Schmallenberg virus infection: An emerging vector borne disease

Abstract

Term emerging infectious diseases de­scribes new or unrecognized diseases that are spreading to new geographic areas and hosts. Schmallenberg virus (SBV) is an enveloped, neg­ative-sense, segmented, single-stranded RNA virus. Analysis of viral sequences has led to the classification of SBV in the Bunyaviridae family and the Orthobunyavirus genus. A very little is known about the life cycle of SBV. The replication cycle of bunyaviruses is exclusively cytoplasmic. SBV appears to cause disease in domestic and possibly wild ruminants. Cattle, sheep, and goats are susceptible. According to experimental challenge trials, calves inoculated intravenously or subcutaneously were seropositive 2 to 5 days post-inoculation. Symptoms are more apparent in adult cows and include loss of appetite, hyperthermia and diarrhoea, which can lead to a 50% reduction in milk production. The viraemia induced by SBV is short-lived, lasting for 2 to 6 days in cattle. Infected females are able to transmit the virus to foetuses (ovine, caprine and bovine), which developed atypical malformations leading most frequently to intra-uterine death or death immediately after birth. Diagnosis of SBV infection relies on the detection of the viral genome by RT-qPCR. At present no therapeutic drugs or vaccines are available for SBV induced disease. One pos­sible option is to control the Culicoides vectors.