The acute stages of infection with swine influenza virus (SIV), porcine respiratory coronavirus (PRCV) and porcine reproductive-respiratory syndrome virus (PRRSV) were shown to differ in terms of clinical and lung inflammatory effects and proinflammatory cytokine profiles in bronchoalveolar lavage (BAL) fluids. Caesarian-derived colostrum-deprived pigs were inoculated intratracheally with one of the three viruses. SIV infection was followed within 1 day post inoculation (d PI) by characteristic respiratory and general signs, and excessive lung epithelial desquamation and neutrophil infiltration (38 to 56 per cent of BAL cells at 1 d PI vs 0 to 1 per cent in controls). High concentrations of bioactive interferon-alpha (IFN -alpha), tumour necrosis factor-alpha (TNF -alpha) and interleukin-1 (IL -1) coincided with peak symptoms and neutrophil infiltration. PRCV infection was asymptomatic and produced a mild bronchointerstitial pneumonitis and neutrophil infiltration (13 to 22 per cent of BAL cells at 4 d PI). IFN -alpha titres parallelled those found during SIV infection, TNF -alpha was negligible and IL -1 undetectable. PRRSV infection induced anorexia and lethargy between 3 and 5 d PI. There was marked infiltration with mononuclear cells in alveolar septa and BAL fluids between 7 and 10 d PI, while neutrophils remained at less than 11 per cent of BAL cells at any time. IL -1 was produced from three throughout 10 d PI, while IFN -alpha production was minimal and TNF -alpha undetectable. These data strongly suggest that proinflammatory cytokines can be important mediators of viral respiratory disease.

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BackgroundPost-weaning diarrhoea (PWD), due to Escherichia coli, is an important cause of economic losses to the pig industry primarily as a result of mortality and worsened productive performance. In spite of its relevance, recent data about the prevalence of virulence genes and pathotypes among E. coli isolates recovered from cases of PWD in Europe are scarce.ResultsThis study investigates the prevalence of fimbrial and toxin genes of E. coli by PCR among 280 farms with PWD across Europe. A total of 873 samples collected within the first 48 h after the onset of PWD (occurring 7–21 days post weaning) were submitted to the laboratory for diagnostic purposes. Isolation and identification of E. coli were performed following standard bacteriological methods and PCR assays for the detection of genes encoding for fimbriae (F4, F5, F6, F18 and F41) and toxins (LT, STa, STb and Stx2e). The prevalence of fimbriae and toxins among E. coli isolates from cases of PWD was: F4 (45.1 %), F18 (33.9 %), F5 (0.6 %), F6 (0.6 %), F41 (0.3 %), STb (59.1 %), STa (38.1 %), LT (31.9 %) and Stx2e (9.7 %). E. coli isolates carrying both fimbrial and toxin genes were detected in 52.5 % of the cases (178 out of 339 isolates), with 94.9 % of them being classified as enterotoxigenic E. coli (ETEC). The most common virotype detected was F4, STb, LT.ConclusionsThis study confirms that ETEC is frequently isolated in pig farms with PWD across Europe, with F4- and F18-ETEC variants involved in 36.1 % and 18.2 % of the outbreaks, respectively.

Objectives  Avian‐like H1N1 and human‐like H3N2 swine influenza viruses (SIV) have been considered widespread among pigs in Western Europe since the 1980s, and a novel H1N2 reassortant with a human‐like H1 emerged in the mid 1990s. This study, which was part of the EC‐funded ‘European Surveillance Network for Influenza in Pigs 1’, aimed to determine the seroprevalence of the H1N2 virus in different European regions and to compare the relative prevalences of each SIV between regions. Design  Laboratories from Belgium, the Czech Republic, Germany, Italy, Ireland, Poland and Spain participated in an international serosurvey. A total of 4190 sow sera from 651 farms were collected in 2002–2003 and examined in haemagglutination inhibition tests against H1N1, H3N2 and H1N2. Results  In Belgium, Germany, Italy and Spain seroprevalence rates to each of the three SIV subtypes were high (≥30% of the sows seropositive) to very high (≥50%), except for a lower H1N2 seroprevalence rate in Italy (13·8%). Most sows in these countries with high pig populations had antibodies to two or three subtypes. In Ireland, the Czech Republic and Poland, where swine farming is less intensive, H1N1 was the dominant subtype (8·0–11·7% seropositives) and H1N2 and H3N2 antibodies were rare (0–4·2% seropositives). Conclusions  Thus, SIV of H1N1, H3N2 and H1N2 subtype are enzootic in swine producing regions of Western Europe. In Central Europe, SIV activity is low and the circulation of H3N2 and H1N2 remains to be confirmed. The evolution and epidemiology of SIV throughout Europe is being further monitored through a second ‘European Surveillance Network for Influenza in Pigs’.

-Apoptosis was studied in the lungs of pigs during an infection with a European strain of porcine reproductive and respiratory syndrome virus (PRRSV) and it was examined if cytokines were involved in the induction of apoptosis. Twenty-two 4-to 5-week-old gnotobiotic pigs were inoculated intranasally with 10 6.0 TCID 50 of the Lelystad virus and euthanised between 1 and 52 days post inoculation (PI). The lungs and broncho-alveolar lavage (BAL) cells were assessed both for virus replication and apoptosis; BAL fluids were examined for interleukin (IL)-1, tumour necrosis factor-alpha and IL-10. Double-labellings were conducted to determine the relation between virus replication and apoptosis and to identify the apoptotic cells. Apoptosis occurred in both infected and non-infected cells. The percentages of infected cells, which were apoptotic, ranged between 9 and 39% in the lungs and between 13 and 30% in the BAL cells. The majority of apoptotic cells were non-infected. Non-infected apoptotic cells in the lungs were predominantly monocytes/macrophages, whereas those in the broncho-alveolar spaces were predominantly lymphocytes. The peak of apoptosis in the lungs at 14 days PI was preceded by a peak of IL-1 and IL-10 production at 9 days PI, suggesting a possible role of these cytokines in the induction of apoptosis in non-infected interstitial monocytes/macrophages. However, the latter hypothesis was not confirmed in vitro, since blood monocytes or alveolar macrophages did not undergo apoptosis after treatment with recombinant porcine IL-1 or IL-10. pig / lung / porcine reproductive and respiratory syndrome virus / apoptosis / cytokine

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Swine influenza viruses (SIVs) of H1N1, H3N2, and H1N2 subtypes, with antigenically different hemagglutinins, are currently cocirculating in pigs in Europe. This study aimed to determine whether the hemagglutination inhibition (HI) test, which is the primary serological test for SIV, is sufficiently specific to discriminate between infections with the three subtypes. In experiment 1, pigs were consecutively inoculated with European H1N1, H3N2, and H1N2 SIVs by the intranasal route, or with the respective subtypes only. In a second experiment, a commercial, inactivated H1N1-and H3N2-based SIV vaccine was administered once to pigs previously infected with one to three SIV subtypes or to influenza-naive pigs. Sequential serum samples were examined in HI and virus-neutralizing (VN) tests to the three strains used for pig inoculations. Of the 160 sera collected after infection with one or two SIV subtypes, only 8 showed cross-reactive antibodies to the remaining subtype(s) in the HI test, and 11 in the VN test. Consecutive inoculations with H1N1 and H1N2 or vice versa were followed by a significant rise in preexisting antibody titers to the first subtype after the second inoculation. When dually infection-immune pigs were inoculated with the third, remaining SIV subtype, nasal virus excretion was undetectable or reduced and the serological response was absent to moderate. A single vaccination of infection-immune pigs resulted in a dramatic rise in HI and VN antibody titers to any of the previously encountered subtypes, whereas SIV-naive pigs barely seroconverted. Most important, pigs previously infected with H1N1 but not with H1N2 developed crossreactive antibodies to H1N2 after the vaccination. In conclusion, the HI test remains adequate for the differential diagnosis of infections with H1N1, H3N2, and H1N2 in European swine populations if it is properly used and if the SIV vaccination status is taken into account. 373

In this study, the efficacy of two attenuated porcine reproductive and respiratory syndrome virus (PRRSV) vaccines was assessed. The virological protection in the lungs of vaccinated pigs upon challenge was studied. Also, challenged pigs were exposed to lipopolysaccharide (LPS) to evaluate clinical protection. Six-week-old pigs were immunized intramuscularly with commercial vaccines based on either an attenuated American or an attenuated European virus strain. Non-immunized pigs and pigs intramuscularly inoculated with the virulent Lelystad strain were included as controls. Six weeks after immunization, pigs were challenged either intratracheally or intranasally with the Lelystad strain, and 3 and 6 days later intratracheally exposed to Escherichia coli LPS. After LPS administration, pigs were monitored for clinical signs. At 4 and 7 days after challenge, pigs were euthanized to determine virus quantities in broncho-alveolar lavage (BAL) fluids and in lungs. Challenge virus was recovered from three out of eight pigs that had been primo-inoculated with the Lelystad strain with titers ranging between 0.3 and 3.1 log(10). Fifteen out of sixteen pigs vaccinated with the attenuated American strain were positive for challenge virus and their mean virus titers were similar to those of non-immunized challenge controls. Eleven out of 16 pigs vaccinated with the attenuated European strain were positive for challenge virus and their mean virus titers were 2.0-2.5 log(10) lower than those of non-immunized challenge controls. Thus, the virological protection in the lungs of vaccinated pigs upon challenge was incomplete, but was more pronounced in the homologous situation. Clinical signs upon LPS exposure in both vaccinated groups were not reproducible in two experiments.