Extreme Athlete, 18, With Worsening Cough

DISCUSSION
Leptospirosis develops when humans come into contact with animal urine infected by leptospires—that is, pathogenic spirochetes excreted via the renal tubules of infected host animals.^9,10 While host animals include dogs, pigs, cattle, reptiles, and amphibians, the animal most commonly associated with human infection is the brown rat (Rattus norvegicus).^11-15

Leptospires enter the human host through mucous membranes, cuts, or abrasions in the skin. Individuals at increased risk for infection include those whose work or other activities expose them “to animal reservoirs or contaminated environments”—including participants in water sports and similar recreation.^11-14 As Mwachui et al explain, “recreational exposure to [Leptospira-]contaminated water has become more important for sport enthusiasts, swimmers and travellers from industrialized countries,” whereas flooding is usually involved in infection in undeveloped countries.¹⁶

The largest outbreak of leptospirosis reported in the US to date occurred in 1998, when heavy rains preceded a triathlon in Springfield, Illinois. When many participants became ill after the event, researchers from the National Center for Infectious Diseases were able to contact and test 834 of the 876 competing athletes; of these, 98 (12%) reported being ill and 52 (11%) tested positive for leptospirosis. Additionally, 14 of the 248 community residents who were sickened (6%) tested positive.¹⁷ According to CDC estimates, between 100 and 200 cases of leptospirosis develop annually in the US, with about half occurring in Hawaii.⁹

Onset of symptoms, which are described as protean and nonspecific, occurs two days to four weeks after exposure, making leptospirosis difficult to diagnosewithout a high degree of suspicion; zoonotic exposure (as with freshwater or mud sports) or a history of travel to Hawaii, Tahiti, Thailand, Indonesia, the Caribbean, and/or Costa Rica may raise suspicion.^12-14,18 In early-phase leptospirosis, symptoms can mimic those of influenza, meningitis, malaria, dengue fever, scrub typhus, rickettsial disease, and typhoid fever (see Table 2).¹⁰ Thus, when a patient presents with these symptoms, it is imperative that the clinician consider leptospirosis.¹⁹Of note: Flu-like symptoms with conjunctival suffusion are considered pathognomonic for leptospirosis.¹⁸

About 10% of patients with early-phase leptospirosis will develop late-phase disease (ie, Weil’s disease), with severe symptoms that include jaundice, meningitis, pulmonary hemorrhage, and acute kidney injury (see Table 3 for a more detailed list).²⁰ The case patient’s history and symptoms were consistent with a diagnosis of early-phase lepto­spirosis.

Epidemiology
In 2015, leptospirosis was estimated to affect more than 1 million persons worldwide, with 58,900 deaths attributed to the disease each year—making leptospirosis the leading cause of death attributable to zoonotic illness.¹¹ Historically, leptospirosis-associated morbidity and mortality have been greatest in resource-poor countries with tropical climates (eg, southern and Southeast Asia, Central America and tropical Latin America, and East Sub-Saharan Africa).^11,12

However, illness resulting from recreational exposures to contaminated water has been linked to increasing travel to exotic destinations, participation in adventure travel, and the growing popularity of extreme sports involving fresh water.⁹ Recreational mud run events, for example, involve swimming in potentially contaminated waters and crawling through flooded farm fields where animal urine can be present—an ideal environment for Leptospira to thrive and for participants to contract the disease.^14,15

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