Human Brucellosis

Synonyms

Undulant Fever, Gibralter Fever

Introduction

Brucellosis in humans is caused by the Brucella abortus, B. ovis, B. suis or B. melitenus bacteria. Transmission occurs via contact with secretions from infected animals or by ingestion and inhalation or the organism.

Brucellosis in humans is usually associated with eating unpasteurized milk and soft cheeses made from the milk of infected animals, primarily goats, infected with Brucella melitensis and with occupational exposure of laboratory workers, veterinarians and slaughterhouse workers. Some vaccines used in livestock also cause disease in humans if accidentally injected.

Clinical Signs

Brucellosis causes fluctuating fevers, sweating, weakness, anaemia, headaches, depression, osteomyelitis and muscular and bodily pain and can become chronic.

The symptoms are like those associated with many other febrile diseases, but with emphasis on muscular pain and sweating. The sweat is said to have a characteristic smell of wet hay. The duration of the disease can vary from a few weeks to many months or even years and has been known to cause high levels of suicide in the veterinary proffession.

Diagnosis

Diagnosis of brucellosis relies on:

Area of the world (if Brucellosis is endemic), knowledge of contact with animals, carcasses or milk products and clinical signs.

Definative diagnosis can be achieved by demonstration of the agent: blood cultures in tryptose broth, bone marrow cultures. The growth of brucellae is extremely slow and the culture poses a risk to laboratory personnel due to high infectivity of brucellae. Antibodies against the agent either with the classic Huddleson, Wright and/or Bengal Rose reactions can be demonstrated, either with ELISA or the 2-mercaptoethanol assay for IgM antibodies associated with chronic disease. Histologic evidence of granulomatous hepatitis (hepatic biopsy) can also be seen microscopically. Radiographs can also be performed to assess for alterations in infected vertebrae: the Pedro Pons sign (preferential erosion of antero-superior corner of lumbar vertebrae) and marked osteophytosis are suspicious of brucellic spondylitis.

Treatment and prevention

Antibiotics like tetracyclines, rifampicin and the aminoglycosides streptomycin and gentamicin are effective against Brucella bacteria.

The gold standard treatment for adults is daily intramuscular injections of streptomycin and oral doxycycline. Gentamicin by intramuscular injection once daily for seven days is an acceptable substitute when streptomycin is not available or difficult to obtain.

The main way of preventing brucellosis is by using fastidious hygiene in producing raw milk products, or by pasteurizing all milk that is to be ingested by humans.

References

Quinn, P.J., Markey, B.K., Carter, M.E., Donnelly, W.J., Leonard, F.C. (2007) Veterinary Microbiology and Microbial Disease Blackwell Publishing

Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences

"Diagnosis and Management of Acute Brucellosis in Primary Care". Brucella Subgroup of the Northern Ireland Regional Zoonoses Group. August 2004