Abstract
Since France is officially free of bovine brucellosis, a single autochthonous outbreak of cattle brucellosis occurred in 2012 in the Bargy, linked to a wild reservoir of B. melitensis in Alpine ibex. On October 12, 2021, a positive ELISA result on pooled milk sample was confirmed during the monthly serological monitoring in a farm of 240 dairy cattle. Two cows presented a positive reaction after brucellin testing and one of them was seropositive. Post-mortem investigations of both cows led to the isolation of three Brucella melitensis isolates from the lymph nodes and milk of a primiparous cow that calved on September 14, 2021 and grazed in 2020 in the Bargy mountain pasture. Sequencing of the 3 isolated strains demonstrated the great genomic proximity with the strains of the 2012 cattle household and those isolated from ibex since 2012. The slaughter of the herd in January 2022 mobilized 12 people on site for 2 days for the collection of 1516 samples (1462 samples from 214 cattle; 54 samples from 18 euthanized calves). Bacteriological cultures were performed from blood, three pairs of lymphnodes, spleen, genital swab and genital tract. Samples were processed by the entire network of approved local laboratories with negative results. Three females presented non-negative serological results at slaughter (1 Rose Bengal (RB) positive, 1 RB and Complement fixation (CF) positive, 1 doubtful ELISA). Additional analyses are underway (molecular analyses, enriched cultures), in order to investigate animals that have presented particular risk factors (abortion, FC or ELISA result close to the threshold, taking colostrum from the infected cow, transhumance). Current results are in favor with a recent infection, together with a limited intra-herd dissemination.
The authors would like to thank the French authorities, the laboratory network (LDA 73, LDA 01, LDA 13, EVA (LDA 31), LABOCEA, PUBLIC LABOS (LDA TARN), TERANA), the slaughterhouse and staff who contributed to the investigations.
Contact author: claire.ponsart@anses.fr
