A cross-sectional survey was conducted in the Belgian cattle population after the first period of infection of the emerging Schmallenberg virus. A total number of 11 635 cattle from 422 herds sampled between 2 January and 7 March 2012 were tested for the presence of Schmallenberg-specific antibodies using an ELISA kit. Between-herd seroprevalence in cattle was estimated at 99.76% (95% CI: 98.34-99.97) and within-herd seroprevalence at 86.3% (95% CI: 84.75-87.71). An Intraclass Correlation Coefficient of 0.3 (P < 0.001) was found, indicating that the correlation between two animals within a herd with respect to their serological status was high. Those results corroborate the conclusion that the Schmallenberg virus was widespread in Belgium during winter 2011. Seroprevalence was shown to be statistically associated to the animal's age (P < 0.0001): with 64.9% (95% CI: 61.34-68.3) estimated for the 6-12 months of age, 86.79% (95% CI: 84.43-88.85) for the 12-24 months of age and 94.4% (95% CI: 93.14-95.44) for the animals older than 24 months. Based on the results of the described serological survey, we can conclude that after the first Schmallenberg virus episode, almost every Belgian cattle has already been in contact with the virus. In consequence, the vast majority of the host animals should have developed post infection protective immunity against the virus.

Schmallenberg virus (SBV), which emerged in Northwestern Europe in 2011, is an arthropod-borne virus affecting primarily ruminants. Based on the results of two cross-sectional studies conducted in the Belgian ruminant population during winter 2011-2012, we concluded that at the end of 2011, almost the whole population had already been infected by SBV. A second cross-sectional serological study was conducted in the Belgian cattle population during winter 2012-2013 to examine the situation after the 2012 transmission period and to analyse the change in immunity after 1 year. A total of 7130 blood samples collected between 1st January and 28 February 2013 in 188 herds were tested for the presence of SBV-specific antibodies. All sampled herds tested positive and within-herd seroprevalence was estimated at 65.66% (95% CI: 62.28-69.04). A statistically significant decrease was observed between the beginning and the end of 2012. On the other hand, age-cohort-specific seroprevalence stayed stable from 1 year to the other. During winter 2012-2013, calves between 6 and 12 months had a seroprevalence of 20.59% (95% CI: 15.34-25.83), which seems to be an indication that SBV was still circulating at least in some parts of Belgium during summer-early autumn 2012. Results showed that the level of immunity against SBV of the animals infected has not decreased and remained high after 1 year and that the spread of the virus has slowed down considerably during 2012. This study also indicated that in the coming years, there are likely to be age cohorts of unprotected animals.

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Background Immunoglobulin E (IgE) is the treatment target of omalizumab, a monoclonal antibody indicated in the treatment of severe allergic asthma. Long-term variability of serum total IgE (sIgE tot ) in asthmatics remains poorly documented. Methods In this prospective study, sIgE tot levels were measured over 1 year at 7 time points in 41 severe asthmatics treated with high-dose of inhaled corticosteroids and long-acting β 2 agonists. 33 patients were atopic based on at least one positive RAST to common aeroallergens. Patients were divided into three groups according to their baseline sIgE tot level: low (< 76 IU/mL; n = 10), intermediate (76–700 IU/mL; n = 20) or high (> 700 IU/mL; n = 11). Patients also completed the six-item Juniper Asthma Control Questionnaire (ACQ 6 ). The sIgE tot variability and factors predictive for this variability were studied, as well as ACQ 6 outcomes. Results The variation in sIgE tot level was mostly the consequence of between patient-variability, which represented 96%, 71% and 96% of the total variability in the low, intermediate and high sIgE tot subgroups, respectively. The residual within-patient variability was therefore limited. In 10/41 patients, sIgE tot levels increased or decreased, for at least one visit, beyond the predefined range of the subgroups to which they were assigned (< 76 IU/mL; 76–700 IU/mL; > 700 IU/mL). There was a significant but weak correlation between sIgE tot and ACQ 6 score over all time points (r = 0.15, p = 0.02), but sIgE tot failed to associate with severe exacerbation. sIgE tot decreased by 3% with any additional year of age for the whole group (p = 0.01) and increased by 5% per one unit of allergen exposure score in atopic patients (p = 0.002). Conclusion In severe asthmatics, limited within-patient variability of sIgE tot levels was observed over 1 year as opposed to marked between-subject variability. sIgE tot decreases with age. Variation in sIgE tot weakly associates with asthma control but not with exacerbation.

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Schmallenberg virus (SBV) is an Orthobunyavirus that induces abortion, stillbirths and congenital malformations in ruminants. SBV infection induces a long lasting seroconversion under natural conditions. The persistence of the protective immunity and the isotype specific antibody response upon SBV infection of sheep has however not been studied in detail. Five sheep were kept in BSL3 facilities for more than 16 months and subjected to repeated SBV infections. Blood was regularly sampled and organs were collected at euthanasia. The presence of SBV RNA in serum and organs was measured with quantitative real-time PCR. The appearance and persistence of neutralizing and SBV nucleoprotein (N) isotype specific antibodies was determined with virus neutralization tests (VNT) and ELISAs. The primo SBV infection protected ewes against clinical signs, viraemia and virus replication in organs upon challenge infections more than 15 months later. Production of neutralizing SBV specific antibodies was first detected around 6 days post primo-inoculation with VNT and correlated with the appearance of SBV-N specific IgM antibodies. These IgM antibodies remained present for 2 weeks. SBV-N specific IgG antibodies were first detected between 10 and 21 dpi and reached a plateau at 28 dpi. This plateau remained consistently high and no significant decrease in titre was found over a period of more than 1 year. Similar results were found for the neutralising antibody response. In conclusion, the SBV specific IgM response probably eliminates SBV from the blood and the protective immunity induced by SBV infection protects sheep against reinfection for at least 16 months.