Schmallenberg Disease

Schmallenberg disease is an arboviral infectious disease that affects cattle, sheep, and other ruminants. It is caused by the Schmallenberg virus (SBV) which is a newly emerged virus in veterinary medicine. The virus was first discovered in Germany in 2011 and rapidly spread throughout Europe. As a seasoned biologist with years of industry expertise, BioVenic has been actively involved in the research and fight against Schmallenberg disease.

Cause

SBV, a negative-sense RNA virus, belongs to the Orthobunyavirus genus in the Peribunyaviridae family. Its genome is divided into three segments.

Fig.1 The structural and genomic composition of SBV virions.^1,2

The primary target of SBV infection is the central nervous system of ruminants, leading to diminished milk production and causing fetal malformation or death in both cattle and sheep.

SBV is transmitted through the bite of infected mosquitoes, especially Culicoides. It cannot be transmitted between animals, except vertically from mother to offspring in utero.

Fig.2 Schematic diagram of the transmission pathways of the Schmallenberg virus.^3,4

The pathogenesis has not been fully elucidated, but it is generally believed that SBV mainly invades the epithelial cells of susceptible animals to replicate, then enters the blood circulation to form viremia, and then enters the central nervous system through the blood and lymphatic circulation, causing animal disease.

The disease is not a zoonosis.

Epidemiology

The rapid spread and multi-species infectivity characterize the epidemiology of SBV. In addition to Europe, some countries in West Asia and Africa have also been affected by the virus. With the deepening of research, the virus has a wide host spectrum. In addition to cattle and sheep, wild deer, dogs, elephants, and African bison are also potential hosts. Under experimental conditions, it can also infect pigs. This brings certain difficulties to the prevention and control of the disease.

Signs and Symptoms of SBV Infection

The disease mainly causes two distinct clinical features.

Clinical symptoms in adult animals are generally mild, such as fever, decreased milk production, diarrhea, and weight loss. The incubation period is 1 to 4 days, and the viremia lasts for 1 to 5 days. Individual animals recover after a few days, and groups gradually stabilize over 2–3 weeks.

If the female animal is infected during a specific period of pregnancy, miscarriage, dystocia or congenitally deformed pups may occur. The incidence of deformities varies with the gestational age at the time of infection and with animal species. Sheep with synchronous pregnancies may have a higher incidence.

Diagnosis of Schmallenberg Disease

Because adult animals are infected without specific clinical symptoms, laboratory methods are required for diagnosis. BioVenic provides customers with development services including immunodiagnostics and molecular diagnostics solutions, including the options below.

• Virus isolation
• Real-time RT-PCR
• ELISA
• Immunohistochemistry (IHC)
• Virus neutralization assay

The duration of viremia after infection in adult animals is shorter, so antibody detection is more appropriate than antigen detection.

Treatment

Unfortunately, there is currently no specific treatment for the Schmallenberg virus. Together with other research institutions, BioVenic continues to explore potential treatments effective against this disease.

Supportive care is usually provided and infected adult cattle and sheep recover. Deformed lambs and calves should be culled.

Control and Prevention

Fewer vaccines are currently available, and BioVenic has been actively involved in the development of effective vaccines aimed at conferring immunity to SBV in susceptible animals. We recommend the following measures,

• Some countries offer commercially available inactivated vaccines for vaccination.
• During active vector seasons, controlling potential vector insects can reduce the spread of the virus.
• Adjusting the breeding season to avoid the active season of insect vectors can reduce the number of deformed fetuses.
• During assisted lambing and calving, strict hygiene measures are enforced.

By staying at the forefront of scientific advancement and working closely with stakeholders, BioVenic strives to protect livestock populations from the devastating effects of Schmallenberg disease. We are committed to helping customers develop Schmallenberg disease diagnostic solutions, vaccines, and more. If you want to cooperate with us, please feel free to contact us.

References

1. Endalew, Abaineh D., et al. "Schmallenberg disease—A newly emerged Culicoides-borne viral disease of ruminants." Viruses 11.11 (2019): 1065.
2. Image retrieved from Figure 1 "Schmallenberg virus (SBV) virion and genome organization." Endalew, Abaineh D., et al, 2019, used under [CC BY 4.0], the image title was changed to "The structural and genomic composition of SBV virions."
3. Collins, Áine B., et al. "Schmallenberg virus: a systematic international literature review (2011-2019) from an Irish perspective." Irish Veterinary Journal72 (2019): 1-22.
4. Image retrieved from Figure 5 "Arbovirus vector-mediated transmission cycle."Collins, Áine B., et al., 2019, used under [CC BY 4.0], the image title was changed to "Schematic diagram of the transmission pathways of the Schmallenberg virus."