Brucellosis in humans: why is it so elusive?

Brucellaspp. are small, slow-growing, Gram-negative coccobacilli that are responsiblefor brucellosis, the most common zoonotic disease worldwide. Brucellosis is a notifi-able disease in most countries. Brucellosis is also considered as an occupational,laboratoryandtravel-acquireddisease.Brucellaspp.aretransmittedthroughconsump-tion of raw animal products (food-borne brucellosis) and animal contact. They may bespread through droplets in the air; they are traditionally classified as a class Bbioterrorism agent. Brucellosis incidents have been reported in relation to domesticanimals. Brucella strains have been isolated from terrestrial and marine mammals.Brucella melitensis, B. suis and B. abortus differ in host range, pathogenicity andvirulence. B. canis infections have rarely been reported. Current global trends onthe incidence of brucellosis are reviewed. Brucellosis is often overlooked and canmimic other conditions; it may be acute, subacute or chronic in presentation, and mayinvolve various body sites. Recent studies on endocarditis, osteoarticular, haematolo-gical,neurologicalandotherinvolvementsarereviewed.Relapsesinbrucellosisshouldalso be considered. Collaboration between the microbiologist and the clinician isimportant for diagnosis, since diagnosis of brucellosis is based on laboratory testing byserologyand,ultimatelybyculture,inthecontextofclinicalpresentationandhistoryofrecentorpastexposure.AdvancedPCR-basedtechniquesmayalsobeusedtodiagnosebrucellosis. Today a combination of antibiotics are recommended in treatment,whereas further therapeutic approaches are possible. New challenges posed by inter-national travel, animal trade, animal movement, and occupational migration to/fromendemiccountriesmayincreaseincidenceofhumancasesandtheriskofre-emergenceof brucellosis in previously brucellosis free regions such as Northern and CentralEurope. Animals are considered to be lifelong carriers of Brucella spp. providing alarge continuous source of human infection. A lower incidence of human brucellosis islikely to result from a decrease in incidence of animal brucellosis. Control andsurveillance strategies may depend on the level of healthcare development and theprevalence of reservoir hosts in the affected region.