Brucellosis

Brucellosis, also known as “undulant fever", or in the Middle East as “Malta fever”, is a “zoonosis” (i.e., a disease or infection that is transmitted primarily from a vertebrate animal to human). Transmission of brucellosis is thus mainly by direct or indirect contact with animals and their products. Ingestion of dairy products remains the major route for animal to human transmission.

• Despite measures for prevention in animals, Brucellosis remains an important human disease in many parts of the world especially in the Middle East, South and central Asia and Central and South America.
• Brucella is slow-growing, small, aerobic, non-motile, non-encapsulated, non–spore-forming, gram-negative coccobacilli. Brucella has many species but Brucella abortus (in Cattle) and Brucella melitensis (from sheep, goats and camels) are the two most common pathogenic species.
• Presentation can be non-specific with different durations ranging from acute (50% of cases), subacute to chronic. Within endemic regions, it is advised that every case of non-specific or prolonged fever, as well as chronic, non-specific lack of energy, raises suspicion of brucellosis with a nutritional and environmental history regarding having contact with cattle or ingestion of unpasteurised dairy products. Subclinical illness refers to serologic evidence of infection without symptoms or recognizable clinical infection.
• The acute illness presents either with mild non-specific symptoms or with toxic disease with rapid development of complications. The duration of symptoms can range from a few weeks up to 3 months. If symptoms are insidious with a duration of more than 3 months then the disease is labelled as sub-acute and if symptoms persist for more than 1 year it is called chronic (chronic illness is usually mostly due to failure of treatment or lack of recognition).
• Brucellosis is a systemic infection that can involve any organ or tissue of the body. When clinical symptoms related to a specific organ predominate, the disease is termed “localized”. Commonly, localization involves organs of the reticuloendothelial system such as lymph nodes, liver, spleen and bone marrow where it forms non-caseating granulomas. Other organs can be involved such as bones, joints, central nervous system [CNS], heart, lung, spleen, testis, liver, gallbladder, kidney, prostate, pancreas, and skin.
• Symptoms in the acute and sub-acute illness include multiple organ systems but commonly fever occurs (95% of cases) along with myalgia, lack of energy, arthritis occurs (up to one third of cases), hepatomegaly (20%) and splenomegaly (12%). In the chronic disease, 20% of cases complain of persistent malaise and low mood with some features similar to chronic fatigue syndrome. Osteoarticular involvement and damage is the most common complication of brucellosis especially in localized disease (40% of all brucellosis cases). Sacroiliitis is the most common manifestation in young persons.
• It is essential to make a diagnosis and give the appropriate antibiotics as early as possible, and for an adequate length of time. In children 8 years of age and older with uncomplicated brucellosis, treatment is doxycycline for six weeks with an amino-glycoside (Streptomycin for 2-3 weeks or Gentamicin for 7 to 10 days). Alternatively, doxycycline plus rifampicin, both for 6 weeks can be given. In children less than 8 years of age, co-trimoxazole is given instead of doxycycline. In complicated Brucellosis (including bones, heart or CNS), prolonged therapy is recommended.

Diagnosis: Evidence in support of the diagnosis as per WHO includes:

• A history of recent exposure to a known or probable source of Brucella spp. This includes common host species, especially cattle, sheep, goats, pigs, camels, yaks, buffaloes or dogs; consumption of raw or inadequately cooked milk or milk products, and, to a lesser extent, meat and offal derived from these animals. In addition, the resistance of the organism and its high infectivity make environmental contamination a probable hazard, although this is always difficult to prove. Occupational exposure and/or residence in an area in which the infection is prevalent, also raise the probability of the diagnosis.
• Isolation of Brucella spp. from the patient by laboratory testing:
• Demonstration by validated polymerase chain reaction of the presence of Brucella genetic material in blood or other tissue sample, or validated serological method of Brucella antigen in blood or other tissue sample or rising antibody titre in any serological test for brucellosis or high sustained IgG antibody titre in the agglutination, complement fixation or ELISA tests with standardized antigens.
• In acute brucellosis, isolation of Brucella from blood or other tissues is definitive. Culture is often negative, especially in long-standing disease.
• Serology is the most generally useful diagnostic procedure approach (the tube agglutination and ELISA procedures are recommended). Methods which differentiate IgM and IgG can distinguish active and past infection. False positive serological reactions may occur. Skin test reactions indicate past exposure not active infection.

More information is available from the Centre for Disease Control and Prevention