S — Schmallenberg virus
Schmallenberg virus is an emerging livestock virus first identified in Europe in 2011 and primarily affects cattle, sheep, and goats. It belongs to the genus Orthobunyavirus within the family Peribunyaviridae and is transmitted by biting midges of the genus Culicoides.
The significance of Schmallenberg virus lies mainly in its impact on animal health, reproduction, and agricultural economics. In adult cattle, infection is usually mild and may present with transient fever, reduced milk yield, diarrhoea, and decreased appetite. However, the most important clinical consequences occur when infection takes place during pregnancy, particularly in sheep and cattle. The virus can cross the placenta and infect the developing fetus, leading to congenital malformations. These include arthrogryposis (joint contractures), spinal deformities such as scoliosis, hydranencephaly (absence of parts of the brain), cerebellar hypoplasia, and stillbirth or abortion. Collectively, these outcomes are often referred to as congenital malformation syndrome. The timing of infection during gestation is critical, as infection during specific developmental windows leads to fetal nervous system damage and musculoskeletal deformities. This has significant economic consequences due to loss of offspring, veterinary costs, and reduced productivity in affected herds.
From a molecular biology perspective, Schmallenberg virus is an enveloped, negative-sense single-stranded RNA virus with a segmented genome consisting of three RNA segments: large (L), medium (M), and small (S). The L segment encodes the RNA-dependent RNA polymerase, the M segment encodes the envelope glycoproteins Gn and Gc, and the S segment encodes the nucleocapsid protein and a non-structural protein (NSs). The NSs protein is particularly important because it suppresses the host interferon response, allowing the virus to evade innate immunity and replicate efficiently in host cells. Viral replication occurs in the cytoplasm, where the RNA polymerase transcribes viral mRNA and replicates the genome via complementary RNA intermediates.
Understanding the molecular biology and pathogenesis of Schmallenberg virus is important for surveillance, vaccine development, and controlling outbreaks in livestock populations.
Schmallenberg virus is an emerging livestock virus first identified in Europe in 2011 and primarily affects cattle, sheep, and goats. It belongs to the genus Orthobunyavirus within the family Peribunyaviridae and is transmitted by biting midges of the genus Culicoides.
The significance of Schmallenberg virus lies mainly in its impact on animal health, reproduction, and agricultural economics. In adult cattle, infection is usually mild and may present with transient fever, reduced milk yield, diarrhoea, and decreased appetite. However, the most important clinical consequences occur when infection takes place during pregnancy, particularly in sheep and cattle. The virus can cross the placenta and infect the developing fetus, leading to congenital malformations. These include arthrogryposis (joint contractures), spinal deformities such as scoliosis, hydranencephaly (absence of parts of the brain), cerebellar hypoplasia, and stillbirth or abortion. Collectively, these outcomes are often referred to as congenital malformation syndrome. The timing of infection during gestation is critical, as infection during specific developmental windows leads to fetal nervous system damage and musculoskeletal deformities. This has significant economic consequences due to loss of offspring, veterinary costs, and reduced productivity in affected herds.
From a molecular biology perspective, Schmallenberg virus is an enveloped, negative-sense single-stranded RNA virus with a segmented genome consisting of three RNA segments: large (L), medium (M), and small (S). The L segment encodes the RNA-dependent RNA polymerase, the M segment encodes the envelope glycoproteins Gn and Gc, and the S segment encodes the nucleocapsid protein and a non-structural protein (NSs). The NSs protein is particularly important because it suppresses the host interferon response, allowing the virus to evade innate immunity and replicate efficiently in host cells. Viral replication occurs in the cytoplasm, where the RNA polymerase transcribes viral mRNA and replicates the genome via complementary RNA intermediates.
Understanding the molecular biology and pathogenesis of Schmallenberg virus is important for surveillance, vaccine development, and controlling outbreaks in livestock populations.