Journal of the Louisiana State Medical Society
leptospirosis or Weil’s disease. 2 Weil’s disease is character- ized by jaundice, thrombocytopenia, acute renal failure, respiratory distress, and cardiac arrhythmias. 2 Weil’s disease occurred in two patients in the triathlon outbreak and has a 5%-10% case fatality rate, with males experiencing more severe illnesses and more fatalities than females. 1 The differential diagnosis of LS is broad and includes most febrile infectious diseases, includingHPS, and relies on a careful exposure history and clinical suspicion supported by serologic testing. Dipstick screening tests using ELISA to detect serum IgM antibodies to leptospires are quick and easy to perform but do not cover all serotypes of pathogenic L. interrogans . The microscopic agglutination test (MAT) is the most reliable test for LS but is more time-consuming and only offered by reference laboratories, such as the CDC (Figure 1). 1,2 Since IgM antibodies cannot be detected until five to seven days into the illness, acute serologic tests may be negative initially and positive later in the illness and during convalescence. Cultures of leptospires from blood or urine are time-consuming and of limited value in clini- cal management. Antibiotic therapy with oral doxycycline, ampicillin, amoxicillin, erythromycin, or azithromycin is recommended for mild cases; with intravenous therapy with ceftriaxone or penicillin G recommended for severe cases. 1,2 Chemoprophylaxis with doxycycline, 200mg/week, has an efficacy rate of 95% and should be considered for soldiers on tropical training maneuvers and for triathletes participating in competitive swimming or paddling events in LS-endemic, tropical areas. 1,3 Although vaccines are under development for LS, none are universally available today; and the best preventive strategies for LS include drinking boiled or bottled water and minimizing exposure to rodent-urine contaminated environments by wearing waterproof boots and clothing. All cuts and abrasions should be covered with waterproof dressings. Triathletes participating in distance swimming events, kayakers, and whitewater rafters should wear goggles to prevent transconjunctival transmission and avoid submersion in and ingestion of river water. 1,3 All healthcare providers should maintain high levels of suspicion for LS after flooding events and freshwater immersions, and public health officers should immediately promote heightened awareness of leptospirosis outbreaks among all flood- affected populations. Like the leptospires, the hantaviruses (family Bunyaviri- dae, genus Hantavirus) are rodent- and insectivore-borne pathogens with a worldwide distribution except in Antarc- tica. However, unlike leptospirosis, hantavirus infections are never mild or asymptomatic, and all result in severe illnesses ranging fromhemorrhagic fevers to hemorrhagic fevers with renal or cardiopulmonary failure with high case fatality rates (36%-76%). 6, 20-22 Among the Old World hantaviruses (Hantaan, Dobrava, Seoul, and Puumala viruses), Hantaan virus was first described as the cause of hemorrhagic fever renal syndrome (HFRS) in US soldiers returning from the Korean War in the early 1950s. 6 All of the Old World hanta- viruses target the kidneys and can cause HFRS. 6
flooding saturate soil and surface vegetation, leptospires percolate into ground and surface waters, contaminating large inland freshwater systems, including lakes and rivers. 3 Human LS infections are transmitted most commonly by direct or indirect contact of mucous membranes, includ- ing conjunctivae, or abraded or broken skin with urine from infected rodents or contaminated surface waters. 1-4 Less commonmodes of transmission include rodent bites, inges- tion of rodent-urine contaminated water or food, inhalation of infectious aerosols of rodent excreta, congenital trans- mission, and transmission following breast-feeding, blood transfusions, and organ transplants. 1,2 Person-to-person transmission is possible but rarely described. After an incubation period of 1 to 30 days (mean 7-14 days), LS displays awide spectrumof clinical manifestations ranging from a mildly symptomatic, almost subclinical, infection as in most cases; to a constellation of abrupt fever, headache, myalgias, nausea, vomiting, and an occasional maculopapular rash that resolves in a week (as in Case 2 of the University of Hawaii outbreak); to a biphasic illness that starts with fever, myalgias, and conjunctival suffusion in the first week, and in 5%-10%of cases progresses to icteric Figure 4: Range of the cotton rat (Sigmodon hispidus), reservoir of Black Creek Canal virus in North America. Source: US Centers for Disease Control and Prevention. Cotton Rat Habitat in North America. Available at http://cdc.gov/ hantavirus/rodents/cotton-rat.html.
190 J La State Med Soc VOL 166 September/October 2014
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