglets through the use of interferon-containing products during specific prevention of porcine pleuropneumonia

Specific prevention is one of the most effective methods for the control of infectious diseases causing considerable economic damage to commercial pig farms, among which is porcine pleuropneumonia. In order to improve the effectiveness of preventive vaccination, various immunomodulators that differ in their origin and mechanism of action are used. The paper presents the results of the study of the effect of such products as biferon-S and prostimul containing species-specific recombinant interferons on the immune status of piglets during specific prevention of porcine pleuropneumonia. Tests were carried out in clinically healthy 30–35-day-old piglets immunized with Ingelvac® APPX vaccine (Boehringer Ingelheim Vetmedica GmbH, Germany). It was found that the use of biferon-S and prostimul together with the vaccine administration is accompanied by immune status improvement in the animals, which is manifested as an increase, in comparison with vaccinated animals that received no interferon-containing products (base case), in serum levels of γ-globulins – by 34.6 and 53.7% (in case of prostimul and β-globulins – by 10.1%), total immunoglobulins – by 32.8 and 37.8%, large circulating immune complexes – by 37.5 and 52.6%, a less significant increase in the levels of small complexes and, as a result, pathogenicity coefficient reduction by 5.4 and 12.4%, respectively. Tests for post-vaccination immunity levels in piglets showed a 3.8-fold increase in the levels of specific antibodies against the antigen of porcine pleuropneumonia agent, and in case of the vaccine administration in combination with biferon-S and prostimul – a 4.0-fold and 4.9-fold increase, respectively. The use of prostimul was accompanied by a more considerable improvement of immune status in the piglets, and this is attributable to the fact that vitamins А, Е and С, which have antioxidant properties and improve the effectiveness of interferons, natural resistance and specific immunity, are included in its composition in addition to recombinant type 1 cytokine.

IFN-γ-/- mice resist Actinobacillus pleuropneumoniae infection by promoting early lung IL-18 release and PMN-I accumulation

Porcine pleuropneumonia is a common infectious disease of pigs caused by Actinobacillus pleuropneumoniae (APP). IFN-γ expression increases in the lung of pigs after APP infection, but the role of IFN-γ during the infection is still obscure. In this study, an IFN-γ-/- mouse infection model was established, and bacterial load, the levels of inflammatory cytokines and the types of neutrophils in the lungs were studied at different times post APP infection. We found that wild-type (WT) mice were more susceptible to APP than IFN-γ-/- mice. At 6 h post infection (hpi), the expression of IL-18 and IL-1β in the lungs of IFN-γ-/- mice were significantly increased compared to WT mice. The bacterial load and levels of inflammatory cytokines (IL-1β and IL-6) of IFN-γ-/- mice were significantly reduced at 12 hpi compared to WT mice. After an initial loss, the numbers of lung polymorphonuclear (PMN)-I cells dramatically increased in the lungs of IFN-γ-/- but not WT mice, whereas PMN-II cells continually decreased. Finally, in vivo administration of IL-18 significantly reduced clinical scores and bacterial load in the lungs of APP-infected mice. This study identifies IFN-γ as a target for regulating the inflammatory response in the lung, and provides a basis for understanding the course of clinical bacterial pneumonia and for the formulation of treatment protocols.

A Multivalent Vaccine Containing Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae Antigens Elicits Strong Immune Responses and Promising Protection in Pigs

Actinobacillus pleuropneumoniae (App) and Mycoplasma hyopneumoniae (Mhp) cause porcine pleuropneumonia and mycoplasmal pneumonia, respectively, and have serious impacts on the swine industry because they retard the growth of pigs. To protect pigs against these diseases, we have developed a multivalent vaccine consisting of App bacterins, APP RTX toxins (Apx toxins), and Mhp bacterin and adhesin protein. This vaccine induced the production of higher levels of antibodies against App and Mhp than the commercial vaccine (Nisseiken Swine APM Inactivated Vaccine). Furthermore, the vaccine efficiently protected pigs against virulent App challenge, showing promise as an efficient vaccine for the prevention of two important respiratory diseases, porcine pleuropneumonia and mycoplasmal pneumonia.

Sero- and apx-typing of German Actinobacillus pleuropneumoniae field isolates from 2010 to 2019 reveals a predominance of serovar 2 with regular apx-profile

Serotyping is the most common method to characterize field isolates of Actinobacillus (A.) pleuropneumoniae, the etiological agent of porcine pleuropneumonia. Based on serology, many farms seem to be infected and antibodies against a wide variety of serovars are detectable, but, so far it is unknown to what degree respective serovars contribute to outbreaks of clinical manifest disease. In this study, 213 German A. pleuropneumoniae field isolates retrieved for diagnostic purposes from outbreaks of porcine pleuropneumonia between 2010 and 2019 were genetically serotyped and analyzed regarding their apx-toxin gene profile using molecular methods. Serotyping revealed a prominent role of serovar 2 in clinical cases (64% of all isolates) and an increase in the detection of this serovar since 2010 in German isolates. Serovar 9/11 followed as the second most frequent serovar with about 15% of the isolates. Furthermore, very recently described serovars 16 (n = 2) and 18 (n = 8) were detected. Most isolates (93.4%) showed apx-profiles typical for the respective serovar. However, this does not hold true for isolates of serovar 18, as 75% (n = 6) of all isolates of this serovar deviated uniformly from the “typical” apx-gene profile of the reference strain 7311555. Notably, isolates from systemic lesions such as joints or meninges did not harbor the complete apxICABD operon which is considered typical for highly virulent strains. Furthermore, the extremely low occurrence (n = 1) of NAD independent (biovar II) isolates in German A. pleuropneumoniae was evident in our collection of clinical isolates.

Actinobacillus pleuropneumoniae: a review of an economically important pathogen

Actinobacillus pleuropneumoniae is one of the causative agents of porcine pleuropneumonia, which is an economically important respiratory disease of pig production. Clinical signs vary based on the severity of disease and lung lesions present, but include fever and severe respiratory signs including coughing and laboured breathing. Numerous serotypes exist which vary in their virulence, and virulence of serotypes has also been shown to be vary between countries. It is important to establish which serotypes are present and active on a farm as well as carrying out seroprofiling to determine the correct time for implementation of control measures such as vaccination. Understanding of transmission routes is vital, including the role of carrier animals on the farm which are persistently infected and can shed the bacteria, therefore infecting other animals. Therefore, as with all infectious diseases, good standards of internal and external biosecurity are important in controlling the disease on farm. Vaccination has been shown to be effective on affected farms in preventing outbreaks, reducing clinical signs if they occur, and most important to the farmer, preventing losses in mortality, feed conversion ratio and growth. Therefore, vaccines are often a good choice for controlling pleuropneumonia on farm and reducing the need for treatment using antimicrobials.

Characterization of nontypeable Actinobacillus pleuropneumoniae isolates

Two Actinobacillus pleuropneumoniae isolates from clinical cases of porcine pleuropneumonia in Japan were positive in the capsular serovar 15–specific PCR assay, but nontypeable (NT) in the agar gel precipitation (AGP) test. Nucleotide sequence analysis of gene clusters involved in the biosynthesis of capsular polysaccharide (CPS) and lipopolysaccharide O-polysaccharide (O-PS) revealed that both clusters contained transposable element IS Apl1 of A. pleuropneumoniae belonging to the IS30 family. Immunoblot analysis revealed that these 2 isolates could not produce O-PS. We conclude that the IS Apl1 of A. pleuropneumoniae can interfere in the biosynthesis of both CPS and O-PS.

Comparative Genomics of Actinobacillus pleuropneumoniae Serotype 8 Reveals the Importance of Prophages in the Genetic Variability of the Species

Actinobacillus pleuropneumoniae is the etiologic agent of porcine pleuropneumonia. Currently, there are 18 different serotypes; the serotype 8 is the most widely distributed in the United States, Canada, United Kingdom, and southeastern Brazil. In this study, genomes of seven A. pleuropneumoniae serotype 8 clinical isolates were compared to the other genomes of twelve serotypes. The analyses of serotype 8 genomes resulted in a set of 2352 protein-coding sequences. Of these sequences, 76.6% are present in all serotypes, 18.5% are shared with some serotypes, and 4.9% were differential. This differential portion was characterized as a series of hypothetical and regulatory protein sequences: mobile element sequence. Synteny analysis demonstrated possible events of gene recombination and acquisition by horizontal gene transfer (HGT) in this species. A total of 30 sequences related to prophages were identified in the genomes. These sequences represented 0.3 to 3.5% of the genome of the strains analyzed, and 16 of them contained complete prophages. Similarity analysis between complete prophage sequences evidenced a possible HGT with species belonging to the family Pasteurellaceae. Thus, mobile genetic elements, such as prophages, are important components of the differential portion of the A. pleuropneumoniae genome and demonstrate a central role in the evolution of the species. This study represents the first study done to understand the genome of A. pleuropneumoniae serotype 8.

ANTIBIOTIC RESISTANCE OF ACTINOBACILLUS PLEUROPNEUMONIAE IN SWINE: PROBLEMS AND SOLUTIONS

Porcine pleuropneumonia is an infectious contagious disease caused by bacteria Actinobacillus pleuropneumoniae. Currently, the disease is widespread in many countries with well-developed pig production. The disease causes significant economic damage to farms due to the large mortality and expenses for treatment of diseased pigs and implementation of veterinary and sanitary measures. Due to increased number of Actinobacillus pleuropneumoniae cases in pigs, and the emergence of actinobacillus-resistant forms, it is necessary to perform a more thorough study and discussion of this problem. The disease epidemic surveillance is based on continuous monitoring aimed at porcine Actinobacillus pleuropneumoniae identification, confirmation and registration, determination of its characteristics and trends in development of sensitivity to antimicrobial preparations. The article addresses the topic of antibiotic use and the antibiotic resistance of microorganisms, which is actual not only for veterinary medicine but also for medicine. The model of swine Actinobacillus pleuropneumoniae was used to study the reasons of antibiotic resistance. Possible approaches to overcoming the resistance of actinobacilli to antibiotics have been discussed. The prospects for the use of antibiotics were discussed in detail to cope with this problem. Targeted surveillance, aimed at monitoring and collecting information on the prescription of antibiotics is of great importance for the solution of the problem of antibiotic resistance. The information obtained from the monitoring can be used for development of the plan and strategy for the use of antibacterial preparations (preparation selection, dose, route of administration, frequency, number of courses), development and implementation of more effective approaches to the treatment of Actinobacillus pleuropneumoniae in pigs, control of the antibiotic-resistant bacteria occurrence and spread.