Chapter 3Infectious Diseases Related To Travel

Marta A. Guerra, Barun K. De

INFECTIOUS AGENT

Brucella is a genus of facultative, intracellular, gram-negative coccobacilli. Ten species of Brucella are defined by phenotypic and antigenic differences, in addition to differential host specificity. Known human pathogens include Brucella abortus, B. melitensis, B. suis, and B. canis. Pathogenicity to humans of several other species is not well known: B. ovis, B. neotomae, B. ceti, B. pinnipedialis, B. microti, and B. inopinata.

MODE OF TRANSMISSION

Eating or drinking contaminated milk products is the most common route of infection for Brucella spp. Brucella can enter the body via skin wounds, mucous membranes, or inhalation. Person-to-person transmission is rare.

EPIDEMIOLOGY

High-risk regions include the Mediterranean basin, South and Central America, Eastern Europe, Asia, Africa, and the Middle East. Brucellosis is primarily an occupational disease among people working with infected livestock or handling the organism in laboratory settings. The infection is present in wildlife and in domestic animals such as goats, sheep, pigs, and cattle. Brucellosis is common in countries that have poorly developed public health systems and no standardized brucellosis-control programs for livestock.

Risk is mainly associated with the consumption of unpasteurized milk and other dairy products in countries where brucellosis is endemic or enzootic. Unpasteurized soft goat cheeses are frequently contaminated with Brucella and associated with the development of brucellosis. People exposed to contaminated fluids and tissue while helping animals give birth, slaughtering and dressing of infected animals, or preparing foods from infected animals are at increased risk of infection. Eating undercooked infected meat is another route of infection.

CLINICAL PRESENTATION

The incubation period is 2–4 weeks (range, 5 days to 5 months). The initial presentation is nonspecific, including fever, muscle aches, fatigue, headache, and night sweats. The fever may be continuous or intermittent (undulant). Systemic infection may localize in the liver, spleen, bone marrow, joints, heart, or reproductive organs. When it occurs, endocarditis is a primary cause of death. Neuropsychiatric symptoms, such as depression or sleep disturbance, may occur rarely. More severe symptoms are generally associated with B. melitensis or B. suis infections than with infections from other Brucella spp.

DIAGNOSIS

Blood culture is the diagnostic gold standard but is not always positive. If blood or bone marrow culture is used, the laboratory must be informed that Brucella is suspected, so that they will process the sample for a longer period of time and protect laboratory personnel. A serum agglutination test is the most common serologic approach, but other serology, ELISA testing, and PCR have been used to make a diagnosis.

TREATMENT

The optimum antimicrobial therapy for brucellosis includes a minimum 6- to 8-week course of a combination of antimicrobial agents. Antimicrobials most commonly used are doxycycline, rifampin, and streptomycin. Relapses may occur with late initiation or premature discontinuation of therapy.

PREVENTIVE MEASURES FOR TRAVELERS

No vaccine is available for humans. Antimicrobial prophylaxis is not recommended. People traveling to countries where brucellosis is endemic or enzootic should avoid ingesting unpasteurized dairy products. In addition, travelers should avoid eating undercooked meat.

BIBLIOGRAPHY

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