Brucelosis

Brucellosis
Undulant Fever, Malta Fever, Mediterranean Fever, Enzootic Abortion, Epizootic Abortion, Contagious Abortion, Bang’s Disease
Last Modified: July 19, 2009

Importance
Brucellosis, a bacterial disease caused by members of the genus Brucella, is an important zoonosis and a significant cause of reproductive losses in animals. Brucellosis is usually caused by Brucella abortus incattle, B. melitensis or B. ovis in small ruminants, B. suis in pigs and B. canis in dogs. Abortions, placentitis, epididymitis and orchitis are the most common consequences, although other syndromes are also reported. The main impact is economic; deaths are rare except in the fetus and neonate. Some Brucella species are also maintained in wildlife populations. Wildlife reservoirs including feral pigs,bison, elk and European hares complicate eradication efforts for B. abortus and B. suis. Marine mammal isolates of Brucella have recently been recognized in many species of pinnipeds and cetaceans, and there are concerns that these organisms might have a detrimental impact on some species. Most species of Brucella can infect animals other than their preferred hosts, when they come in closecontact. B. abortus, B. melitensis, B. suis, B. canis and marine mammal Brucella species are human pathogens. In humans, brucellosis can be a serious, debilitating and sometimes chronic disease that may affect a variety of organs. Most cases are caused by occupational exposure to infected animals or the ingestion of unpasteurized dairy products. In the U.S., B. suis has been eliminated from commercialpigs and B. abortus has nearly been eradicated from domesticated ruminants. As a result, human brucellosis is rare. However, this disease remains a common and serious problem in some parts of the world. In addition, some species of Brucella could be used in a bioterrorist attack.

Etiology
Brucellosis results from infection by various species of Brucella, a Gram negative, facultativeintracellular coccobacillus or short rod in the family Brucellaceae. Six named species occur in animals: B. abortus, B. melitensis, B. suis, B. ovis, B. canis and B. neotomae. One or more unnamed species of Brucella have been found in marine mammals. Formal names proposed for marine mammal isolates are B. maris for all strains, or B. pinnipediae for strains from pinnipeds (seals, sea lions and walruses) andB. cetaceae for isolates from cetaceans (whales, porpoises and dolphins). Some species of Brucella contain biovars. Five biovars have been reported for B. suis, three for B. melitensis, and up to nine for B. abortus. Each Brucella species is associated most often with certain hosts. B. abortus usually causes brucellosis in cattle, bison and buffalo. B. melitensis is the most important species insheep and goats, but B. ovis can also cause infertility in rams. B. canis causes disease almost exclusively in dogs. B. neotomae is found in rodents, but has not been linked to disease. B. suis contains more diverse isolates than other Brucella species, and these isolates have broader host specificity. B. suis biovars 1, 2 and 3 are maintained in pigs; European hares are also a reservoir for biovar2. Biovar 4 mainly affects reindeer and caribou, and is not normally found in pigs. This biovar was formerly known as B. rangiferi. Biovar 5 occurs in rodents. In humans, brucellosis can be caused by B. abortus, B. melitensis, B. suis biovars 1-4 and, rarely, B. canis or marine mammal Brucella. Live vaccines for B. abortus and B. melitensis, as well as the B. canis M- strain (a less virulentstrain used as an antigen for serological testing), are also pathogenic for humans. B. ovis, B. neotomae and B. suis biovar 5 have not been linked to human disease. Genetic and immunological evidence suggests that all members of the genus Brucella are closely related, and some microbiologists have proposed that this genus be reclassified into a single species (B. melitensis), which contains many...