Seroprevalence was highest in the eastern part of the country, bordering Germany, where the virus was first identified.

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BackgroundAt the end of 2011, a new orthobunyavirus, tentatively named Schmallenberg virus (SBV), was discovered in Germany. This virus has since been associated with clinical signs of decreased milk production, watery diarrhoea and fever in dairy cows, and subsequently also with congenital malformations in calves, lambs and goat kids. In affected countries, initial surveillance for the infection was based on examination of malformed progeny. These suspicions were followed up by real-time reverse transcription polymerase chain reaction (RT-PCR) on brain tissue. For epidemiological purposes, a serological assay was, however, needed.ResultsA virus neutralisation test (VNT) was developed and optimized, and subsequently evaluated. This VNT has a specificity of >99% and the sensitivity is likely also very close to 100%. The assay is highly repeatable and reproducible. The final assay was used to test for antibodies in cows, ewes and does from herds known to be infected or suspected to be so. Targets for sampling in these herds were the mothers of malformed offspring. In herds with an RT-PCR confirmed SBV infection, more than 94% (190 out of 201) of the ewes and 99% (145 out of 146) of the cows were seropositive. In herds with suspicion of SBV infection based on birth of malformed offspring only (no or negative RT-PCR), more than 90% (231 out of 255) of the ewes and 95% (795 out of 834) of the cows were seropositive. In goats, on the other hand, only a low number of seropositives was found: overall 36.4%, being 16 out of 44 goats tested.ConclusionsGiven the characteristics of this VNT, it can be used at a relative high throughput for testing of animals for export, surveillance, screening and research purposes, but can also be used as a confirmation test for commercially available enzyme-linked immunosorbent assays (ELISA’s) and for (relative) quantification of antibodies.Suspicions of SBV infections that were confirmed by RT-PCR were almost always confirmed by serology in cows. Due to individual registration and identification of cows and calves, affected offspring could almost always be traced back to the mother. Ewes on the other hand were not always the mothers of affected lambs, but were in many cases herd mates with unaffected lambs. This indicated a high within-herd seroprevalence of antibodies against SBV.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 tests. The presence of BVDV and BDV in a swine population may thus affect the 32 transmission of CSFV, but also the diagnosis of a CSFV infection. In this study, the 33 seroprevalence against BVDV and BDV in two categories of swine, sows and finishing pigs, 34 in the Netherlands was determined. Furthermore, several risk factors, associated with the 35 presence of swine and ruminants on the same farm or in the immediate surroundings, were 36 evaluated. In sows, the seroprevalence against BVDV was 2.5% on the animal level, and 37 11.0% on herd level. In finishing pigs these prevalences were 0.42% and 3.2% respectively. 38Antibodies against BDV were found in 3 sows only. Risk factors, associated with a BVDV-39 seropositive status in breeding pigs, were the presence of cattle on the same premises and 40 a high density of sheep and/or goats herds in a radius of 3 kilometres. While BVDV and BDV 41 hardly pose any threat to the swine population themselves, knowledge, and therefore regular 42 monitoring, on the presence of these viruses in the swine population is important with 43 respect to CSF eradication. It will allow for a better interpretation of diagnostic test results, 44 both in terms of possible false positives and false negatives, but may also bring about 45 additional measures or surveillance protocols in times of CSF outbreaks to avoid surprises 46 caused by cross-reactivity with ruminant pestiviruses. 47 48