Adventure racers contracted illness after contact with water and soil; most likely etiologic agent?

• A. Borellia recurrentis
• B. Brucella canis
• C. Francisella tularensis
• D. Leptospira interrogans

Answer: (D)

Exposure to water and soil points to Leptospira interrogans because this bacterium thrives in moist environments and is shed in the urine of animals. Infection occurs when someone comes into contact with water or soil contaminated with that urine, and the organism enters through cuts in the skin or through mucous membranes. In adventure racers, wading through rivers, swamps, or mud created by animal-contaminated water is a classic scenario. The illness often starts with fever and body aches and can progress to severe forms such as Weil disease, which includes jaundice and kidney failure if not treated.

The other organisms are associated with different routes: for example, louse-borne transmission causes relapsing fever, Brucella from direct animal contact or ingestion of animal products, and Francisella tularensis from direct contact with infected animals, ticks, or contaminated water in various settings. The water/soil exposure pattern most strongly aligns with leptospirosis.