Veterinary laboratories in France, Germany and Switzerland have identified a previously unknown orthobunyavirus of the Simbu serogroup, closely related to Schmallenberg virus, in dairy cattle showing acute illness. The virus has been associated with signs of diarrhoea, fever, reduced appetite and a marked, though generally temporary, decline in milk production. Cases have been reported in eastern France, Switzerland and southern Germany since July. While some dairy farms remain unaffected, others have experienced widespread illness.
Related to – but distinct from – Schmallenberg virus
Metagenomic analyses in France first detected the virus in blood samples collected from affected cattle. Preliminary phylogenetic studies indicate that it belongs to the Shamonda/Schmallenberg genotype within the Simbu serogroup. German researchers subsequently confirmed a closely related virus, with whole-genome sequencing suggesting the emergence of a distinct virus. Taxonomic classification is underway.
Transmitted by biting midges
Like Schmallenberg virus, the new virus is likely transmitted by Culicoides biting midges. Although current outbreaks mainly involve acute clinical disease in adult cattle, experts stress that reproductive effects, including abortion and congenital malformations, remain possible and require close monitoring.
Diagnostics and surveillance
Routine PCR tests for Schmallenberg virus have been negative, probably because of genetic differences between the two viruses. Diagnostic laboratories in France are therefore developing specific molecular tests, with EDTA blood samples and abortion material currently considered the preferred samples for diagnosis. Based on current knowledge, the disease does not appear to pose a risk to humans and is not considered highly contagious between animals.
Veterinarians are encouraged to remain vigilant, report suspect cases promptly and strengthen surveillance for abortions and stillbirths in both cattle and sheep while the epidemiology and clinical impact of this emerging virus continue to be investigated.
(photo ©Fabian Betto/Unsplash)