The Leptospira bacterial genus are responsible for leptospirosis. These bacteria can infect both humans and animals. Leptospirosis is one of the most common infectious diseases that can be transmitted naturally from animals to humans. Sources of infection are the urine or urine-contaminated media (e.g., water, food, and soil) of infected animals such as rodents, cattle, cats, and dogs.
The clinical presentation of the disease is biphasic with an anicteric acute or septicemic phase that is followed by an immune or secondary phase. Approximately 90% of those affected present with mild flu-like symptoms, such as fever, muscle pain, and headache. About 10% of these cases may progress to more severe icteric leptospirosis known as Weil’s disease, which is characterized by internal hemorrhaging and multiple organ dysfunction and/or failure.
Non-specific changes can be suggestive of a leptospirosis diagnosis. In acute anicteric leptospirosis, erythrocyte sedimentation rate (ESR) is elevated and white blood cell counts may range from slightly below normal to elevated. Markers of liver function such as aminotransferases, alkaline phosphatase, and bilirubin are slightly elevated with no jaundice. Urine analysis frequently shows microscopic hematuria (blood in urine) as well as proteinuria (protein in urine) and pyuria (the presence of pus in the urine).
Cerebrospinal fluid (CSF) may show normal or slightly elevated pressure on lumbar puncture. Moreover, CSF may initially show polymorphs or lymphocytes, with a predominance of the latter on later examination. Renal impairment is shown by increased plasma creatinine levels with a varying degree of azotemia, depending on the severity of the disease. Icteric leptospirosis presents with significantly raised bilirubin and serum creatinine phosphokinase levels.
In order to confirm diagnosis, specific microbiological tests are necessary. These include serological, microscopic, and isolation tests. Leptospires can be stained and visualized by using dark-field microscopy or by immunofluorescence or light microscopy. Blood cultures can be taken during the first week of acute illness and examined by means of microscopy. Detecting antigens of leptospires is of greater specificity and potentially greater sensitivity than dark-field microscopy.
Serology is done to diagnosed most cases of leptospirosis. Patients typically have antibodies present within 5 to 7 days after the first appearance of symptoms. The microscopic agglutination test (MAT) is the definitive serological test.
Treating leptospirosis depends largely on the duration and severity of the symptoms. Leptospirosis is treatable with a course of antibiotics for 5 to 7 days in mild disease. The antibiotic of choice is penicillin or doxycycline. Doxycycline can also be used prophylactically in the short term in conditions where exposure risk is high. In addition to antibiotics, painkillers such as ibuprofen and paracetamol may be used to help relieve associated symptoms.
Those patients who present with mild flu-like symptoms of acute anicteric leptospirosis only require treatment for their symptoms. However, further medical help is required if the patient develops jaundice at any point. Hospitalization may be necessary for those patients with more severe presentation of anicteric leptospirosis and in those with severe headache, a lumbar puncture may lead to relief.
Icteric leptospirosis, due to the possibility of life-threatening complications, requires hospitalization. Rehydration is vital in cases of pre-renal azotemia with careful monitoring of kidney function. Those patients who show signs of acute renal failure may require urgent dialysis to replace renal function. Monitoring of cardiac and respiratory function may also be necessary in patients who present with problems of these organ systems.
Reviewed by Susha Cheriyedath, MSc