Survival patterns of Streptococcus suis serotypes 1 and 14 in porcine blood indicate cross-reactive bactericidal antibodies in naturally infected pigs.

Streptococcus suis serotype (cps) 1 and cps14 have been detected in association with severe diseases such as meningitis and polyarthritis in pigs. Though these two cps are very similar, only cps14 is an important zoonotic agent in Asia and only cps1 is described to be associated with diseases in suckling piglets rather than weaning piglets. The main objective of this study was to assess restriction of survival of cps14 and cps1 in porcine blood by IgG and IgM putatively cross-reacting with these two cps. Furthermore, we differentiate recent European cps1/14 strains by agglutination, cpsK sequencing, MLST and virulence-associated gene profiling. Our data confirmed cps1 of clonal complex 1 as an important pathotype causing polyarthritis in suckling piglets in Europe. The experimental design included also bactericidal assays with blood samples drawn at different ages of piglets naturally infected with different S. suis cps types including cps1 but not cps14. We report survival of a cps1 and a cps14 strain (both of sequence type 1) in blood of suckling piglets with high levels of maternal IgG binding to the bacterial surface. In contrast, killing of cps1 and cps14 was recorded in older piglets due to an increase of IgM as demonstrated by specific cleavage of IgM. Heterologous absorption of antibodies with cps1 or cps14 is sufficient to significantly increase the survival of the other cps. In conclusion, IgM elicited by natural S. suis infection is crucial for killing of S. suis cps1 and cps14 in older weaning piglets and has most likely the potential to cross-react between cps1 and cps14.

A robust PCR for the differentiation of potential virulent strains of Haemophilus parasuis.

BACKGROUND: Haemophilus parasuis is the etiological agent of Glässer's disease in swine. H. parasuis comprises strains with heterogeneous virulence capacity, from non-virulent to highly virulent. Determination of the pathogenic potential of the strains is important for diagnosis and disease control. The virulence-associated trimeric autotransporters (vtaA) genes have been used to predict H. parasuis virulence by PCR amplification of their translocator domains. Here, we report a new and improved PCR designed to detect a different domain of the vtaA genes, the leader sequence (LS) as a diagnostic tool to predict virulence. METHODS: A collection of 360 H. parasuis strains was tested by PCR with LS specific primers. Results of the PCR were compared with the clinical origin of the strains and, for a subset of strains, with their phagocytosis and serum resistance using a Chi-square test. RESULTS: LS-PCR was specific to H. parasuis, and allowed the differential detection of the leader sequences found in clinical and non-clinical isolates. Significant correlation was observed between the results of the LS-PCR and the clinical origin (organ of isolation) of the strains, as well as with their phagocytosis and serum susceptibility, indicating that this PCR is a good predictor of the virulence of the strains. In addition, this new PCR showed a full correlation with the previously validated PCR based on the translocator domain. LS-PCR could be performed in a wide range of annealing temperatures without losing specificity. CONCLUSION: This newly described PCR based on the leader sequence of the vtaA genes, LS-PCR, is a robust test for the prediction of the virulence potential of H. parasuis strains.

Mycoplasma hyopneumoniae infections in peri-weaned and post-weaned pigs in Belgium and The Netherlands: Prevalence and associations with climatic conditions.

Mycoplasma hyopneumoniae (M. hyo) is an important pathogen in modern intensive pig farming in Europe. The objectives of the present study were (1) to use the tracheobronchial swab (TBS) technique to obtain data on the distribution of M. hyo infections in recently weaned pigs in Belgium and The Netherlands, and (2) to look for associations between infection prevalence and specific climatic conditions. One hundred and seventy-six pig herds were randomly selected and 30 piglets sampled on each farm: 18 at 3-5 weeks of age and 12 at 6-11 weeks. Mucus collected from the tracheobronchial bifurcation and suspended in saline was subjected to PCR analysis for M. hyo. In 27% of herds (n= 44) at least one piglet tested positive for M. hyo at 3-5 weeks of age, and 29% (n= 47) at 6-11 weeks of age. The individual animal prevalence at the two ages was 7.1% and 10.9%, respectively. The probability of 3-5 week old piglets being M. hyo-positive was negatively associated with the precipitation rate (odds ratio [OR] = 0.971) during the week preceding the sampling. In the older post-weaning group, the odds of being M. hyo-positive at piglet level were significantly affected by season (OR of detection during autumn compared to summer 20.9). Thus, under Belgian and Dutch field conditions, piglets may be infected with M. hyo very early in life, with prevalence increasing further during the post-weaning period.

[Serological course investigations of Haemophilus parasuis and Mycoplasma hyorhinis in three pig farms]. / Serologische Verlaufsuntersuchungen auf Haemophilus parasuis und Mycoplasma hyorhinis in drei schweine-haltenden Betrieben.

The aim of the study was to investigate the infection dynamic of Haemophilus (H.)parasuis and Mycoplasma (M.) hyorhinis in 3 farms. A total of 61 piglets were clinically investigated at 1., 3., 5., 7., 9., 11., 14., 18. and 22. weeks of life and a blood sample was taken from each piglet as well as from the sows. The serum samples were tested using ELISA for antibodies against H. parasuis and M. hyorhinis. Clinical signs indicating polyserositis were seen in farm 1 and 3. For both pathogens, a decline of the maternal antibodies could be detected up to the 5th or 7th week of life. The duration of persistence depended on the level of the maternal antibodies. In farm 1, all animals were tested positive for antibodies against H. parasuis during the fattening period. In farm 3, several sows were tested positive in the M. hyorhinis ELISA, therefore, positive results in sows can indicate a higher infection dynamic during the fattening period. For H. parasuis as well as for M. hyorhinis a significant correlation between the level of the antibodies in the sows and their piglets could be seen.

[Evaluation of immunoglobulin G concentration in colostrum of mares by ELISA, refractometry and colostrometry]. / Postpartale Immunglobulin-G-Konzentrationen im equinen Kolostrum mittels ELISA-Methode, Kolostrometrie und Refraktometrie.

In 360 samples of colostrum and 36 samples of blood of warmblood mares, the concentration of immunoglobulin G (IgG) was evaluated in the post partal period with an ELISA and the results were compared to values obtained with 2 field methods--refractometry and colostrometry. A significant correlation (p < 0.0001) was determined between ELISA and colostrometry (r = +0.88) and between ELISA and refractometry (r = +0.93). So both field-methods seem suitable for evaluation of the colostral IgG-concentration in mares. Further the kinetic of the IgG concentration in colostrum, the volume of colostrum and the total amount of IgG was measured in the 12 hours post partum (p.p.) in each half udder of 36 mares of different parity. Immediately p.p. primiparous mares have a greater mean concentration of IgG (68 mg/ml) than multiparous mares (51 mg/ml). However, multiparous mares have a mean colostral volume of 1020 ml whereas, in primiparous mares, a mean volume of 527 ml was determined within the first three hours p.p. As a result of this the total amount of IgG was lower in primiparous (31.5 g) than in multiparous mares (48.5 g). A significant decrease of IgG concentration was measured in multiparous mares in the 1.5 hours following partum versus 3 hours in primiparous mares. The mean IgG concentration in the blood serum of the 36 mares immediately p.p. was 13.4 +/- 3.6 mg/ml. No significant correlation was observed between values of IgG concentration in the blood and in the colostrum of the mares.

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).

[Possibilities and limits of serological diagnosis in pig stocks in the case of Mycoplasma hyopneumoniae infection]. / Möglichkeiten und Grenzen serologischer Diagnostik im Rahmen der Bestandsbetreuung von Schweinen am Beispiel der Mycoplasma- hyopneumoniae-Infektion.

When conducting their investigations to diagnose infectious diseases in swine, practitioners are often forced to use reduced numbers of animals in their samples in order to minimize costs for farmers. A cross-sectional study was conducted approximating such field conditions to show the limits of interpretation with reduced sample sizes in case of Enzootic Pneumonia. Compared with other respiratory pathogens, Mycoplasma hyopneumoniae, the etiologic agent of Enzootic Pneumonia spreads very slowly, mainly when animals are in direct contact. Furthermore, the interpretation of serological results is difficult because several weeks must usually pass for serological reactions to become apparent. Serological testing is normally used to confirm a clinical diagnosis by detecting an increase in antibodies against the etiologic agent. Samples are collected at the beginning of disease and four to six weeks later. An increasing number of serological positive animals in a herd is usually interpreted as spread of infection. The ,,true" prevalence we observed in our investigation was used to make a statistical analysis describing the probability of detecting an increasing prevalence from 0.07 to 0.33 with a reduced sample size. We showed that the probability of detecting an increase of two seropositive animals was 44% if 5 samples per group were analysed. When only 3 samples were analysed per group, this probability decreases to 21%. Compromise must be found between epidemiological necessary and financially acceptable sample size; this could be a minimum of 10 samples per age group.

Evaluation of a LAM ELISA for diagnosis of paratuberculosis in sheep and goats.

A milk and serum ELISA containing lipoarabinomanan (LAM) antigen was evaluated in sheep and goats versus agar gel immunodiffusion (AGID) test and polymerase chain reaction (PCR) using milk and lymph nodes. Milk and serum samples were obtained from six, two, and four flocks with unknown, negative and positive status of infection, respectively. By comparison of serum ELISA activity and PCR results, the positive and negative predictive values were calculated. Receiver operation characteristic (ROC) analysis was used for calculating the specificity and sensitivity at different cut-offs.