Weil's disease is a severe and potentially life-threatening zoonotic infection caused by Leptospira, a spirochetal bacterial pathogen. Fever, constitutional symptoms, gastrointestinal irritation and muscle ache progressing to hepatorenal failure, pulmonary dysfunction, and involvement of other organs is the typical clinical presentation. Clinical criteria and microbiological studies are needed to make the diagnosis.
Leptospirosis is a widely recognized infection caused by a spirochetal bacteria, Leptospira spp., and virtually any region of the world is considered to be endemic for this infection    . These microbial organisms are responsible for chronic renal infections in a range of animal hosts (livestock, medium-sized mammals, rodents, bats, amphibians and various other), who excrete them through urine and contaminate soil, water or even food, which are the primary sources of human exposure   . After the acquisition of Leptospira through abraded or damaged skin/mucosal membranes when in contact with contaminated water or soil, the mean incubation period is about 7-14 days (ranging from 2-30 days)    . Although the clinical presentation can be quite variable, fever accompanied by chills, myalgia, headaches, meningismus, a nonproductive cough and gastrointestinal complaints (diarrhea, nausea, vomiting and abdominal pain) are seen in the majority of cases    . In approximately 10% of patients, a severe form of leptospirosis develops and the term Weil's disease is used to describe the life-threatening organ dysfunction that is encountered, primarily involving the liver and the kidneys    . Acute kidney injury (AKI) manifesting as oliguria, or even anuria in the setting of renal failure, together with jaundice, are hallmarks of Weil's disease    . In addition, thrombocytopenia and several other factors contribute to hemorrhagic episodes, most frequently in the pulmonary system (presenting as hemoptysis), whereas epistaxis, petechiae, ecchymoses, melena or hematemesis can also develop . Multiorgan failure, acute respiratory distress syndrome (ARDS), circulatory collapse and altered consciousness may all ensue in Weil's disease, which is why mortality rates reach up to 30%, especially in the absence of early recognition and proper therapy  . Moreover, older patients and those who suffer from loss of consciousness are at a significantly higher risk for fatal outcomes  .
Because of the possibly life-threatening outcome of Weil's disease, the diagnosis must be made as early as possible. Signs and symptoms of Weil's disease and the initial stages of leptospirosis are not specific for the disease, making a detailed patient history pivotal in identifying recent exposure to contaminated waters, either through the occupational setting (veterinarians, farm and rice workers, hunters, shelter workers, etc.) or during recreational activities (swimming, fishing, caving, rowing) . Furthermore, a thorough physical examination can reveal the potential site where the bacteria may have gained entry into the circulation, but also assess the extent of symptoms and organ involvement, after which a meticulous laboratory workup is necessary. A complete blood count (CBC) renal and kidney function tests, urinalysis and in the setting of meningitis-like symptoms, a lumbar puncture are vital . Typical findings for leptospirosis and Weil's disease are leukocytosis, thrombocytopenia, elevated blood urea nitrogen (BUN), creatinine, and liver transaminases (alanine and aspartate aminotransferases, or ALT and AST), hyperbilirubinemia, proteinuria, pyuria, hematuria, and pleocytosis in the cerebrospinal fluid (CSF), respectively   . Moreover, serum inflammatory markers, such as erythrocyte sedimentation rate (ESR), will also be raised  . A definite diagnosis, however, is made after confirming Leptospira in urine, blood, or CSF obtained from the patient. In the initial stages of the infection (first 10 days), microscopic detection of bacteria from any of the mentioned samples is widely recommended, primarily because results are provided within the hour, whereas cultivation, equally effective in the first several days, takes at least a few weeks to yield conclusive results   . However, low specificity/sensitivity rates require additional testing in most cases . Thus, confirmation of immunoglobulin (Ig) M-specific antibodies through microscopic agglutination test (MAT) or enzyme-linked immunoassay (ELISA) and use of molecular methods - polymerase chain reaction (PCR), are advocated in the later stages of the disease    .