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

Abstract

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.

European interlaboratory comparison of Schmallenberg virus (SBV) real-time RT-PCR detection in experimental and field samples

“…1,[4][5][6]10,14,16,23,30 SBV has infected ruminants at an impressive pace, resulting in a seroprevalence of up to 100% in some SBV-affected regions and extensive spread throughout Europe as far as Turkey in Asia. 2,8,17,22,28,29 Biting midges of the Culicoides genus have been determined as the major source of SBV infection. 6,7,19 Adult ruminants infected with SBV show no or mild clinical signs.…”

Limited interlaboratory comparison of Schmallenberg virus antibody detection in serum samples

“…In addition there were differences in readout (different percentages of destruction/inhibition per well). (Loeffen and others 2012; Mansfield and others 2013). For two laboratories, the in-house ELISA was developed in a collaborative study (Van der Heijden and others 2013).…”

Kırıkkale’de yetiştirilen koyunlarda Schmallenberg virüs seroprevalansı ve bazı coğrafi özelliklerle ilişkisi

“…Almanya ve Hollanda'nın sınır bölgesinde, 2011 yı-lının sonbaharında, sütçü ineklerde yeni bir orthobunyavirüs belirlenmiştir (4,6,9,11,14). Simbu sero grubunun üyesi olan bu yeni virüs, Schmallenberg virüs (SBV) olarak adlandırılmıştır.…”

“…Hastalık; sığırlarda ateş, iştahsızlık, süt üretiminde azalma, kondüsyon kaybı ve ishalle karakterizeyken (11,14,18), koyun ve keçilerde kongenital malformasyonlarla beraber abortus ve ölü doğum gözlenmektedir (18). Kuzu, oğlak ve buzağılarda transplasental enfeksiyonlarla; artrogripozise, columna vertabralis (kifoz, lordosis, skolyoz, tortikolis) ve kafatası (makrosefali, brachygnathia inferior) bozuklukları gibi şiddetli kongenital malformasyonlara, çeşitli beyin (hidranensefali, porensefali, serebellar hipoplazi, beyin kökü hipoplazisi) ve spinal cord hasarlarına neden olabilmektedir (6,7).…”