Bovine viral diarrhea virus (BVDV) outbreaks continue to pose severe economic and health threats to cattle herds, as demonstrated by a recent multi-year case study in a Salers herd in the Puy-de-Dôme department of France. According to veterinary reports detailing the farm’s management between January 2023 and October 2024, the establishment suffered heavy losses totaling approximately 80,000 euros excluding tax, driven by the birth of persistently infected (PI) calves that triggered widespread immunosuppression and neonatal mortality.
The Impact of BVDV Outbreaks on Herd Health and Mortality
During the 22-month period, the Puy-de-Dôme herd recorded 32 calves that were euthanized following positive ear-notch test results, alongside 21 stillborn calves and 20 deaths attributed to various neonatal pathologies. According to veterinary assessments, the catastrophic episode stemmed from a massive circulation of the BVD virus, which severely compromised herd immunity and increased vulnerability to secondary infections such as cryptosporidiosis and coronavirus. Financial losses reached roughly 80,000 euros excluding tax, placing immense pressure on the farm operators alongside the psychological toll.
Origins of Contamination and the Role of Neighboring Herds
Epidemiological investigations conducted alongside the local GDS (Groupement de Défense Sanitaire) revealed no prior history of BVD on the farm, where ear-notch screening and purchase testing had previously maintained a clean status. Expert appraisal dated the introduction of the virus to three pregnant heifers grazing on an isolated pasture between May and November 2022 without any animal introductions.
Understanding Persistently Infected (PI) Calves as Viral Reservoirs
BVDV is a pestivirus capable of crossing the placental barrier during gestation, frequently leading to embryonic loss, abortions, or the birth of PI calves. According to veterinary pathology data, PI calves recognize the virus as self and fail to develop antibodies, acting as constant, hidden viral reservoirs until clinical disease erupts in the herd. Animals exposed to the virus subsequently can develop mucosal disease, characterized by oral ulcers and hemorrhagic diarrhea, which carries a consistently fatal prognosis. Ear-notch cartilage testing at birth remains the primary diagnostic tool used to identify and cull these animals to safeguard herd health.