Schmallenberg virus: a seroprevalence survey in cattle and sheep, France, winter 2011–2012

Abstract

In France, a national surveillance plan to monitor congenital Schmallenberg virus (SBV) outbreaks was set up in January 2012, and has shown that SBV had become widespread throughout the country since mid-2011. However, the number of SBV-infected farms cannot accurately be estimated through congenital SBV reporting alone. Therefore, GDS France (National Animal Health Farmers' Organization) conducted serological investigations in cattle and sheep holdings in several departments in spring 2012 to assess SBV exposure in 2011. A serological study was also conducted in the department of Saône-et-Loire (southern Burgundy) to establish an accurate local overview of circulation of virus in 2011 among cattle. The study was conducted following guidelines elaborated by the French Platform for animal health surveillance. Results indicated differences in within-herd seroprevalence between cattle herds and sheep herds in departments where outbreaks of congenital SBV were reported in early 2012 and a great heterogeneity in seroprevalence between areas (even between areas geographically close to each other). In departments which had been severely affected in early 2012, the overall impact of SBV infection in cattle herds during the 2012-2013 calving season will probably be low. On the other hand, given the low proportion of immunised ewes in sheep SBV outbreaks, sheep flocks which were already affected in early 2012 may once again face congenital cases of SBV.

Risk Factors for Malformations and Impact on Reproductive Performance and Mortality Rates of Schmallenberg Virus in Sheep Flocks in the Netherlands

“…No significant difference in seroprevalence was found between case and control flocks. This is in line with a serosurvey on SBV in sheep in France [5]. Because of the relatively low number of flocks that submitted sufficient samples for a reliable within-flock seroprevalence estimation, it was decided to estimate within-flock seroprevalence based on flocks that submitted 50 or more samples.…”

“…Between clinically affected and not-clinically affected flocks no significant differences in seroprevalences were found [5]. A seroprevalence of 89.0% was found in sheep samples sampled between November 2011 and March 2012 in the Netherlands [6].…”

“…In areas with reporting of congenital malformations due to SBV in France, a within-flock seroprevalence of 30% was found in sheep in winter 2011–2012 [5]. Between clinically affected and not-clinically affected flocks no significant differences in seroprevalences were found [5].…”

A freedom from disease study: Schmallenberg virus in the south of England in 2015

“…Additionally, there is a single report of SBV-specific antibodies in a dog, but other studies have failed to find evidence of infection in carnivores (Wensman and others 2013, Mouchantat and others 2015). European studies, conducted in 2011, 2012 and 2013, found animal-level prevalence to range between 8 to 100 per cent and 8.5 to 93.3 per cent in cattle and sheep, respectively (Elbers and others 2012, Gache and others 2013, Nanjiani and others 2013). Herd-level prevalence of UK sheep in 2012/2013 was found to range between 40 and 90 per cent (Nanjiani and others 2013).…”

Schmallenberg virus: an update

“…This has been shown even in areas where prevalence is high and so it does not follow that flock positivity always conforms (Gache and others 2013). Vaccine may not always suppress viraemia, but it will offer protection in these circumstances and will lessen the likelihood of recrudescence of disease at repeated intervals.…”