Lameness in fattening pigs - Mycoplasma hyosynoviae, osteochondropathy and reduced dietary phosphorus level as three influencing factors: a case report.

BACKGROUND: Multiple diagnostic procedures, their results and interpretation in a case with severe lameness in fattening pigs are described. It is shown that selected diagnostic steps lead to identification of various risk factors for disease development in the affected herd. One focus of this case report is the prioritization of diagnostic steps to verify the impact of the different conditions, which finally led to the clinical disorder. Assessing a sufficient dietary phosphorus (P) supply and its impact on disease development proved most difficult. The diagnostic approach based on estimated calculation of phosphorus intake is presented in detail. CASE PRESENTATION: On a farrow-to-finishing farm, lameness occurred in pigs with 30-70 kg body weight. Necropsy of three diseased pigs revealed claw lesions and alterations at the knee and elbow joints. Histologic findings were characteristic of osteochondrosis. All pigs were positively tested for Mycoplasma hyosynoviae in affected joints. P values in blood did not indicate a P deficiency, while bone ashing in one of three animals resulted in a level indicating an insufficient mineral supply. Analysis of diet composition revealed a low phosphorus content in two diets, which might have led to a marginal P supply in individuals with high average daily gains with respect to development of bone mass and connective tissue prior to presentation of affected animals. Finally, the impact of dietary factors for disease development could not be evidenced in all submitted animals in this case. CONCLUSIONS: Mycoplasma (M.) hyosynoviae was identified to be an important etiologic factor for disease. Other, non-infectious factors, such as osteochondrosis and claw lesions might have favored development of lameness. In addition, a relevant marginal P supply for pigs was found in a limited time period in a phase of intense growing, but the potential interaction with infection by M. hyosynoviae is unknown. The presented case of severe lameness in fattening pigs revealed that three different influences presumably act in pathogenesis. Focusing only on one factor and ignoring others might be misleading regarding subsequent decision-making for prevention and therapy. Finally, clinical symptoms disappeared after some changes in diet composition and anti-inflammatory treatment of individual animals.

[Comparison between oral fluid samples and pooled serum samples for the detection of antibodies against Porcine Reproductive and Respiratory Syndrome Virus in weaning pig herds]. / Vergleich von Speichelproben und ­gepoolten Serumproben für den ­Nachweis von Antikörpern gegen das Porzine Reproduktive und Respiratorische ­Syndrom Virus in ­Aufzuchtbeständen.

INTRODUCTION: Monitoring of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) in pig farms is performed usually by testing for antibodies against PRRSV in serum samples. A new method is the detection of PRRSV antibodies in porcine saliva. In this study serum samples and saliva were collected in nine farms suspicious for PRRSV and tested for the presence of PRRSV antibodies. In total 220 serum and 41 saliva samples were taken from pigs at the age of 8 weeks (± 1 week). One saliva and one pooled serum sample (1:5) were tested from each pen. In total 11 (Cut-off 0.4/0.3) or 14 (Cut-off 0.2) serum samples and 23 saliva out of 41 pens were positive for PRRSV antibodies. Cohen`s Kappa testing showed a moderate agreement (κ = 0.446). Saliva samples compared to pooled serum samples were very sensitive, the specificity was 60 and 67, respectively.

INTRODUCTION: La surveillance du virus du syndrome reproducteur et respiratoire porcin (PRRSV) dans les élevages de porcs est généralement effectuée en recherchant des anticorps contre le PRRSV dans des échantillons de sérum. Une nouvelle méthode est la détection des anticorps anti-­PRRSV dans la salive porcine. Dans cette étude, des échantillons de sérum et de salive ont été prélevés dans neuf exploitations suspectes de PRRSV et testés quant à la présence d'anticorps PRRSV. Au total, 220 échantillons de sérum et 41 échantillons de salive ont été prélevés sur des porcs à l'âge de 8 semaines (± 1 semaine). De chaque boxe, un échantillon de salive et un échantillon de sérums regroupé (1: 5) ont été testés. Au total, 11 échantillons de sérum (seuil 0,4/0,3) ou 14 (seuil 0,2) et 23 de salive sur 41 boxes étaient positifs quant aux anticorps anti-PRRSV. Le test Kappa de Cohen a montré une corrélation modérée (κ = 0,446). Les échantillons de salive étaient très sensibles par rapport aux échantillons de sérum regroupés, la spécificité n'était toutefois que de 60 respectivement 67.

Phenotypic antimicrobial resistance in Escherichia coli strains isolated from swine husbandries in North Western Germany - temporal patterns in samples from laboratory practice from 2006 to 2017.

BACKGROUND: Since 2011, antibiotic usage has decreased continuously in livestock in Germany. Whether this is accompanied by a reduction in bacterial antimicrobial resistance has not been proven so far. In this study 3054 Escherichia coli (E. coli) isolates from pigs which had suffered from disease on 2161 farms in North Western Germany were evaluated retrospectively from 2006 to 2017 for trends in their antimicrobial resistance pattern. Data were substantially related to the "pre-reduction period" and were therefore suggested as a basis for this task. Minimal inhibitory concentrations for selected antimicrobial substances were evaluated for E. coli strains isolated from different organs of diseased swine sampled for routine diagnostic. In total, 81% of E. coli were isolated from faeces or the gastrointestinal tract, 11% from the genito-urinary tract and 8% from other organs. Susceptibility testing and classification of isolates in accordance with clinical cut-offs followed the Clinical and Laboratory Standards Institute (CLSI). If no clinical cut-offs were available for the respective combination of species, substance and organ, other published clinical cut-offs were used. RESULTS: Differences in susceptibility patterns between isolates from the gastrointestinal and genito-urinary tract were found for most substances. Isolates from the genito-urinary tract were less frequently resistant to ampicillin, apramycin, colistin, neomycin, spectinomycin and tetracycline and more frequently resistant to enrofloxacin and florfenicol. A multifactorial logistic regression model revealed time-dependent decreases in frequency of resistant isolates for neomycin, spectinomycin and tetracycline. For colistin, the highest percentage of resistant isolates with 16.0% was found in 2015 followed by a decrease to the level of 2009-2010 in 2017. A decrease in frequencies of ampicillin-resistant isolates was dependent on the age-group and time period. Irrespective of the year, less than 15% E. coli isolates were resistant to apramycin, cephalosporins, colistin, enrofloxacin, florfenicol, gentamicin and neomycin. CONCLUSION: An overall time-dependent decrease in the percentage of resistant E. coli isolates was found for some substances. These data from diseased animals indicate an impact of a general reduction in antibiotic usage on development of bacterial antimicrobial resistance in the field and can support the decision-making of swine practitioners for treatment options in swine.

[Diagnostic procedure after abortions in sows after simultaneous infection with leptospira and chlamydia]. / Diagnostische Abklärung von Aborten bei Zuchtsauen nach Leptospiren- und Chlamydieninfektion.

INTRODUCTION: In a farrowing farm 2 first parity sows aborted on day 95 and day 110 of gestation due to an infection with leptospira and chlamydia. The double infection was diagnosed by PCR examination of abortion material. Serum samples of both sows and additional 8 sows taken three weeks after abortions were sent to two different labs for serological examination for antibodies against leptospira and chlamydia using a microagglutination test and a complement fixation test, respectively. In both labs the tests for antibodies against chlamydia were negative. Titers against diverse leptospira serovars varied between both labs and were low, so that they were not indicative for the involvement of the two pathogens regarding abortion. This case report indicates the diagnostic difficulties of direct and indirect detection methods for leptospira and chlamydia to assess the impact of these pathogens on observed reproductive failure.

Update on Actinobacillus pleuropneumoniae-knowledge, gaps and challenges.

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.

Detection of PR-39, a porcine host defence peptide, in different cell sub-linages in pigs infected with Actinobacillus pleuropneumoniae.

Innate immunity is critically important for the outcome of infection in many diseases. It was previously shown that cathelicidin PR-39, an important porcine multifunctional host defence peptide, is elevated in bronchoalveolar lavage fluid and respiratory tract tissue after experimental infection with Actinobacillus pleuropneumoniae (A.pp.). To date, neutrophil polymorphonuclear leukocytes (PMNs) are thought to be the only source of PR-39. The aim of this study was to further characterize PR-39⁺ cells and selected immune cell populations in lung tissue during the peracute (7-10 hours), acute (2 days), reconvalescent (7 days) and chronic (21 days) stages of experimental infection with A.pp. serotype 2. In total, six mock-infected control pigs and 12 infected pigs were examined. Using immunofluorescence double-labeling, antibodies against PR-39 were combined with antibodies against CD3 (T-cells), CD79 (B-cells), Iba1 (activated macrophages), TTF-1 (lung epithelial cells expressing surfactant proteins), macrophage/L1 protein and myeloperoxidase (MPO, cells of the myeloid linage). In the peracute and acute phases of infection, total PR-39⁺ cells and myeloid linage cells increased, whereas CD3⁺ cells and TTF-1⁺ cells decreased. Double labeling revealed that most Macrophage/L1 protein+ cells and to a lesser extent MPO⁺ cells co-expressed PR-39. In addition, few bronchial epithelial cells and type 2 alveolar epithelial cells (both identified with TTF-1) produced PR-39. Occasionally, CD3⁺ T cells expressing PR-39 were seen in infected animals. Taken together, this study identifies cell types, other than PMNs, in lungs of A.pp.-infected pigs that are capable of producing PR-39. In addition, these findings provide further insights into the dynamics of different immune cell populations during A.pp.-infection.

Administration of non-pathogenic isolates of Escherichia coli and Clostridium perfringens type A to piglets in a herd affected with a high incidence of neonatal diarrhoea.

A bacterial cocktail of living strains of Clostridium perfringens type A (CPA) without ß2-toxin gene and non-pathogenic Escherichia coli was administered orally to newborn piglets before first colostrum intake and on 2 consecutive days on a farm with a high incidence of diarrhoea and antibiotic treatment in suckling piglets associated with E. coli and CPA. This clinical field study was driven by the hypothetic principle of competitive exclusion of pathogenic bacteria due to prior colonization of the gut mucosal surface by non-pathogenic strains of the same bacterial species with the aim of preventing disease. Although CPA strains used in this study did not produce toxins in vitro, their lack of pathogenicity cannot be conclusively confirmed. The health status of the herd was impaired by a high incidence of postpartum dysgalactia syndrome in sows (70%) and a high incidence of neonatal diarrhoea caused by enterotoxigenic E. coli and CPA during the study. No obvious adverse effect of the bacterial treatment occurred. On average, more piglets were weaned in litters treated (P=0.009). Visual pathological alterations in the small intestinal wall were more frequent in dead piglets of the control group (P=0.004) and necrotizing enteritis was only found in that group. A higher average daily weight gain of piglets in the control group (P<0.001) may be due to an increased milk uptake due to less competition in the smaller litters. The bacterial cocktail was tested under field conditions for its potential to stabilize gut health status in suckling piglets before disease development due to colibacillosis and clostridial infections; however, the gut flora stabilizing effect of the bacterial cocktail was not clearly discernible in this study. Further basic research is needed to confirm the positive effects of the bacterial treatment used and to identify additional potential bacterial candidates for competitive exclusion.

Infrared thermography of the pig thorax: an assessment of selected regions of interest by computed tomographical and anatomical parameters.

Current methods of diagnosis of respiratory diseases in swine are invasive, time-consuming and expensive. Infrared thermography (IRT) of the thorax might provide a new method of high specificity to select swine affected with lung alterations for further diagnostics. In this study, layer thickness of different tissues was determined in frozen thorax slices (FTS) by computed tomography (CT) and then related to skin temperatures measured by IRT in healthy pigs. The aim was to determine appropriate regions of interest (ROI) for evaluation of IRT images. Organ layer thicknesses measured in CT images correspond to those measured in FTS. Temperature differences between lung ROIs and abdomen ROIs were positively correlated with lung layer thickness at certain localizations, and negatively correlated with the thickness of the thorax wall and of inner organ layers. Reference values of differences between skin temperatures were established for two ROIs on the thorax with potential practical use for lung health status determination. Respective ROIs were located on vertical lines crossing the 7th (right) and the 10th (left) thoracic vertebrae. The presence of ribs affected skin temperature significantly.

[Septicaemia in piglets associated with a positive finding of a methicillin-resistant S. aureus strain]. / Septikämisches Krankheitsbild bei Saugferkeln mit MRSA-Nachweis.

Staphylococcus (S.) aureus has been associated with septicaemia, mastitis, vaginitis, metritis, osteomyelitis, and endocarditis. This case report demonstrates S. aureus-induced septicaemia in suckling pig- lets. Three days after birth, littermates displayed severe ecchymosis and cyanosis, with a 50% mortality rate. The surviving littermates were cross-fostered, but died 1 day later. Other piglets, which were allowed to suck at the sow, developed similar clinical signs. Haematological findings were anaemia, thrombocytopenia, and leukopenia; therefore, neither isohaemolytic anaemia nor septicaemia could be excluded as differential diagnoses. At necropsy, petechial bleeding on inner organ surfaces and free blood in body cavities were found. Bacteriological examination of the sow's milk and of the spleen of one piglet detected a methicillin-resistent S. aureus strain (MRSA CC398), which was in all likelihood the cause of the disease. Potential differential diagnoses are discussed.

[Field trial on the simultaneous vaccination against porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae]. / Feldstudie zur simultanen Vakzination gegen das porzine Circovirus Typ 2 und Mycoplasma hyopneumoniae.

OBJECTIVE: The objective of the present study was to investigate whether a combined or concurrent application of two vaccines against Mycoplasma hyopneumoniae (M. hyo.) and porcine circovirus type 2 (PCV2) in suckling piglets can be as effective as the single use of both products. MATERIAL AND METHODS: A total of 598 piglets were allocated to five groups. In the 1st and 3rd weeks of life the placebo Porcilis® Diluvac forte and the two vaccines Porcilis® M HYO ("M HYO") and Porcilis® PCV ("PCV") were administered according to the following scheme: group A: placebo/PCV; group B: M HYO/M HYO; group C: placebo/placebo; group D: M HYO/M HYO + PCV (combined single dose); group E: placebo/M HYO + PCV (different injection sites). Lung lesions due to M. hyo. infection were recorded at slaughter, and average daily weight gain, morbidity, mortality, serum PCV2 load and specific humoral immune responses were compared between the groups. Local and systemic side effects were recorded. RESULTS: Sporadic impairment of the herd health status due to piglet diarrhoea (n = 111) from the 1st to 3rd weeks of life were not associated with M. hyo. or PCV2. A tendency towards a higher average daily weight gain was found in vaccinated pigs compared to the control group. Slight differences between groups in terms of lung lesions, morbidity and mortality were not significant. M. hyo. and PCV2 antibody-titers were significantly higher in vaccinated than in non-vaccinated pigs. One pig from both group A (PCV2) and group C (placebo) displayed local reactions at the vaccination site. CONCLUSION AND CLINICAL RELEVANCE: A positive effect on animal health can be achieved by vaccination against M. hyo. and PCV2 in herds with suboptimal health status. A simultaneous vaccination either by a combined or concurrent application has no negative effect on health status. Simultaneous vaccination yielded the same positive effect on average daily weight gain as single vaccinations. Therefore, a simultaneous vaccination against M. hyo. and PCV2, which reduces workload and is beneficial for animal welfare, can be recommended.

[Evaluation of the efficacy of a combination therapy of an antibiotic and a NSAID following an experimental Haemophilus parasuis infection in nursery piglets]. / Wirksamkeitsbeurteilung einer Kombinationstherapie aus Antibiose und NSAID nach experimenteller Haemophilus-parasuis-Infektion bei Absetzferkeln.

OBJECTIVE: The aim of the present study was to evaluate the combination therapy of an antibiotic (enrofloxacine-arginine, Baytril® RSi) and a non-steroidal anti-inflammatory drug (NSAID, ketoprofen, Dinalgen® 60 mg/ml) against a Haemophilus parasuis (HPS) infection in nursery piglets. MATERIAL AND METHODS: Forty-eight 3-week-old pigs were divided into four groups (group 1: non-infected controls; group 2: HPS infection; group 3: HPS infection/Baytril® RSi; group 4: HPS infection/Baytril® RSi/Dinalgen®) and housed within the isolation facility. After an acclimatization period of 10 days, the piglets in groups 2-4 were intratracheally infected with 1 x 107 colony forming units (CFU) HPS serovar 5, whereas animals of group 1 received physiological saline. Total clinical scores and joint scores were calculated daily after clinical examination. Seven days after the infection, piglets were humanely euthanized. At necropsy, pathological findings on serosal surfaces were scored according to severity and extension. RESULTS: Group 1 had the lowest clinical and pathological scores, followed by groups 4, 3 and 2. Piglets treated with the combination of an antibiotic and an NSAID showed the lowest body temperatures (significant). The average daily weight gain (ADWG) was not significantly different between the groups, but piglets of group 4 tended to reach a higher mean ADWG (340.5 g/d) than animals of the non-infected group 1 (323.8 g/d), the Baytril® RSi-treated group 3 (278.0 g/d) and the positive control group 2 (247.0 g/d). Piglets of the positive control group (group 2) achieved the highest values in the clinical, joint and serositis scores. CONCLUSION: The study demonstrated that a simultaneous treatment with enrofloxacine-arginine (Baytril® RSi) and ketoprofen had a superior therapeutic effect compared to a single antibiotic treatment with Baytril® RSi in nursery piglets experimentally infected with HPS.

[Computed tomography of the pig lung. An innovative approach to the definition of the pulmonary health status]. / Computertomographie der Lunge des Schweines. Ein innovativer Ansatz zur Definition des Lungengesundheitsstatus.

OBJECTIVE: In veterinary medicine computed tomography (CT) imaging has gained importance in recent years, especially for diagnostics in pets, but also during the course of experimental studies in animal models for human medicine. In this study the applicability of CT as an imaging method for the depiction of the porcine thorax and in particular of the pig lung was evaluated. MATERIAL AND METHODS: CT examinations were performed with 11 healthy pigs of two age groups. For evaluation, CT findings were related to clinical, radiological, macroscopical, microscopical, and microbiological findings. RESULTS: Clinically relevant anatomical structures were determined and recorded using transverse slices. In ventral recumbency, lung parenchyma density measurements at the levels of the second, fourth and seventh thoracic vertebrae resulted in significantly higher densities of the ventral in comparison to those of the dorsal lung quadrants. CONCLUSION AND CLINICAL RELEVANCE: Computed tomography is a valuable tool for the high-contrast depiction of the porcine lung without superposition. In future studies this CT reference base for unaltered pig lungs may facilitate the identification of anatomical structures within the porcine lung as well as the assessment of pathological lung alterations.

[Principle differences of the vocal folds in humans and swine: a few essential morphologic criteria]. / Prinzipielle Unterschiede am Stimmapparat von Mensch und Schwein: Einige wesentliche morphologische Kriterien.

The histological composition of the Lamina propria in pigs - especially in the cranial fold of the glottis - gives reason to expect other phoniatric properties than in man. Age-related changes must be considered.

[Comparison of the diagnostic significance of clinical, radiographic and ultrasonographic results after an experimental aerosol infection of pigs with Actinobacillus pleuropneumoniae]. / Vergleich der diagnostischen Aussagekraft klinischer, röntgenologischer und sonographischer Befunde bei der experimentellen Infektion des Schweines mit Actinobacillus pleuropneumoniae.

Scoring schemes for clinical, ultrasonographic and radiographic findings in pigs were developed based upon a standardized animal model for Actinobacillus pleuropneumoniae infection.The results of these methods were compared to each other as well as with the corresponding pathomorphological findings during necropsy. Altogether 69 pigs of different breeding lines (Hampshire, Pietrain and German Landrace were examined. Positive correlations were found between the results of all three methods as well as with the necropsy scores (p <0.0001). Different pathomorphological findings were detected either by radiographic or by ultrasonographic examination dependent upon the type of lung tissue alterations: Alterations of the pleura as well as sequestration of lung tissue on the lung surface could be clearly identified during the ultrasonographic examination while deep tissue alterations with no contact to the lung surface could be detected reliably by radiographic examination. Both methods complement each other, and the application of a combined ultrasonographic and radiographic examination of the thorax allows a comprehensive inspection of the lung condition. Particularly during the acute phase of the disease the extent of lung tissue damage can be estimated more precisely than by clinical examination alone.

Comparison of three common methods of lung lavage in healthy pigs.

Bronchoscopic, endotracheal and transtracheal lung lavage were evaluated in 38 healthy pigs taken from a nucleus herd in a good state of health with respect to their applicability in practice and the traceability of bacteria, cellular parameters and the antimicrobial peptide PR-39 in the respective lavage fluid samples. The total cell count, qualitative morphological cellular characteristics as well as PR-39 could be determined in all lavage fluid samples, while quantitative cell differentiation was not possible in endotracheal lavage samples. The comparison of the three methods resulted in a higher proportion of polymorphonuclear neutrophil granulocytes (PMNs) and higher concentrations of PR-39 in transtracheal samples. For this reason different valuation standards with respect to PMNs and PR-39 concentrations are presupposed for transtracheal lavage samples. The occurrence of pavement epithelial cells as well as the number of contaminating bacterial species per sample was the lowest in transtracheal lavage. Mycoplasma hyopneumoniae polymerase chain reaction appeared to have the highest diagnostic sensitivity in combination with bronchoscopic lavage. In conclusion, bronchoscopic and transtracheal lavage were considered to be more appropriate for bacteriological and cytological diagnostics than endotracheal lavage.

Respiratory disease markers in porcine bronchoalveolar lavage fluid.

In bronchoalveolar lavage fluid (BALF) of pigs originating from different herds bacteria, cells and the antibacterial peptide PR-39 were examined to gain information about the lung health status. In a high health nucleus herd 56% and in low health herds 20-100% of the examined pigs were found positive for potentially pathogenic bacteria. Based on these findings, a novel definition for bacterial respiratory tract disease was established using an 8% cut-off for the relative number of neutrophils in bronchoscopic and a 40% cut-off in transtracheal BALF in combination with the occurrence of potentially pathogenic microorganisms. The antibacterial peptide PR-39 was highly correlated to this definition of respiratory disease. An assessment of the bacteriological respiratory health status appears to be possibly based on the determination of PR-39 concentrations in BALF using different cut-off values according to the lavage method (2.5 nM for bronchoscopic and 5 nM for transtracheal BALF).

Studies on the effect of specific egg antibodies against Escherichia coli infections in piglets.

The effect of chicken egg powder enriched with immunoglobulins specific for rotavirus antigen and fimbrial adhesions F4, F5, F6 of enterotoxigenic Escherichia coli (ETEC) (Globigen 66 S, Lohmann Animal Health, Cuxhaven, Germany) was studied in 465 sucking piglets on a commercial farm. Half of those piglets were given Globigen 66 S as an additive to milk replacer from day 2 until day 12 of life in addition to sows' milk. These piglets showed a higher intake of milk replacer and a lower prevalence of diarrhoea on days 2 and 3 of life. Statistical evaluation showed, that the effect of sows' milk on the duration of diarrhoea and on piglet weight gains was more pronounced than the effect of Globigen 66 S. Anti-ETEC F4-antibody-activities were measured using an indirect ELISA (enzyme-linked immunosorbent assay). There was an inverse relationship between the intensity of diarrhoea and colostral antibody-activity (r = -0.2). Comparison of binding affinities of avian and porcine antibodies for F4 showed only a limited common spectrum of epitopes, so, in all probability, they might complement each other in the intestine.

Enzyme activities, protein content and cellular variables in the pulmonary epithelial lining fluid in selected healthy pigs.

Reference values of cellular and non-cellular components in the bronchoalveolar lavage fluid (BALF) were established from the BALF specimens obtained from 52 healthy pigs. Using urea as an endogenous marker of dilution, the reference values in the epithelial lining fluid (ELF) were calculated: total cell count 2.71 x 10(9) - 56.49 x 10(9) litre(-1) ELF, alveolar macrophages 2.02 x 10(9) - 49.91 x 10(9) litre(-1) ELF, lymphocytes 0.10 x 10(9) - 4.74 x 10(9) litre(-1) ELF, polymorphonuclear neutrophils 0.01 x 10(9) - 3.48 x 10(9) litre(-1) ELF, protein 0.10 - 13.13 g litre(-1) ELF, lactate dehydrogenase 127-1843 Units litre(-1) ELF, and alkaline phosphatase 86-994 Units litre(-1) ELF. The problems of quantification of BALF components are discussed and a standardized lavage protocol in swine is described, which is essential for the interpretation of diagnostic findings and for the comparison of different BALF specimens.

Actinobacillus pleuropneumoniae iron transport and urease activity: effects on bacterial virulence and host immune response.

Actinobacillus pleuropneumoniae, a porcine respiratory tract pathogen, has been shown to express transferrin-binding proteins and urease during infection. Both activities have been associated with virulence; however, their functional role for infection has not yet been elucidated. We used two isogenic A. pleuropneumoniae single mutants (DeltaexbB and DeltaureC) and a newly constructed A. pleuropneumoniae double (DeltaureC DeltaexbB) mutant in aerosol infection experiments. Neither the A. pleuropneumoniae DeltaexbB mutant nor the double DeltaureC DeltaexbB mutant was able to colonize sufficiently long to initiate a detectable humoral immune response. These results imply that the ability to utilize transferrin-bound iron is required for multiplication and persistence of A. pleuropneumoniae in the porcine respiratory tract. The A. pleuropneumoniae DeltaureC mutant and the parent strain both caused infections that were indistinguishable from one another in the acute phase of disease; however, 3 weeks postinfection the A. pleuropneumoniae DeltaureC mutant, in contrast to the parent strain, could not be isolated from healthy lung tissue. In addition, the local immune response-as assessed by fluorescence-activated cell sorter and enzyme-linked immunosorbent spot analyses-revealed a significantly higher number of A. pleuropneumoniae-specific B cells in the bronchoalveolar lavage fluid (BALF) of pigs infected with the A. pleuropneumoniae DeltaureC mutant than in the BALF of those infected with the parent strain. These results imply that A. pleuropneumoniae urease activity may cause sufficient impairment of the local immune response to slightly improve the persistence of the urease-positive A. pleuropneumoniae parent strain.