Schmallenberg study from Belgium: almost all adult cows infected, 28% of the fetuses at risk

[Gert van der Hoek]

Emerging Infectious Disease Journal - CDC - Volume 18, Number 9—September 2012

Schmallenberg Virus in Domestic Cattle, Belgium, 2012

Abstract

To determine prevalence of antibodies against Schmallenberg virus in adult cows and proportion of infection transmitted to fetuses, we tested serum samples from 519 cow/calf pairs in Belgium in spring 2012. Of cattle within 250 km of location where the virus emerged, ≈91% tested positive for IgG targeting nucleoprotein. Risk for fetal infection was ≈28%.

In conclusion, this study confirms that the emerging virus was absent from the area examined in spring 2011 and provides evidence that 1 year later almost all adult cattle had seroconverted.

Furthermore, the results suggest that the risk for infection of the fetus in an immunologically naive herd is ≈28% and that in utero infections can occur without sequelae visible at birth if the infection occurs when the fetus’s immune system is mature enough to control virus spread.

In the case of Akabane virus, the cow’s natural immunity prevents subsequent infections of the fetus (8). It seems likely, therefore, that the Schmallenberg virus infection itself, and its resulting economic effects on farms in the regions concerned, might disappear in 2012.

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