Pleuritis in slaughter pigs: Relations between lung lesions and bacteriology in 10 herds with high pleuritis

Pleuritis in slaughter pigs has increased in recent years in the Netherlands. The aim of the present study was to determine what respiratory pathogens were involved in pleuritis.In total, lungs of 968 slaughter pigs from 10 herds with high prevalence of pleuritis were morphologically examined for size, location, and type of lesions. Moreover, histology and bacteriology were performed.Examination of gross lung lesions showed 45% pleuritis, 14% pleuropneumonia and 38% catarrhal pneumonia. Peribronchiolar cuffing was found in 61 of 142 samples. Actinobacillus pleuropneumoniae was cultured from 22 lung samples from four herds. Pasteurella multocida was cultured from 55 lung samples in eight herds. No specific pattern with respect to the causal pathogens was found.In conclusion, no single infectious cause of pleuritis was found. A variety of infectious agents combined with environmental factors should be considered as a cause of pleuritis.     

Control of Mycoplasma hyopneumoniae infections in pigs

Mycoplasma hyopneumoniae, the primary pathogen of enzootic pneumonia, occurs worldwide and causes major economic losses to the pig industry. The organism adheres to and damages the ciliated epithelium of the respiratory tract. Affected pigs show chronic coughing, are more susceptible to other respiratory infections and have a reduced performance. Control of the disease can be accomplished in a number of ways. First, management practices and housing conditions in the herd should be optimized. These include all-in/all-out production, limiting factors that may destabilize herd immunity, maintaining optimal stocking densities, prevention of other respiratory diseases, and optimal housing and climatic conditions. Strategic medication with antimicrobials active against M. hyopneumoniae and, preferably, also against major secondary bacteria may be useful during periods when the pigs are at risk for respiratory disease. Finally, commercial bacterins are widely used to control M. hyopneumoniae infections. The main effects of vaccination include less clinical symptoms, lung lesions and medication use, and improved performance. However, bacterins provide only partial protection and do not prevent colonization of the organism. Different vaccination strategies (timing of vaccination, vaccination of sows, vaccination combined with antimicrobial medication) can be used, depending on the type of herd, the production system and management practices, the infection pattern and the preferences of the pig producer. Research on new vaccines is actively occurring, including aerosol and feed-based vaccines as well as subunit and DNA vaccines. Eradication of the infection at herd level based on age-segregation and medication is possible, but there is a permanent risk for re-infections.     

A field evaluation of two vaccines against Mycoplasma hyopneumoniae infection in pigs

Background

A field trial was carried out with two Mycoplasma hyopneumoniae vaccines in order to investigate the benefit of vaccination under field conditions in modern Danish pig production facilities with pigs being positive for M. hyopneumoniae. The M. hyopneumoniae infection of the herd was confirmed through blood samples that were positive for antibodies against M. hyopneumoniae combined with gross lesions of the lungs related to M. hyopneumoniae at slaughter and detection of M. hyopneumoniae by polymerace chain reaction in these lesions.

Results

A total of 2,256 pigs from two herds were randomly divided into three groups. Group 1 received 2 mL ThoroVAX^®VET, Group 2 received 1 mL Ingelvac^®MycoFLEX, and Group 3 was a non-vaccinated control group. The vaccination was performed by a person who was not involved in the rest of the trial and vaccination status thereby blinded to the evaluators.The prevalence of lung lesions related to M. hyopneumoniae were significantly lower for pigs vaccinated with ThoroVAX^®VET but not for pigs vaccinated with Ingelvac^®MycoFLEX^®, when compared to non-vaccinated pigs. There was no significant effect of vaccination on growth rate, antibiotic consumption or mortality.

Conclusion

This trial demonstrated that vaccination with Thoro^®VAX VET was effective in reducing the prevalence of lung lesion in pig units infected with M. hyopneumoniae.     

Long-term immunogenicity and protection against Mycoplasma agalactiae induced by an oil adjuvant vaccine in sheep

The long-term protective immunity of an inactivated mineral-oil adjuvanted Mycoplasma agalactiae vaccine was evaluated in sheep. The antigen suspension was emulsified with a mixture of three mineral oils (Montanide ISA-563, Marcol-52, Montane-80 at the ratio of 30%, 63%, and 7%, respectively). Twenty-two animals were divided in 2 groups (A and B) and immunised with two doses of the vaccine (group A, n = 14) or used as unvaccinated control (group B, n = 8). Five months after the second vaccination, seven animals of group A and four animals of group B were challenged by nasal route with M. agalactiae. The remaining seven vaccinated and four control animals were challenged intranasally eight months after vaccination. The vaccine was able to induce a full-protective immunity preventing the clinical signs of contagious agalactia and the infection by M. agalactiae in all groups of animals irrespective of the time of challenge after booster administration.     

Production and characterization of recombinant transmembrane proteins from Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is the etiological agent of swine enzootic pneumonia (EP), a chronic respiratory disease which causes significant economic losses to the swine industry worldwide. More efficient strategies for controlling this disease are necessary. In this study, we cloned17 genes coding for transmembrane proteins from M. hyopneumoniae, among which six were successfully expressed in Escherichia coli and had their immunogenic and antigenic properties evaluated. All proteins were immunogenic in mice and sera from naturally infected pigs reacted with the recombinant proteins, suggesting that they are expressed during infection. These antigens may contribute for the development of new recombinant vaccines and diagnostic tests against EP.     

A recombinant chimera composed of repeat region RR1 of Mycoplasma hyopneumoniae adhesin with Pseudomonas exotoxin: in vivo evaluation of specific IgG response in mice and pigs

Using the binding and translocation domain of Pseudomonas exotoxin A [domain III deleted PE termed PE(ΔIII)] as a vehicle, this study characterized and evaluated a novel application of PE toxin in Mycoplasma hyopneumoniae adhesin used as an immunogen. PCR and sequence analysis revealed that 16 copies of AAKPV(E) in tandem repeat region 1 (RR1) of M. hyopneumoniae 97 kDa adhesion were successfully fused to the downstream of PE(ΔIII) to create a subunit vaccine, i.e. PE(ΔIII)-RR1. This chimeric protein, over-expressed in inclusion bodies of E. coli BL21(DE3)pLysS, was characterized by a monoclonal antibody (MAb) F2G5 prepared against RR1 of the 97 kDa adhesin and was readily purified. The data indicated that the epitope recognized by MAb F2G5 was located in the structure of PE(ΔIII)-RR1. Using ELISA and Western blot analyses, the specific IgG immune response against RR1 and whole adhesin in mice immunized with PE(ΔIII)-RR1 was found more marked than that in mice immunized with the M. hyopneumoniae whole cells. Similarly, PE(ΔIII)-RR1 also stimulated a remarkable IgG response against RR1 in pigs compared to that in pigs immunized with the conventional M. hyopneumoniae vaccine. The PE(ΔIII)-RR1 would be potentially useful for the future development of a M. hyopneumoniae adhesin vaccine.     

Seroprevalence and risk factors associated with seropositivity in sows from 67 herds in north-west Germany infected with Mycoplasma hyopneumoniae

Risk factors for the spread of Mycoplasma hyopneumoniae in sows have not been studied although vertical transmission from sows to their offspring is considered a significant risk factor in the development of enzootic pneumonia in growers and finishers. Seropositivity for M. hyopneumoniae in sows, as assessed by commercial ELISA, is a possible indicator of infection pressure among sows. The objective of this study was to estimate seroprevalence and associated risk factors of a sow being seropositive for M. hyopneumoniae. A cross-sectional study was carried out in 2578 sows from 67 herds in north-west Germany. Data concerning general herd characteristics, acclimatisation practices, indoor and outside contacts, as well as data describing the immediate local environment were collected during a herd visit via questionnaire. Blood samples were seropositive in 65% of the 2578 sows, and all herds had ≥14% seropositive sows. Data analysis was performed in two steps. First, univariate analysis of predictor variables for the risk of a sow being seropositive for M. hyopneumoniae was performed using chi-square test. Secondly, all variables associated with the risk of a sow being seropositive (P ≤ 0.25) were included in a multivariate model using a generalised linear model. The risk of a sow being seropositive for M. hyopneumoniae was increased in herds with two- or three-site production (OR 1.50), when piglets were not vaccinated against M. hyopneumoniae (OR 1.81), in herds with a 2-week farrowing intervals (OR 1.84) and in herds without all-in/all-out management of the farrowing units (OR 1.37). The lack of an acclimatisation period for replacement boars was also associated with the risk of a sow being seropositive (OR 2.10). The results indicate that M. hyopneumoniae seropositivity is common in sows in north-west Germany and is influenced by various management factors. It is recommended that evaluation of sow herd management should be included in any strategic health plan to control M. hyopneumoniae infection.     

Seroprevalence and risk factors of Mycoplasma suis infection in pig farms in central China

Mycoplasma suis, the causative agent of porcine infectious anemia, causes large economic losses to the swine industry worldwide. A questionnaire-based survey was conducted in 69 pig farms in Hubei Province, China, from November 2011 to August 2013 to ascertain the prevalence and associated risk factors of M. suis. Four thousand and four blood samples from pigs of all the age groups were tested for M. suis antibodies using the established rMSG1–ELISA assay. Among these 4004 samples, 1615 blood samples from multiparous sows were examined to identify the association between seroprevalence and different seasons. Information on risk factors collected from farmers or attending veterinarians was recorded on a pre-designed questionnaire. The overall test seroprevalence of M. suis infection at the animal level was 31.9% (1277/4004; 95% CI: 30.5%, 33.4%), whereas at the farm level, this value was 95.65% (66/69; 95% CI: 87.8%, 99.1%). The seroprevalence of M. suis was higher in replacement gilts (40.6%; 95% CI: 35.1%, 46.3%), multiparous sows (48.2%; 95% CI: 45.8%, 50.7%) and boars (44.4%; 95% CI: 34.5%, 54.8%), as compared to piglets (13.0%; 95% CI: 9.4%, 17.3%), weaned-piglets (10.8%; 95% CI: 8.9%, 13.0%), and growing-finishing pigs (25.0%; 95% CI: 22.0%, 28.3%). In terms of seasons, the prevalence of M. suis in pigs was significantly higher in summer (65.3%; 95% CI: 61.0%, 69.5%) and autumn (65.0%; 95% CI: 59.0%, 70.6%) compared to spring (30.1%; 95% CI: 26.0%, 34.4%) and winter (36.4%; 95% CI: 31.4%, 41.5%). Farm-level risk factors were identified by multivariable logistic regression analysis. The associated factors retained in the final multivariable logistic regression model were drug treatment, presence of mosquitoes and flies, and frequency of disinfection. Drug treatment (OR = 0.24; 95% CI: 0.07, 0.88; P = 0.031) and frequency of disinfection (OR = 0.23; 95% CI: 0.06, 0.90; P = 0.035) were protective factors, and the presence of mosquitoes and flies (OR = 5.994; 95% CI: 1.56, 23.00; P = 0.009) was a risk factor for M. suis infection on farms. The results of the present study provide the first insight into the impact of associated determinants on M. suis infection in central China.     

Expression of Mycoplasma bovis variable surface membrane proteins in the respiratory tract of calves after experimental infection with a clonal variant of Mycoplasma bovis type strain PG45

The pathomorphological findings and the expression and distribution of variable surface protein antigens (Vsp) of Mycoplasma (M.) bovis were characterised immunohistochemically in lungs of eight calves following inoculation with a Vsp A-expressing clonal variant of M. bovis type strain PG45. Within 48 h post inoculation (p.i.) an innate immune response dominated by macrophages and neutrophils develops. The monoclonal antibodies (mAbs) 1A1 and 1E5 detected M. bovis Vsp antigens in paraffin tissue sections of seven calves. Vsp antigens were widely distributed and were already present at day two p.i. within macrophages and other lung compartments. Taken together, the results demonstrate that the bovine is unable to eliminate M. bovis during the time period examined. Based on the different immunohistochemical labelling patterns obtained with the mAbs, the results also support the speculation that the in vivo variability of Vsps together with immunological factors may contribute to the chronicity of pulmonary disease.     

Mycoplasma synoviae cell invasion: Elucidation of the Mycoplasma pathogenesis in chicken

Fluorochrome-labelled cells of two field isolates and Mycoplasma synoviae (Ms) were inoculated onto monolayer cultures of fluorochrome-labelled HEp-2 cells and monitored by confocal laser scanning microscopy (CLSM). Ms was detected initially adhered to and subsequently inside the host cells. Between 24 and 48 h of infection, Ms was detected in the perinuclear region, and after 72 h of infection was confirmed by gentamicin invasion assay. High and low passage Ms strains showed no differences in adherence or invasion. The morphology and the actin filaments of the infected HEp-2 cells were preserved throughout the study period. The observed invasion by Ms is consistent with the biology of Mollicutes, and could explain the difficulties in recovering field isolates of the mycoplasma and in controlling the infection in birds even after long-term antibiotic treatment.     

Characterization of the in vitro core surface proteome of Mycoplasma mycoides subsp. mycoides, the causative agent of contagious bovine pleuropneumonia

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides (Mmm) is a severe cattle disease, present in many countries in sub-Saharan Africa. The development of improved diagnostic tests and vaccines for CBPP control remains a research priority. Polyacrylamide gel electrophoresis and mass spectrometry were used to characterize the Triton X-114 soluble proteome of nine Mmm strains isolated from Europe or Africa. Of a total of 250 proteins detected, 67 were present in all strains investigated. Of these, 44 were predicted to be lipoproteins or cytoplasmic membrane-associated proteins and are thus likely to be members of the core in vitro surface membrane-associated proteome of Mmm. Moreover, the presence of all identified proteins in other ruminant Mycoplasma pathogens were investigated. Two proteins of the core proteome were identified only in other cattle pathogens of the genus Mycoplasma pointing towards a role in host–pathogen interactions. The data generated will facilitate the identification and prioritization of candidate Mycoplasma antigens for improved control measures, as it is likely that surface-exposed membrane proteins will include those that are involved in host–pathogen interactions.     

Evaluation on the pathogenicity of Erysipelothrix tonsillarum for pigs by immunosuppression with cyclophosphamide or dexamethasone

The pathogenicity of Erysipelothrix tonsillarum was evaluated in pigs immunosuppressed with cyclophosphamide (CY) or dexamethasone (DM). Animals were treated with 15 mg/kg CY (n = 8, five injections), 1 mg/kg DM (n = 8, nine injections) or left untreated (n = 8). On the fifth day after the beginning of drug treatments, swine were inoculated with one of two E. tonsillarum serovar 7 strains (approximately 10⁶ CFU per pig). In the CY-treated group, both circulating neutrophil and lymphocyte counts decreased, whereas in the DM-treated group, lymphocyte counts decreased but neutrophil counts increased. During the observation period, none of the CY- or DM-treated pigs developed clinical signs or gross lesions, as well as non-treated pigs. Growth agglutination antibody titres in all pigs remained unchanged. Our findings indicate that E. tonsillarum strains are avirulent for swine, regardless of immune status.     

Occurrence of Mycobacterium spp. and other pathogens in lymph nodes of slaughtered swine and wild boars (Sus scrofa)

Mycobacterium spp. and other pathogens were investigated in 258 swine lymph nodes (129 with and 129 without apparent lesions), and 120 lymph nodes (60 with and 60 without lesions) from wild boars (Sus scrofa). A total of lymph nodes from swine and wild boars were collected of different animals. Submaxillar and mesenteric lymph nodes were submitted to microbiological examination and colonies suggestive of Mycobacterium spp. (alcohol-acid bacilli) were submitted to PCR Restriction Assay (PRA). In swine with lymphadenitis, Mycobacterium spp. (24.1%) and Rhodococcus equi (13.2%) were the most prevalent microorganisms, while in lymph nodes without lesions were identified a complex of microorganisms, including of environmental mycobacteria. In wild boars with lymphadenitis, ß-haemolytic Streptococcus (10.0%), Mycobacterium spp (8.4%) and R. equi (6.6%) were the most frequent. Among mycobacterias were identified predominantly Mycobacterium avium subspecies type 1 (48.3%) and M. avium subspecies type 2 (16.1%), followed by Mycobacterium intracellulare, Mycobacterium szulgai,Mycobacterium fortuitum, Mycobacterium gordonae, Mycobacterium simiae, Mycobacterium nonchromogenicum and Mycobacterium intracellulare type 2.     

Prevalence and antibiotic resistance profiles of Enterococcus species in chicken at slaughter level; absence of vanA and vanB genes in E. faecalis and E. faecium

The prevalence of enterococci in neck skin samples of poultry from Ankara region in Turkey was investigated and their antibiotic resistance patterns were determined. In the study, 83 of 106 analyzed neck skin samples were positive for Enterococcus, with E. faecium as the most prevalent species (48%) followed by E. durans (23%) and E. faecalis (19%). Lower numbers were detected for E. gallinarum, E. hirae, E. mundtii and E. casseliflavus. Using the disc diffusion method, it was established that over 90% of E. faecium and E. faecalis isolates were high-level resistant against erythromycin and tetracycline. Four E. faecium isolates were additionally resistant to chloramphenicol, gentamicin and streptomycin, though they were susceptible to penicillin G. The most frequently observed multiple resistance in E. faecium (25%) was against erythromycin, tetracycline, chloramphenicol and streptomycin. Of the E. faecalis isolates, 44% were multiple resistant to erythromycin, tetracycline and streptomycin. Vancomycin resistance could not be demonstrated phenotypically and vanA or vanB genes were not detected by multiplex PCR in any of the isolates. Nevertheless, the observed resistance patterns are of concern for public health.     

Occurrence of Mycobacterium avium subspecies paratuberculosis and Neospora caninum in Alberta cow-calf operations

Mycobacterium avium subsp. paratuberculosis (MAP) and Neospora caninum (NC) are two pathogens causing important production limiting diseases in the cattle industry. Significant impacts of MAP and NC have been reported on dairy cattle herds, but little is known about the importance, risk factors and transmission patterns in western Canadian cow-calf herds. In this cross-sectional study, the prevalence of MAP and NC infection in southwest Alberta cow-calf herds was estimated, risk factors for NC were identified, and the reproductive impacts of the two pathogens were assessed.     

Reduced lung lesions in pigs challenged 25 weeks after the administration of a single dose of Mycoplasma hyopneumoniae vaccine at approximately 1 week of age

Two independent studies assessed the duration of immunity of an inactivated adjuvanted Mycoplasma hyopneumoniae vaccine against mycoplasmal pneumonia in seronegative (study A, n = 52) and seropositive (study B, n = 52) pigs. The pigs were allocated randomly to treatment and were then injected with a single dose of either the vaccine or a placebo at approximately 1 week of age. Twenty-five weeks after treatment administration, the pigs were challenged with a virulent strain (LI 36, Strain 232) of M. hyopneumoniae and the extent of lung lesions consistent with mycoplasmal pneumonia was assessed 4 weeks later.In study A, the geometric mean lung lesion score (expressed as least squares mean percentages of lung lesions) was significantly (P = 0.0001) lower in vaccinated (0.3%, n = 20) than in control pigs (5.9%, n = 24) seronegative to M. hyopneumoniae at enrolment; similarly, in study B, the extent of lung lesions was significantly reduced (P = 0.0385) in seropositive vaccinated pigs (2.0%, n = 22) compared to controls (4.5%, n = 26). At the end of the investigation period, 4 weeks after challenge, mean antibody sample-to-positive (S/P) ratios were significantly higher both in seronegative (P = 0.0012) and seropositive (P = 0.0001) vaccinated pigs (mean values = 0.77 and 0.81, respectively) than in controls (mean values = 0.51 and 0.38, respectively).     

Screening of microfilaricidal effects of plant extracts against Dirofilaria immitis

Canine dirofilariasis is a common tropical parasitic disease of companion animals, caused by infestation of Dirofilaria immitis filarids within the pulmonary arteries and extending into the right heart. Increased reports of adverse reactions elicited by current microfilaricidal agents against D. immitis such as neurological disorders, circulatory collapse and potential resistance against these agents, warrant the search for new agents in forms of plant extracts. The use of plant extracts in therapeutic medicine is commonly met with scepticism by the veterinary community, thus the lack of focus on its medical potential. This study evaluated the presence of microfilaricidal activities of the aqueous extracts of Zingiber officinale, Andrographis paniculata and Tinospora crispa Miers on D. immitisin vitro at different concentrations; 10 mg/ml, 1 mg/ml, 100 μg/ml, 10 μg/ml and 1 μg/ml within 24 h, by evaluation of relative microfilarial motility as a measure of microfilaricidal activity. All extracts showed microfilaricidal activity with Z. officinale exhibiting the strongest activity overall, followed by A. paniculata and T. crispa Miers. It is speculated that the microfilaricidal mechanism exhibited by these extracts is via spastic paralysis based upon direct observation of the microfilarial motility.     

Occurrence of Giardia and Cryptosporidium in pigs on Prince Edward Island, Canada

In a cross-sectional study of 633 pigs from 21 herds on Prince Edward Island, Canada (PEI), the prevalence of infection with Cryptosporidium and Giardia, and the genotypes and species of isolates were determined in order to establish the zoonotic potential of pigs in this region. As determined by direct immunofluorescence microscopy (DFA), 18 herds (86%) and 163 animals (26%; 95% CI: 22-29%) tested positive for Cryptosporidium, while just 3 herds (14%) and 6 animals (1%; 95% CI: 0.4-2%) tested positive for Giardia. Cryptosporidium spp. isolates were detected in 39% (95% CI: 34-44%) of weanlings (1-3 months of age) and 9% (95% CI: 6-13) of sows (>8 months of age). Molecular characterization using the 18S rDNA and HSP70 gene fragments revealed the presence of Cryptosporidium sp. pig genotype II, C. suis, C. parvum, and Cryptosporidium sp. mouse genotype. Among the 113 isolates of Cryptosporidium spp. successfully genotyped, pig genotype II (61%) predominated, with C. suis (36%) being the next most prominant isolate. C. parvum (2%; two isolates) and Cryptosporidium sp. mouse genotype (0.9%; one isolate) were only occasionally isolated. The only two Cryptosporidium-positive genotyped isolates from sows included one each of C. suis and Cryptosporidium sp. pig genotype II.All but one of the six Giardia positive isolates were detected in weanling pigs. None of the Giardia-positive isolates was amenable to PCR. This study demonstrates that Cryptosporidium spp. are highly prevalent in pigs on PEI, Canada, are found mostly in weanlings (1-3 months of age). Furthermore, the pigs are primarily infected by the host-specific genotypes and species, Cryptosporidium sp. pig genotype II and C. suis, whereas the zoonotic C. parvum is rare. Giardia duodenalis is only occasionally found in pigs. These findings suggest that domestic pigs on PEI, Canada, likely do not pose a significant health risk to humans from these parasites.