24 months after introduction of Schmallenberg virus in a dairy farms in the Netherlands 80% of the adult cows in that herd still had measurable antibodies against SBV.
Schmallenberg virus (SBV) swept through the major part 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. A serological survey of blood sample from a representative sample of cattle in the Netherlands indicated a high seroprevalence of antibodies against SBV.
The vaccine against SBV has been developed, which can prevent infection. Presently, there are no data available to refute the assumption that natural SBV infection results in long-term immunity, as was seen earlier with natural infection of cattle with bluetongue virus serotype.Immunity and vaccination
Immunity gained through natural infection can block the production of serum antibodies when vaccine is administered. Newborn calves acquire passive immunity from their dams by ingestion and absorption of antibodies present in colostrum. Therefore, it is important to consider the age at which the calves loose their maternal antibody, previous to starting a vaccination campaign. Vaccine should therefore not be administered to young animals born from infected dams during the period in which the calves have maternally derived antibodies. The study shows that maternal antibodies were lost on average four to six months after birth. There was a positive relationship between the VNT titer of the dam and the corresponding calf sampled on the same day.SBV a highly efficacious virus
The study demonstrates that 80% of adult dairy cows in the investigated dairy herd still had measurable antibodies against SBV at least 24 months after the estimated time of introduction of the virus into the herds. This means that after natural infection, animals most likely are protected for re-infection for a considerably period of time. SBV seems to be highly efficacious in finding susceptible animals in an almost entirely immune herd. This could put young seronegative dams at risk for clinical SBV infection.