Abstract
BackgroundSchmallenberg virus (SBV) has swept through the major part of Europe in the period 2011–2013. A vaccine against SBV has been developed and may be a possible preventive instrument against infection. Presently, there is no data available to refute the assumption that natural SBV infection results in long-term immunity. In that respect, it is of interest to know how long (protecting) virus-neutralizing antibodies are present in naturally infected animals. New-born calves acquire passive immunity from their dams by ingestion and absorption of antibodies present in colostrum, which can block the production of serum antibodies when vaccine is administered to calves with maternally derived antibodies. In that respect, it is useful to know how long it takes for maternal antibodies against SBV to disappear in young animals born from infected dams.ResultsLongitudinal whole-herd serological monitoring using virus neutralization test (VNT) indicated that 80% of adult dairy cows still had measurable antibodies against SBV at least 24 months after the estimated introduction of the virus into the herd. Median 2Log VNT titer of the adult dairy cows (≥1 year) dropped from 8.6 to 5.6 in a period of 17 months. Median 2Log VNT maternal antibodies titers of calves sampled within 30 days after birth was 8. Calves lost their maternally-derived antibodies after 5–6 months. There was a definite positive relationship between the VNT titer of the dam and the VNT titer of the corresponding calf (age ≤ 30 days) of dam-calf combinations sampled on the same day: the higher the VNT titer of the dam, the higher the VNT titer (maternal antibodies) of the calf.ConclusionsOur field data support the assumption that natural SBV infection in adult cows results in persistence of specific antibodies for at least two years. Based on the observed decay of maternally-derived antibodies in calves, it is presumed safe to vaccinate calves against SBV at an age of approximately 6 months.
Highlights
Schmallenberg virus (SBV) has swept through the major part of Europe in the period 2011–2013
There is no data available to refute the assumption that natural SBV infection results in long-term immunity [1], as was seen earlier with natural infection of cattle with bluetongue virus serotype 8 [5]
It can be assumed that the adult cows became infected around the time that SBV RNA was detected for the first time in Culicoides biting midges caught at this dairy farm on 14 September 2011 [8]
Summary
Schmallenberg virus (SBV) has swept through the major part of Europe in the period 2011–2013. There is no data available to refute the assumption that natural SBV infection results in long-term immunity. It is of interest to know how long (protecting) virus-neutralizing antibodies are present in naturally infected animals. It is useful to know how long it takes for maternal antibodies against SBV to disappear in young animals born from infected dams. Schmallenberg virus (SBV), a novel Orthobunyavirus, has swept through the major part of Europe in the period 2011–2013, reaching as far North as Finland, Turkey in the East, and Spain in the South [1,2].
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