The value of pre-exposure prophylaxis: A case series of US Marines infected with leptospirosis

Leptospirosis is an ever-present threat found in the freshwater areas in many tropical and sub-tropical regions throughout the world and travelers to these areas are at increased risk of infection. This study describes a case series of 47 US Marines who experienced a single point leptospirosis exposure in 2014 and were admitted to a military treatment facility.

Descriptive statistics were conducted for patient demographics, symptoms, laboratory results, and outcomes. Hypothesis tests were conducted to identify significant outcomes (length of hospitalization, severity of infection, intensive care unit (ICU) admission, and cholecystectomy). Patient data was applied to five leptospirosis scoring models to assess their accuracy in the context of this population.

The patients were all male (n = 47, 100%), had a median age of 22 (range 19-37), a mean body mass index of 24.3 (SD 2.5), and most were taking antibiotic prophylaxis (n = 40, 85.1%). Most patients experienced thrombocytopenia (n = 37, 78.7%), proteinuria (n = 35, 74.5%), and transaminitis (n = 37, 78.7%). Correct classification of infection varied among the models from 42.6% (n = 20) to 10.6% (n = 5). Not taking pre-exposure prophylaxis was significantly correlated with severe infection (p = 0.02), undergoing a cholecystectomy (p = 0.01), and being admitted to the ICU (p < 0.01). No other results were found to be both clinically and statistically significant.

Leptospirosis diagnostic models currently in use may be less effective in predicting disease severity in young and healthy populations who are taking antibiotic prophylaxis. The use of pre-exposure prophylaxis significantly correlates with less severe health outcomes.