Eco-Challenge participants contracting fever after exposure to water contaminated with animal urine are most likely infected with which organism?

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

Answer: (D)

Exposure to water contaminated with animal urine points to leptospirosis, caused by Leptospira interrogans. This organism is a spirochete that humans typically become infected with through skin or mucous membrane contact with water or soil contaminated by the urine of infected animals (often rodents). Activities like swimming, wading, or working in floodwaters provide a route for the bacteria to enter through small cuts or abrasions, leading to fever, myalgias, headache, and sometimes conjunctival suffusion. In more severe cases, it can progress to kidney failure and jaundice (Weil disease).

The other organisms have different common transmission routes that don’t fit this exposure pattern. Borrelia recurrentis is spread by body lice and causes relapsing fever. Brucella canis is acquired from contact with infected animals or consuming unpasteurized dairy products. Francisella tularensis causes tularemia from handling infected animals, insect bites, or inhalation, not typically from contaminated water.