First case of Brucella suis biovar 1 infection in a dog in Switzerland

As one of the most common zoonoses globally, brucellosis threatens not only animals but also humans with Brucella (B.) melitensis, B. abortus and B. suis biovar 1&3, being more virulent for humans than B. canis, B. ovis and B. suis biovar 2. Canine brucellosis is caused mainly by B. canis, however, B. suis infections in dogs have been reported sporadically in Europe and more frequently in Australia. B. suis infection in dogs is mainly associated with hunting or wild-animal exposure and rarely with consumption of commercial raw meat products. In Switzerland, B. canis is sporadically diagnosed in dogs and B. suis biovar 2 is present in wild boar and brown hare. We report a case of brucellosis in a dog from Switzerland, neither having a history of hunting nor travel-associated risk of exposure. The intact male dog showed clinical signs (fever and epididymitis) consistent with brucellosis, which was confirmed by culture and molecular methods in urine and by serological methods. Culture and subsequent whole genome sequencing revealed the isolate as B. suis biovar 1, ST-14. The most closely related strain was shown to be a strain isolated in 2021 from a dog in Germany. Based on the lack of any previous report, infection by B. suis in dogs has not previously been diagnosed in Switzerland. This case highlights the need for vigilance regarding this less expected pathogen of high zoonotic importance in dogs.