Schmallenberg virus: seroprevalence, risk and protective factors in aborted dairy cows in Algeria

The Schmallenberg virus (SBV), an orthobunyavirus, recently emerged in Germany in 2011. It spreads rapidly via the Culicoides vector, causing a decline in milk production, abortions and malformations in cattle, sheep and goats. These significant economic losses for farmers, as well as the difficulty in diagnosing the disease due to its similarity to other abortive diseases such as bluetongue, epizootic haemorrhagic disease, bovine viral diarrhea and infectious bovine rhinotracheitis, make it an important subject of study in Algeria. The aim of this study was to detect the presence of antibodies against the Schmallenberg virus in dairy cows that had aborted in Algeria. 458 serum samples from cows that had aborted, belonging to 159 farms, were tested for the presence of anti-SBV antibodies using an indirect ELISA kit, supplemented by a survey questionnaire designed to identify risk factors associated with exposure to the Schmallenberg virus. The individual seroprevalence obtained was 46.3 % (212/458), with the year of visit in 2016 (odds ratio [OR] = 9.84; P = 0.007) and 2019 (OR = 14.39; P = 0.004) and the winter season (OR = 2.05; P = 0.037) being factors associated with an increased risk of individual exposure. Another factor identified as being associated with a reduced risk of exposure was the 4th month of gestation (OR = 0.41; P = 0.038). The seroprevalence of the herd was 73.6 % (117/159). At the herd level, herd size was the only factor associated with an increased risk of exposure to SBV (OR = 1.04; P = 0.01). The factors were associated with a reduced risk of exposure (implementation of a rodent and pest control plan, and presence of moulds in animal feed). The implementation of surveillance and prevention protocols for this disease is essential to protect animal health and the economy of cattle farms.