Pathology and diagnosis of brucellosis (Brucella spp.) in veterinary species

Brucellosis is an infectious disease that affects a wide range of animals, caused by bacteria belonging to 13 species and several biovars within the Brucella genus (B. melitensis, B. abortus, B. suis, B. ovis, B. neotomae, B. canis, B. ceti, B. pinnipedialis, B. microti, B. inopinata, B. papionis, B. vulpis, B. nosferati, and unclassified strains). Brucella spp. infects small ruminants, cattle, swine, dogs, wild mammals, reptiles, amphibians, and fish, and most Brucella spp. have zoonotic potential. Characterization of lesions in animal brucellosis remains paramount in the diagnosis in endemic regions and even for countries free of brucellosis, where passive surveillance plays an indispensable role in upholding and sustaining their status. Pathology also contributes to understanding the pathogenesis and associating emerging pathogenic Brucella spp. with disease in animals. Here, we review the pathology of brucellosis in animals with an emphasis on cross-species transmission of "classical" Brucella spp. to nonpreferential hosts and "atypical" Brucella spp. We conclude that Brucella is an expansive genus identified in numerous animals, but there are still significant gaps in the knowledge of the pathology of brucellosis in unusual hosts and emerging Brucella spp. This is a great opportunity for veterinary pathologists to spearhead advancements in the knowledge of the pathogenesis and diagnosis of Brucella spp. infections. The isolation of a Brucella spp. and the correlation with lesions should follow molecular diagnostics to define the genetic signature of the isolate, providing a better understanding of epidemiology and contributing to the control of brucellosis across animal and human populations.