Development of a virus neutralisation test to detect antibodies against Schmallenberg virus and serological results in suspect and infected herds

• Published in: Acta veterinaria scandinavica 2012-08, Vol.54 (1), p.44-44, Article 44
• Main Authors: Loeffen, Willie, Quak, Sjaak, de Boer-Luijtze, Els, Hulst, Marcel, van der Poel, Wim, Bouwstra, Ruth, Maas, Riks
• Format: Article
• Language: English
• Subjects: akabane virus; Animals; Antibodies; Antibodies, Viral - blood; Birth defects; Bunyaviridae Infections - diagnosis; Bunyaviridae Infections - epidemiology; Bunyaviridae Infections - veterinary; Bunyaviridae Infections - virology; Cattle; Cattle Diseases - diagnosis; Cattle Diseases - epidemiology; Cattle Diseases - virology; Cell culture; Dairy cattle; Enzyme-linked immunosorbent assay; Female; Genetic disorders; Germany - epidemiology; Goat Diseases - diagnosis; Goat Diseases - epidemiology; Goat Diseases - virology; Goats; Infection; japan; Milk; Milk production; Neutralisation test; Neutralization Tests - methods; Neutralization Tests - veterinary; nigeria; Orthobunyavirus; Orthobunyavirus - immunology; Orthobunyavirus - isolation & purification; Polymerase Chain Reaction - veterinary; Product development; Reproducibility of Results; Schmallenberg virus; Sensitivity; Sensitivity and Specificity; Serodiagnosis; Seroepidemiologic Studies; Serology; Seroprevalence; shamonda; Sheep; Sheep Diseases - diagnosis; Sheep Diseases - epidemiology; Sheep Diseases - virology; Specificity; Studies; Viral antibodies; Viruses
• ISSN: 1751-0147; 0044-605X; 1751-0147
• DOI: 10.1186/1751-0147-54-44

At 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. A 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. Given 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.