Abstract
Although successfully eradicated in some parts of the world, brucellosis remains one of the most significant zoonotic diseases. Here, we describe human cases of brucellosis in the British Isles, where bovine brucellosis, caused by B. abortus, has been successfully eradicated, and ovine/caprine brucellosis, caused by B. melitensis, has never been reported. In total 188 cases of brucellosis were confirmed by biotyping of isolated cultures submitted by hospitals to the WOAH an FAO Refernce Laboratory for Brucellosis (APHA, UK), largely isolated from blood, between 2000 and 2020. A significant number of bacterial isolates submitted were excluded as Brucella and a subset of these isolates were identified by 16S rRNA sequencing to be organisms potentially confounding hospital automated or semi-automated bacterial identification systems. The vast majority of confirmed Brucella cases were caused by B. melitensis (91%) and, where data were available, all appeared associated with travel to endemic regions - most commonly Somalia, Turkey, India, and Saudi Arabia. These findings confirm that B. melitensis appears by far the most significant Brucella species associated with human brucellosis globally. There were a smaller number of cases of B. abortus (6.4%), none of which were associated with international travel outside of the British Isles (UK and Republic of Ireland). They appear to reflect more recent eradication of bovine brucellosis from Ireland, or - in one case - possible reactivation of latent brucellosis acquired prior to eradication in Great Britain. Although known to be a potentially significant human pathogen, only two cases (1.1%) were caused by B. suis. Molecular typing of isolates by multi-locus variable number tandem repeat analysis (MLVA) and multi-locus sequence typing (MLST) revealed clustering consistent with the likely geographical origin of cases and, where no travel history was available, could be useful in indicating the potential source of infection.
